Abstract:In order to understand the impact of rainfall intensity on runoff distribution and subsurface flow process in the red soil slope with embedded gravel, the artificial simulated rainfall method was used to determine the subsurface flow characteristics of generation time, runoff rate and runoff process. The red soil gentle slope (10°) and steep slope (25°) were taken as research objects with different gravel contents (0, 10%, 20%, 30%) and rainfall intensities (60, 90, 120 mm/h). The results indicated that:(1) The runoff generation time of red soil slope with different contents of embedded gravel was close 15 min under 60 mm/h rainfall intensity, and varied greatly under 90 mm/h and 120 mm/h. The increase of rainfall intensities from 60 mm/h to 120 mm/h, the runoff quantity and runoff rates decreased with varying degrees, and the runoff rates in red soil embedded gravel with 20% and 30% at slope gradient 25° deceased 86.7% and 89.0% respectively. When the rainfall intensity was 120 mm/h, the peak values of subsurface flow were only 10.7% and 10.2% respectively of the 60 mm/h. (2) The proportions of surface runoff increased 32.8%~1 009.4% with the increasing rainfall intensities on the experimental slopes of 10° and 25°. The proportions of surface runoff were 8.0%~66.3% under rainfall intensity 60 mm/h, 76.1%~93.5% under 120 mm/h. The proportions of subsurface flow decreased 46.1%~93.9% with the increasing rainfall intensities. The proportions of subsurface flow were 7.3%~30.0% under 60 mm/h rainfall intensity, 1.1%~9.6% under 120 mm/h. (3) The binary linear regression results showed all the relationships of peak flow of subsurface flow (Ip), coefficient of subsurface flow (It), subsidence rate of subsurface flow (K) with rainfall intensity and gravel content reached the significant levels (P<0.05). Rainfall intensity and gravel content played the opposite roles in the subsurface flow process at slope gradient 10°, while both roles were same at 25°.

Abstract:Through the method of outdoor artificial rainfall simulation, the effects of different slopes (5°, 15°, 25° and 35°) and different planting patterns of Prunus humilis (one row, two rows and three rows) on nitrogen loss and runoff production in gneiss hillsides were studied. The results showed that:(1) The runoff yield time was advanced with the increasing of the slope gradient, and the average runoff yield time was delayed by 59.23% from three rows planting to one row planting, and it was delayed by 32.28% from two rows planting to one row plant, and the runoff yield intensity and fluctuation range of the different planting patterns followed the order of one row > two rows > three rows. (2) During the rainfall process, the nitrogen loss and the loss concentration of different planting patterns were sequenced as one row > two rows > three rows. Under the different slopes, the nitrogen loss and the loss concentration were sequenced as 5° < 15° < 25° > 35°, and the critical slope gradient was 25°. (3) On the same slope, the loss of nitrate nitrogen was the largest when the planting pattern was two rows to three rows, which decreased by 16.78%, 44.71%, 41.33% and 41.89%, respectively. (4) During the nitrogen loss process, nitrate nitrogen loss accounted for 40.35%, ammonium nitrogen loss accounted for 10.13%, and nitrate nitrogen was the main form of loss. (5) In the same planting pattern, there was a quadratic function between the loss amount and the loss concentration of the nitrogen and the slope, the correlation coefficients (R²) ranged from 0.531 to 0.999. On the same slope, the loss amount and the loss concentration of the nitrogen had linear relationship with the planting pattern, and the correlation coefficients (R²) ranged from 0.102 to 0.999. (6) Planting pattern was negatively correlated with nitrate nitrogen loss and ammonium nitrogen loss, which was the main factor affecting nitrogen loss. In the gneiss hillsides, planting P. humilis in multi-row staggered way could significantly reduce nitrogen loss.

Abstract:In order to study the regulation mechanism of intercropping on soil erosion, the rainfall infiltration rules of maize-potato intercropping and ridging under different rainfall intensities (40 and 80 mm/h) and slope gradients (10° and 15°) were evaluated by stimulated rainfall method. The results suggested that:(1) The infiltration terminal time of maize-potato intercropping (IC) was later than that of maize sole crop (MC) under the same slope and rainfall condition during the growth period, and the difference of infiltration start time was not significant. During the experimental periods, the infiltration amount of IC was significantly higher than that of MC (P<0.01), but not significantly different from that of potato sole crop (PC) (P>0.05). During the growth period, the infiltration amount of IC were 25.75%~69.07% and 21.76%~50.95% higher than that of MC under the rainfall intensities of 40 mm/h and 80 mm/h, respectively, The infiltration rate of IC was higher than that of MC under the same rainfall intensity, but there was no significant difference between IC and PC. (2) The infiltration amount of intercropping with high ridging (IC+HR) was significantly higher than those of intercropping with low ridging (IC+LR) (P>0.05), maize sole crop with high ridging (MC+HR) (P<0.01) and maize sole crop with low ridging (MC+LR) (P<0.01). Under the rainfall intensity of 40 mm/h, infiltration amount of IC+LR, IC+HR and MC+HR was 10.10%~28.14%, 25.75%~65.96% and 41.59%~75.46% higher than that of MC+LR, respectively, while under the rainfall intensity of 80 mm/h, the corresponding values were 9.12%~18.03%, 21.76%~44.34% and 36.45%~57.05%, respectively. Thereby, intercropping increased rainfall infiltration and reduced the occurrence of surface runoff, which provided an important reference for understanding the mechanism of soil erosion controlling by crop cultivation. In addition, intercropping with high ridging could effectively increase rainfall infiltration, which was important for guiding regional water resources management and sustainable development of agriculture.

Abstract:Hedgerow is effective in soil and water conservation, and the distance between hedgerows is the key parameter for their allocation. At present, the equidistance is often designed in the most hedgerow arrangements, but the effect of equidistant hedgerows at different slope sections is not clear. Equidistant hedgerows at different slope sections in the northeast black soil region were selected as the object. A runoff erosion experiment with sediment was carried out to simulate the runoff sediment yield process of hedgerows with equal spacing in different slope segments under the condition of 5° slope, 100 mm/h rain intensity. The results showed that:Compared with the control of bare land, hedgerows in all slope segments could prevent slope runoff, and the lag time was shortened gradually with the downward slope segments. The runoff and sediment yield of hedgerows in different slope sections were basically consistent on time scales. The upper and middle slopes were relatively stable, and the lower slopes showed obvious fluctuation at the later stage. The changing trend was closely related to the erosion morphology in the slope, and the overall trend was smaller than that of the control. Hedgerows in the different slope sections reduced the runoff by 5.40%~10.16%, and reduced sediment by 51.90%~75.72%. Although it had a positive effect on runoff and sediment reduction, the erosion module in the lower slope reached 259.96 t/km², exceeding the soil loss tolerance of the northeast black soil area. It could be concluded that the equidistant hedgerow should be improved for its application in the northeast black soil area. This study could provide an important scientific basis for the hedgerow design in the northeast black soil area.

Abstract:By analyzing the soil and water loss monitoring observation data (2010-2016) of the Suining Soil and Water Conservation Experimental Station, this article studied the effects of Vetiveria zizanioides and Leucaena leucocephala hedgerows with different planting years which were layout in purple sloping farmland under natural rainfall conditions. The results showed that:(1) During the study period, when the hedgerows began to play its soil and water conservation role, the average annual runoff reduction rate reached 10.5%~20.0%, and the average annual sediment reduction rate reached 53.5%~54.5%. The reduction rates of hedgerows on average annual runoff fluctuated in different planting years, but its effect on reducing sediment gradually stabilized. (2) The Vetiveria zizanioides hedgerow (10°) showed the best influence on soil and water conservation, giving its reduction effects on runoff and sediment in its first planting year. Leucaena leucocephala hedgerows (10°) gave the inferior effectiveness on soil and water conservation, which sediment-reducing effect was one-year earlier than the runoff-reducing effect. The effects of Vetiveria zizanioides hedgerows (15°) were the worst, showing the lower runoff reduction rates than others. (3) In general, hedgerows could weaken the effects of slope gradients on soil and water loss on sloping farmland, in which runoff loss was decreased by 28.9%, sediment loss by 11.3%, and could also weaken the correlation between rainfall and runoff and sediment. (4) The runoff coefficient and sediment loss caused by the rainfall in hedgerow plots gradually stabilized with the increasing planting years. Torrential rain (12 hours precipitation over 140.0 mm) caused the highest runoff coefficient, followed by heavy rain (12 hours precipitation between 70~140 mm), the runoff coefficient caused by torrential rain and heavy rain were reduced by 15.0%~34.4% in the Vetiveria zizanioides hedgerow (10°) and Leucaena leucocephala hedgerow (10°) plots. The average sediment loss per millimeter of rainfall,was decreased by 34.1%~48.5% in hedgerow plots.

Abstract:Although vegetation coverage has been restored and the ecological environment has been greatly improved through efforts of decades, the soil erosion is still serious in the red soil hilly region of Southern China. Taking the typical Lian River watershed as the study area, the effects of vegetable landscape patterns on runoff and sediment were analyzed using the long-term historical land use, runoff (1958-2017), and sediment data (1964-2017). The results showed that:The runoff in the basin was decreasing, but the sediment was increasing. Forestland was the dominant landscape, and fruit land had the largest growth rate. At landscape level, patch size coefficient of variation(PSCV),and Shannon's diversity index(SHDI) were positively associated with runoff,while contagion index(CONTAG) was negatively associated with runoff. Number of patches(NP),Patch density (PD),Edge density (ED), Area-weighted mean shape index(AWMSI),and Shannon's diversity index(SHDI)were negatively associated with sediment. At class level,the class area (CA) and edge density (ED) of farmland were negatively associated with runoff,however positively associated with sediment. The PSCV and AWMSI of forestland were positively associated with runoff,CA was negatively associated with runoff, and NP and PD were positively associated with sediment. The CA and ED of shrub forest were negatively associated with runoff. All the landscape pattern indexes of fruit land were positively associated with runoff and negatively associated with sediment. The NP and PD of grassland were negatively associated with runoff.

Abstract:In order to study the response of soil structure and soil exchangeable capacity of forest and grass to different measures of Grain for Green Project in Pisha sandstone area, we selected Pinus tabuliformis forest (YS), Caragana korshinskii forest (NT), Populus simonii forest (XY) and Stipa bungeana grassland (ZM) as the research objects and buckwheat slope farmland (QM) as the control. Multi-fractal theory was used to determine the soil particle size distribution (PSD), which measured the fractions of CEC, ECEC and the composition of ECEC (Na⁺, K⁺, Ca²⁺, Mg²⁺), as well as their distribution status and their correlations.The results showed that:(1) The PSD distribution, heterogeneity and dispersion of grassland and woodland were higher than those of sloping farmland after the implementation of conversion of cropland to forest. In the different soil profiles. Grassland was conducive to increasing the distribution range of fine-grained components and particle size of surface soil. However, in the improvement of the above indicators, woodland was more conducive to the deep soil. Moreover, the increase of soil silt contents and PSD distribution range in Caragana korshinskii forest were the most significant among all the measures (P<0.05). (2)In terms of soil exchangeability, alkaline earth metals (Ca²⁺, Mg²⁺) were the main components of exchangeable base in the studied area. The CEC and ECEC values of soil under different measures were ranked as NT > YS > XY > ZM > QM. The exchangeable capacity of grassland surface soil was better than that bottom soil, while that of woodland was opposite. (3)Clay, silt and fine sand were the fine-grained soils and coarse-grained soils that determine soil exchangeable capacity in the studied area, and silt content was the main contributing factor of CEC and ECEC values. Multifractal dimension could well describe the relationship between soil exchangeable capacity and soil particles. It was found that among all the measures of Grain for Green Project, Caragana korshinskii had the best improvement effect on soil particle composition and soil exchangeable performance.

Abstract:The effect of different fertilizers application on nitrogen and phosphorus loss in a bamboo forest was studied by a field experiment. Results showed that the contents of nitrogen and phosphorus in runoff and leachate in the bamboo forest varied in a peak shape with time. In runoff, the total nitrogen and phosphorus contents were 1 844.43 g/hm² and 152.58 g/hm² under the treatment of bag-coated fertilizer that were reduced by 18.75% and 40.94% respectively compared with the control. While in leachate, the total nitrogen and phosphorus contents were 108.84 kg/hm² and 3.32 kg/hm² that were 15.35% and 22.91% lower than the control. Seven days after the fertilizer application, the amount of ammonia volatilization accounted for 75.06% of the total lost, but it was only 68.06% in 28 days in the bag-coated fertilizer treatment. Furthermore, the amount of ammonia volatilization lost in bag-coated fertilizer treatment was 32.08% lower than the control. Therefore, the method of bag-coated fertilizer application should be effective in preventing nitrogen and phosphorus loss and subsequently increase the fertilizer use efficiency in the bamboo forest.

Abstract:In order to investigate the effects of rainfall intensity and vegetation coverage on the runoff and sediment yield on granite red soil slope, this study analyzed regularity of runoff and sediment yield and their correlation under different rainfall intensities (0.5, 1.0, 1.5 mm/min) and vegetation coverages (0, 20%, 40%, 60%) through indoor artificial simulated rainfall test. The results showed that:(1) Under the same rainfall intensity, the initial flow time was delayed with the increasing of vegetation coverage, and it was advanced with the increasing of rainfall intensity. The greater the rainfall intensity, the earlier the flow time was. (2) The runoff rate and erosion rate of each slope decreased with the increasing of vegetation coverage, and the higher the vegetation coverage was, the smaller the fluctuation range of runoff rate and erosion rate was, and the more stable the erosion process was. (3) On the slope covered by vegetation, the sediment was mainly water-stable aggregates less than 0.25 mm. The proportion of water-stable aggregates greater than 0.25 mm in the sediment increased with the increasing of rainfall intensity, and the increase range decreased with the increasing of vegetation coverage. (4) Vegetation coverage and rainfall intensity were significantly correlated with runoff generation time, runoff rate and erosion rate (P<0.01). The correlation between slope runoff generation process and rainfall intensity was greater than that between slope runoff generation process and vegetation cover change. The correlation between slope sediment yield and vegetation cover change was greater than that between slope sediment yield and rain intensity change. The relationship between cumulative runoff and cumulative sediment yield on vegetation covered slope was in consistent with power function model(R²>0.98)under different rainfall intensities. The results could provide a scientific reference for soil erosion control and ecological restoration in red soil hilly area of southern China.

Abstract:In order to reveal the variation regularity of runoff and sediment yield by rill erosion in the main soil types of cinnamon soil and brown soil sloping land in Western Liaoning, and to provide a theoretical basis for the prediction of soil erosion in this area, two soils were analyzed under the conditions with slope of 10° and 15° and rainfall intensities of 40, 60 and 80 mm/h by using artificial simulated rainfall system. The results showed that the runoff of cinnamon soil increased with the increase of rainfall intensities, and the maximum value appeared in the process of rainfall with rainfall intensity of 80 mm/h at the slope of 15°. On the contrary, the sediment content decreased with the increase of rainfall intensities. When the slope was 15°, the runoff of cinnamon soil decreased with the increase of rainfall intensities. At the end of rainfall, the three rainfall intensities were all concentrated at 0.05 g/mL; the runoff and sediment contents in brown soils at 10° and 15° had no obvious law; the relationship between the total runoff and sediment of the two soils showed that the total runoff of cinnamon soils was larger than that of brown soils, while the total erosion was smaller than the latter, indicating that brown soils were more prone to rill erosion.

Abstract:To determine the relationships between soil detachment capacities and hydrodynamic parameters under Terrace Banks in hexagonal prefabricated net format with different vegetation types, we collected the undisturbed soil samples in Terrace Banks planted with Ophiopogon japonicus, Allium tuberosum and bare land (control) in situ respectively, and conducted the simulated rill flume (4 m long, 0.12 m wide, 0.1 m height) scouring experiments in laboratory. Flume scouring experiments were carried out under the combinations of 3 slopes (15°, 20°, 25°) and 5 flow rates (39.86, 59.98, 79.67, 100.45, 121.16 L/min) with 3 replicates (i.e., a total of 135 scouring experiments). The results showed that soil detachment capacities were significant differences under various vegetations (P<0.05), and ranked as Ophiopogon japonica (2.24 kg/(s·m²)) > bare land (1.34 kg/(s·m²)) > Allium tuberosum (1.09 kg/(s·m²)). The power functions could be used to describe the relationships of soil detachment capacities with shear stress (R²=0.75), stream power (R²=0.73), unit stream power (R²=0.46) and unit energy (R²=0.63). The shear stress threshold presented as τ_c Ophiopogon japonicus (8.75 Pa) > τ_c Allium tuberosum (6.47 Pa) > τ_c bare land (1.93 Pa), indicating that vegetation planted in the Terrace Banks in hexagonal prefabricated net format could enhance the soil resistance to detachment.

Abstract:Poly-gamma-glutamic acid (γ-PGA) is a new type of environmental friendly polymer material. It has good water absorption, super adsorption and biodegradability, and has great potential for water saving. In this paper, the effects of different γ-PGA application rates (0, 1%, 3%, 5%) on soil water infiltration and soil water and salt transport were studied through indoor soil column simulation experiments. The results showed that with the increase of γ-PGA application rates, both the infiltration capacity and the wetting front movement velocity of soil decreased, and the stable infiltration rate also decreased significantly. Compared with the control, the cumulative infiltrations with 1%, 3% and 5% γ-PGA applied decreased by 16.22%, 40.34% and 54.72% respectively. The advancing distances of wetting fronts decreased by 17.74%, 52.32% and 61.61% respectively. The simulation results of two kinds of infiltration model parameters showed that the absorption rate (S) in Philip formula decreased from 1.669 to 0.854 when the amount of γ-PGA was increased. The empirical coefficient (K) in the Kostiakov formula reduced from 0.855 to 0.792. The empirical index (β) increased from 0.356 to 0.480, and there was a linear negative correlation between the amount of γ-PGA application and the parameters of S and K. The slopes were -16.583 and -1.195 respectively. The application of γ-PGA changed the water and salt distribution in soil profile.With the increase of γ-PGA application, the water content of surface soil (0-10 cm soil layer) increased, while that of deep soil (below 10cm soil layer) decreased, but the change trend of the salinity in soil profile was opposite to that of soil water. This indicated that γ-PGA could reduce the infiltration of soil water and significantly increase the water holding capacity of soil. At the same time, γ-PGA could significantly improve the salt leaching in the soil surface. This study provides a theoretical basis for the use of γ-PGA in water saving and removal of soil salt as a soil amendment.

Abstract:The effects of earthworm casts on soil aggregate composition, water-erosion stability and water transport characteristics during infiltration were studied by indoor soil aggregate composition analysis and one-dimensional soil vertical infiltration test. The results showed that:(1) The earthworm casts could effectively reduce the soil bulk density and increase the number of large aggregates of 0.25~2 mm. The fractal dimension D decreased from 2.84 to 2.65 by 6.69%, improving the water-resistant stability of soil aggregates significantly. (2) When the application ratio was 1/20, the migration distance of the wet front could be significantly increased, and then the wet front distance was reduced to some extent as the application ratio increased. But both were larger than the treatment without earthworm casts. The relationship between the wet front migration distance and the infiltration time under each treatment could be described by a power function. (3) The increase of the proportion of earthworm casts could significantly increase the cumulative infiltration amount and infiltration rate. When the ratio was 1/3 at the same time, the cumulative infiltration amount increased by 48.74% compared with the non-applied. The Kostiakov-Lewis model had the highest simulation accuracy, which simulated value was closer to the measured.

Abstract:Soil is an important resource for human survival. Soil aggregate, as the basic unit of soil structure, can not only improve soil fertility, regulate the bioavailability of nutrients, nut also, but nutrients also enhance soil anti-erosion ability. In this research, four fertilization patterns were applied in a rice-wheat rotation system at Shanghai Zhuanghang long-term positioning test station for six years, which were non-fertilization (CK), conventional inorganic fertilization (CF), straw returning to field with slow release fertilizer (SRF), and mixed organic fertilizer with chemical fertilizer treatment (OCF). It provides a theoretical basis for revealing the influence mechanism of fertilization methods on the formation and evolution of soil fertility. SRF and OCF increased the SOC contents in 0-20 cm and 20-40 cm soil by 10.06%, 19.23% and 9.84%, 16.79%, respectively. OCF also increased the level of C/N in 0-20 cm (16.44%). There was no significant difference in TN contents in both 0-20 cm and 20-40 cm soil layers under CF, SRF, and OCF. But they were all higher than that of CK. Compared with CK, SRF significantly improved R_0.25 in 0-20 cm soil layer by 10.93%. OCF increased the R_0.25 in 20-40 cm, compared with the other three treatments (32.62% CK, 19.75% CF, 19.44% SRF) (p<0.05). Compared with CF, SRF and OCF increased MWD (1.54%~16.92%, 2.17%~28.26%) and GMD (5.88%~14.71%, 13.04%~39.13%), decreased D (1.11%~2.09%,4.99%~5.44%) in the 0-20 cm and 20-40 cm soil layers, with the more prominent effect for OCF (p<0.05). In conclusion, both SRF and OCF were beneficial to soil fertility improvement, and effect of OCF was more significant. The correlations between MWD and GMD and soil SOC and TN were significant, which, therefore, were suitable for revealing the relationships between aggregation and the soil nutrient contents. However, there was no significant correlation between soil nutrients and D.

Abstract:Soil macropore is the main channel for preferential transport of soil moisture, air,chemical substances and pollutants, so the studies on its formation mechanism are of great importance. In the past, the quantification of macropore was limited to the traditional methods. But nowadays, quantitative analysis of three-dimensional morphological characteristics of soil macropore and its influencing factors are the research focus. In this paper, CT scanning and image processing techniques were used to quantify the 3-D characteristic parameters of macropore, and the basic physical and chemical properties of soil and root length density were also determined. The correlations between soil physicochemical properties, soil roots and the 3-D characteristics of soil macropore were analyzed. The results showed that there was no correlation between soil density, soil sand contents and characteristic parameters of macropore; soil organic matter contents and root length density were significantly positively correlated with volume density, surface area density and number density of macropore, and significantly negatively correlated with mean tortuosity of macropore. Soil organic matter and roots had a positive impact on the 3-D characteristics of soil macropore, the more roots and organic matter contents, the more macropore contents, and the worse bending degree of macropore. In the future, the effects of root system and organic matter should not be neglected in the studies of forest tending and management, soil water movement mechanism and groundwater pollution assessment.

Abstract:In order to study the changes of soil hydrological function after the main long-period plantations were changed into short-period Eucalyptus plantations in Guangxi, the basic physical properties and water storage function of soil were studied by combining field sampling with laboratory analysis. Compared with long-period plantation before, the changes of soil water storage capacity after afforestation of Eucalyptus were mainly manifested by the increases of reservoir capacity and residual water storage space in 20-40 cm soil layer. With the increase of soil depth, and soil bulk density increased gradually, the saturated water holding capacity and total porosity decreased gradually, meanwhile, soil reservoir capacity and residual storage space also showed a decreasing trend. The influence of Eucalyptus afforestation on soil physical properties occurred mainly in 20-40 cm soil. The soil reservoir capacity and residual water storage space increased compared with the long rotation period plantation. The soil reservoir capacity of one-year-old, three-year-old and five-year-old Eucalyptus plantations was 11.25%, 19.14% and 14.33% higher than that of the corresponding long-term plantations, while the residual storage space was 9.16%, 113.01% and 23.62% higher than that of the corresponding long-term plantations respectively. And the soil water storage capacity under 40 cm soil layer deceased. The results could provide a theoretical basis for evaluating the soil effect of Eucalyptus plantation.

Abstract:Relying on the Tianshan Forest Ecosystem Positioning Station, fixed observation areas were set in the typical regional forest and grassland, and the snow cover characteristics (snow density, liquid water content and snow temperature), runoff yield, erosion amount and conventional meteorological indicators of the forest and grassland were monitored during the snow melting period, and the snow melting process of forest and grassland was compared and analyzed. The results showed that the interception of snowfall by canopy of forest was about 56.8% during snow melting period, the average snow cover depth of grassland was 2.5 times that of forest. The decline rate of snow depth in the forest was higher than that in grassland at the late stage of snowmelt runoff, which due to the snow intercepted by the canopy fell under gravity. The producing time of snowmelt runoff was earlier in forest than that in grassland, and the variation of snow cover density and liquid water content in forest and grassland was similar during the runoff period, and the peak value was in the middle layer of snow, however, the average snow density and average liquid water content of the snow in the forest were 0.48 g/cm³ and 0.61%, which were both greater than those in the grassland (0.29 g/cm³and 0.52%). The peak value of the snow temperature in the forest was on the surface of the snow, while that in the grassland was on the bottom of the snow, the average snow temperature of the forest was -0.032℃, which was lower than the grassland by 0.046℃. And the liquid water content of the snow was significantly positively correlated with the temperature of the snow layer (r=0.611, p<0.05). The runoff yield and surface erosion of grassland runoff plot were twice and six times as much as those of forest. The percentage of surface erosion of forest and grassland to total runoff was 0.21% and 0.71%, respectively. The scouring effect of snowmelt runoff to the surface in forest is smaller than that in the grassland during the process of snowmelt runoff production, which reflected the soil consolidation of the forest. The research results provided theoretical basis and data basis for small-scale study of snow melting process.

Abstract:In order to study the variation characteristics of soil moisture under different land use types in the moderate slope sandy area of loess hilly region, time domain reflectometry (TDR) was used in three land use types, which were maize farmland, Caragana korshinskii forest land and alfalfa grassland, in Wuzhai County, Shanxi Province. The soil moisture of 0-100 cm soil layer was observed for three years, and the seasonal variation and vertical distribution of soil water content of different land use types were grasped. The results showed that the seasonal variation curves of soil moisture in the three kinds of lands all showed M type distribution. The seasonal variations of the three kinds of lands were similar, but the difference of soil water content reached an extremely significant level (P<0.01), which showed as follow alfalfa grassland > C. korshinskii forest > maize farmland. The soil water content of maize farmland and C. korshinskii forest showed S distribution with the increasing of soil depth, while the variation trend of alfalfa grassland was completely opposite to the other two lands. There was a significant correlation between the soil water content of 0-20 cm soil layer and precipitation in maize farmland, and there was a significant correlation between the soil water content of 0-60 cm soil layer and precipitation in C. korshinskii forest and alfalfa grassland. The soil water content had obvious vertical distribution characteristics. In 0-100 cm soil layer, with the increasing of soil depth, the CV of maize farmland decreased gradually and then remained stable, however, the CV of C. korshinskii forest decreased continuously, the CV of alfalfa grassland fluctuated at first and then decreased obviously. The coefficient of variation of surface soil water content was higher than that of deep layer. In the range of 0-100 cm, the soil layer of maize farmland could be divided into rapid change layer and active layer from top to bottom, and the soil layers of C. korshinskii forest and alfalfa grassland could be divided into three layers, which were rapid change layer, active layer and sub-active layer. The results of this study showed that forest land and grassland were better than farmland in conserving soil moisture, and forest and grassland were suitable land use patterns in the moderate slope sandy area of loess hilly region. It provided a theoretical basis for the management of soil moisture and the rational development and utilization of soil and water resources in this area.

Abstract:In order to explore the characteristics of soil water conservation function of different vegetation types in the Xarxili Nature Reserve, a total of 13 representative grassland, shrub and forest plots were selected in the reserve area, and soils of different vegetation types were used as experimental materials. Soil water conservation capacity of grassland, shrub and forest was quantitatively analyzed by a combination of field investigation and laboratory tests. The results showed that:(1) With the increasing of soil depth, the soil bulk density of the grassland increased gradually, and the minimum value was 0.69 g/cm³ at 0-10 cm soil layer. The changes of soil water holding capacity and water storage capacity of grassland were consistent, which followed the order of 0-10 cm > 10-20 cm > 20-30 cm. (2) With the increasing of soil depth, the variation of soil bulk density of shrub was quite different, ranging from 0.98 to 1.63 g/cm³, and the minimum value appeared at 0-10 cm soil layer. The water conservation capacity index contents were significantly different in different soil depths (P<0.05), and the water holding capacity of shrub was generally listed in the order of 0-10 cm > 10-20 cm > 20-30 cm>30-40 cm > 40-50 cm, and the water capacity increased first and then decreased with the increasing of soil depth. (3) There was a significant difference between the hydrophysical properties of forest soil and soil water conservation index (P<0.05). With the increasing of soil depth, the soil bulk density increased gradually, and the minimum value was 0.45 g/cm³ at 0-10 cm soil layer. The water holding capacity of forest soil was mainly 0-10, 20-30 and 40-50 cm, accounting for 71.6% of the total water holding capacity, the water storage capacity was relatively small in the water conservation function.

Abstract:To make clear the influence of species composition and community structure on redistribution of rainfall and nutrient, three typical riparian forest, Larix kaempferi forest, Quercus mongolica forest, Acer ukurunduense forest were selected as objects of study in the mountain regions of eastern Liaoning Province from May to October 2014. The rainfall process and nutrients characteristics in atmospheric rainfall, throughfall and stemflow were analyzed. The results showed that during the research period, the total precipitation was 278.6 mm, and the throughfalls of Larix kaempferi forest, Quercus mongolica forest, Acer ukurunduense forest were 81.9%, 77.9% and 73.1% of total rainfall, respectively, and stemflow were 1.2%, 4.4% and 4.3%, respectively. The concentrations of NH₄⁺-N, Cl^-, NO₃^--N and total phosphorus (TP) in throughfall and stemflow were higher than those of atmospheric rainfall, and the concentrations and inputs of NH₄⁺-N, Cl^-, NO₃^--N and TP in different forest types were different significantly. The riparian forest with different species composition and community structure influenced rainfall distribution through the morphological and structure characteristics of community, and changed water physical and chemical properties through the physical, chemical and physiological characteristics of forest canopy gaps, resulting in the changes of the concentrations and inputs of NH₄⁺-N, Cl^-, NO₃^--N and TP variously combined with rainfall amount and intensity.

Abstract:The aim of the current study was to examine the dynamic changes of soil physicochemical properties and microbial quantities, and to provide theoretical basis for the improvement and restoration of the degraded grassland in Gannan alpine meadow. The soil samples were collected from light degradation (LD), moderate degradation (MD), extreme degradation (ED) and control grassland (CK) in May, July and October, 2017, to investigate the physiochemical characteristics and the microbial quantities. The results showed that the soil water content of CK was significantly lower than that of the degraded grassland in May and July, while significantly higher than that of the degraded grassland in October. With the aggravation of degradation degree, soil pH value gradually increased, while the content of organic carbon, total nitrogen and total phosphorus gradually decreased. The number of soil bacteria was more sensitive to grassland degradation, followed by actinomycetes and fungi. The soil microbial quantities of CK and LD decreased more obviously with the increasing of soil layer depth. Redundancy analysis and the Monte Carlo permutation test showed that the environmental factors affecting soil microbial quantities were different in each month. Soil microbial quantities were significantly affected by total phosphorus and soil water content in May, while other factors except soil pH had significant effects in July. Except soil pH value and C/N, vegetation coverage, aboveground and underground biomass and other environmental factors had significant effects in October. All of the above results revealed that the responses of soil physicochemical characteristics and soil microbial quantities to grassland degradation had have seasonal variation in Gannan alpine meadow, the influencing factors and weights in different periods also needed to be paid attention to in grassland management.

Abstract:In order to study the water conservation capacity of the litter in coastal shelterbelt forest on coastal sandy land, the litter accumulation amount, water-holding rate, water-holding capacity and water-absorption rate of different decomposition stages were investigated in four typical plantations with same age (Casuarina equisetifolia forest, Pinus elliottii forest, Eucalyptus urophylla×Eucalyptus grandis forest and Acacia culacocarpa forest) of coastal sandy area by the methods of field survey and laboratory soaking extraction. The results showed that the litter accumulation amount of the four plantations decreased in the order of C. equisetifolia forest (19.12 t/hm²) > P. elliottii forest (17.51 t/hm²) > E. urophylla×E. grandis forest (10.90 t/hm²) > A. culacocarpa forest (10.13 t/hm²), and the percentage of litter accumulation amount in semi-decomposed layer was higher than that in un-decomposed litter. The maximum water-holding rate of the four plantations was 140.55%~206.47%, which followed the order of E. urophylla×E. grandis forest > A. culacocarpa forest > C. equisetifolia forest > P. elliottii forest. The maximum water-holding capacity was 20.75~30.85 t/hm², which was sorted as C. equisetifolia forest > P. elliottii forest > E. urophylla×E. grandis forest > A. culacocarpa forest. The maximum water-holding rate and maximum water-holding capacity of litter in the four plantations were both greater in semi-decomposed litter layer than those in un-decomposed litter layer, and the water-holding rate and water-holding capacity of litter also changed logarithmically with immersing time at different decomposition stages. The average water-absorption rate at different decomposition stages varied greatly in the first 0.25 hours among the four plantations, in the un-decomposed layer, the water-absorption rate of E. urophylla×E. grandis forest was the maximum (2.05 mm/h), and in the semi-decomposed litter layer, the maximum value (4.32 mm/h) was found in P. elliottii forest. The litter water-absorption rate presented a power function with immersing time at the different decomposition stages. The effective interception depth of litter was in the order of C. equisetifolia forest (2.45 mm) > P. elliottii forest (2.04 mm) > E. urophylla×E. grandis forest (1.87 mm) > A. culacocarpa forest (1.72 mm). On the whole, the litter of C. equisetifolia forest had the strongest water-holding capacity, followed by P. elliottii forest, E. urophylla×E. grandis forest and A. culacocarpa forest, indicating that C. equisetifolia forest and P. elliottii forest were more conducive to water conservation in coastal sandy area.

Abstract:Pot experiment and indoor thermostatic incubation experiment was conducted to study the effects of single and combined application of biochar and traditional organic materials (wheat straw and chicken manure) on organic carbon storage, activity and carbon pool management index of loamy fluvo-aquic soil and sandy soil in Henan Province, meanwhile, the effect of wheat straw returning and carbon-making returning on soil organic carbon mineralization and the regulation of biochar on soil original organic carbon mineralization were compared furtherly. The results showed that under the same application amount, the biochar and organic materials could increase soil organic carbon (TOC), and the highest TOC content was found in the soil treated by biochar, the content of TOC were increased by 63.15% and 115.62% in loamy fluvo-aquic and sandy soil, respectively. Moreover, biochar significantly increased soil stable organic carbon content and carbon pool index (CPI), while decreased soil carbon activity index (AI) and the effectiveness of carbon (SC), but had no significant effect on the content of potassium permanganate oxidizable carbon (POXC) and carbon pool management index (CPMI), and adding straw significantly increased POXC content, basic respiration and CPMI of two kinds of soils. Through indoor soil incubation experiment, the SOC mineralization rate and cumulative mineralization amount of the two types of soils were increased by straw at the early stage of cultivation (0~37 days), but there was little impact on SOC mineralization if the straw was made into biochar and added to the soil. The priming effects of biochar on soil native SOC mineralization were restricted by its application amount, exogenous active organic carbon input and soil type. In the soil without straw returning, high biochar (2%) showed stronger negative priming effect on soil organic carbon mineralization, while low biochar (0.55%) showed more apparent negative priming effect soil organic carbon mineralization in the straw returning field. Therefore, from the perspective of carbon sequestration and emission reduction, compared with the direct returning straw to field, returning the straw prepared into biochar was a more reasonable way of utilization, and the application amount of biochar should be considered according to soil fertilization management measures and soil types. Application biochar with a mass ratio of 2% could significantly inhibit the mineralization of soil native organic carbon and reduce CO₂ emissions, but it should not be applied during the rapid decomposition period of straw.

Abstract:Based on a long-term experiment, the effects of different fertilization on labile organic matter (LOM) and carbon management index (CMI) in different soil layers were explored. Four typical fertilization treatments were selected as:(1) No fertilizer (CK); (2) mineral nitrogen, phosphorus, and potassium (NPK); (3) NPK plus manure (NPKM); (4) NPK plus straw (NPKS). The highly, moderately and lowly LOM and CMI were measured and analyzed. The results showed that the soil organic matter (SOM) content and its difference among treatments were decreased with increment of soil depth. Compared with CK, the SOM content under the treatments with fertilizer was significantly higher, and the highest one was under NPKM with 13.91~33.55 g/kg. The Non-LOM and lowly LOM accounted for the major part of the total SOM, and the proportion increased with depth. CK showed the highest proportion with 35.6%~56.6% and 17.7%~50.7%, respectively. The CMI increased under the fertilization treatments, and varied among soil layers. At 0-40 cm, the CMI of highly and moderately LOM under NPKS was obviously higher than that under the other treatments as 149.54, 147.01, 237.65, respectively. The CMI under NPKM was the highest at 40-60 cm as 237.65, 537.67, respectively. In sum, the SOM and LOM content and their difference among treatments decreased with increment of soil depth. The fertilization improved SOM and LOM content, and the optimum one was NPKM. The CMI of highly and moderately LOM was higher under NPKS at upper layer (0 - 40 cm), and which was higher under NPKM at below layer (40 - 60 cm). Generally, the soil fertility was improved under NPKM, and followed by NPKS.

Abstract:The effects of biochar application on the microbial community, enzyme activity and soil nutrient availability in dryland soils of central Guizhou were studied through pot experiment. The results showed that after applying 5%~15% (biochar/soil mass ratio) biochar to different types of dryland soils, the number of fungi, actinomycetes, bacteria and nitrifying bacteria, ammoniated bacteria and the activity of phosphatase, catalase and urease in yellow soil and yellow sand soil increased obviously, especially in yellow sand soil. The number of actinomycetes, fungi and nitrifying bacteria in the lime soil, as well as the activity of phosphatase and catalase increased significantly, but the number of ammoniated bacteria and urease activity decreased significantly. In addition, the content of available N, P, K, Ca, Mg and B in yellow soil and yellow sand soil increased in different degrees, but the content of available Fe, Mn, Cu and Zn decreased in different degrees. The content of available P, K, Fe, Mn, Cu and B in the lime soil increased in different degrees, but the available N, Ca, Mg and Zn in the lime soil decreased in different degrees. The content of available Zn in these three dryland soils all decreased obviously after applying biochar. The application of 5%~15% biochar in yellow soil, yellow sand soil and lime soil could obviously increase the yield of cabbage and lettuce, of which the yellow sand soil applied with biochar was the best in increasing yield, followed by lime soil. There were significant differences in the changes of soil available nutrients among different types of dryland soils after applying biochar. When applying biochar, a certain proportion of nitrogen, phosphorus, potassium and appropriate amount of trace element fertilizers should be used according to soil characteristics, which could promote the growth of crops.

Abstract:In order to study the carbon variation in cotton field under drip irrigation, the soil respiration rate and net photosynthetic rate were observed continuously during the cotton growth period using Li-8100A soil carbon flux automatic analyzer and LCpro+ photosynthetic apparatus. The results showed that the diurnal variation of soil respiration rates showed a unimodal curve with the peak at 16:00, while the diurnal variation of net photosynthetic rates in cotton field showed an alternating pattern of unimodal and bimodal curves. Both months showed a trend of increasing first and then decreasing, and the soil respiration rates and net photosynthetic rates reached the maximum in July. There were differences in soil respiration rates and net photosynthetic rates between different regions. The soil respiration rates were as follows inter-ridges > ridges > bare land, and the net photosynthetic rates was inter-ridges > ridges. The small area of cotton field showed carbon sinks throughout the growth period. From June to September, the total net carbon fixation in cotton fields was 2 203.7 C g/m², and the carbon sequestration by photosynthesis was 2.67 times that of soil respiration.

Abstract:The contents of soil organic carbon and its components in six different forest types (including broad-leaved forest, coniferous forest, spruce-fir forest, betula ermanii forest, betula ermanii-tundra transition and tundra) on the northern slope of Changbai Mountain were studied by means of field sampling and laboratory analysis. The distribution of soil organic carbon, iron-aluminum oxides and clay mineral groups were analyzed. The results showed that in different forest types, the contents of organic carbon, humin carbon, particulate organic carbon, 2~0.25 mm macroaggregate carbon and 0.25~0.053 mm microaggregate carbon in broadleaf forest soils were the highest. The content of easily oxidized carbon in soil of spruce-fir forest was the highest while that of water-soluble organic carbon, humic acid carbon, fulvic acid carbon and particulate organic carbon were the lowest. In addition, the contents of humic acid carbon and fulvic acid carbon in the soil of betula ermanii forest were significantly higher than those of other forest types. The content of water-soluble organic carbon in the soil of betula ermanii-tundra transition were significantly higher than those of other forest types, while the contents of organic carbon and easily oxidized carbon in the soil of tundra were significantly lower than those of other forest types. Correlation analysis showed that soil organic carbon contents were positively correlated with amorphous alumina contents (P<0.05), fulvic acid carbon contents were positively correlated with free alumina contents (P<0.05), and organic carbon contents of 0.25~0.053 mm microaggregate were positively correlated with the contents of two kinds of alumina (P<0.05). These results indicated that the significant differences in organic carbon and its components were observed under different forest types.

Abstract:In order to explore the changes of soil nitrogen, phosphorus and potassium contents and nutrient balance after applying biogas slurry in alluvial paddy soil in Chengdu Plain, and realize the green development of biogas slurry resource utilization. Field experiments were conducted. Ten gradients of biogas slurry application rate were set up, and clear water and conventional fertilizers were taken as control. The effects of different amounts of biogas slurry on soil nitrogen, phosphorus, potassium and other nutrients contents were studied, and the balance of nutrients in the field was comprehensively analyzed. The results showed that the contents of total nitrogen, alkali-hydrolyzed nitrogen, total potassium and available potassium were higher when the biogas slurry application rate was 108.0~126.0 t/hm², which were 1.35~1.42 g/kg, 63.31~65.34 mg/kg, 12.90~13.26 g/kg and 45.45~59.25 mg/kg. With the increasing of biogas slurry application, the total phosphorus content of soil (0.92~1.10 g/kg) did not change significantly, while the available phosphorus content (8.49~18.85 mg/kg) decreased by 11.0%~59.9% compared with the clear water control. The balance of nitrogen, phosphorus and potassium in the biogas slurry treatment groups were -25.61~66.68, -7.99~-15.34 and -81.33~-145.82 kg/hm². When the amount of biogas slurry was more than 108.0 t/hm², the nitrogen balance was basically maintained. With increasing of biogas slurry application, phosphorus deficit was alleviated, while the potassium deficit was aggravated. Applying appropriate amount of biogas slurry could increase the contents of nitrogen and potassium in soil, but it was difficult to meet the balance of phosphorus and potassium in soil by applying biogas slurry alone. Therefore, the application rate of biogas slurry should be controlled in the range of 108.0~144.0 t/hm² in the actual production, and combined with 10~15 kg/hm² phosphate fertilizer and 115~120 kg/hm² potassium fertilizer to achieve the desired effect.

Abstract:To characterize the changes in vertical distributions of soil moisture and nitrate following conversion to apple orchard from cropland in the Loess Plateau, 40 600 cm depth soil profiles were sampled from farmland (as control), 8, 17 and 25 yr old apple orchards in Luochuan county to determine soil moisture content, nitrate concentration and their storage. The results showed that 8 yr old apple orchards were similar to cropland in soil nitrate concentrations (SNC) and residual soil nitrate (RSN), and also presented equal (Jiuxian) or even higher (Huanbai) values of soil moisture content (SWC) and soil water storage (SWS) when compared with cropland. In contrast, the 17 and 25 yr old apple orchards significantly decreased SWS by 150 and 230 mm, respectively, which was mainly associated with the SWC changes in soils deeper than 300 cm. SNCs in the 0-500 cm layers increased significantly with the standing ages of apple orchard, and RSNs accumulated in the 0-600 cm profile were 6 830 and 8 370 kg/hm², corresponding to 17 and 25 yr old apple orchards, respectively, which were appreciably higher than that of 8 yr old apple orchard (440 kg/hm²) and cropland (695 kg/hm²). Thus, we concluded that converting cropland to apple orchard could result in soil water deficit, especially in > 300 cm soil depth, and nitrate accumulation, so, the strategies including water-conserving and strict controls on N fertilizer should be adopted to mitigate the unfavorable impacts caused by the enlargement of apple orchard in the Loess Plateau.

Abstract:In order to clarify the effect of acid rain on soil carbon (TC), nitrogen (TN), phosphorus (TP) content, and ecological stoichiometry characteristics, taking the paddy field in Fuzhou Plain as the research object, setting the control (CK), simulated acid rain(pH 2.5, 3.5, 4.5) treatment in the early rice and late rice growth period, the TC, TN and TP contents in paddy soil of Fuzhou Plain were measured and analyzed under the influence of acid rain. The results showed that the TC, TN, and TP contents in the soil under the acid rain treatments were higher than those in the CK (P<0.05). The average TC content in the soil at the maturity stage was lower than that at the greening stage and the jointing stage (P<0.01). The average TN content of each treatment in soil at the jointing stage of rice was less than that at the regreening stage and maturity stage (P<0.01). The average soil TP content at maturity stage was less than that at regreening stage and jointing stage (P<0.01). During the whole growth period, the C/N, C/P, and N/P ratios in the soil under acid rain treatment ranged from 7.87~10.86, 8.38~9.91 and 0.82~1.26, respectively. The C/N, C/P, and N/P ratios were smaller than that of the CK (P<0.05). Compared with early rice, the N/P ratio of late paddy decreased significantly, and the C/N, C/P, and N/P ratios were higher at the regreening stage than in the CK (P<0.05). The C/N ratio at jointing stage was higher than that at regreening and maturity stages (P<0.01). The difference of C/P ratio was not significant during the growth periods of early and late rice. The N/P ratio of each treatment at jointing stage of early and late rice was lower than that at regreening and maturity stages (P<0.01). In general, acid rain treatment increased soil carbon, nitrogen, and phosphorus contents in paddy soils, and the ecological stoichiometry characteristics in paddy soils was also significantly affected by acid rain, moreover, appeared obviously growth period variation.

Abstract:A field positioning experiment was conducted in spring maize continuous cropping area of Shanxi Province for four consecutive years, which included six fertilization treatments:No application of nitrogen fertilizer (CK), one-time basal application of urea (CU1), topdressing of urea (CU2), resin coated urea (PCU), sulfur coated urea (SCU) and multi-enzyme gold sustained-release urea (MEU). It was set up to study the effects of slow controlled release nitrogen fertilizers on spring maize yield, consumption of nitrogen fertilizer and nitrogen balance to provide reference for scientific management technology of spring maize nitrogen nutrition. The results showed that:(1) Slow controlled release nitrogen fertilizer treatment could significantly increase spring maize yield and promote nitrogen uptake. Compared with CU1, SCU, MEU, PCU and CU2 increased the yield of spring maize by 17.51%, 9.88%, 9.62% and 9.48%, respectively, while the agricultural utilization efficiency of nitrogen fertilizer was increased by 7.5, 4.2, 4.1 and 4.1 kg/kg, respectively. (2) There were significant differences in the uptake of fertilizer nitrogen by crops and the residual amount of fertilizer nitrogen in 0-100 cm soil layer with different fertilizers. Apparent use efficiency of nitrogen of SCU, MEU, PCU, CU2 and CU1 were 36.1%, 32.5%, 26.5%, 26.7% and 19.5%, respectively. Residual fertilizer nitrogen in 0-100 cm soil layer accounted for 28.5%, 31.6%, 35.7%, 35.5% and 39.1% of the nitrogen application, respectively. Additionally, compared with one-off urea application, slow controlled release nitrogen fertilizer could significantly reduce the loss of fertilizer nitrogen, by 22.65%, 18.81%, 8.99% and 8.47% for SCU, MEU, PCU and CU2 respectively. (3) Comprehensive analysis of nitrogen balance in different treatments showed that the SCU had the highest nitrogen uptake, 261.5 kg/hm², followed by MEU, 253.5 kg/hm². The residues amount in 0-100 cm soil layer in SCU was the lowest among the slow controlled release nitrogen fertilizer treatments, 124.1 kg/hm², and 131.04 kg/hm² for MEU and 140.09 kg/hm² for PCU. The apparent loss of nitrogen in SCU was the lowest, 106.3 kg/hm², and 111.6 kg/hm² for MEU and 125.1 kg/hm² for PCU. In the soil of main spring maize producing areas in Shanxi Province, slow controlled release nitrogen fertilizer could significantly promote the absorption of nitrogen and reduce nitrogen loss. Sulfur coated urea and multi-enzyme gold sustained-release urea have relatively good effects.

Abstract:In order to find out the change characteristics of soil total nitrogen (TN), organic carbon (SOC) and its components (dissolved organic carbon (DOC), microbial biomass carbon (MBC), light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC)) after four years of carbon and nitrogen addition, local field experiment of nitrogen application with different carbon sources was conducted at the Rainfed Agricultural Experimental Station of Gansu Agricultural University in Lijiabao Town, Anding District, Dingxi City, central Gansu Province. Three factors including straw, biochar and nitrogen were set up in the experiment. The straw was set at two levels, including no straw and straw application, and the experiment involved two biochar levels, which were no biochar and biochar application, and the nitrogen application was at three levels of no application, 50 kg/hm² and 100 kg/hm², totally nine treatments. The results showed that the contents of TN, organic carbon and their components decreased with the deepening of soil layer under different treatments. Application of biochar increased the concentrations of SOC, TN, DOC, MBC, LFOC and HFOC. Application of straw significantly increased the contents of SOC, TN, DOC, MBC and LFOC, but only significantly increased HFOC content in 0-5 cm soil layer. Application of nitrogen significantly increased the concentrations of SOC, TN, DOC, MBC and LFOC. Among the treatments, application of biochar showed the best improve effect on the concentrations of SOC, TN and HFOC, and adding straw represented the best enhancement effects on the concentrations of DOC, MBC and LFOC. From the perspective of improving soil quality, straw combined with nitrogen was the recommended application mode, which had a higher soil carbon availability that facilitated the carbon utilization of the microorganisms, and benefited the growth of crops. Considering the improvement of soil carbon sequestration, biochar combined with nitrogen was the recommended application mode, which was beneficial to the carbon sequestration.

Abstract:A field experiment was conducted to study the contents of organic carbon, total nitrogen, dissolved organic carbon, dissolved total nitrogen and readily oxidized organic carbon in spring maize field under three different environmental conditions:Natural atmospheric CO₂ concentration (as the control, marked as CK), open-top chamber (OTC) system with CO₂ concentration of 700 μmol/mol (marked as OTC+CO₂) and OTC system with current atmospheric CO₂ concentration (marked as OTC). The results showed that compared with OTC, the elevated CO₂ had no significant effect on the contents of soil organic carbon, total nitrogen, dissolved organic carbon and readily oxidized organic carbon (P > 0.05), but decreased the dissolved total nitrogen by 18.17% (P<0.05) at V12 stage, and increased the dissolved total nitrogen by 108.56% (P<0.05) at R3 stage. Compared with CK, OTC+CO₂ treatment decreased the soil organic carbon (expect R6) and total nitrogen (expect V12) during the whole period of maize, by 4.47%~14.42% and 6.78%~12.48% (P<0.05), respectively. The OTC+CO₂ decreased the dissolved organic carbon at V6 stage, dissolved total nitrogen at V12 stage and readily oxidized organic carbon at R1 and R6 stages; but increased dissolved organic carbon at R3 stage (P<0.05). In conclusion, the elevated CO₂ had no significant effect on organic carbon and its fractions, total nitrogen, but significantly affected dissolved total nitrogen. The impact of OTC on the results could not be ignored when using the OTC system to do the research about elevated CO₂ concentrations.

Abstract:Through indoor pot experiment, two introduced species, i.e. Lupinus micranthus and Purus frumentum were cultured in Pisha sandstone-amended aeolian sandy soil, aeolian sandy soil, Pisha sandstone, loessial soil, Pisha sandstone covered by aeolian sandy soil and Pisha sandstone covered by loessial soil. The objective of this study was to investigate the differences in growth, nitrogen and phosphorus nutrition of two introduced species planted in Pisha sandstone-amended aeolian sandy soil and primary soil types in the contiguous areas of Shanxi, Shaanxi and Inner Mongolia, and provide references for the vegetation restoration of this area. The results showed that:(1) Pisha sandstone-amended aeolian sandy soil was better for the growth of plant root system, the total biomass was large, the above-ground biomass of L. micranthus in the Pisha sandstone-amended aeolian sandy soil was 242% higher than that in loessial soil, and the underground biomass was 186% higher than that in the aeolian sandy soil, the root length and volume were 388% and 290% higher than those in the aeolian sandy soil, respectively; (2) The root system of the two introduced plants showed different adaptive characteristics in different soil treatments, specific root length of L. micranthus was the largest in the Pisha sandstone-amended aeolian sandy soil and the least in the aeolian sandy soil, while that of P. frumentum was the largest in the loessial soil and the least in the Pisha sandstone-amended aeolian sandy soil. The volume fraction of roots less than or equal to 0.45 mm diameter was only 9.99% for L. micranthus and 13.94% for P. frumentum in the Pisha sandstone-amended aeolian sandy soil, which were smaller than those in other soils; (3) The nitrogen and phosphorus concentrations of plants in all treatments were lower than those under normal growth conditions, indicating that plant growth was restricted by nitrogen and phosphorus. The nitrogen-phosphorus ratios in all plants were less than 14, suggesting that plant growth was more severely limited by nitrogen than by phosphorus. Compared with several original soil types, the Pisha sandstone-amended aeolian sandy soil had better physiochemical properties and a higher productivity, and more suitable for plant growth, it could be applied to vegetation restoration in the contiguous areas of Shanxi, Shaanxi and Inner Mongolia in northwestern China. However, appropriate application of nitrogen and phosphate fertilizers should be considered to accelerate the process of vegetation restoration.

Abstract:This field experiment was conducted with different varieties of potato ("Atlantic" "Purple Potato" "Ji Zhang Potato 12") in Zhangbei area to explore the effects of microbial inoculants with P and K-solubilizing bacteria (MI containing the effective strains of Bacillus megaterium and Bacillus mucilaginous) on potato yield, quality, soil available P, K and soil phosphatase. The results showed that the application of microbial inoculant increased the yields of three varieties of Potato (P<0.05), especially for "Ji Zhang Potato 12"by 24.54%, while the average increase of yield was only 6.96% for the other two. Moreover, the quality of potatoes was improved, especially for Purple Potato. The contents of Vc, soluble protein and soluble sugar were significantly increased by 320.21%, 29.40% and 7.12%, respectively (P<0.05). In addition, the application of microbial inoculant regulated the contents of available phosphorus and potassium in the soil and the related soil enzymes activities during the whole growth period. The available P and K contents of the soil cultivated with the cultivars of "Atlantic"and "Ji Zhang Potato 12"were higher than those of CK, and reached a significant level at the middle and late growing stages. At the same time, the activities of soil acid and alkaline phosphatase were increased, with an average increase of 37.52% and 32.30% respectively. Overall, P and K-solubilizing microbial inoculant is suitable for the growth of potato in Zhangbei area, especially for "Ji Zhang Potato 12".

Abstract:In order to determine the effects of herbaceous plants on the release process of soil nitrogen and phosphorus, a simulation experiment of reservoir water level fluctuation was conducted under Cynodon dactylon and Alternanthera philoxeroides. The results showed that:(1) After the end of flooding (32 days), the soil total nitrogen (TN) and total phosphorus (TP) decreased by 11.75% and 25.28%, respectively in Alternanthera philoxeroides, and by 3.62% and 25.77%, respectively in Cynodon dactylon. (2) The dry-wet alternative environment mainly affected the changes of ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N) and available phosphorus in the soil, and had little effect on TN and TP contents in the soil. (3) The death of Cynodon dactylon increased the amount of soil TN, NH₄⁺-N and TP, indicating that the inundated vegetation filter belt could purify N, P and other pollutants in the runoff. However that part of nutrients absorbed by the plants would in turn release to water system by the decomposition of plant biomass. The decomposition of the plant biomass once again entered into the water system or the soil, and thus the purpose of effectively preventing and controlling agricultural non-point source pollution could not be achieved. This study provides a theoretical basis for the using of vegetation buffer zone to prevent and control the eutrophication of water system in the Danjiangkou Reservoir.

Abstract:Aiming at the problem of soil salinization in salinized irrigation area, the Urad irrigation area in the lower reaches of Hetao Irrigation District was taken as the research area, the spatial and temporal distribution and variation of water content and salinity (EC value) in surface soil (0-20 and 20-40 cm) and deep soil (40-100 cm) as well as the influence of groundwater depth on soil salinity were analyzed by the method of field measurement combined with laboratory experiment and statistical method of geostatistics. The results showed that:(1) Except for 0-20 cm in June (9.779%), the variation coefficient of surface soil water content was 12.384%~19.667%, which was moderate variability, and the variation coefficient of deep soil water content was small (3.513%~9.757%), which was weak variability. The variation coefficient of EC in surface soil was between 100.845% and 129.279%, which was a strong variability, while that in deep soil was between 83.685% and 98.853%, which was moderate variability. With the increasing of soil depth, the variability of water content and salinity decreased. (2) The soil water content and salinity in different periods had spatial structure characteristics within a certain range, which could be simulated by Gaussian model. The spatial correlation of soil water content in each layer was 0.038%~20.408%, and the spatial correlation of soil salinity in each layer was 0.043%~8.374%, both were less than 25%, indicating a strong spatial correlation, and this could be considered to be mainly caused by structural factors, and the spatial variability caused by autocorrelation was strong. (3) The soil salinity in the research area was mainly concentrated in the north salt wasteland. Due to strong evaporation, the capillary water in the aerated zone raised, and the soluble salts in the deep soil and groundwater were brought to the surface layer of the soil, resulting in the increasing of salinity, which was the typical salt-accumulation type. The immediate control and treatment were needed. At the same time, the soil salinity was greatly affected by the groundwater depth, the soil salinity increased with the decreasing of the groundwater depth. The relationship between the groundwater depth of the wasteland and the soil salinity satisfy was linear, and the relationship between he groundwater depth and soil salinity of the cultivated land was exponential. The soil salinity content in the 0-20 cm soil of the wasteland varied greatly with the depth of groundwater. The change trend of soil salinity with the depth of groundwater was smaller in 20-40 cm and 40-100 cm layers. When the groundwater depth of the cultivated land was 1~1.6 m, the soil salinity content changed greatly with the depth of groundwater. When the groundwater depth was more than 1.6 m, the soil salinity content changed little with the groundwater depth. This study provided an important theoretical basis and reference for the prevention and improvement of salinized soil in the lower reaches of Hetao Irrigation District.

Abstract:A pot experiment was conducted to clarify the mitigation effect of liquid organic fertilizer on continuous cropping obstacle caused by phenolic acid in soil. Ferulic acid and vanillic acid were mixed equally and applied to potato substrate soil at different concentrations (0, 50, 100 and 150 mg/kg) to simulate the autotoxin substances secreted by potato continuous cropping, and different concentration gradients liquid organic fertilizer (0, 225, 450 and 675 kg/hm²) were applied to clarify the effects of liquid organic fertilizer on potato growth and soil enzyme activity under phenolic acid stress. The results showed that single exogenous phenolic acids reduced the potato plant height, stem diameter, leaf area and dry weight in different degree. With the increasing of phenolic acid concentration, the activity of urease, acid phosphatase and invertase in soil decreased by 2.74%~10.95%, 11.11%~20.55% and 5.29%~12.96% compared with the control, respectively, the activity of catalase and polyphenol oxidase increased, while FDA hydrolase activity showed low promotion and high inhibition. Applying liquid organic fertilizer improved the potato plant height, stem diameter, leaf area and dry weight. Soil enzymes activities all increased, the activity of urease, acid phosphatase, invertase, catalase, polyphenol oxidase and FDA hydrolase increased by 10.80%, 21.40%, 18.20%, 29.60%, 37.69% and 12.31% at most, respectively, compared with the control. But excessive concentration of liquid organic fertilizer decreased its enhancement of activity of phosphatase, urease and catalase, and inhibited the activity of FDA hydrolase. Therefore, reasonable application of liquid organic fertilizer could promote the growth and development of potato, improve soil enzyme activity and enhance the stress resistance of potato, thereby alleviating the phenolic acid stress on potato.

Abstract:In order to improve crop yield under drip irrigation with brackish water and to clarify the effects of different leaching time on desalination and increasing yield, a salt leaching was conducted at the jointing stage (T1), tasseling stage (T2) and filling stage (T3) respectively in the Jingbu saving water experiment station of the Hetao irrigation area, Inner Mongolia. With no leaching in the growth period as control (CK), a total of 4 treatments were carried out to study the effects of leaching at different growth stages on soil water and salt and crop yield under mulched drip irrigation with brackish water. The results showed that the soil water contents increased by 18.9% from 0-60 cm after leaching at different growth stages, and the soil water contents of 0-40 cm under T1, T2 and T3 were significantly higher than that of CK, which durations were 12, 25, 28 days respectively. After the salt leaching, the soil water storages and water consumptions increased by 20.92% and 21.52%, respectively. The average salt contents below mulch decreased by 78.0% after leaching, and the salt content decreased by 0.20, 0.36, 0.44 mS/cm after leaching at jointing and tasseling and filling stage respectively. After leaching, the desalination rates below mulch increased by 55.01% from 0-60 cm, and by 125.79% from 60-100 cm. The desalination rates beyond mulch after leaching was higher than that below mulch by 38.9% averagely. The salt leaching at the jointing stage significantly increased maize yield and its components, by 18.8% for yield, by 6.8%, 5.5% and 7.0% for spike length, ear width and grain number, respectively, and by 7.8% (P<0.05) for harvest index. The salt leaching at the tasseling stage increased yield by 8.1% (P<0.05), but the effect of leaching at the filling period was not significant (P>0.05). Therefore, the salt leaching at the jointing stage resulted in the less salt stress, under which crop yield could be increased obviously.

Abstract:The reducing of yellow water quota and increasing of irrigation area aggravated the shortage of agriculture water resources and soil salinization in the Hetao Irrigation District. It is of great significance to alleviate the stress of agricultural water, improve saline soil by adopting reasonable irrigation methods, and establish a good soil environment which is suitable for crop growth in the irrigation district. In order to investigate the transport characteristics of soil salt and nitrate nitrogen under ridge with plastic mulch-furrow irrigation in the Hetao Irrigation District, four times field irrigation experiments were conducted to determine the effect of high water and high fertilizer (I1F1), high water and low fertilizer (I1F2), middle water and high fertilizer (I2F1), middle water and low fertilizer (I2F2), low water and high fertilizer (I3F1), low water and low fertilizer (I3F2) on soil salinity and soil nitrate nitrogen. The results showed that the irrigation amounts shows higher influence on soil salinity than fertilizer amounts under ridge with plastic mulch-furrow irrigation. The soil salt content of middle water treatment always maintained a suitable and stable level. The amount of irrigation and fertilizer had different effects on soil nitrate nitrogen content. The nitrate leaching in the later stage of middle and low water treatments was significantly lower than that of high water treatment. The treatment of middle water and low fertilizer under ridge with plastic mulch-furrow irrigation increased soil moisture availability, inhibited soil salinity, and reduced the leaching of nitrate nitrogen on the ridge, had a good desalination effect on the basis of saving water and fertilizer which provide a suitable soil environment for the growth and development of crops and conducive to the accumulation of biomass. In a certain extent, the contradiction between the reduction of yellow water quota and the severe waste of water resources in leaching salt throught flooding irrigation was solved. It provided theoretical basis and technical support for the promotion of ridge with plastic mulch-furrow irrigation technology in the Hetao Irrigation District.

Abstract:Under conditions of large-scale open-closed type rain-proof shelter, effects of regulated deficit irrigation (RDI) on grain yield and quality of winter wheat (Triticum aestivum L.) and their relationship were studied by the method of tubular soil cultivation, and the aim was to find suitable appropriate stages to impose RDI and degrees of water deficit, offering technical parameters to the establishment of RDI model with water-saving, high yield and good quality. A two-factor (RDI stages and the amount of water deficit) randomize block design was adopted in the pot experiment. Three water regulation deficit stages (beginning of spring growth (I), stem elongation (Ⅱ) and grain filling (Ⅲ)) were set up, and each stage included three levels of water deficit (60%~65%, 50%~55% and 40%~45% of the maximum field capacity for light, moderate and severe deficit, respectively). The results indicated that the grain protein content of winter wheat was not always negatively correlated with soil water content. There were differences in effects of RDI on grain protein content at different growing stages. The correlation between grain protein content and soil water moisture was negative at the stage Ⅱ. Light (60%~65%) or middle degree (50%~55%) of water deficit before jointing stage did not significantly reduce grain yield, protein yield and amino acid content, or even slightly increase grain yield, but severe degree (40%~45%) of water deficit would lead to significant yield reduction. However, even slight water deficit resulted in serious yields reduction after jointing stage. Light degree of water deficit at grain filling stage did not significantly decrease grain yield, but enhanced the water-saving effects and slightly increased amino acid yield. The results also showed that the correlation between grain yield and protein content was not always negative, which could be weakened or changed under certain conditions. There were significant differences in the relationship between grain yield and quality traits at different RDI stages Therefore, it was suggested that coordinating high grain yield in contradiction to good grain quality might be possible. The results of this study preliminarily confirmed that RDI was a practicable technique for coordinating relationship between grain yield and quality characters in winter wheat.

Abstract:Moderately salinized sunflower field in Hetao Irrigation District were used to explore the effects of moistube-irrigation on the changes of soil water and salt distribution and crop yield to support the generalization and application of moistube-irrigation technology. Two soil buried depths (10, 20 cm) and four irrigation quotas (Full irrigation:T1, T5, mild water shortage:T2, T6, moderate water shortage:T3, T7, severe water shortage:T4, T8) were set up to study the changes of soil water and salt distribution and sunflower yield and water use efficiency (WUE). The results showed that in the same depth of moistube, as the irrigation quotas increased, the soil moisture was the higher and soil salinity was lower. The buried depth of moistube was an important factor affecting the distribution of soil water and salt. In the same irrigation quota, compared with the buried depth of 20 cm, The soil moisture contents with the buried depth of 10 cm was larger in 20-30 cm, the coefficient of variation of soil water content was less in 10-60 cm, and the salt content was significantly reduced. Under the condition of full irrigation and moistube buried depth of 20 cm, it was beneficial to inhibit the accumulation of soil salt in the root zone of sunflower. After the ripening of sunflower in 2015, the average relative salt accumulation rate of 0-60 cm treated by T1 was 9.3%, which was respectively lower than those of T2 and T5 treatment by 53.3% and 45.9% respectively. After the ripening of sunflower in 2016, the soil of 0-60 cm showed desalting and the amount of desalination decreased with the decrease of irrigation quotas, and increased with the increase of buried depth. At the same burial depth, the yield gradually increased with the increase of irrigation water volume. Under the same irrigation quota, moistube with buried depth of 20 cm had an increasing trend and the difference was significant compared with the depth of 10 cm. In summary, in the case of sufficient irrigation and moistube buried depth of 20 cm, the soil salt accumulation rate of 0-60 cm was 9.3%, and the crop yield was the highest, and the WUE was higher. It is recommended that the moistube buried depth of 20 cm and sufficient irrigation should be carried out in the sunflower field, and the soil should be leached by autumn flooding to decrease salt of surface layer in the Hetao area. This study provides a reference for the application of moistube-irrigation in moderately salinized areas.

Abstract:In order to improve the water and fertilizer use efficiency of drip fertigation for protected vegetables, the effects of drip fertigation strategies on yield and quality of greenhouse vegetables, and soil nitrogen distribution, nitrogen balance and nitrogen use efficiency in soil-vegetable system were investigated for 15 months in a solar heated greenhouse. The results showed that the fruit yield and the contents of total nitrogen and nitrate were affected significantly by fertigation strategies. The yield, total nitrogen and nitrate content were all higher in the treatment of fertilizing at the early stage of irrigation, and the nitrogen uptake by vegetable increased first and then decreased with the time of fertilization progressing backwards. After harvest, the soil nitrogen contents of the treatment of fertilizing at the end stage of irrigation were the lowest in all soil layers, while the nitrogen consumptions were the highest. In the treatment of fertilizing at the medium stage of irrigation, the apparent loss and surplus of nitrogen in soil-vegetable system were 15.35%~59.13% less than those in other treatments. Nitrogen fertilizer partial productivity and nitrogen apparent efficiency of the treatment of fertilizing at the medium irrigation stage were higher than those in other treatments. The average nitrogen fertilizer apparent utilization rate of the three stubbles in the T2 treatment was 7.09%, 7.41% and 11.48% higher than that in other treatments, respectively. In conclusion, fertigation strategies had a significant comprehensive impact on the yield, quality and nitrogen distribution of soil-vegetable system, and the strategy of applying fertilizer at the medium stage of irrigation schedule was recommend.

Abstract:Field plot experiments were conducted to study the effects of biochar on soil physi-chemical properties, heavy metal passivation and enzyme activities in the red paddy soil polluted by heavy metals. Biochar was added in different amounts of 0, 10, 20, 30 and 40 t/hm², respectively. The soil samples were collected from 0-17 and 17-29 cm soil layers. The soil integrated fertility index (IFI) was used to assess the soil fertility. The results showed that biochar could increase soil fertility by reducing soil bulk density and improving soil porosity, saturated water content, pH, cation exchange capacity (CEC) and the content of soil organic matter (SOM), the available phosphorus, ammonium nitrogen, total nitrogen and dissolved organic carbon (DOC). Meanwhile, biochar could improve activity of soil urease, catalase and urease. The content of available Cd and Pb in soil decreased with the increasing of biochar application amount, whereas the available As content increased first and then decreased with the increasing of biochar amount. The content of available Cd, As and Pb were all minimum when the biochar application was 40 t/hm². According to the evaluation of soil quality by IFI, the order of soil fertility composite quality was followed A30 > A40 > A20 > A10 > CK, the corresponding soil fertility composite quality indexes were 0.64, 0.62, 0.57, 0.47, 0.44, respectively. The evaluation results suggested that the optimal amount of biochar was 30 t/hm² for improving the red paddy soil fertility. In conclusion, appropriate amount of biochar application could remedied the red peddy soil polluted by heavy metal and enhance soil fertility.

Abstract:The distribution and potential ecological risk of heavy metals in the topsoil (0-20 cm) of the Yellow River Delta were investigated. The results showed that the average contents of Cu, Zn, Cr, Cd, Pb, Ni, As and Hg in the topsoil were 27.87, 79.19, 69.01, 0.383, 21.98, 33.42, 13.76 and 0.025 mg/kg, respectively, and these values were all less than the national standard value Ⅱ, except the content of Cd. The spatial distribution of above heavy metals decreased from northwest to southeast, and the highest content was found in experimental zone, while the lowest was found in core area. The evaluation of potential ecological risk index of Hakasnon showed that Cd was medium-strong ecological hazard, and the other heavy metals were minor ecological hazards, the potential risks of the different heavy metals followed the order of Cd > Hg > As > Ni > Cu > Pb > Cr > Zn. The comprehensive potential ecological risk of the protected area was minor to moderate ecological hazard, and the ecological hazard level of each functional area was experimental zone>buffer zone>core zone. Heavy metals were greatly affected by human activities, which were higher in areas close to human activities and lower in distant areas.

Abstract:One-year static cultivation experiments were conducted to investigate the effects of fish bone meal on immobilization remediation of cadmium (Cd), basic physiochemical properties and enzyme activities in acid and alkaline Cd contaminated soils. The results showed that with the increasing of fish bone meal amount, the pH, organic matter and cation exchange capacity increased in acid and alkaline soils, while the water content decreased by 2.90%~6.19% and 0.10%~1.81% compared with the control. The extractable Cd content of the TCLP (toxicity characteristic leaching procedure) in soil decreased with the increasing of fish bone meal, which decreased by 49.7% and 17.0% at most, respectively, when compared with the control. After the addition of fish bone meal to alkaline soil, the activity of catalase increased significantly (p<0.05), while the peroxidase activity was restrained, and the urease activity was promoted only under the treatment of addition fish bone meal less than 1%. However, in the acid soil, the activity of catalase, peroxidase and urease increase by 90.5%, 65.4% and 75.8% at most, respectively. The number of organic carbon functional groups was changed after applying fish bone meal, and the content of phenolic compounds, aliphatic C and aromatic C increased. The content of available Cd in soil was extremely negatively correlated with the organic matter content and the catalase activity (p<0.01), and it was obviously negatively correlated with pH and cation exchange capacity (p<0.05). Therefore, using fish bone meal was efficient for remediation of Cd contaminated soil.

Abstract:The ameliorative effects of rice cultivation (5~30 years) on soda saline-alkali soil in western Jilin Province of northeast China were studied through field survey and laboratory analysis. The results showed that compared with the virgin soil before cultivating rice, the pH value and the contents of total salt, exchangeable sodium, alkalization degree, the contents of CO₃^2-, HCO₃^-, Cl^-, Ca²⁺, Na⁺ and silt plus clay (<0.053 mm) fractions of soil decreased significantly after rice planting, while the contents of SO₄^2-, total organic carbon, water soluble organic carbon, humic acid carbon, fulvic acid carbon, alkali-hydrolyzable nitrogen and large aggregates (2~0.25 mm) in soil increased significantly. At the same time, the contents of alkyl carbon and alkoxycarbon in organic carbon increased whereas those of aromatic carbon and carbonyl carbon decreased in soil, resulting in an increase of the ratio of aliphatic carbon/aromatic carbon and a decrease of the ratios of alkyl carbon/alkoxycarbon and hydrophobic carbon/hydrophilic carbon. The above changes were usually more obvious with the extension of the rice planting years. The results indicated that rice planting could not only reduce soil alkalinity and salt content, but also increase the content and quality of soil organic carbon and improve soil structure. Therefore, rice planting was an effective way to ameliorate soda saline-alkali soil.

Abstract:Humic acid could improve the effect of fertilizers. Tomato was used as material in this experiment, the effects of humic acid synergist on the growth of tomato seedlings and the activity of nitrogen metabolism enzymes were studied in order to provide a reference for the development and application of humic acid. In this sand culture experiment, the humic acid was added to Hoagland nutrient solution with 0 (HA0), 1 (HA1), 2 (HA2), 5 (HA3) and 10 mL/L (HA4) respectively with 6 replications for each treatment. After culture for 30 days, the plant growth index, nutrients contents, nitrate reductase activity, glutamine synthase and glutamate dehydrogenase activities were measured. Adding proper amount of humic acid could promote the growth of tomato seedling, and the dry weight of root system of HA3 treatment increased by 31.68% than that of HA0. The dry weight of aboveground of tomato treated with HA3 was the largest. Adding Humic Acid could increase chlorophyll contents in Tomato leaves at the seedling stage. The contents of chlorophyll and carotenoid in tomato leaves treated with HA3 were the highest, which were 17.11% and 24.04% higher than that of HA0, respectively. The addition of proper amount of humic acid could increase the assimilation of nitrogen in roots and shoots of tomato at seedling stage. The accumulation of nitrogen in root, shoot and total nitrogen of tomato treated with HA3 was increased by 20.24% and 21.54% than that of HA0, respectively. The addition of humic acid could regulate the nitrogen metabolism process of tomato roots and leaves, and increase the activities of nitrogen metabolizing enzymes. Compared with HA0, the nitrate reductase activity of roots treated with HA4 was the highest, and the activity of glutamine synthase with HA3 was the highest. The maximum activity of glutamate dehydrogenase was found in root system treated with HA2. The activities of nitrate reductase, glutamine synthase and glutamate dehydrogenase in tomato leaves treated with HA3 were the highest, which increased by 38.27%, 64.54% and 106.63% respectively compared with HA0. The addition of humic acid could promote the growth and absorption of nitrogen and increase the activities of nitrogen metabolizing enzymes at tomato seedling stage. The best effect was found under the addition of 5 mL/L. When the addition was lower than 5 mL/L, it could promote the growth and nitrogen metabolism of tomato seedlings.

Abstract:Taking Quercus acutissima -Cerasus -Robinia pseudoacacia mixed forest (MYC), Quercus acutissima -Pinus thunbergii -Acer mono mixed forest (MHW), Quercus acutissima -Pinus thunbergii -Cotinus coggygria mixed forest (MHH), and Quercus acutissima -Pinus thunbergii -Ailanthus altissima mixed forest (MHC) grown in the burned area of Weihai as research object, soil properties and species diversity were surveyed under four different afforestation patterns with naturally updated woodland (CK) as the control. The effects of different afforestation modes on soil remediation and the status of subforest vegetation renewal were analyzed. The results showed that:(1) MHH had the lowest soil bulk density in 0-40 cm soil layer, the best soil aeration performance, and the best soil water retention. MHC was the second and MYC the worst. All of these three were different significantly from CK (P<0.05); (2) The soil organic carbon, carbon nitrogen ratio (C/N), total phosphorus, total potassium and available potassium contents in MHH were the highest in 0-40 cm soil layer. MHC had the highest total nitrogen and available phosphorus contents in 0-40 cm soil layer. There was no significant difference in soil organic carbon, carbon/nitrogen ratio (C/N), total phosphorus, total potassium and CK between MYC and MHW (P<0.05). (3) MHH's Margalef index, Shannon-Wiener index, Simpson index and Pielou index were relatively higher; (4) After comprehensive analysis, it could be concluded that MHH had the best soil remediation effect on moderately burned land, and the regeneration rate of understory vegetation was the fastest, followed by MHC. MYC and MHW could improve soil physical properties obviously, but had no obvious effect on soil nutrients and understory plant regeneration.

Abstract:A pot experiment was conducted to evaluate the effects of different proportions of biogas residue (BR) on growth of ryegrass (Lolium perenne L.) and physico-chemical properties of lead-zinc smelting slag. BR was incorporated into slag at rates of 0, 1%, 3%, 5%, 7% and 9%, respectively. The comprehensive effects of biogas residue on nutrient content, microbiological characteristics, forms of heavy metals of lead-zinc smelting slag and biological characteristics of ryegrass were studied. The results showed that addition of BR improved slags properties and thus facilitated growth of ryegrass. Compared with the control, BR application significantly increased nutrients (nitrogen, phosphorus and potassium), organic matter, enzyme activity (alkaline phosphatase, invertase, urease and catalase), the number of microbes (bacteria, fungi and actinomycetes) and microbial activity (respiratory intensity) (p<0.05). Different proportions of BR also significantly enhanced the total fresh weight, root length and plant height of ryegrass and significantly reduced the heavy metal content of plant tissues (the ground and underground part) (p<0.05). BR addition and ryegrass growth promoted the transformation of acid-extractable state of heavy metals (Cu, Cd, Zn and Pb) into the residual state, and then decreased the bioavailability of heavy metals in slag. Canonical correspondence analysis (CCA) revealed that the application amount of BR at 5%, 7% and 9% effectively improved the micro-environmental conditions of slag, among which, the lower addition amount of BR (5%) could also significantly improve the micro-environmental conditions of slag and promote the healthy growth of plants for restoration. Therefore, considering the relationship between the cost and effects caused by BR, the 5% addition amount of biogas residue could be used as the optimal application ratio for the improvement and phytoremediation of lead-zinc smelting slag.

Abstract:To compare the effects of different soil tillage methods (ploughing, rotary tillage and no tillage) on rice yield composition and cadmium accumulation and distribution traits in rice panicles in southern double-cropping rice fields, and to explore the optimal soil tillage method for double-cropping rice in cadmium-contaminated rice fields, taking "Lingliangyou 211"and "Weiyou 46"as early and late rice varieties, the available cadmium content in soil, rice yield components and spike cadmium accumulation and distribution of double-cropping rice under five soil tillage methods (double-cropping no-tillage, double-cropping ploughing, double-cropping rotary tillage, ploughing in early rice and no-tillage in late rice, rotary tillage in early rice and no-tillage in late rice) were studied in Yisuhe Town, Xiangtan County, Hunan Province in 2015 to 2017. The experimental field was cadmium-contaminated rice fields, and the total cadmium content was 0.86 mg/kg. The results showed that the yield of double cropping rice was the highest in the treatment of double-cropping ploughing, followed by the treatments of ploughing in early rice and no-tillage in late rice, double-cropping rotary tillage and rotary tillage in early rice and no-tillage in late rice, and that of no-tillage in double cropping rice was the lowest. The highest yield of ploughing treatment was due to the higher number of effective panicle and grains per panicle. (2) The cadmium content in panicle generally showed an increasing trend from full heading to maturity stage. In the first year of early and late rice, the cadmium content in panicle at full heading stage was the highest in no-tillage treatment, but no-tillage could significantly reduce the growth rate of cadmium content in panicle from full heading to maturity stage. The cadmium content in panicle at maturity stage was higher in ploughing treatment and lower in no-tillage and rotary tillage treatment, there were difference between no-tillage and rotary tillage treatment, but they were different among years and seasons. (3) Cadmium content in different parts of rice panicle at maturity stage followed the order of branches > husks > brown rice. The cadmium content in brown rice was higher in no-tillage treatment in the first year, but in the second and third years, that of no-tillage was lower than that of ploughing and rotary tillage. (4) The cadmium accumulation in panicle of early and late rice was lower in rotary tillage treatment in the first year, but it was lower in no-tillage treatment in the second and third years. (5) Compared with other treatments, double-cropping no-tillage significantly improved the soil available cadmium content, while double-cropping rotary tillage decreased the soil available cadmium content. The three-year locational test showed that soil tillage methods had a significant impact on available cadmium in soil, yield components and cadmium accumulation and distribution in rice panicles of double-cropping rice in cadmium-contaminated paddy field. From the perspective of ensuring the yield of double-cropping rice, reducing cadmium content in rice and saving labor, ploughing in early rice and no-tillage in late rice was the optimal soil tillage method for medium cadmium-contaminated double-cropping rice fields.

Abstract:Sand culture experiment were carried out to study the effects of PEG pretreatment on physiological characteristics of Lolium perenne seedlings under salt stress and cadmium stress. The experimental seedlings were dealt with 0%, 5%,10%,15%,20% and 25% (the corresponding water potential was 0, -0.05, -0.15, -0.30, -0.50 and -0.77 MPa, respectively) PEG-6000 pretreatment nutrient solutions, respectively, and then the seedlings were cultured separately by stress solutions containing 150 mmol/L NaCl and 10 mg/L Cd²⁺, respectively. Then the leaf chlorophyll(Chl)content, activities of antioxidant enzyme (such as catalase (CAT),superoxide dismutase (SOD), guaiacol peroxidase (POD) and ascorbate peroxidase (APX)), contents of osmoregulation substances, such as proline, soluble sugar and malondialdehyde (MDA) in leaves were determined. The test results showed that the 15% (-0.30 MPa) PEG pretreatment under the salt stress and the 10%(-0.15 MPa) PEG pretreatment under the Cd²⁺ stress could effectively increase the leaf chlorophyll contents of L. perenne seedlings, reduce the contents of MDA and proline, increase the content of soluble sugar and increase the activities of antioxidant enzymes. The above results showed that the L. perenne dealt by PEG pretreatment under stress was regulated by various physiological and biochemical factors. The dynamic changes of physiological indexes were important regulatory mechanisms for L. perenne in respons to stress, which reflected its adaptability to stress and its cross-adaptation ability under various stresses.

Abstract:To effectively improve the efficiency of plant extracting heavy metals from polluted soils, green safe organic materials were used as activating agents to replace safety hazards, non-degradable chelating agents and surfactants. The activation effects of different activating agents on soil heavy metal Cd and their effects on plant Cd accumulation were explored. The effects of three kinds of activating agents of milk vetch (MV), potassium humate (KH) and citric acid (CA) on the bioavailability and morphological characteristics of Cd in Cd-contaminated farmland soil and the accumulation of Cd by activator-fortified willay were studied by incubation and pot expriments with 0.3% application rate. The results showed that:(1) Adding an activator changed soil pH value. At the end of the culture, the effect of KH treatment on soil pH was better than that of MV, which was significantly lower than the control by 0.50 units (p<0.05), while the pH of the soil treated with CA was significantly higher than that of the control by 0.26 unit (p<0.05); Adding an activator could increase the soil organic matter content. At the end of the culture, the effect of KH treatment on the soil organic matter content was better than the other two activating agents, which was significantly higher than the control by 2.97 g/kg (p<0.05). (2) Adding activator could increase the effective Cd content of soil, but the activation effect of different activating agents was different. On the 20th day after culture, the effective Cd content of the soil treated with MV and KH reached the highest, which was better than that of CA treatment, which was higher than the control by 0.38 mg/kg (p<0.05) and 0.17 mg/kg respectively. When cultured for 10~30 days, the effective Cd content of CA treated soil increased gradually. After 30 days, the effect of CA treatment on soil effective Cd content was better than the other two activating agents, which was significantly higher than the control treatment by 0.39 mg/kg (p<0.05). (3) Adding activating agents changed the Cd form of soil. Cultured for 10~30 days, all three activating agents could activate soil residue Cd and increase the percentage of acid extractable Cd. (4) The three activating agents treatments had no significant effect on the plant height and biomass of the willow, but all increased the morphological parameters of the roots. The root length, surface area and root volume of CA treatment were significantly higher than the control, which increased by 75.54%, 80.05% and 82.93% (p<0.05) respectively. KH treatment significantly increased the Cd content in the leaves, branches and roots of the willow, which was higher than the control by 133.44% (p<0.05), 75.21% and 264.64% (p<0.05) respectively, and greatly improved enrichment and purification of Cd in soil by willow. The use of organic materials as activating agents could effectively improve the bioavailability of heavy metals in soils, and should have a good application prospect in combination with plant extraction of heavy metals.

Abstract:In order to determine the feasibility of biochar to repair glyphosate-contaminated soil, the adsorption effect of soil on glyphosate was studied by adding different proportions and types of biochar to the soil. After adsorption kinetics fitting, isothermal adsorption analysis and infrared spectroscopy were used. The results showed that glyphosate was strongly adsorbed in soil, rice husk carbon, bamboo charcoal and bamboo fillet carbon. Compared with soil, the other three biochars had the shorter adsorption equilibrium time. Adsorption kinetics conformed to the quasi-second-order kinetic equation, and isothermal adsorption conformed to the Freundlich adsorption isotherm equation. In the Freundlich adsorption isotherm equation, all 1/n values were < 1, which showed that the adsorption of glyphosate by soil and three biochars was non-linear, and the degree of non-linearity was bamboo fillet carbon > bamboo charcoal > red soil > rice husk carbon. Adding biochar to red soil could increase the adsorption of glyphosate in red soil. The higher the ratio of biochar addition, the higher the amount of glyphosate adsorbed by the soil. When the proportions of biochar added in soil were the same, bamboo charcoal was added to red soil to make the highest amount of glyphosate adsorbed on soil, followed by bamboo charcoal, and rice husk charcoal. The infrared spectra before and after the adsorption of glyphosate by three biochars demonstrated that phenol, amine, aromatic hydrocarbon, carboxylic acid, carboxylate and adipoether played the important role in the adsorption process.

Abstract:Under the pot experiment, DBP/DEHP was added exogenously with the concentrations of 0,20,50,100,200 mg/kg respectively to study the effect of PAEs on tobacco growth and its accumulation characteristics in soil-tobacco systems. The results showed that the addition of exogenous DBP/DEHP had no significant effect on the aboveground biomass and stem diameter of tobacco, and the plant height of tobacco showed different trends with the concentration of exogenous DBP/DEHP. The plant height of tobacco remained unchanged in yellow soil, decreased in yellow brown soil, and increased in red soil. The root activity of yellow soil decreased with the increase of exogenous DBP/DEHP concentration, while there was no significant change in yellow brown soil. DBP/DEHP concentration had a significant effect on tobacco antioxidant ezyme activity in some soils, but had no effect on soil denydrogenase and urease activity. With the increase of the concentrations of PAEs, the DBP/DEHP contents in the soil increased, with the highest increase for the DBP contents in the yellow brown soil, which reached its 3.56 times that of CK under the 200 mg/kg DBP. The concentrations of DEHP in yellow brown soil and red soil increased significantly, which were 27.47 times and 27.34 times of CK, respectively when adding 200 mg/kg DEHP. Compared with CK, most tobacco leaves and roots were improved in DBP/DEHP with different degrees. With the increase of the concentration of exogenous DBP/DEHP, the accumulation of DBP/DEHP in soil and tobacco leaves will be promoted to some extent.