Abstract:Karst rocky desertification is a growing problem in southwest China, which has seriously threatened the ecological and environmental security, the people’s livelihood and even the social development in the region. This paper systematically reviews the research progress of karst rocky desertification, including the concept of karst rocky desertification, the types, criteria and causes of desertification, and so on. Meanwhile, this paper summarizes the research trends of soil and water loss in karst area and expounds the relationship between rocky desertification and soil erosion, and highlights the existing problems and shortcomings in the current research on underground soil and water loss in karst area. And then according to the current research hot spots and shortcomings of the prospects, the research focus of next stage is proposed, i.e., to re-establish the type of rocky desertification standards based on the current work. Through the innovation of research methods and technical, the karst groundwater erosion mechanism and quantitative research would be promoted. And paying more attention to the problem of groundwater pollution in karst slope land, the scientific and effective measures for preventing and controlling surface loss and underground leakage are to be developed.

Abstract:As the industrialization is becoming a trend for soil and water integrated regulation on rocky desertification control, its technology system is coupled with mountainous agroforestry models and techniques. The results from statistically analyzing 158 related literatures were: (1)The literature shows a peak cluster curve by years of publication, which indicates necessity of further studies. (2)The previous researches involved several aspects, including experiment monitoring, applied technology research, theory and mechanism study, model construction, demonstration and benefit analysis. Among these studies, a priority had been given to experimental testing by monitoring the physical and chemical improvement of soil properties under the agroforestry as well as its influence on ecological, economic and social benefits. (3)The researched areas were mainly distributed in northern China and the karst area in southern China. The combining studies on the soil-and -water-integrated treatment and the mountainous agroforestry were mainly conducted in the arid/semi-arid regions and the karst areas with engineering droughts (droughts caused by the special geological conditions in Karst areas). This paper also revealed the frontier theories about agroforestry and the comprehensive soil-and-water governess of rocky desertification from five aspects: theoretical research, technological research and development, model construction, test demonstration, monitoring and evaluation. It is finally concluded that the previous researches lag behind in the areas of comprehensively theoretical study and the significant technology development. Studies on the following areas should be further strengthened: ‘five water’ on storage and dynamic conversion; joint operation of water and soil resources from both surface and underground space; technology research and development in preventing water and soil leakage from slopes; industrial technology for saving water and adding value; optimizing allocation technology research, on forest-crops-grass stereoscopic space; developing agroforestry with technology of integrated regulation on soil and water loss to achieve ecological restoration in rocky desertification regions and boost the development of regional economy.

Abstract:To predict the amount of nitrate nitrogen loss efficiently, the characteristics and influencing factors of nitrate nitrogen in slope land were studied by analyzing literature data of simulated rainfall experiments. RUSLE model was used to estimate nitrate nitrogen loss. Based on quantitative analysis of influencing factors and loss of nitrate nitrogen, an empirical formula of nitrate nitrogen loss with surface runoff was established, and the accuracy of the formula was verified by literature experiment data. The results indicated that the values of R, erosive force of rainfall, ranged in 200～3 220 (MJ·mm)/(hm2·h) and mainly distributed in 500～2 100 (MJ·mm)/(hm2·h), R factor was a reflection of potential soil erosion caused by rainfall. Soil erodibility was an important index to evaluate soil sensitivity and was affected by soil properties, the values of soil erodibility factor K were distributed between 0.007 to 0.095 (t·hm2·h)/(hm2·MJ·mm). Vegetation cover and management factor could be easily controlled to alleviate soil erosion and nutrient loss, the values of C factor were distributed between 0.006～0.930. Water conservation measures was a limiting factor of soil and water conservation, the ranges of water conservation measures factor P were 0.08～0.81. The values of factor P in different conservation measures showed that engineering mode＜comprehensive mode＜cultivation mode＜grass mode. Hence, engineering mode was the most efficient measure to reduce soil and water loss. The amounts of nitrate nitrogen loss were positively related with each influencing factor, which could be described by power function. In order to verify the accuracy of the empirical formula, six rainfall events collected from the previous researches, which haven’t been used in assessment of parameters. The relative error between calculated values and measured values of nitrate nitrogen loss amount with surface runoff was 30.28% and the model certainty coefficient was 0.772. The predicted formula developed in this study could accurately predict nitrate nitrogen loss because of the calculated data concur with the measured data. Further, these findings provided a theoretical basis for predicting nitrate nitrogen loss and optimizing the control measures of prevent nitrate nitrogen loss from rainfall events.

Abstract:In order to investigate the effects of different slope gradients (5°, 8°, 15° and 25°) and rainfall intensities (60, 90, 120 and 150 mm/h) on TN (total nitrogen) loss in surface runoff and subsurface flow, an artificial simulated rainfall experiment was conducted, and decomposed granite soil was taken as the experiment object. As the test design, the rainfall duration was 90 min after the appearance of surface runoff, and the test ended up when the subsurface flow disappeared. The results showed that: (1) The loss concentrations of TN in surface runoff declined rapidly at the early stage, and increased with the reduction of rainfall intensity and the increasing of slope gradient, and then tended to be stable. (2) The loss concentrations of TN in subsurface flow were significantly higher than those in surface runoff, and the curves of TN loss concentration in subsurface flow all followed a law of “rising-falling-slightly rising-steady”. Generally, the loss concentrations increased with the reduction of rainfall intensity and the increasing of slope gradient. (3) The total losses of TN in surface runoff and subsurface flow were both increased with the increasing of rain intensity and slope gradient. Subsurface flow was the main approach of TN loss on slope, and its proportion could reach 91.26% to 99.61%. The proportion of TN loss in surface runoff increased with the enhancement of rainfall intensity. (4) Rainfall intensity and runoff volume were both extremely significantly positively related to the TN loss in surface runoff and subsurface flow, while slope gradient only significantly positively correlated with the TN loss in subsurface flow. (5) There was a critical rainfall intensity between 90 mm/h and 120 mm/h, over which, the TN loss in surface runoff and its proportion in total loss would sharply rise.

Abstract:In this paper, the artificial simulated rainfall combined with the indoor backfill soil trough was used to study the difference among the characteristics of the runoff and sediment yield in the red soil slopes with different parent meterials: granite, quaternary and red sandstone. Results showed that the order of surface runoff time of the three parent materials was granite＜red sandstone＜quaternary, averaging runoff rates and the total amount of runoff were granite＞red sandstone＞quaternary, where the runoff amount of granite red soil under 45 mm/h rainfall was 1.79～2.47 times of those of red sandstone and quaternary, and the averaging runoff rate was 1.58～2.32 times of those of the latter two. Under the rainfall conditions of 45 mm/h, the sediment concentration of the field was the quaternary＞granite＞red sandstone, while, it was granite＞red sandstone＞quaternar under 135 mm/h. The rain intensity had a greater influence on the sediment yield of red soil slope, and the sediment concentration under 135 mm/h was 8.31～11.32 times of 45 mm/h. As for the runoff composition, the proportion of interflow in runoff was highest in quaternary red soil among the materials, which was about 8%～44% in the two rain intensities. The larger rain intensity, the more obvious effect of the surface confluence, which could reach up to 79%～90% of the total runoff under 135 mm/h. The runoff time of interflow was same as that of the surface runoff: granite＜red sandstone＜quaternary, the interflow of granite red soil was smallest, accounting for only 53%～67% of the quaternary, and even 42%～52% at the peak runoff. After the rainfall, the regression of interflow could be predicted by an exponential function, all the decision coefficients were above 0.82 for all conditions, showing a good predictability.

Abstract:The objective of this study was to investigate the relationship between soil detachment rate and sediment concentration of ridge contour during maize growing stages. This paper took sloping farmland of purple soil in Hilly Area of Central Sichuan basin as the research object. The filed artificial rainfall experiment was carried out for determination of characteristics of soil detachment rate and sediment concentration during maize growing stages, and to find the relationship between soil detachment rate and sediment concentration. The results showed that: (1) The soil detachment rate increased with the increasing rainfall intensity during maize growing stages, and the soil detachment rate under 2.0 mm/min rainfall intensity were 1.87 and 4.59 times greater than that under 1.0 and 1.5 mm/min rainfall intensity, respectively. During maize growing stages in the field, the soil detachment rate showed a falling-and-rising trend, and was significantly higher in the seedling stage than that in other growing stages under the same rainfall intensity. (2) Within maize growing stages, the sediment yield increased firstly and then decreased under different rainfall intensities. The largest sediment yield was (306.6 g) in the seedling stage, and the least (64.6 g) was in tasseling stage. The sediment yield increased with the increasing rainfall intensity in growing stages except for tasseling stage, while the difference was significant among rainfall intensities in seedling stage and jointing stage. The sediment concentration in runoff showed a fluctuating trend during the maize growing stages in the rainfall process, and the fluctuation range increased with the increasing rainfall intensity. (3) A power function relation was listed between soil detachment rate and sediment concentration in runoff during maize growing stages, and the correlation was significant. The results provide references for revealing the mechanism of soil erosion in sloping farmland of purple soil and the construction of regional water erosion prediction model.

Abstract:To quantitatively evaluate the effects of three different infiltration amounts on soil preferential flow, the morphological image processing technology, statistical sample variability analysis, variance analysis, and correlation analysis were used in this study. G20, G40, and G60 were taken to represent these plots with three different infiltration amounts (20 mm, 40 mm, and 60 mm respectively). Dyeing experiments with Brilliant Blue FCF (C.I. Food Blue 2) were conducted in grassland in Simian Mountain of Chongqing. The results showed that: (1) Dye coverage generally decreased with the increasing soil depth, and sharp decreases were found at the depths of 3 cm in G20 and 12 cm in G40, respectively. (2) The total dye coverage and length index of preferential flow were positively correlated with infiltration amounts (P＜0.01). (3) Water infiltration was promoted to deeper soil layers as the infiltration amounts increased, and the maximum depth of water infiltration reached 60 cm. (4) The non-uniformity of dyed coverage in preferential flow area and the maximum infiltration depth decreased with the increasing infiltration amounts with their variation coefficients ranging from 1.88 to 0.47, and 0.52 to 0.07, respectively. However, the effects of infiltration amounts on actual infiltration depth was even more complicated.

Abstract:This study explored the feasibility of ecological grass furrow to assist drainage and control non-point pollution in agricultural land of southwest China. Experiments were conducted in farmland block unit. Traditional soil furrow in farmland plots was taken as CK. Through the scouring test of the ecological grass furrow to explore the benefits of ecological grass furrow to runoff pollutant reduction. This experiment used simulated sewage，according to different requirements to adjust the sewage composition to explore the reduction effect of ecological grass furrow on pollutant. The research results showed: (1) The 5° agricultural land furrow had a certain reduction for the sewage runoff COD load, and the reduction was between 8.86% to 14.00%. However, when the ecological grass furrow gradient reached 10°, the COD pollution load in the runoff increased by 20.38% to 33.02%. (2) For the removal efficiency of total nitrogen, it was found that the total nitrogen load in the runoff was significantly higher in agricultural land furrow than that in the traditional soil furrow, and the removal efficiency ranged between 2.46% and 33.39%. (3) For the total amount of phosphorus loss, when the flow rate was 4.5 L/min, the phosphorus loss in the ecological grass furrow was larger than the designed runoff of 3 L / min, and the difference of phosphorus loss was between 0.005 9 and 0.037 7 g/m2, the rate was between 4.71% and 25.02%. When the agricultural land furrow reached 5°, the loss of phosphorus in furrow increased with the increase of runoff, and reached 63.32%. When the agricultural land grass furrow gradient reached 10°, the proportion of phosphorus loss in furrow increased with the sediment loss, and reached 70.95%.

Abstract:In order to explore the water and nitrogen transport characteristics under water and fertilizer integration of film hole irrigation with muddy water irrigation, through the indoor fertilizer infiltration test, the migration characteristics of infiltration, wetting front migration, soil moisture, ammonium nitrogen and nitrate nitrogen were studied under different soil initial water content (6.02%，7.40%，8.23%，10.08% and 13.20%). The relationship between cumulative infiltration volume, the wetting front migration distance and the soil initial water content of liquid fertilizer infiltration of film hole irrigation with muddy water were established. An empirical model was proposed to calculate the cumulative infiltration volume and the wetting front migration distance under different soil initial water content. Results showed that: The cumulative infiltration, the wetting front migration distance, the water transport in wetting body, the distribution and transformation of nitrogen were all affected by the soil initial water content. At the same infiltration time, the cumulative infiltration reduced, while the wetting front migration distance increased, with the increase of soil initial water content. The higher the soil initial water content was, the larger the wetting volume was, and the wider water, ammonium nitrogen and nitrate nitrogen in soil distributed. The higher the soil initial water content was, the smaller the value of infiltration parameter K was, and the larger the value of infiltration index α was. After irrigation, ammonium nitrogen was mostly distributed in the wetting body with humid radius which was less than or equal to the range of 5 cm. Meanwhile, ammonium nitrogen content decreased with the increase of soil depth in the wetting body when the wetted radius was larger than 5 cm and less than 10 cm. The ammonium nitrogen content obviously decreased when the humid radius was larger than 10 cm. Nitrate nitrogen was mainly distributed in the range from the center of the membrane pore to the wetting radius of 10 cm. The nitrate nitrogen content in the horizontal direction and the vertical direction decreased with increasing distance from the center of the film hole, the nearer was away from film hole center the higher nitrate nitrogen content was in both vertical and horizontal direction. The greater the initial soil water content was, the higher the mass fraction of ammonium nitrogen and nitrate nitrogen was at the same position. With the redistribution of soil moisture, the wetting front gradually went down, the wetting of ammonium nitrogen gradually downwardly migrated and its content decreased. Nitrate nitrogen concentration front transported with time prolongation, the soil nitrate nitrogen content decreased in the upper layer and gradually increased in the lower layer new wetting body, the content of nitrate nitrogen in wetting body tend to uniformly distribute. The research results could lay the foundation for further study on the transport and transformation of nitrogen fertilizer under the film hole irrigation with muddy water.

Abstract:To study the characteristics and hydrological dynamics of rainfall runoff on sloping land, the overland flow and subsurface flow on the weathering granite sloping land at different rainfall intensities (30, 60, 90, 120, 150 mm/h) and slope gradients (5°, 8°, 15°, 25°) were comparatively studied with the method of artificial simulated rainfall. The results showed that the initial starting time of both the overland flow and subsurface flow advanced with the increase of rainfall intensity and slope gradient. The initial starting time of subsurface flow obviously lagged behind that of overland flow. With extension of rainfall time, the subsurface flow rate at different slope gradients turned to be stable after an increasing trend. The greater the rainfall intensity was, the earlier the subsurface flow rate reached the peak. And subsurface flow rate began to run down after the rainfall stopped for some time. In most cases, the proportion of subsurface flow was larger than that of the overland flow. The proportion of overland flow increased with the growth of rainfall intensity. Slope gradient, however, had little influence on the proportion of overland flow. The runoff correlation between the overland flow and rainfall intensity was relatively large, and the runoff coefficient of subsurface flow was mainly affected by slope gradient. The runoff modulus of overland flow, subsurface flow and mixed flow (overland flow and subsurface flow occurred simultaneously) showed a strong positive correlation with rainfall intensity and displayed the following order: mixed flow＞subsurface flow＞overland flow.

Abstract:Effects of grass coverage degree (30%, 60%, 90%) and rainfall intensity (1, 1.5, 2, 2.5, 3 mm/min) on the soil infiltration process on the 15° grass slope were studied under simulated rainfall condition in the third subregion of loess hilly region. The results were as follows: (1)Soil infiltration rate increased with the increase of grass cover and rainfall intensity, while the soil infiltration rate increased significantly with the increase of grass coverage rate. The initial infiltration rate of soil and rainfall intensity presented exponential relationship. The soil stability infiltration rate and rainfall intensity showed the power function relations. (2)The cumulative soil infiltration and rainfall time had a good power function relationship. The cumulative infiltration of soil increased significantly with the increase of grass coverage rate. The effect of rainfall intensity on soil cumulative infiltration showed phase-based difference. (3)The increase of grass cover could significantly increase the soil infiltration coefficient, the soil infiltration coefficient decreased with the increase of rain intensity. Under the coverage of field grass (about 60%), the effective rainfall intensity of grass cover in increasing soil infiltration coefficient was between 1～1.5 mm/min. (4)The relationship between soil infiltration rate and rainfall time was fitted by four infiltration models, and the Horton formula was found could well simulate the soil infiltration process.

Abstract:The research area of this study was the Wangmao ditch small watershed in Suide county of the Loess Plateau of China. Combining with the field investigation and laboratory test, the variations of stable isotopes (δ2H) in the vadose zone under three different land use types were studied in a single rainfall event. The results showed that: (1) The soil water content ranged from 6.74% to 21.42% in grassland, from 6.74% to 19.08% in woodland, and from 7.86% to 20.74% in farmland. The variation ranges of soil water storage were from 265.6 mm to 384.0 mm in grassland, from 275.1 mm to 368.7 mm in woodland, and from 289.5 mm to 334.6 mm in farmland. The variation ranges of δ2H in soil water were from -113.41‰ to -71.84‰ in grassland, from -115.10‰ to -50.98‰ in woodland, and from -112.28‰ to -63.78‰ in farmland. (2) There were two trends in soil water content changes in grassland, woodland and farmland, but with difference in time nodes. (3) There were significant differences in the hydrogen isotopic changes of soil water in different land use types. The farmland and grassland were favorable for the soil water retention, but it was not easy for the woodland to maintain soil moisture. (4) The peak values of soil water storage under different land use types were inversely related to the water storage capacity. The higher the peak value, the lower the corresponding water storage capacity. (5) There were preferential flow phenomena in all land uses studied, with the largest preferential flow in woodland. The path of preferential flow was extended in grassland and woodland , whereas in farmland, it might be affected by the quality and recharge of groundwater .

Abstract:In order to clarify the reasonable soil thickness of man-made tillage layer in the bare rock and gravel land remediation project, a simulation experiment of indoor soil column was conducted. The effect of soil thickness on particle migration process in bare rock and gravel soil was studied. According to the characteristics of bare rock and gravel soil reclamation project, the soil layers thickness treatments included 5 cm, 10 cm, 15 cm and 20 cm respectively. The bottom of the column was filled with the 5-cm-thick glass beads with a diameter of 10 mm. From the start of water seepage from the bottom of the soil column, the collecting test of leakage fluid was taken for 6 h. The results showed that: (1) The thicker soil had greater water retaining capacity and stronger stability. The water leakage in the four soil layers decreased with the increasing soil thickness. The water leakage rate increased at first and then reduced, ultimately, tended to be stable. (2) The migration quantity was negatively correlated with the soil thickness, showing an exponential function of y=3.19e-0.11x (R2=0.96). (3) The water leakage was often accompanied by the migration of the soil particles in the earlier stage, and the thinner the soil thickness was, the greater amount of water leakage and soil particles were. As the leakage process progressed, the quantity of soil particles migration was gradually decreased. (4) The content of silt was the highest in the migration particles, followed by the clay, and the sand content was the lowest. The migration characteristics of different soil particles varied with time. These findings provide scientific basis for the development and consolidation of bare rock gravel land.

Abstract:In order to reveal the effect of different coverage measures on the slope erosion of topsoil-bank, the simulated rainfall experiments were conducted in this study. Three coverage measure treatments, which were non-coverage (CK), geonet-coverage and plant-coverage, were set on the topsoil-bank. The slope ratio of topsoil-bank was 1∶1.5 and the plant used in this study was Trifolium repens L. The rainfall intensities were 0.5，1.0，1.5 mm/min, respectively. The runoff and sediment yield law of the slope surface with the different coverage measures under the different rainfall intensities were studied. The results showed that the coverage measures had significant effects on slope erosion compared to CK under different rainfall intensities. The most runoff and sediment were produced in CK, followed by the geonet-coverage, and the least was plant-coverage. During the whole experiment, compared to CK, the geonet-coverage decreased the runoff by about 50%, while plant-coverage gave a more remarkable decrease (82%). Both geonet-coverage and plant-coverage treatments reduced sediment by more than 94%. In conclusion, coverage measures could inhibit the erosion of rain on the slope, and help reduce the runoff and sediment, among which the plant-coverage had a better role than geonet-coverage.

Abstract:Slope-gully model system of the Loess Plateau was established based on the controlled scouring experiments. Study of the effects of slope length on the erosion power factors of slope-gully system could provide scientific guidance for the mechanism of water erosion process in slope-gully system. This study set up five water flow rates (6, 8, 10, 12, 14 L/min) and three slope lengths (4, 6, 8 m). The results showed that the Reynolds number increased with the increasing water flow rates acrossing each section of the slope-gully system, and the Reynolds number in the slope was higher than in the gully. Froude number also increased in the slope-gully system and the increased rate of Froude number in the gully was obviously higher than that in the slope. The Froude number had the highest value when the water flow rate was 10 L/min. The runoff velocity in the gully was obviously higher than in the slope under the same water flow rate, and the runoff velocity in the slope was much stable than in the gully. The resistance coefficients sharply reduced to 0.03～0.05 from section 2 under different slope length and water flow rate of 10 L/min. The fluctuation of resistance coefficients was less with the decreased slope length under the same water flow rate (except for 10 L/min). Runoff erosion power was significantly correlated with Reynolds number, Froude number, runoff velocity. The relationship between runoff erosion power and Reynolds number was a logarithmic function, while the power functions occurred between runoff erosion power and Froude number, flow velocity and resistance coefficients. These results showed that the slope length obviously affected the erosion hydraulic parameters in the slope gully system, and these findings could provide scientific bases for the research of erosion energy transfer in the slope-gully system.

Abstract:The wind erosion of farmland in the agro-pastoral acetone of northern China is very serious, which causes degradation of soil resources. Taking Bashang district as a typical area of agro-pastoral acetone, by field sampling and comparing the differences in soil properties between farmland and nearby natural grassland, the loss characteristics of fine particles in farmland soils led by wind erosion as well as its impact on soil physical and chemical properties were studied in the paper. The results showed that, compared with natural grasslands with weak wind erosion, the contents of clay and silt in farmlands decreased by 30% and 14%, respectively. The grain sizes of lost soil concentrated in 0～40 μm, of which the loss of fine particles with sizes of 1.8～24.0 μm was the largest. The loss of fine particles in farmland soils resulted in the increase of sand and gravel in farmland soils by 7% and 75%, respectively, also the averaged particle size of soil increased 16%. Those indicate that the farmland soils have serious tendency of coarsening and desertification under the long-time effect of wind erosion. With the loss of fertile fine particles, the soils of farmland became barren. The results showed that the contents of carbon (C) and total nitrogen (N) in farmland soils decreased significantly, with a declining range of about 29% and 24%, respectively. The ratio of C to N (C/N) also declined obviously and the content of soil fertility reduced. However, the loss of fine particles had no significant influence on the proportion of erodible particles in soil. The change of soil erodibility by wind was not obvious in farmland soils.

Abstract:Ridge-furrow planting with plastic film mulching (RM) is widely applied in Northwest China. This study aimed to understand the effects of RM on summer maize growth, yield, water use efficiency (WUE) and soil water dynamics. Two treatments were arranged: ridge-furrow planting with plastic film mulching (RM, crops were planted in the bare furrow with the ridge covered with plastic film) and flat planting without mulching (NM). The Logistic and modified Logistic equations were used to simulate plant height and leaf area index (LAI), and HYDRUS-2D model was used to simulate soil water dynamics after rainfall. The results showed that the maximum growth rates of plant height were 5.1 and 5.2 cm/d on the 39th and 41th day after sowing, under RM and NM respectively. The maximum growth rate of LAI under RM was 14.6% higher and occurred 2 days earlier than that of NM. The ear length, kernel number per ear, 100-kernel weight, yield and WUE of RM were 7.8%, 15.4%, 1.3%, 6.0% and 3.1% higher than those of NM, respectively. The simulated results of HYDRUS-2D model showed that RM increased the average soil water content in 0—200 cm profile, especially in 0—20 cm layer after rainfall. Finally, it could be concluded that RM could increase yield and conserve water when comparing with NM, however, the effect on increasing yield is depend on the meteorological condition of summer maize growth stage, if the weather is too wet or too dry, RM may has little profit on yield.

Abstract:Taking Yunnan laterite as the research object, this paper studied the effects of different factors on the swell-shrink characteristics of Yunnan laterite and the influencing factors such as wetting-drying cycle time, wetting-drying cycle times and initial dry density were taken into account through the method of expansion and shrinkage test combined with image processing. The results showed that the expansion process of laterite can be divided into 3 stages: rapid expansion, slow expansion, and stable expansion. The contraction process could also be divided into 3 stages: slow contraction, rapid contraction, and stable contraction. With the increase of wetting time, the vertical expansion rate, moisture content, porosity and other expansive parameters of laterite increased as the “厂” type. The shrinkage parameters such as vertical shrinkage, transverse shrinkage, volume shrinkage and so on increased with the time of dewetting, showing the change of “S” type, and the moisture content and porosity decrease gradually. With the increase of humidification times, the stability of vertical expansion rate, the transverse expansion rate, and the volume expansion rate increased sharply first and then decreased slowly. With the increase of dehumidifying times, the vertical shrinkage, the transverse shrinkage, and the volume shrinkage increased firstly and then fluctuated slowly. With the increase of initial dry density, the vertical expansion rate, the vertical shrinkage rate, and the volume expansion rate increased, while the transverse expansion rate, transverse shrinkage rate, and volume shrinkage rate decreased.

Abstract:Based on the Pisha sand stone in the Inner Mongolia ZhunGeErQi as the research object, in this paper, through the field sampling of undisturbed soil and laboratory simulation of soil-column experiment, soil water infiltration were analyzed by one-dimensional vertical infiltration experiment to study the process of water infiltration on the loess soil, aeolian sandy soil and Pisha sand stone. The results showed that the infiltration rate and cumulative infiltration changed trend was: aeolian sandy soil＞loess soil＞Pisha sand stone in the undisturbed soil, and aeolian sandy soil＞Pisha sand stone＞loess soil in the disturbed soil. The wetting front and the cumulative infiltration showed the same trend both in the undisturbed and disturbed soil. Fitting the relationship between infiltration rate and time with Kostiakov empirical formula, Philip model and Green-Ampt equation, the results showed both Kostiakov infiltration equation, Green-Ampt and Philip equation were suitable for simulating the change of cumulative infiltration capacity for the disturbed and undisturbed soils, but Kostiakov formula was more accurate fitting the water infiltration on the disturbed and undisturbed soil than other models.

Abstract:Engineering piles is a special man-made geomorphic unit and has been found much more serious in soil erosion. The studying of hydrodynamic process in the engineering piles is of great necessity, for the engineering piles with three-dimensional is quite different from the traditional slope. In this paper, a self-made platform was used to simulate the three-dimensional pyramidal engineering piles and an indoor artificially simulated rainfall experiment was carried out under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm/min) to study the hydrodynamic process and shape characteristics of rills of engineering piles with different mass percentage of gravel (0, 10%, 20%, 30%, 40%). The results showed that: (1) Flow velocity and runoff intensity increased with the increase of rain intensities and decreased with the increase of gravel contents. Both the rainfall intensity and gravel contents had the significant influences on flow velocity and runoff intensity, and the influence of rainfall intensity was greater. (2) The runoff was in the laminar and subcritical flow state, and Reynolds number and Froude number increased with the increase of rain intensities and decreased with the increase of gravel contents. (3) Erosion detachment rate increased exponentially with the increase of rainfall intensities, and decreased linearly with the increase of gravel contents, there were significant power function relationships between erosion detachment rate and shear stress, stream power, unit flow power and unit energy of water-carrying, among which stream power had the best correlationship, indicating it was the optimal factor to describe soil erosion. (4) The rill occurring time advanced and the length, width, depth of rill increased with rainfall intensities increasing, while the rill occurring time was delayed, the depth and width of rill decreased gradually with the increase of gravel contents under the same rainfall intensity.

Abstract:To investigate the effects of extreme soil erosion on physical and chemical properties of soil and crop yield, simulated experiments were conducted in topsoil (30 cm), transition layer (40 cm) and parent material layer (＞70 cm) of Mollisols farmlands. Treatments including 70 cm topsoil removal, 30 cm topsoil removal, no eroded soil, 30 cm sediment deposition and 70 cm sediment deposition were set respectively. The results showed that compared with no eroded soil, soil bulk densities, soil mass water contents, soil water storages of the other four treatments were all significantly increased in tillage layer (0—20 cm), while soil porosities, contents of soil water stable aggregates were greater than 0.25 mm, mean weight diameters, geometric mean diameters, field capacities, saturated moistures and soil nutrient contents of the four treatments were all significantly decreased. Furthermore, compared with no eroded soil, corn yields of the treatments of 30 cm and 70 cm soil removal reduced by 42.1% and 52.6%, respectively. There was no significant difference in corn yield between no eroded soil and 30 cm sediment deposition. Corn yield of the treatment of 70 sediment deposition significantly decreased by 12.4%. Thus, extreme soil erosion, no matter topsoil removal or sediment deposition, will lead to the decline of soil quality, reduce soil fertilizer supply and conservation ability , then reduce corn yield.

Abstract:This study investigated the size distributions of aggregates and primary particles in the sediments eroded from five typical soils in China under natural rainfalls. The experiment was conducted on five runoff plots packed with the Red Soil, Purple Soil, Loess, Cinnamon Soil and Black Soil. Sediment samples in four runoff events of these plots under natural rainfall were collected during June to September in 2013 and 2014. Using the pipette method and wet sieving technique, the compositions and size distributions of primary particles and aggregates were measured. Moreover, the sediment aggregates with different sizes were sieved and determined for the size distribution of primary particles. The results showed that: (1) The sediment size distribution was affected by both soil texture and rainfall intensity. The aggregate size distribution was more suitable as a better indicator for sediment transport. (2) Larger portions of silt-sized (0.002～0.05 mm) and clay-sized (＜0.002 mm) aggregates were obtained in the sediments of five types of soils. (3) However, no obvious enrichment of primary particles was observed in the eroded sediments of any soil but the Red Soil, which possessed slightly elevated percentages of silt and clay in the corresponding sediments. (4) When further analyzing the primary particle-size composition of sediment aggregates with different size, the highest percentage of clay particles was determined in the silt-sized aggregates of the Red Soil. For the rest four types of soils, the mechanical composition of eroded sediment and the mechanical composition of the aggregates at all sizes were all similar to the source soil.

Abstract:The citrus orchard slope and bare control slope were used as the research objects, the long-term dynamic processes of runoff and sediment yield and the variation of the relationship between runoff and sediment were studied based on the observation data from 2001 to 2015. The results showed that the annual runoff and soil erosion modulus of citrus trees slope decreased significantly from sapling stage, early fruit stage to full fruit stage, and tended to be stable in the full fruit stage. Sapling period was the key period of soil and water conservation in red soil orchard. The soil erosion intensity could be very strong in this period, while the soil erosion intensity could be reduced to below the allowable loss of soil in the full fruit period. The relationships between the runoff and the sediment and rainfall dramatically changed in the fourth year, while the relationships between the runoff and the sediment and rainfall of the bare slope maintained. The benefit of sediment reduction in citrus orchards was greater than that of runoff reducing in each year, and the benefits of runoff and sediment reduction increased rapidly and remained relatively stable over time, showing an exponential function. It meant that the benefits of runoff reduction and sediment reduction of fruit trees were very time variable, reduced sediment by reducing runoff as well as reduced sediment by changing the relationship between runoff and sediment. The results would provide a basis for evaluating the benefits of soil and water conservation measures in orchards, and provide a reference for the rational allocation of soil and water conservation measures.

Abstract:In order to reveal the response of the soil erosion and organic carbon loss on purple slope farmland with contour ridges to slope gradient, characteristics of the runoff, sediment yield and organic carbon loss on different slopes were studied during maize seedling stage through surveying field runoff plots and simulating rainfall artificially. The results showed that during maize seedling stage, the surface runoffs on different slopes were stable in the initial stage of rainfall, and they gradually increased with the duration of rainfall. On 10° slope, the interflow did not change at the beginning of rainfall, and gradually increased with rainfall duration, while on 15° and 20° slopes, the interflow showed a gradually increasing trend with rainfall duration. The erosion intensities of different slopes listed in the order of 20°＞15°＞10°, and erosion intensity of 20° slope was significantly higher than those of 10° and 15°slopes. The concentrations of total organic carbon (TOC) and dissolved organic carbon (DOC) in surface runoff decreased with the increasing of rainfall time on different slopes, and the organic carbon mass concentration followed the order of 20°＞15°＞10°, while the TOC and DOC concentrations in interflow firstly increased and then decreased, and organic carbon mass concentration followed the order of 10°＞15°＞20°. And the concentrations of TOC and DOC in surface runoff were not very different with those in interflow; TOC and DOC migration fluxes in interflow were both greater than those in surface runoff on different slopes, organic carbon migration flux in surface runoff followed the order of 20°＞15°＞10°, while organic carbon migration flux in interflow showed contrary order, and DOC migration flux accounted for 90% of TOC migration flux in runoff. The organic carbon content in sediment decreased with the increasing of slope gradient, and on the same slope, the organic carbon content in sediment decreased with the duration of rainfall. The organic carbon was enriched obviously in sediment, and the enrichment ratio decreased with the increasing of slope gradient. Therefore, the organic carbon in runoff was mainly lost in the form of DOC on purple sloping farmland, and interflow was the main mode of the DOC migration.

Abstract:In degraded red soil area, taking the Pinus massoniana forest mixed by shrub and grass measures with 4 different management years as the object of study, and the unmanaged severely degraded pine as control, the effects of management years on soil nutrients were studied. The results showed that: (1) The range of soil organic matter, total nitrogen and total phosphorus contents were 0.81～28.10 g/kg, 0.18～1.15 g/kg and 0.03～0.18 g/kg, respectively, and all contents increased with the increase of management duration, and first fast and then slow in increasing rates. Total potassium contents ranged in 0.92～4.65 g/kg, with the highest in the 40—60 cm soil layer after managed for 13 years, the increasing rate was first slow then fast. (2) There was a correlation between soil nutrient content and management years: management years gave a significant correlation with soil organic matter and total N contents（P＜0.05）, and a highly significant correlation with total P（P＜0.01）. But no correlation was observed between soil total K content and management years. These findings suggested that the soil nutrient contents of Pinus massoniana forest soil was related to the management years, and provided scientific basis for ecological management and restoration.

Abstract:In order to effectively prevent and control the soil and water loss and pollution in Camellia oleifera field, by using the location observation of runoff plot under natural rainfall conditions, the effects of intercropping with Lolium perenne L. and Vulpia myuros C. Gmelin on soil nutrient loss in C. oleifera field were studied. The results showed that: (1) The intercropping of L. perenne and V. myuros with C. oleifera could improve soil water content and surface coverage, reduce soil bulk density, and increase soil fertility significantly through improving soil organic matter and nutrient contents in topsoil. (2) During April-July, the intercropping of L. perenne and V. myuros with C. oleifera could reduce surface runoff by 18.5%～58.9% and 17.9%～70.3%, respectively. (3) The reducing effect on surface runoff nutrient loss was best under intercropping with V. myuros, the total loss of total nitrogen, total soluble nitrogen, total phosphorus, total soluble phosphorus, total potassium and total soluble potassium decreased by 62.48%, 56.17%, 59.72%, 57.97%, 62.97% and 61.76%, respectively, compared with the control. The reducing effect on nutrient loss was least under the intercropping with L. perenne, but the reduced rates were even 30.95%, 24.42%, 25.03%, 28.22%, 32.97% and 30.42%, respectively for the indexes mentioned above. The nutrient concentrations of nitrogen, phosphorus and potassium in different forms were lower than those of the control. These findings showed that the effect of intercropping with green manures on soil and water conservation was remarkable in C. oleifera field, especially with V. myuros.

Abstract:A single-point irrigation installation was used to simulate drip irrigation, where the effects of different fertilization methods on soil nutrient migration were studied. Two application methods of phosphate (P) and potash (K) fertilizers were designed: applied before irrigation as base fertilizer and applied with irrigation water, and the temporal and spatial distributions of soil P and K after drip irrigation were observed. The results showed that the soluble P and K fertilizers were migrated with the infiltration of drip irrigation, and the high value of available P appeared near the edge of the wet zone, while the available K evenly distributed in the moist area. Soil P accumulated only in the wet zone depth of 20 cm and the horizontal direction of 15 cm within the soil caused by the water flow. When the total application amount of P fertilizer was consistent, the maximum content of available P in soil applied with water was significantly higher than that applied as base fertilizer. When applied with water, the distribution of available K in soil was also uniform, whereas high value area was formed near the drip point. Applying K fertilizer with irrigation water could slow down the migration rate of available K to a certain extent.

Abstract:Pinus massoniana forest after the restoration of eroded degraded land in the typical red soil of southern China was selected as the research object. Dissolved organic carbon (DOC) extracted from the fresh leaves and the leaf litter of P. massoniana and Dicranopteris dichotoma was leached through such soil cores of eroded degraded land in indoor simulation, and the adsorption characteristics and influencing factors of DOC from different sources in P. massoniana forest during vegetation restoration was analyzed. The results showed: (1) The adsorption of red soil eroded degraded land on DOC from different sources had obvious difference, the maximum of DOC average interception from the fresh leaves of P. massoniana was 2.39 mg/kg, the minimum of DOC average interception from the fresh leaves of D. dichotoma was 1.67 mg/kg. DOC from the fresh leaves of P. massoniana was more susceptible to surface soil adsorption, while DOC from the fresh leaves of D. dichotoma was easy to enter the deep soil, different sources of DOC composition and properties was the main reason for this difference. (2) With the increase of vegetation restoration years, the DOC concentration of soil leachate increased, and the soil interception ability of DOC decreased. DOC interception was positively correlated with the content of silt and soil pH, negatively correlated dissolved organic carbon and soil organic carbon and the content of sand. Soil organic carbon content could explain 51.4% of the change of DOC interception, and is the key factor affecting the ability of soil DOC interception. (3) The spectral characteristics showed that aromatic compounds and humic substances were easily adsorbed by soil, and the substances with stronger adsorption capacity could desorb hydrophilic humic substances in soil. The change of DOC spectral characteristics after leaching was determined by the chemical composition of DOC from different sources and the properties of soil organic carbon. The adsorption characteristics of eroded degraded red soil on DOC from different plant sources was mainly controlled by DOC and soil SOC properties, and this provided important reference value for further understanding the mechanism of carbon sequestration in degraded red soil.

Abstract:In this study, the vertical distributed soils from Wutai Mountain were used as the object, and the subalpine meadow soil (A), mountain meadow soil (B), brown soil (C), leached cinnamon soil (D) and calcareous cinnamon soil (E) were collected from high to low according to the vertical distribution. The distribution characteristics of Ca—SOC and Fe(Al)—SOC in soils and all level water-stable aggregates (＞2 mm, 2～0.25 mm, 0.25～0.053 mm and ＜0.053 mm) were analyzed. The results showed that: from A to E, the content of Ca—SOC in soils didn’t change significantly, while the content of Fe(Al)—SOC increased firstly and then decreased. With the decrease of aggregates′ particle size, the change trend of Ca—SOC and Fe(Al)—SOC′s content in A was opposite (the former increased firstly and then decreased, the latter decreased firstly and then increased), and decreased first and then increased in B. Also, the change trend of Ca—SOC and Fe(Al)—SOC′s content in D was opposite to that of B, which was increased firstly and then decreased. In addition, the Ca—SOC and Fe(Al)—SOC′s content in C decreased gradually, while increased gradually in E. The correlation analysis showed that the soils and ＞2 mm aggregates had a significant positive correlation between Fe(Al)—SOC and TOC, the correlation coefficient were rsoil=0.898 (P＜0.05) and r＞2 mm=0.978 (P＜0.01). The content of Fe(Al)—SOC in soils and all level aggregates was significantly higher than that of Ca—SOC, and the contents of Ca—SOC and Fe(Al)—SOC in 2～0.25 mm and 0.25～0.053 mm aggregates were significantly positive correlated. Therefore, in Wutai mountain soil, the bonding ability of Fe—Al bond and the stability of Fe—Al complex were higher than Ca—SOC, besides, the content and distribution ratio of Fe(Al)—SOC in soil and all level aggregates were significantly higher than that of Ca—SOC.

Abstract:Taking the reclaimed soil backfilled with coal ash in the Ji’ning region as the research objects, the spatial distribution characteristics of organic carbon components (WDOC, POC, MOC, LFOC, HFOC, MBC) in the reclaimed soil under three different utilization modes: garden land, cultivated land and forest land. The results showed that: (1) The total carbon (TC), soil organic carbon (SOC) and soil organic carbon density (SOCD) of the three different utilization modes were lower than the control. The sizes of TC, SOC and SOCD in different utilization modes: garden land＞forest land＞cultivated land. (2) The difference of organic carbon components between different utilization modes was significant (P＜0.05), there were significant positive correlations between the organic carbon and other components. By correlation analysis, specific gravity analysis and sensitivity analysis, the lower contents of MOC and HFOC resulted in the lower soil organic carbon in reclaimed soil than the control. (3) According to the organic carbon component enrichment index, the composition of the garden was recovered well in the 0—40 cm soil layer, the forest land recovered well in 40—60 cm, bute not so much for the recovery in cultivated land. For the composite index of 0—60 cm soil layer, it turned out that garden land＞forest land＞cultivated land. In a word, through analyzing the organic carbon composition, the best utilization mode is garden land, which is worth further promotion.

Abstract:In order to explore soil aggregates stability of sedimentation zone in front of hedgerows in purple soil area, taking purple soil under these zones as the research object, this article set 10° blank control (T1), 10° Leucaena leucocephala hedgerows (T2), 10° Vetiveria zizanioides hedgerows (T3), 15° blank control (T4) and 15° Vetiveria zizanioides hedgerows (T5). The composition of air-dried aggregates and water-stable aggregates was measured by the Savinov method. Using a series of evaluation indicators (save probability, stability index, percentage of aggregate destruction, mean weight diameter, geometric mean diameter, mean weight soil specific area, bias coefficient, peak convex coefficient), this article analyzed soil aggregates stability characteristics of sedimentation zone in front of hedgerows on different slopes and different hedgerow types. The results indicated that: (1) The number of water-stable aggregates in T2 and T3 was significantly larger than that of T1, and the T5 was slightly larger than that of T4. There was a pre-process that hedgerows could produce effect in soil conservation of steep slopes. (2) In the same slope position, the stability index of soil aggregates in sedimentation zone in front of hedgerows was: T3＞T2＞T1, T5＞T4, while PAD showed T1＞T2＞T3, T4＞T5. Compared with blank control, hedgerows showed that it can enhance effect on anti-erodibility of soil aggregates. (3) At the same slope position, the MWD, GMD and CS of air-dried aggregates and water-stable aggregates showed T3＞T2＞T1, T5＞T4, whereas the MWSSA showed opposite trend. Vetiveria zizanioides hedgerows were more beneficial to enhance the stability of aggregates than that of Leucaena leucocephala hedgerows. (4) PAD could well describe the stability of aggregates before and after wet and sieve treatment. The CS of air-dried aggregates could be used as the best index to evaluate the mechanical stability of aggregates. The MWD and GMD of water-stable aggregates could better express the water stability of the aggregates.

Abstract:The aim of this study was to investigate the effect of biochar application on the water holding capacity and fertility of the soil composited with feldspathic sandstone and sand. A pot experiment with five treatments [0 g/kg biochar (CK), 10 g/kg biochar (T10), 20 g/kg biochar (T20), 30 g/kg biochar (T30), 50 g/kg biochar (T50)] was conducted over a corn growing season. Results showed that the application of biochar significantly decreased soil bulk density, but it was not a linear correlationship between the reduction of soil bulk density and biochar application rates. Specifically, soil bulk density was the minimum with 30 g/kg biochar applied, but 50 g/kg biochar application instead increased soil bulk density. There was a positive correlation between field water capacity and biochar application rates ranging from 0 g/kg to 30 g/kg, but the application of 50 g/kg biochar decreased soil field water capacity. Soil pH, total salt content, organic matter content and available potassium content increased with the increases of biochar application rates. Soil available phosphorus content firstly increased with biochar application rate but then decreased when 50 g/kg biochar was applied. Briefly, soil pH, total salt content were 8.80, 2.51 g/kg respectively with 50 g/kg biochar applied. Furthermore, it was also found that the dry weight of maize roots, the dry weight of maize aboveground part, the 100-grain weight and the yield per plant showed a significant increase with the increases of biomass application rates ranging from 0 g/kg to 30 g/kg, but the application of 50 g/kg biochar decreased these biomass indexes significantly. Overall, the application of biochar could improve soil physicochemical properties and fertility and the growth and yield of maize, but the effect would be lowered when biochar application rate is more than 30 g/kg. Accordingly, the recommended biochar application rate is 30 g/kg to improve soil quality and crop yield under the present experimental conditions.

Abstract:Taking Mu Us sandland as the study areas, the ecological stoichiometric characteristics of wetland soils with different types and their indications were studied. Results showed that: (1) The distribution of organic carbon and total nitrogen contents appeared the same tendency, Their contents were declined with the distance from the center of the lake. (2) The vertical distribution of organic carbon, total nitrogen and total phosphorus in the sediments of the lakeside zone were declined with the depth of soil layer, their contents were in the order of 0—10 cm＞10—20 cm＞20—40 cm. The variation of total phosphorus in the sediments of the lakeside zone lagged behind organic carbon and total nitrogen, and the horizontal distribution of the total phosphorus was different from those of organic carbon and total nitrogen, but the vertical distribution was similar to the latter two. (3) Soil water and soil bulk density were the key factors influencing the nutrient distribution and the changes of C/P and N/P rations of sediments. Analysis of ecological stoichiometry characteristics showed that C/N, C/P and soil carbon storage in the area that far from the center of the lake appeared the same tendency, the tendency was related with the distance from the center of the lake. The C/N ratios of the area that closed to the center of the lake had no signification correlation with soil carbon storage.

Abstract:In order to improve paddy water and fertilizer management measures in Jianghan Plain, a field plot experiment with two irrigation regimes (conventional flooding irrigation, CF; shallow irrigation and deep storage, SIDS) and three nitrogen (N) managements (farmers' fertilization practice, FFP; 30% urea+70% controlled release compound fertilizer, 30%N+70%CRF; optimized and reduced nitrogen fertilizer application, OPT-N) was carried out to study the effects of water and fertilizer managements on losses of N and phosphorus (P), nutrition uptake of rice and nutrition accumulation of soil during different growth stages. The results were: (1) Compared with CF, SIDS reduced the irrigation quantity, total water use, runoff and leakage by 41.7%, 18.5%, 45.8% and 21.9%, respectively, but increased rainfall use efficiency by 16.2%. The amounts of total N (TN) from runoff and leakage in SIDS were 32.6%～35.9% and 22.8%～32.0% respectively lower than in CF. SIDS also decreased the amounts of total P (TP) from runoff and leakage by 36.4%～53.1% and 16.2%～33.3%, respectively. Meanwhile, the paddy runoff and leaching losses of TN and TP from re-greening to jointing and booting stages accounted for more than 70% of the whole growing season. (2) Compared with FFP, 30%N+70% CRF and OPT-N decreased runoff of TN by 19.7%～29.2% and 15.1%～25.2%, leaching losses of TN by 25.4%～51.7% and 20.9%～26.4%, leaching losses of TP by 18.4%～24.5% and 20.4%～31.6%, respectively, but no obvious difference was found in runoff of TP. (3) Considering the nutrients uptake of rice and nutrition accumulation in soil, compared with FFP, SIDS increased yield by 4.4%, but had no significant effects on N and P accumulation in soil (0-40 cm depth). Compared with FFP, 30%N+70% and OPT-N improved 5.6% and 0.4% yields respectively, and also giving the high and stable available N and available P in soil (0—20 cm depth). In generally, the combination of SIDS and 30%N+70% CRF could be effective in saving water, reducing N and P losses, promoting rice yields and improving soil fertility.

Abstract:The temporal and spatial variability of topsoil nitrogen (N) status across the different regions and soil types in Jilin province was evaluated by using traditional statistic method combines with GIS technique, based on the data of topsoil total N and alkali-hydrolyzable N in soil testing and recommended fertilization program during 2005—2013. Moreover, the historic changing trend of topsoil N status was also discussed by compared with the data obtained during the second national soil survey. Results showed that the total N content in topsoil ranged between 0.4 and 3.9 g/kg with a mean of（1.62±0.60）g/kg, and the alkali-hydrolyzable N content ranged between 15 and 360 mg/kg with a mean of（145.0±59.5）mg/kg in the present Jilin province. The total N and alkali-hydrolyzable N contents in topsoil showed same oeders among the various soil types, these were highest in dark brown soil with the values of（2.02±0.57）g/kg and（190.2±72.8）mg/kg, and followed by albic soil, paddy soil, black soil, meadow soil, chernozem, and aeolian sandy soil. In view of the province as a whole, the spatial distribution of N status in topsoil was characterized by being high in the east and low in the west, and a positive and significant correlation was shown between the total N content and the alkali-hydrolyzable N content in the county scale. Compared with the second soil survey, the total N and the alkali-hydrolyzable N contents in topsoil showed obviously ascending trends in the scale of whole Jilin province, the change magnitude of topsoil N status were mostly significant in the central region but relatively low in the west region. The great discrepancies were also observed in the change trends of topsoil N status among various soil types. Of which, black soil, chernozem, meadow soil, and aeolian sandy soil showed increasing trends, while dark brown soil, albic soil, and paddy soil showed decreasing trends. Compared with other soil types, the increasing magnitude was significant in aeolian sandy soil, and the decreasing magnitude was significant in dark brown soil. In conclusion, there were enormous differences in spatial distribution and historic change in the N status of cropland topsoil in Jilin province. Based on the temporal and spatial characteristics of topsoil N status between regions and soil types, we suggested that N fertilizer rate in crop production should be strictly controlled in the major grain producing areas of the central region to improve N use efficiency and reduce environmental risk, and crop N fertilizer management should be improved according to local conditions in the east and west regions to enhance soil fertility and to achieve high yield and high efficiency.

Abstract:In order to clarify the input threshold of nitrogen fertilizer in the wheat season in Chaohu Lake Basin, the effects of different nitrogenous fertilizer levels (treatments of N0, N1, N2, N3, N4 and N5, applicated 0, 157.5, 210.0, 262.5,310.0,420.0 kg/hm2) on yield, nitrogen accumulation in plant, nitrogen utilization, residual inorganic nitrogen amount in 0—20 cm soil and nitrogen loss in runoff were studied. At the same time, regression model was used to fit the correlation between them. The results showed that: (1) Compared with no nitrogen fertilizer, nitrogen fertilizer increased wheat yield, and the yield increased by 64.8% in the treatment of N3, which was the maximum. While, wheat yield declined when applying nitrogen fertilizer over 290.9 kg/hm2 through the analysis used quadratic function. (2) Nitrogen accumulation in plant and nitrogen use efficiency both showed a trend of increasing first and then decreasing with the increasing of nitrogen application, and when the actual nitrogen application amount was 296.6 kg/hm2, the nitrogen accumulation amount in the aboveground of wheat was the highest, and nitrogen utilization efficiency was the highest when the nitrogen application was 158.5 kg/hm2. (3) With the increasing of nitrogen application amount, the residual inorganic nitrogen in 0—20 cm soil and the nitrogen loss in runoff both increased gradually, but there was no significant change before nitrogen application amount was 310.0 kg/hm2. However, when the application amount reached 420.0 kg/hm2, the residual amount of inorganic nitrogen and nitrogen in runoff changed obviously, with an average accumulation amount of 67.0 kg/hm2 and an average loss rate of 8.3 kg/hm2. Therefore, when the nitrogen application amount was too high, it would increase the risks of soil inorganic nitrogen residues and nitrogen loss in runoff, and cause pollution to the environment. Combined with soil fertility conditions in Chaohu Lake, considering the effects of integrated fertility test and application amount on wheat yield, nitrogen accumulation in plant, nitrogen use efficiency, residual inorganic nitrogen in soil and runoff loss in this study, we thought the input threshold of nitrogen fertilizer was 157.5 to 262.5 kg/hm2.in Chaohu Lake Basin.

Abstract:A field experiment was carried out in rice planting field in Northeast China, to investigate the effect of controlled release nitrogen fertilizer side strip application on rice yield and nitrogen losses. Five treatments were set up, including no nitrogen fertilizer as control (CK), farmer conventional fertilization (FP), high amount controlled release nitrogen fertilizer (HN), medium amount controlled release nitrogen fertilizer (MN), and low amount controlled release nitrogen fertilizer (LN). The effects of controlled release nitrogen fertilizer side strip application on rice yield, nitrogen recovery rate, agronomic efficiency, runoff loss, and total nitrogen concentration in leaching water at different levels were studied. Results showed that the grain yield in HN treatment and MN treatment that reduce 10% to 20% nitrogen fertilizer use show no significant change compared with that in FP treatment. The number of spikes and grain number per spike in HN treatment were 10.79% and 15.38% higher than that in FP treatments, respectively. When the nitrogen fertilizer was reduced by 30% (LN treatment), the grain yield of rice was significantly decreased. In HN treatment, the recovery rate of nitrogen fertilizer increased by 5.23%, and the agronomic efficiency of nitrogen fertilizer was 6.48 kg/kg higher than that in FP treatment. Compared with the FP treatment, controlled release nitrogen fertilizer Side Strip Application treatments reduced the total nitrogen concentration and runoff loss in surface water, nitrogen loss reduction rate in HN treatment, MN treatment and LN treatment varied between 37.32%～47.10%. Controlled release nitrogen fertilizer Side Strip Application can reduced the risk of nitrogen losses, delayed both the total nitrogen concentration in the leaching water and the peak time of the total nitrogen concentration, .and be considered as an environment-friendly fertilization technology that takes rice yield into account.

Abstract:The apparent surplus and deficiency of soil N in winter wheat-summer maize rotation were investigated under different N application rates (N0, N100, N180, N255, N330) in consecutive six years in Qingyuan, Hebei. Results showed that the cumulative apparent nitrogen balances changed from the deficit in N0 and N100 treatments to the surplus in N180, N255 and N330 treatments, which reached up to 382, 1 173 and 2 116 kg/hm2, respectively. The large annual variations of the apparent N balances were found, but the differences of the N balances between the two crops were small, which were 155 kg/hm2 and 134 kg/hm2, respectively. Meanwhile, it was observed that the apparent soil N balances were negatively correlated with the changes of soil inorganic N and the precipitation, but positively correlated with N application rates. In addition, the apparent soil N surplus in the earlier stage and deficit in the later stage during the growing seasons of winter wheat and summer maize were observed. These findings above indicated that reasonable N recommendation should be established from two aspects including soil apparent N balance and N allocation within a growing season.

Abstract:In this study, Luanhe basin was chose as the study area, and sensitivity analysis and double mass curve were used to analyze the effects of climate change and human activities on runoff. The results showed that the runoff in Luanhe basin decreased obviously, and the runoff in the change period (1980—2000) decreased 52.59 mm (50.43%) compared with the reference period (1956—1979); the sensitivity coefficients of runoff to precipitation and potential evapotranspiration were 0.336 1 and -0.123 5, respectively; in this change, the impact of climate change was 22.23 mm, while the impact of human activities was 32.07 mm and accounted for 57.26%, which was far greater than the climate change (39.69%).The human activities were the main impact factors causing the decrease of runoff in the Luanhe River basin.

Abstract:In order to reveal effects of calcium fertilizer application and different fertilizer application on the improvement of available Ca2+ and calcium-activation on acid soil of coastal areas, experiments were conducted from 2015 to 2016 to study the effects of different fertilizer applications on available calcium content, plant characters, pod yield and kernel quality of peanut. Six treatments were single inorganic fertilizer (CK1), inorganic/slaked lime fertilizer (T1), inorganic/organic fertilizer (CK2), inorganic/organic/slaked lime fertilizer (T2), inorganic/organic/microbial fertilizer (CK3), and inorganic/organic/microbial/slaked lime fertilizer (T3). The results showed that both CK2 and CK3 could increase the content of water soluble calcium and exchangeable calcium when compared with CK1 in some degree, for example, the average content of water soluble calcium in 0—20 cm soil layer at different growth stages increased by 48.13% and 66.50%, and the average content of exchangeable calcium increased by 39.12% and 60.88%, respectively. Calcium fertilizer treatments, such as T1, T2 and T3, significantly improved the water soluble calcium and exchangeable calcium content, but T1 showed less effect on their increase than T2 and T3. Among which, The average content of water soluble calcium and exchangeable calcium in 0—20 cm soil layer at different growth stages of T3 increased by 163% and 174% compared with CK3, respectively. These results showed that the organic fertilizer and the microbial fertilizer could significantly improve the calcium-activation in acidic soil. Different fertilizer applications significantly increased the main stem height, branch number, leaf number of main stem, dry weight per plant, leaf area index and the plant number per unit area. Different fertilizer applications also significantly increased the pod yield by increasing the pod number per plant and pod plumpness, and the treatments also improved the content of protein, total amino acids and fat, and increased O/L values. Compared with CK3, T2, CK2, T1 and CK1, the yield of T3 increased by 14.38%, 4.99%, 18.31%, 25.65% and 52.52%, and the kernel quality of T3 was the best. Calcium fertilizer combined with organic and microbial fertilizer could increase the calcium activation degree and effective calcium content, and significantly increase the pod yield and kernel quality of peanut on acidic soil.

Abstract:In order to understand the decomposing mechanism of the straw returning to field under rotary tillage, the different treatments based on amounts of straw returning were set up. Soil microbial biomass, soil enzymes activities and available nutrients contents were measured at maize jointing stage, male stage, middle maturity stage and mature stage respectively. The results showed that: (1) The straw returning could promote the soil microbial reproduction, increase the soil enzymes activities and the content of alkali hydrolyzable nitrogen, but decrease the contents of available phosphorus and available potassium. The number of fungi, bacteria, actinomycetes and sucrase and cellulase activities increased substantially under the straw returning amount of 11 250 kg/hm2. Urease and phosphatase activities and the contents of alkali hydrolyzable nitrogen increased under 7 500 kg/hm2, but the available phosphorus and available potassium decreased. (2) There were positive correlations between the number of soil fungi, bacteria, actinomyces and cellulase activity, but the fungi quantity was negatively related to phosphatase activity after planting for 40 days. Actinomycetes quantity was positively related to phosphatase and sucrase after 60 days, and related to sucrase after 140 days. (3) There were correlations among the soil enzymes activities. Urease was positively related to cellulose, and phosphatase was positively correlated with sucrase in 67 days. Sucrase was positively related to cellulose, and urease was negatively related to sucrase and cellulose in 140 days. (4) There were correlations between the soil enzymes activities and the available nutrients contents. Urease in 40 days and 112 days, cellulase in 67 days, phosphatase in 112 and 140 days had positive correlations with alkali hydrolyzable nitrogen contents.

Abstract:A kind of tetracyclines-oxytetracycline was used as target pollutant to analyze the potential influences of veterinary antibiotics pollution on maize growth. A potted maize experiment was conducted to study the influences of oxytetracycline-contained soils on the biomass, photosynthesis parameters and antioxidant enzymes during the growth stage of maize in the soils with different substrates: microbial inoculants(JF), mushroom bran (JK), wormcast (QY), and biomass charcoal (S) etc. with the single and combined application. The results showed that oxytetracycline had a greater inhibiting effect on the roots of maize than on the aboveground. The length and dry weight of maize roots under the treatments of JK, microbial inoculants+wormcast (JQ), microbial inoculants +biomass charcoal (JS) increased by 9.1%,9.4%,13.7% and 66.46%，183.4%，46.72% respectively than the OTC treatment. The addition of substrates reduced the inhibiting effect of Oxytetracycline on the net photosynthetic rate, stomatal conductance and transpiration rate of maize effectively. JK increased the chlorophyll contents in three stages of maize, the increases in seedling, jointing and maturation stages were 7.78%, 33.33% and 12.03% respetively. The CAT and POD activities under JS increased by about 48% and 43.2% than the OTC. The addition of S, JQ and JK reduced the proline contents by 59%, 16.5% and 55.4% respectively than the OTC in the seeding, jointing and maturation stages. In general, doxycycline had an obvious inhibiting effect on maize growth, but adding different substrates could alleviate the adverse effects on maize’s physiological traits. The addition of JK, JS, S）and JQ had significant positive effect on maize’s growth. These findings provided the theoretical basis for screening the substrates that could reduce antibiotics’ influences on maize’s growth, as well as for the assessment of oxytetracycline risk to crops.

Abstract:In order to select the optimal concentration of dazomet for old apple orchard soil fumigation, a pot experiment was carried out. The pot experiment was designed to have 4 concentration treatments, i.e. Treatment CK(0, untreated old orchard soil), Treatment T1(0.02‰), Treantment T2(0.1‰), Treatment T3(0.5‰). All the pots in the experiment were filled up with the same soil from a 25 years old apple orchard. And the dynamic change of soil culturable microorganisms number(bacteria, fungi), community structure and diversity index under different concentrations dazomet fumigation was studied using microorganisms plate culture, a real-time quantitative PCR（qPCR）, biolog-Eco and terminal restriction fragment length polymorphism (T-RFLP) methods.The results showed that the soil microorganism number significantly decreased with the increase of applying dazomet content. At 30th day, compared with the control, the (T1, T2, T3) bacteria number reduced by 57%, 81% and 87%, the fungi number reduced by 75%, 81%, 100%. The gene copy numbe of Fusarium proliferatum which analysised by Real-time PCR was reduced by 57%, 80%, 85%. Biolog-Eco showed microbial activity (using the average well development, AWCD) recovered gradually in the soil after fumigation, but the applied concentration was higher, the recovery speed was slower. At 30th day, AWCD of T1(0.02‰) significantly lower than that of CK, the processing AWCD had no difference with CK when 60 days, but AWCD of T3(0.5‰) was still significantly lower than that of CK until 90 days. T-RFLP principal component analysis showed that all treatments changed the soil microbial community structure in old apple orchard. Dazomet concentration was greater, the more significant change of microbial community, but community structure was not very stable under high concentration of dazomet fumigation. Cluster analysis showed that the community structure of T1 and T2 became more and more similar to that of CK over time, while the community structure of T3(0.5‰) always kept low similarity with CK. Microbial diversity analysis showed that Shannon index and Margalef index of T3(0.5‰) significantly reduced, Simpson index improved. In conclusion, 0.5‰ dose of dazomet fumigation could significantly reduce microbial number and activity, change the microbial community and slow the recovery of microorganisms.

Abstract:In order to find out the effects of mild salt stress on photosynthetic physiology, growth index and yield of cotton under drip irrigation, six different salt stress (CK: 1.5 g/kg, T1: 3.0 g/kg, T2: 4.0 g/kg, T3: 5.3 g/kg, T4: 6.2 g/kg, T5: 7.3 g/kg) were applied in barrel cultivated cotton, and the changes in physiological growth and yield were studied to provide the theoretical basis for cultivation and management of cotton in salinity soil. The results showed that with the increase of salt stress and the extension of stress time, the photosynthetic physiological indexes of cotton showed a downward trend (P＜0.01). The effect of T1 and T2 on cotton net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO2 concentration (Ci) and leaf water use efficiency (WUE) were not significant (P＞0.05), while the effect of T3, T4, and T5 on photosynthetic physiological indexes showed significant inhibition (P＜0.05); Pn, Tr, Gs, and Ci in early growth under salt stress were decreased, and Ls value increased with increasing salt stress. Pn, Gs, and Ls in the opening stage were less than in the bud stage, and Ci was greater in the opening stage than in the bud stage. Plant height and leaf area in the early stage was significantly affected by salt stress, increased rapidly in the later stage in T2 and T3, and maximized in T3. Compared with CK, T1 and T2 did not affect yield, cotton boll number per plant, and boll quality, but the yield in T3 decreased rapidly. Through the sub salt tolerance function, the salt critical value of cotton in the whole growth period of 0—40 cm soil was 5.441 9 g/kg (St), and the salt tolerance limit was 44.201 6 g/kg (S0). Yield had a good fitting degree with Pn, WUE, plant height (H), and leaf area (S), the correlation coefficients were 0.69, 0.73, 0.50 and 0.72, respectively. In conclusion, mild salt stress led to the photosynthetic rate decline of cotton through stomatal limitation in growth stage, and through non stomatal limitation factors in late growth stage compared with moderate and severe salt stress. Photosynthetic parameters and salt stress degree were closely related, and cotton yield and photosynthetic indexes showed a good correlation.

Abstract:In this paper, five different contents of Bacillus subtilis (0, 1, 3, 5, 7 g/kg) were setted, aimed to study the effect of B. subtilis on evaporation of soil surface and water and salt distribution in saline-alkali soil. The results showed that: (1) With the application of B. subtilis, the cumulative evaporation and evaporation rate in saline-alkali soil decreased obviously, comparing to that in control soil columns, especially after the initial 2 days. The cumulative evaporation and evaporation rate of soil with different B. subtilis content (0, 1, 3, 5, 7 g/kg) was smaller than that without B. subtilis application, and reached smallest when B. subtilis content was 3 g/kg. In the 41st day after evaporation, the cumulative evaporation of treatments with 1, 3, 5 and 7 g/kg B. subtilis were decreased by 16.63%, 21.39%, 11.26% and 5.96% compared with that in 0 g/kg, and the variations between the treatments were significant (P＜0.05). (2) Both Black and Rose model could fit soil evaporation process well with different B. subtilis contents. For the Black evaporation model, with the increase of B. subtilis contents, evaporation parameter B firstly decreased and then increased compared with the control treatment (P＜0.05). For the Rose evaporation model, with the increase of B. subtilis contents, stable evaporation parameters C and moisture diffusion parameter D firstly decreased and then increased, which were obviously less than the treatment received 0 g/kg B. subtilis (P＜0.05). When the B. subtilis was 3 g/kg, the minimum values of C and D were obtained, which further confirmed that B. subtilis could increase soil water holding capacity. When the B. subtilis content were 1, 3, 5 and 7 g/kg, the water contents were greater than that in the control. (3) At the depth of 6 cm, the water content in the treatments with B. subtilis of 1, 3, 5 and 7 g/kg increased by 28.24%, 37.40%, 20.00%, 6.87% respectively, compared with that in the control. (4) Soil salt contents were also significantly decreased with the application of B. subtilis. The salt content in the treatments with B. subtilis of 1, 3, 5 and 7 g/kg decreased by 32.26%, 46.89%, 26.34%, 14.65% respectively, compared to that in the control. (5) After applying B. subtilis, the soil residual water content θr, saturated water content θs and coefficient associated with intake value α were all increased and shape coefficient n was decreased in van Genuchten equation. In summary, application of 3 g/kg B. subtilis could inhibit salt and improve soil water holding capacity in saline-alkali.

Abstract:To optimize the management practices during the transition period "Grain for forage" in North China, the production potentials of biomass and crude protein and the ammonia (NH3) emissions under 4 different rotations were investigated with field experiment. A field experiment including 5 crop rotations was conducted, of which the traditional winter wheat-summer maize rotation (W-SuM) was considered the reference to evaluate the production potentials of biomass and crude protein in other rotations such as ryegrass -summer maize (R-SuM), ryegrass-spring maize (R-SpM), ryegrass-double summer maize (R-DM) and double summer maize (DM), and their NH3 emissions were also measured in situ with Draeger-tube method (DTM). Results indicated that among the 5 crop rotations, the R-DM rotation had the greatest biomass (31 012 kg/hm2) and crude protein (2 529 kg/hm2) production, which were 14.3% and 8.2% greater respectively than those in the W-SuM rotation. The annual NH3 volatilizations from these rotations ranged from 13.43 to 23.77 kg/hm2, accounting for 4.2%～5.6% of their N applications, which were both in an order of R-DM＞W-SuM＞R-SpM＞R-SuM＞DM. Meanwhile, the seasonal distributions of NH3 emissions under different rotations differed, e.g. the contribution of NH3 volatilization in summer season in DM rotation was much greater than those in other rotations. The ryegrass-double summer maize rotation was high likely to produce the greater biomass and crude protein.

Abstract:The sedimentary, aqueous phase and suspended particles were collected from 29 landscape waters in the main urban area of Wuhu. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the samples were measured. The concentration distribution characteristics of PAHs and the correlation with organic carbon (TOC) and black carbon (BC) were also studied. The characteristic ratio method and PMF were used to analyze the source of PAHs in the samples. Effect internal method and risk entropy method were applied to evaluate the ecological risk. The results showed that the PAHs concentrations in sedimentary, aqueous phase and suspended particles, ranged from 43.48 to 6 388.40 ng/g, from 0.08 to 52.23 ng/L, and from 2.46 to 60.46 ng/L, respectively, with the average concentration of 1 307.47 ng/g, 8.60 ng/L, 13.71 ng/L respectively. The correlations between PAHs and TOC and BC were evident, especially in middle and high molecular homologues, and the correlation with BCCr was the most significant. The PAHs of landscape water in Wuhu came mainly from biomass and coal combustion, and partly from the combustion of petroleum substances and oil pollution. The PMF revealed that biomass combustion reached up to 50.66% for sedimentary and 52.51% for suspended particles and aqueous phase. The ecological risk assessment showed that the landscape water in Wuhu was in the middle pollution level, which should be taken seriously. These findings provided the scientific basis for the management of urban water pollution.

Abstract:Coal gangue is always used as a soil amendment to improve the poor soil. However, in this study, coal gangue was used as an amendment to phytoremediate the copper mine tailings. Based on the pot experiment, coal gangue was added into the copper mine tailings at the ratio of 0, 1%, 2.5%, 5%, 10% and 15% respectively, and the physical and chemical properties of amended tailings and the growth and physio-ecological characteristics of Vetiveria zizanioides were measured. Results showed that application of coal gangue increased the pH value, organic matter and nutrition elements contents and decreased the available heavy metals contents (Cd, Cu, Pb and Zn) in amended tailings, which improved the poor condition of copper mine tailings. With the increasing addition rates of coal gangue, heavy metals contents in the plant were decreased, biomass and photosynthetic pigments were increased first and then decreased. Meanwhile, soluble protein and proline contents were increased with the increasing addition rates of coal gangue, but MDA contents were decreased. Low addition of coal gangue selectively increased the activities of SOD and CAT, which alleviated the oxidative stress. To sum up, addition of coal gangue into copper mine tailings could stabilize the available heavy metals, and would increase the resistance ability of Vetiveria zizanioides to cope with the harsh environment within a certain addition limit.

Abstract:In order to explore the response mechanism of Brassica campestris to the Cd2+, Pb2+ single and combined stress (Cd2+—Pb2+), a culture room experiment was conducted, where the Brassica campestris seedlings were treated with different concentrations of Cd2+ and Pb2+. The biomass, the content of antioxidant defense enzyme activities [i.e., peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) activities] and malondialdehyde (MDA), and the enrichment of heavy metal ions were measured. In addition, the metallothionein gene BcMT2a which was associated with heavy metal enrichment was cloned and its expression was also analyzed. The results were as follows: except the low concentration of Cd2+ (10 mg/L), which could promote the root length and aboveground growth of Brassica campestris, both the Cd2+ and Pb2+ single and combined stress could inhibit the development of root length and the growth of aboveground of Brassica campestris. And with the increasing concentrations of heavy metal ion, the inhibition effects were gradually strengthened. The order of inhibition effects of heavy metal ions was Pb2+＞Cd2+—Pb2+＞Cd2+. In the antioxidant enzyme system, POD and SOD activity were higher, and showed a trend of increasing first and decreasing then, as well as CAT activity. MDA content reached the maximum when Cd2+ concentration was 40 mg/L. The order of heavy metal ions accumulation in the organs of Brassica campestris was root＞stem＞leaf. The protein encoded by BcMT2a gene is a hydrophathy and mutant protein predominantly present in the nucleus. In a certain concentration rage, the relative expression of BcMT2a increased with the increase of Cd2+, Pb2+ and both combined concentrations, and the trend of relative expression was consistent with the result of the antioxidant enzyme system. These findings indicate that the antioxidant enzyme system and BcMT2a have a clear response under the different concentrations of Cd2+, Pb2+ and Cd2+—Pb2+ in Brassica campestris, and they can increase the tolerance of Brassica campestris to Cd2+ and Pb2+ stress.

Abstract:To analyze the desorption characteristics of aluminum in planosol soil with aluminum pollution, balanced oscillating method was applied to study the aluminum desorption behavior and the influence of different factors in planosol soil. The results showed that the aluminum desorption in planosol soil reached equilibrium after 720 min. At 25 ℃, the content of soil organic matter was 42.2 g/kg, and the desorption capacity of aluminum in planosol soil was only about 1.5% of the adsorption capacity. The Langmuir equation fit well on the desorption isotherm of aluminum in planosol soil (r=0.985 9**) and showed that the surface uniform monolayer dominated desorption. The thermodynamic parameters ΔG＜0, ΔH＞0, ΔS＞0 indicated that the aluminum desorption was a spontaneous, endothermic, and entropy increase process. The content of soil organic material decreased from 42.2 g/kg to 27.8 g/kg, the maximum desorption of aluminum in planosol soil increased from 25.87 mg/kg to 66.11 mg/kg, and the phenomenon of desorption hysteresis was enhanced. When the pH dropped to 3, the aluminum desorption capacity rapidly rose to 226.4 mg/kg, which was 8 times more than that at pH 5～7. With the increased concentration of NaCl and Na2SO4 in the desorption solution, the desorption capacity of aluminum also increased. In a word, the desorption capacity of aluminum that absorbed into planosol soil was relatively weak, but the desorption capacity of aluminum greatly increased, and the risk of pollution sharply increased with the decreased pH and the content of organic matter, and the increased content of inorganic salt.

Abstract:In order to provide evidence for the fine synthesis and scientific application of urea-formaldehyde (UF), the study was to investigate the relationships between the nutrient release characteristics of UF and the driving factors, and the effects of optimized products on rape (Brassica campestris L.) growth. The response surface methodology was used to investigate the response of urea formaldehyde molar ratio (U/F), temperature and time to the slow available nitrogen and activity index (AI) of UF. Meanwhile, the nitrogen (N) release rate of UF and soil N supply were measured in the rape pot experiment. The results showed that the quadratic polynomial mathematical model of the slow available N and AI of UF were established and both of them were significant. The slow available N and AI of UF fertilizer were mainly affected by U/F (X1), followed by reaction time (X2). The optimal parameters for UF production, which with the highest AI and maximum slow available nitrogen content were: U/F 1.48, reaction temperature at 45.26 ℃ and reaction time for 1.71 h. Under these conditions, the slow-release effective nitrogen reached 12.63%, with AI as 67.86%. Meanwhile, the N release rate of UF in soil was slowly and soil inorganic N contents were increased with UF fertilization, especially in the later rape growth period. Compared with treatments of urea at the same rates of N application, the mixture of urea application and UF at 7∶3 ratio increased rape yields by 23.93%～24.50%. However, nearly the same yield occurred with single fertilization of UF. Moreover, even the rate of N application was reduced 20%, the mixture treatment still increased the rape yield by 8.38% compared to the high amount urea treatment. Eventually, the mixture of Urea and UF, were the best mode for gaining greatest yields of rape and higher N use efficiency.

Abstract:In order to investigate the water conservation function of litter and soil in typical forest lands and provide the basis for tree species selection and stand improvement by functional orientation in Gully region of Loess Plateau, the Robinia pseudoacacia L., Pinus tabulaeformis, and mingled forest were chosen as subjects in this article at Caijiachuan watershed in Ji County of Shanxi province in 2017. The water conservation function was studied by quantitative research with Immersion method and cutting-ring method applied to litter and soil in typical forest lands. The results showed: (1) The total litter storage capacity of the three kinds of forest lands ranged from 105.49 to 148.38 t/hm2, and the storage capacity of semi-decomposed litter was higher than that of undecomposed litter. The total litter thickness of mingle forest composed with R. pseudoacacia L. and P. tabulaeformis was the highest as 3.8 cm, the second was R. pseudoacacia L. forest as 3.6 cm, while the Pinus tabulaeformis was the lowest, 3.4 cm. (2) By analyzing the rules of maximum water-holding capacity and maximum water-holding rate, the mingle forest was the highest and the R. pseudoacacia L. and P. tabulaeformis was the second and the third respectively, the values were 117.99 t/hm2 and 387.12%, 106.19 t/hm2 and 324.31%, 82.86 t/hm2 and 305.76%, respectively. (3) The effect interception amount and the effect interception rate of litter in broad-leaf forest was more than that in coniferous forest. The effect interception amount ranged from 83.66 to 195.72 t/hm2, and the effect interception rate ranged from 121.75% to 292.21%. The relationship between the water-holding capacity and the immersion time fitted Logarithmic Function, and the relationship between the water-absorption rate and the immersion time fitted Exponential Function. (4) The average of soil bulk density of three kinds of forest land ranged from 0.99 to 1.01 g/cm3, and the total soil porosity varied from 49.39%～50.09%, and the soil water-holding capacity varied from 32.99～81.73 t/hm2. By analyzing soil infiltration rate and infiltration time, we found that there is a power function relation between them. Considering the water-holding abilities of the litter and soil of three kinds of forest lands, the water conservation abilities of the mingle forest was the highest, while that of the P. tabulaeformis was the lowest. Therefore, the existing R. pseudoacacia L. and P. tabulaeformis forest should aim at mingle forest in the stand improvement.

Abstract:Evergreen broad-leaved forest is well-preserved, and is playing an irreplaceable role in water conservation and ecological regulation in forest areas in Mid subtropical zone. In order to investigate the canopy interception and allocation and evaluate forest hydrological function and benefit of the evergreen broad-leaved forest in mid subtropical area quantitatively, positioning experiments were implemented during two rainy seasons of from 2016 to 2017 in Mopan Mountain national nature reserve. The amount of throughfall, stemflow and precipitation were measured and interception loss was subsequently calculated. Based on the observations of 26 rainfall events, canopy interception process of evergreen broad-leaved forest was simulated using the modified Gash model. The results showed that most of the observed rainfall had the low intensity, low duration and moderate rain. The amount of rainfall, throughfall, trunk flow and canopy interception were 994.07 mm, 562.90 mm, 16.90 mm and 406.40 mm, respectively, during the study period. According to the modified Gash model, the simulated amounts of throughfall, stemflow and canopy interception were 548.63 mm, 21.75 mm, 403.28 mm, respectively, and their relative error were 2.60%, 22.29% and 3.34% respectively compared to the measured. The results of sensitivity analysis showed that the sequence of simulated results of canopy interception from large to small was c, , S, , St, Pt.

Abstract:Astragalus membranaceus could accumulate selenium (Se) generally, but the uptake and translocation Se in this plant are still not clear. The soil pot experiment was conducted to explore the effects of different concentrations (0, 2, 4, 6, 8 mg/kg soil) as sodium selenite (SeIV) and sodium selenate (SeVI) added in soil on Se uptake, translocation and accumulation in Astragalus membranaceus. The results showed that the application of Se at the rate of 2～6 mg/kg as SeIV increased the shoots and roots dry weights of Astragalus membranaceus by 34.55%～38.24%,, compared to the control, whereas the application of Se with more than 2 mg/kg as SeVI inhibited the growth of Astragalus membranaceus. Moreover, the application of different concentrations Se as SeVI and SeIV increased Se concentrations in the shoots and roots, and there were the significant and positive relationships between Se concentrations added in soil and that in plants (SeVI: r=0.884**; SeIV: r=0.973**). With the increasing of Se application rates, the Se uptake capacity of Astragalus membranaceus was higher than the control, and the bioaccumulation factors and transfer factors were more than 1, and Se concentrations in plant shoots were higher than those of roots, which indicated that exogenous Se might improve the uptake and transport of selenium in Astragalus membranaceus. In conclusion, sodium of selenite and selenate added in the soil with pH＞7.0 could enhanced the uptake, transport and accumulation of Se in Astragalus membranaceus, and the application of 2～6 mg/kg in soil would be better for the growth of this plant and Se accumulation in the shoots and roots.