Abstract:The impact of agricultural non-point source pollution on environmental safety has surpassed urban living pollution and industrial pollution, and has become the main source of water pollution. The vegetation buffer zone can effectively intercept agricultural non-point source pollutants and reduce the discharge of pollutants into water bodies. Through the collection of domestic and foreign scholars' research results on buffer zones, this paper summarized the research on the ability of buffer zone to reduce agricultural non-point source pollution and the optimal width of buffer zone. The results showed that:(1) The 5 m herb buffer zone had the best interception effect on pollutants. When the buffer zone width exceeded 5 m, it was recommended to use the grass-blown buffer zone, which needed more than 30 m to function. (2) When the buffer zones width was the same, the suspended matter and phosphorus were more easily to be intercepted than nitrogen. The optimal width of the buffer zone for the suspension and phosphorus removal was recommended to be 15 m (reduction rate of 70% or more). But for nitrogen removal, the recommended width was 30 m (the reduction rate was 80%). (3) The interception of pollutants by vegetation buffer zone was affected by many factors such as buffer width, slopes and vegetation types. But the relationships between buffer zone width and reduction rates was not always proportional. When buffer zone width increased to a certain size, the reduction rates of pollutants would not change significantly. The slopes of the buffer zone were not always inversely proportional to the reduction rates. A slight slope could promote runoff infiltration and thus increase the reduction rates of the buffer zone.

Abstract:Based on the observed data on runoff plots of Anjiagou watershed in 2014-2016 in Dingxi City, Gansu Province, the effects of vegetation types and rainfall regimes on slope erosion and sediment yield were studied. The results showed that:the erosive rainfall could be classified into three patterns:pattern A was an aggregation of rainfall events with short duration and medium to high intensity, pattern B with moderate rainfall and low intensity, and pattern C with heavy rainfall and low intensity. The rainfall frequency of runoff and sediment generation was pattern B > pattern C > pattern A. The runoff coefficients of pine forest (6.915%~9.379%), wheat field (5.838%~9.034%) and alfalfa land (6.610%~9.671%) were 1.7~2.5 times than that of ice grassland (2.724%~5.246%) and 2~3 times of seabuckthorn forest (2.296%~3.863%) respectively. The runoff coefficient of pattern A was greater than those of pattern B and C. Pattern B and C were the main rainfall patterns of runoff generation. Annual average amount of soil loss was as followed:wheat field (1.478~3.478 t/hm²)>alfalfa land (0.558~2.079 t/hm²)>pine forest (0.459~0.887 t/hm²)>ice grassland (0.097~0.253 t/hm²)>seabuckthorn forest (0.012~0.038 t/hm²). The amount of soil loss of wheat fields was 3~5 times than that of pine forest, and 14 times of ice grassland, reached 123, 130 and 92 times of that of seabuckthorn forest at the slope gradient of 10°, 15° and 20°, respectively. The contribution rate of pattern C to sediment yield of pine forest was the largest, pattern B was the second, and pattern A was the smallest. The contribution rates of pattern A to sediment yield of seabuckthorn forest reached 79%~86%. So high intensity and short duration rainfall was the main rainfall pattern causing soil loss in seabuckthorn forest. The contribution rates of pattern A to sediment yield increased with the increases of slope gradients in wheat field and alfalfa land. At the slope gradient of 20°, rainfall with medium to high rain intensities was the main rainfall pattern causing soil loss. There was a very significantly positive linear correlation (P<0.01) between the runoff depth and the amount of soil loss in wheat field, alfalfa land, pine forest and ice grassland, and the increment speed of soil loss was:wheat fields > alfalfa land > pine forest > ice grassland. At the same time, the increment speed of sediment yield was accelerated as the slope gradients increased. These findings could provide theoretical basis for building the soil erosion prediction model and important practical significance to scientifically guide the allocation of soil and water conservation measures on slope land.

Abstract:Based on one-dimensional vertical infiltration experiments, we studied the effects of thickness of gravel (0, 3, 6, 9, 12 cm) on water infiltration and redistribution in water repellent soils with constant bulk density, and the infiltration process were simulated using different models. The results showed that the migration distance of the wetting fronts were increased significantly (p<0.05). Within the same period, all the cumulative infiltrations, which were positively correlated with the thickness of gravel, were higher under gravel covered treatments than that of the control group (p<0.05) in water repellent red soil. Both the stable infiltration rate and initial infiltration rate of the water repellent red soil could be described by exponential function with the thickness of gravel cover, and the coefficients of determination were 0.91 and 0.87 respectively. Compared with the control group, the gravel cover increased the stable infiltration rate and initial infiltration rate of water repellent tidal soil, the stable infiltration rate had a quadratic relationship with the thickness of gravel, the coefficient of determination was 0.78. The stable infiltration rate reached the maximum when the thickness of gravel was 6 cm. The water content in the section of water repellent soils was increased, with the largest increases of 180.8% and 57.6% respectively in red soil and tidal soil. Under the condition of isolated evaporation, the water contents of the upper layer in the water repellent soil under different thicknesses of gravel cover (above the wetting front) showed:stop infiltration > redistributed for 1 day > redistributed for 3 days > redistributed for 7 days. Horton infiltration model had the best fitting effect on water repellent soil infiltration under gravel cover, which made it suitable to analyze and predict the infiltration process in water repellent soils under gravel cover.

Abstract:Effects of short-duration rainstorm and slope gradients on the runoff and sediment yield were studied in bare iron tailings slope using the indoor artificial rainfall simulation method. The results showed that:(1) Under different rainfall intensities, the runoff, sediment yield, and runoff sediment content of different slope gradients show a dynamic trend with the increase of rainfall duration. The difference was that the runoff gradually stabilizes after 15~24 minutes. (2) Under different rainfall intensities, the relationship between runoff, sediment yield, and slope gradients of bare iron tailings slope had a critical rainfall intensity, and the range of this critical rainfall intensity was about 90 mm/h, and the range value of specific critical rainfall intensity needed further studies and determination. (3) Under different rainfall intensities, the sediment yield and runoff sediment content between different slope gradients increased with the rainfall intensity, and the relationship between them and slope gradually changed from negative correlation to positive correlation. (4) When the rainfall intensity increased from 60 mm/h to 120 mm/h, the runoff and sediment yield with rainfall intensity under different slope conditions showed a generally gradual upward trend, and there were local special cases. When the slope increased from 25° to 35°, the relationship between runoff and sediment yield under different rainfall intensities was not obvious; but under the same slope gradient condition, the runoff and sediment yield basically increased with the increase of rainfall intensity. The research results provide reference for the study on the mechanism of rainfall intensity and slope on the abortion sand production of bare iron tailings.

Abstract:Based on the rainfall data from 1989 to 2016 in Suining Soil and Water Conservation Experimental Station, four rainfall patterns were classified,which were rainfall pattern Ⅰ (long duration and light rainfall intensity), rainfall pattern Ⅱ (long duration and moderate rainfall intensity), rainfall pattern Ⅲ (short duration and moderate rainfall intensity) and rainfall pattern IV (short duration and heavy rainfall intensity). Meanwhile, four periods were selected according to the tillage patterns to analyze the yield law of runoff and sediment on sloping farmland. The results showed that:(1) During 1991-1992, contour ridge and furrow treatment closed at both ends was the best pattern to preserve soil and water, and there was no significant difference among the rainfall patterns (P>0.05). The effect of slope furrow ridge treatment on soil and water conservation decreased with the increasing of the angle between ridge and furrow.(2) During 2004-2005, sediment yield of sloping ridge plots was 10~20 times that of cross ridge plots, while runoff yield was 1~3 times, which indicated that the reducing sediment effect of the cross ridge was better than its reducing runoff effect, and the soil and water conservation effect of planting Hemerocallis citrine Baroni was better than that of planting Zea mays. (3) During 2006-2008, planting hedgerow of Leucaena leucocephala disturbed the surface soil of the farmland at the initial stage, therefore the runoff and sediment yields of hedgerow plots were larger than that of the control plots, and there was no significant difference in runoff yield among different rainfall patterns(P>0.05). The sediment yield of Z. mays/Ipomoea batatas and Triticumaestivum plot on the cross slope under rain pattern Ⅱ was significantly higher than that of other rain patterns (P<0.05), which was 4.4~26.7 times that of other rain patterns. (4) During 2013-2016, the hedgerow had been colonized for three years, the soil and water conservation effect of hedgerow plots were better than that of control plots, and the sediment reduction effect was better than runoff reduction effect, and the soil and water conservation effect of Vetiveria zizanioides hedgerow was better than that of L. leucocephala hedgerow. Under rainfall pattern Ⅲ, there was very significant difference in sediment yield among the plots (P<0.01). On the whole, contour ridge and furrow treatment closed at both ends was the best way for soil and water conservation. Hedgerow had obvious effect on reducing sediment yield, but it increased sediment yield at the initial stage, and occupying farmland and affecting machine ploughing were also weak points. Therefore, suitable tillage and cropping patterns should be selected in combination with natural economic conditions.

Abstract:Freezing-thawing is one of the main external forces of soil and water loss on slopes during spring thawing period. In order to study the erosion and sediment yield process under the condition of runoff scouring on frozen-thawed slopes, two slope gradients (10, 15 degrees), three flow rates (3, 6, 9 L/min) and two initial thawing depths (6, 12 cm) were used to carry out field scouring tests with close-range photography. The sediment yield under different thawing depths, slopes and discharge conditions was analyzed by measuring technique. The close-range photogrammetric measurements and measured values were fitted by linear regression equation. The results showed that under the same conditions of initial thaw depth and slope, the soil erosion and sediment yield on the freeze-thaw slope increased with the increase of flow and slope; with the passage of time, the sediment yield would be smaller and smaller. At the same flow and gradient, the sediment yield increased with the initial thaw depth. When the flow rate and thaw depth were the same, the sediment yield increased with the increase of slope. When the discharge, thaw depth and slope were the largest, the erosion and sediment yield on the slope reached the maximum. Compared with the close range photogrammetry, the average error of the measured sediment yield was 90.67%. The close range photogrammetry technology can be applied to soil erosion monitoring under freeze-thaw conditions.

Abstract:The effects of honeysuckles with different ages on soil erosion on gneiss slopes were studied using artificial rainfall simulation. Results showed that planting honeysuckle significantly reduced soil erosion by rain water on gneiss slopes. Honeysuckle delayed initial runoff time, reduced runoff modulus and sediment transport modulus. Moreover, the effects increased with the increasing ages of the honeysuckles. Compared with bare soil, the one-, three-and six-year-old honeysuckles delayed runoff time by 0.71%, 23.33% and 39.20% respectively; the six-year honeysuckles reduced runoff modulus and runoff depth by 75% and 51%, respectively, and reduced sediment transport modulus by 23.42%~57.60%. Honeysuckle also improved soil erosion resistance. Compared with bare soil, the WAS_0.25 of the one-, three-and six-year-old honeysuckles on slopes increased by 11.52%, 19.37% and 24.35% respectively. Compared with the one-year-old honeysuckles, root biomass of the three-year and six-year honeysuckles increased by 82.67% and 191.26% respectively in the near-root zone. Honeysuckle root biomass was strongly and positively correlated with the total flow reduction rates (R²=0.801) and total sediment reduction rates (R²=0.911). In general, honeysuckle could control soil erosion on gneiss slopes and improve soil erosion resistance to some extent.

Abstract:The natural rainfall was observed in the runoff plots with 10° slope in red soil region. Five treatments:bare land as control (CK), down slope tillage (DT), hedgerows with down slope tillage (DT+HG), contour ridge tillage (CT) and straw mulch (SM) were designed. The effects of cultivation measures and rainfall intensities on runoff depth, sediment yield and nutrient losses were evaluated. The results showed that the runoff depth and sediment loss were increased with the increasing rainfall intensities during the rainfall events. With the cultivation measures changed from DT to DT+HG, CT and SM, the effectiveness of the cultivation measures on reducing runoff, nitrogen and phosphorus was increased respectively. The average annual runoff reduction (91.77%) of SM was the highest. But the sediment reduction (98.91%) of DT was the highest. The SM, CT and DT+CT measures were effective in preventing soil erosion and nutrient loss caused by the heavy rainfall. Cultivation measures influenced the sediment size distribution. The DT+HG and SM treatments were more effective on trapping coarser particles compared with DT and CT treatments. This study was helpful for selecting the suitable cultivation measures and provided data support for the protection and regulation of soil and water losses and non-point pollution in sloping cropland.

Abstract:A process-collectable splash erosion plate was designed to analyze the impacts of parent materials on splash erosion in the Poyang lake basin. The simulated rainfall experiments were conducted with five rainfall intensities (30, 60, 90, 120, 150 mm/h) in this paper. The splash erosion features of red soils were studied under different parent materials including quaternary sediments (SQ), granite (SG) and red sandstone (SR), respectively. The results showed that the total splash erosion differed significantly between parent materials. SR was more sensitive to the rain drop and generated the highest splash erosion, but the value of SQ was the lowest. Soil texture, organic matter and free iron oxide were more effective to the splash erosion. The total splash erosion increased logarithmically with the increased rainfall intensities. Over 80% of the splash sediments were distributed within the distance of 15 cm, the more concentratedly with the higher rainfall intensities.

Abstract:Based on the diverse topography and geomorphology and the complex mechanism of soil erosion in the hilly area of central Hunan Province, China, nine runoff plots with different soil and water conservation measures in three runoff fields of Jingtou (yellow soil), Qiubo (purple soil) and Lianhe (red soil) were selected to explore the effects of different erosive rainfall patterns, soil types and soil and water conservation measures on runoff and sediment transport on slopes. The results showed that the annual runoff and sediment yield decreased as the following sequence:red soil > purple soil > yellow soil under the condition of similar annual rainfall. The runoff reduction effect in each runoff plot was little, but the sediment reduction was effective. Especially, the grassland measures in yellow soil, water conservation forest in purple soil, and fruit-forest and grassland measures in red soil had obvious sediment reduction effects, and their annual reduction rates were 87.89%, 55.88%, 37.99% and 41.07%, respectively. The heavy intensity, short duration, low rainfall and high frequency rainfall accounted for more than 50% of the erosive rainfall events in each runoff plot. It was also the dominant rain type of the runoff and sediment yield in the runoff plots of yellow and red soils, as well as the dominant rain type of the sediment yield in purple soil. The moderate intensity, long duration, high precipitation and low frequency rainfall caused the largest runoff and sediment yield in each single rainfall event in all runoff plots. These results could be of great significance for improving the relevant theories of soil erosion, and provide important guidance and theoretical value for the development of regional soil and water conservation.

Abstract:In the present study, multiple regression equation and surface response analysis were used to investigate the effects of soil bulk densities and water contents on the amount and rates of disintegration in a purple soil. The results showed that:(1) Under the same bulk density, the amount of soil disintegration decreased with the increase of water contents, and the soil disintegration time varied with water contents. The total time of soil disintegration was extended with the increase of water contents, and the amount of soil disintegration was mainly concentrated in the first three minutes of the soil disintegration stage. (2) Under the same water content, the amount of soil disintegration decreased but the soil disintegration time increased with the increase of soil bulk densities, and the amount of disintegration was mainly concentrated in the first four minutes. (3) Under the same bulk density and water content, the soil disintegration rates decreased with the increase of soil bulk densities and water contents. Compared with bulk density, water content had a greater influence on the soil disintegration rates. The interaction of bulk density and water content had a significant effect on the soil disintegration rates, indicating that the soil disintegration rates decreased with the increase of bulk density and water content. Our findings provided some reference for controlling erosion of the purple soil.

Abstract:Vegetation cover structure is a key factor affecting slope erosion process. Based on the simulated rainfall experiment carried out on a slope covered by natural vegetation in Luoyugou watershed of loess hilly region, the effects of three different cover structures on slope runoff and sediment yield were studied under the condition of 90 mm/h rainfall intensity. These three cover structures included the underground root system, the underground root system plus the surface crust, as well as the combination of underground root system, the surface crust and the vegetation canopy. The results were as follows:(1) The root system of the vegetation played a leading role in enhancing soil infiltration, the amount of soil infiltration and the steady infiltration rate on the vegetation root slope increased by 67% and 39.7%, respectively, compared with those on bare slope. (2) For the three vegetation cover structures, the surface crust had the best regulation effect on the runoff and sediment yield, and the contribution rate of runoff reduction and sand reduction was 43% and 67%, respectively. (3) There was a power function relationship between the accumulative runoff yield and accumulative sediment yield in the vegetation root plot and the bare plot, and the relationship turned out to be linear function with the superposition of vegetation cover structure. (4) The multi-level vegetation cover structure could prolong the development period and shorten the active period of the slope erosion process. The research results were important for quantitative evaluation of the effects of vegetation measures on water and sediment reduction.

Abstract:The effect of the adjusted density on the steady yield and water use of spring maize covered with film in dry land was discussed in order to provide a basis for the high and stable yield of spring maize in rain-fed area of dry land. The experiment was conducted from 2014 to 2017 in the Loess Plateau, Zhenyuan, Gansu (107°39'E,35°30'N) in a split plot design. The compact and dense and high-yield spring maize variety Xianyu 335 was used as the test material, 55 cm and 75 cm were set up with two kinds of row spacing covering planting, 6.0×10⁴ plants/hm², 7.5×10⁴ plants/hm², 9.0×10⁴ plants/hm² and 10.5×10⁴ plants/hm² 4 planting density levels. The soil moisture of 0-200 cm soil layer in different spring maize growth period was measured by drying method, and the grain yield and soil profile water change of continuous cropping spring maize were studied in the Loess Plateau. The results showed that under the experimental design distance, there is a low moisture area between 0-200 cm in the soil profile of 55 cm and 75 cm in the dry year, and the lowest water content of two row spacing 40-200 cm soil layer is in the section of 160 cm soil layer, the soil moisture content of 55 cm row spacing is 8.9%, the soil moisture content of 75 cm row spacing is 8.7%. The soil moisture of 20-120 cm soil layer changed more sharply with the influence of precipitation and plant growth water consumption. Regardless of the annual precipitation pattern, the soil dry layer was not produced in the 0-200 cm soil depth under two row spacing. Compared with the 55 cm row spacing, the distance to the low humidity area of the 75 cm row spacing enlarged in varying degree with the change of years, but there was no significant difference in the same density water consumption of the 7.5×10⁴~10.5×10⁴ plants/hm² under the two rows. The 4 years average yield of the 75 cm row spacing was higher than that of the 55 cm row spacing, and better stable yield was achieved in 9.0×10⁴ plants/hm² and below planting density. The yield increased from low to high density by 2.2%, 5.8%, 4.1% and 3.0% respectively, while the average water use efficiency increased by 1.1%, 5.9%, 0.3% and -1.5% respectively, and the yield of the same density and water use efficiency in different row spacing were the same. The research showed that in the Loess Plateau, 55 cm and 75 cm row spacing with 7.5×10⁴ plants/hm² planting density for continuous cropping has stable yield, and will not lead to soil water deficit to produce dry soil layer, which is the ideal planting pattern of continuous cropping stable plant spacing.

Abstract:To study the characteristics of Benggang soil expansing and contracting with the moisture changes, soil samples of the red soil layer in the typical Benggang area of Anxi County, Fujian Province were collected. Through the experiment of non-charge expansion and shrinkage, non-charge expansion rates and the linear shrinkage rates of the soil samples under different initial dry densities (1.3, 1.4 and 1.5 g/cm³) and different initial soil water contents (15%, 20%, 25% and 30%) were analyzed. The results showed that the soil expansion rate was larger when the initial dry density increased in the low soil moisture. When the initial dry density was the same, the soil expansion rates decreased with the increases of initial water contents. When the initial soil moisture content was the same, the soil sample expansion rates increased as its initial dry density increased. There was a difference in the shrinkage process of soil samples with different treatments. The soil shrinkage rate with high initial water content was large, and the soil expansion and contraction processes were inconsistent and both processes were irreversible. The result revealed the relationships between soil water contents and dry densities and Benggang erosion.

Abstract:In order to explore the effects of sodium salt content on the stability of silty engineering slope in marine saline-alkali land, limit moisture content and shear strength experiments were carried out to investigate the influence of Na⁺ content on the soil mechanics parameters including limiting moisture content, shear strength and other parameters. Moreover, combined with the calculation of the infinite slope safety factor, the influence of soil Na⁺ content on slope stability under different saturation conditions was defined. The results showed that with the increasing of Na⁺ content, the plastic limit of soil sample increased slowly, while the liquid limit decreased. In addition, average cohesion and average internal friction angle both decreased with the increasing of Na⁺ content. For the same soil texture, the slope safety factor (FS) decreased with the increasing of Na⁺ content when the soil saturation was constant. When the Na⁺ content was constant, the greater the soil saturation, the less the FS was, and the FS reached the minimum value when soil was fully saturated. The higher the soil saturation, the greater the decrease amplitude of FS with the increasing of Na⁺ content.

Abstract:This research was conducted to explore the effects of new tillage and fertilization methods on soil water, phosphorus (P) spatial dynamic distribution, P uptake and utilization, and maize yield. In 2016-2017, three treatments of tillage and fertilization methods were designed, including T1 (no-tillage + upper NPK), T2 (subsoiling + whole layer NPK), T3 (application of N, P, K fertilizers to designated soil depth with subsoiling). The results showed that compared with T1, the total P accumulations of T2 and T3 in the mature period were increased by 15.9% and 21.2% respectively.The production efficiencies, apparent utilization rates and agronomic efficiencies of T2 and T3 were increased by 14.5%, 11.0%, 84.5% respectively. Compared with T2, the production efficiency, apparent utilization rate and agronomic efficiency of T3 were enhanced by 8.4%, 11.6% and 47.8% respectively. Compared with T1, the soil water contents of T2 and T3 were both improved by 6.6%. The available P of T3, in which P fertilizer was applied to the deeper soil layer, was increased by 10.2 mg/kg than T1, effectively increasing the available P content in the 20-40 cm soil layer. Maize yields of T2 and T3 were increased by 11.7% and 22.6% respectively compared with T1. Maize yield in T3 was increased by 9.7% compared with T2. Therefore, the new tillage and fertilization method could improve the water retention performance of deep soil, increase the available P in the lower layer of the soil, then promote the P absorption of maize, increase the P fertilizer use efficiency, resulting in the enhanced maize yield and the reduced soil water and P nutrition losses.

Abstract:The typical fieldriges on the purple soil sloping farmlands in the Three Gorges Reservoir area were chosen to study the effects of reinforcement materials on soil shearing strength of fieldriges by laboratory unconsolidated undrained triaxial compression tests. The test results indicateds that:(1) The three tested materials showed that soil cohesion increased first and then decreased with the increasing of reinforcement amount. The cohesion of the fieldriges with different reinforced materials followed the order of c_{wheat husks} > c_{bamboo wool} > c_{rice straw} > c_{unreinforced soil}. When the cohesion of fieldriges soil was the largest, the reinforcement amount of wheat husks, bamboo wool and rice straw were 0.8%, 0.5% and 0.3%, respectively. But the effect of reinforcement materials on soil internal angle was not obvious. (2) Compared with unreinforced soil, the shearing strength of fieldriges soil with reinforcement materials all increased. As the reinforcement amount increased, the limit principal stress difference increased and then decreased, and the maximum of the limit principal stress difference all appeared at the optimal reinforcement amount of wheat husks, bamboo wool and rice straw respectively. Under the four kinds of confining pressures, the maximum value of the limit principal stress difference of reinforced fieldriges soil all showed that (σ₁-σ₃) _{wheat husks} > (σ₁-σ₃)_{bamboo wool} > (σ₁-σ₃)_{rice straw} > (σ₁-σ₃)_{unreinforced soil}. (3) Under the optimal reinforcement amount, the deviatoric stress-strain curves of three reinforced fieldriges soil samples all displayed a hardening type.

Abstract:In order to clarify the wind erosion effect and soil loss law in the degraded area of alpine meadow, the outbreak area of the Ochotona Curzoniae mound in the degraded alpine meadow of Henan County in Qinghai Province was taken as the research object. The field artificial simulated wind erosion tests were carried out with different wind speeds. The law of the soil loss and nutrient loss of the rodent mound was analyzed and discussed. The results showed that:(1) The amount of soil loss under wind erosion take a tendency of initied fast followed by slow. When the wind speed was gradually increased from 6.0 m/s to 12.0 m/s, the amount of soil loss increased by about 6.3 times. (2) The heights and diameters of the rodent mound were significantly different with time during the wind erosion process. Their changing rates corresponded to the rates of soil loss. Wind erosion promoted the evaporation rates of soil moisture, thereby promoting the soil erosion of the rodent mound. (3) The soil nutrient loss in the Ochotona Curzoniae mound increased with the increases of wind speed and soil loss, indicating that the law of nutrient loss and soil loss were the same. The loss of organic matter, total potassium, available potassium and alkali nitrogen was relatively large. These findings show that wind erosion is one of the important factors that aggravate the soil loss and nutrient infertility in the Ochotona Curzoniae outbreak area of degraded alpine meadows.

Abstract:In order to study the changes of growth index and yield of winter wheat and summer maize under different soil bulk densities and different degrees of water deficit, a bucket-planting experiment was conducted. Three soil bulk densities were set up:1.2 g/cm³, 1.4 g/cm³, 1.6 g/cm³, and three lower limits of soil moisture control:50%, 60% and 70% of field water-holding capacity, respectively. The root system, growth index, water consumption, yields and water use of winter wheat-summer maize were studied. The results showed that with the increases of water deficit, the growth index, biomass, water consumption and yield of winter wheat and summer maize decreased. With the increases of soil bulk densities, the biomass and yield of winter wheat increased first and then decreased, and the water consumption and water use efficiency of winter wheat decreased; the yield, water consumption and water use efficiency of summer maize decreased. In the experiment, 1.4 g/cm³ and 1.2 g/cm³ were the optimum soil bulk densities for winter wheat and summer maize, respectively. The interaction between soil bulk density and water treatment had a significant effect on plant height, water consumption and water use efficiency of summer maize, but there was no significant effect on biomass and yield of winter wheat and summer maize. These results could provide a theoretical reference for increasing yield and increasing efficiency of crops and efficient utilization of soil and water resources in Huanghuai area.

Abstract:In order to explore the effects of different conservation tillage measures on soil water conservation, and the effects of different fertilization treatments on yield and income of spring maize in continuous cropping spring maize field of dryland, field experiments were conducted in 2014 to 2016. We studied the water conservation effects of three types of tillage methods (no-tillage, subsoiling and plowing) during winter leisure periods, and the effects of the combination of three kinds of tillage treatments and three fertilization treatments (high organic fertilizer, medium organic fertilizer and low organic fertilizer) on the soil water dynamics, yield and economic benefits of spring maize during maize growth period. The results showed that no-tillage and subsoiling were better in water conservation. In the winter leisure periods of the two experimental years, no-tillage and subsoiling were 1.3 and 0.9 percent points higher than that of ploughing. Compared with plowing treatment, the average soil water storage in 0-200 cm soil layer in two years was increased by 20.8 mm and 22.1 mm in no-tillage and subsoiling treatments, respectively. During the growth period of maize, under the condition of high organic fertilizer, the average soil water storage in the 0-200 cm soil layer of no-tillage and subsoiling treatment was 44.2 mm and 34.6 mm higher than that of plowing treatment. The yield, WUE and net yield of the high organic fertilizer and subsoiling treatment were the highest, and the average yield, WUE and net yield of two years were 9 332.40 kg/hm², 22.01 kg/(hm²·mm)and 5 104.1 yuan/hm², respectively, followed by high organic fertilizer and no-tillage treatment, the yield and income of the high organic fertilizer and subsoiling treatment was increased by 7.4% and 3.9%, respectively, compared with the high organic fertilizer and no-tillage treatment. Considering comprehensively the effect of soil water conservation and the effect of increasing yield and income of maize, high organic fertilizer and subsoiling treatment was the best combination for continuous cropping maize field in arid area.

Abstract:Selecting oyster shells with the best adsorption performance of phosphorus as the fillers, and three bio-retention simulation devices (column A:aquaculture oyster shell; column B:beach oyster shell; column C:aquaculture oyster shell with submergence area) were constructed in the laboratory. The effects of oyster shell as fillers on the removal of nitrogen, phosphorus and COD, which were common pollutants in urban runoff in Qingdao, were studied by using road runoff simulation as inflow, and the removal mechanism of pollutants was discussed. The results showed that the removal efficiency of total phosphorus was the best in three kinds of biological detention devices filled with oyster shell. Under the condition of influent phosphorus concentration of 0.57~1.83 mg/L, the average removal rates of the unsubmerged area and the submerged area were 96.12% and 91.02%, respectively. There was no significant difference in the phosphorus removal efficiency between aquaculture oyster shell and beach oyster shell, and the submergence area was not conducive to phosphorus removal. The effluent concentration of ammonia nitrogen (NH₄⁺) in the three simulation devices was higher than the influent concentration in the first five influents. Whereas, after extending the drying period, the NH₄⁺ removal rate of the devices all increased, and the average NH₄⁺ removal rate of B column (58.83%) was greater than that of A column (48.77%) and C column (53.06%), and the submergence area had no obvious effect on NH₄⁺ removal. Due to the leachate of organic matter in the filler, serious COD leaching occurred in the first influent. However, the removal efficiency of COD increased rapidly and stabilized in the subsequent influent process, and the removal rates of three columns were 50.34%, 23.47% and 47.75%, respectively. Because of the inhibition of denitrification, the removal efficiency of nitrate nitrogen (NO₃^-) was not good. Overall, the oyster shell could be used as filler in Qingdao biological detention facilities. In order to enhance the removal efficiency of NO₃ ^- in the detention facilities, it was necessary to adopt intensified nitrogen removal measures.

Abstract:In order to explore whether cover mats are suitable for covering urban bare soil and the appropriate amount of glue and the particle size for the cover mats, the compressive resistance, water permeability, and water holding capacity of 10 different cover mats with different glue dosages (glue content accounts for 20%, 25%, 30%, 35% and 40% of the garden waste)and different particle sizes (small particle size 0~1 cm and large particle size 1~3 cm) were analyzed in laboratory experiments. The results showed that the compressive resistance of different cover mats significantly increases with the increment of the glue dosage, and the compressive resistance of cover mats before soaking was better than that after soaking. The cover mat with small particle size had relatively good water permeability when the amount of glue was lower than 30%, and the water permeability significantly decreased when the amount of glue was higher than 30%, and the permeability coefficient was between 1.09 and 9.35 cm/s. The water permeability of cover mats with large particle size was basically unaffected by the amount of glue applied. The water permeability was good, and the permeability coefficient was generally between 0.25 and 0.33 cm/s. The water holding capacity of the cover mats had a significant logarithmic relationship with the soaking time, Q=aln(t)+b, R²>0.95. The water absorption rate of the cover mats showed a significant power function relationship with the soaking time, V=ktⁿ, R²>0.99. The maximum water holding capacity (rate) and effective storage capacity (rate) both increased firstly and then decreased with the increment of glue dosage. The effective storage capacity of the small particle size cover mat was between 120.78~142.21 t/hm², and the effective storage rate was between 93% and 113%. The effective storage capacity of the large particle size cover mat was between 71.71~83.35 t/hm², and the effective storage rate was between 54% and 65%. In summary, the results can provide theoretical basis and practical support for urban bare soil coverage.

Abstract:In a small watershed with a typical agro-forest complex ecosystem and peak-cluster valley landform of the central Guizhou,¹³⁷Cs and magnetic susceptibility were used as compound fingerprinting factors to analyze the fingerprint characteristics of carbonate rock surface soil (from hill slopes and depressions), deep soil (from river bank or fissures and grikes), and clastic rock pieces. A multivariate mixing model was used to trace the probable sources of suspended sediment in discharge generated during rainstorm events, and calculate the main source and the relative contribution of the sediment from surface and underground outlets of small watershed. The results showed that the concentration of ¹³⁷Cs and magnetic susceptibility were significantly different in the three types of sources. The average ¹³⁷Cs and magnetic susceptibility values of surface soil, deep soil and clastic rock pieces were 3.39 Bq/kg and 310.07×10^-8 m³/kg, 0.50 Bq/kg and 180.69×10^-8 m³/kg, 0 Bq/kg and 7.90×10^-8 m³/kg, respectively. The relative contributions of surface soil, deep soil and clastic rock pieces to the sediments of the surface outlet were 16.2%, 4.3% and 79.5%, respectively, and the goodness of model fit was 99.97%. The relative contributions of surface soil, deep soil and clastic rock pieces to the sediments of the underground outlet were less than 0.1%, 37.9% and 62.1%, respectively, and the goodness of model fit was 83.80%. The sediment sources in this karst watershed differed from those in typical non-karst terrain, the specific characteristics were:(1) The sediment from carbonate surface soil was few, and carbonate surface soil contributed mainly to the surface water system, while contributed little to river sediment; (2) Clastic rock pieces were the primary source of both surface and underground river sediments; (3) Deep soil contributed slightly, and it contributed more to underground rivers than to surface rivers. In addition,¹³⁷Cs and magnetic susceptibility could be used as compound fingerprinting tracers to trace the sediment source of the surface and subsurface rivers in this karst area, and also could be applied to determine the relative contribution rate of sediment sources.

Abstract:Studying the effects of different nitrogen application amount on soil fertility before spring sowing could help determine the suitable nitrogen application amount in Hetao Irrigation Area. In this study, four nitrogen application levels (high-nitrogen N₃:325 kg/hm², medium-nitrogen N₂:225 kg/hm², low-nitrogen N₁:125 kg/hm², and no nitrogen application N₀) were set up in the field experiment. The spatial and temporal distribution of water and salt and the changes of total nitrogen, alkali-hydrolysis nitrogen and organic matter contents were studied during freezing-thawing period. Then the soil fertility was evaluated by principal component analysis. The results showed:Firstly, after autumn water application, soil moisture content was significantly higher than before. The surface soil moisture content increased. When it just began to freeze, soil water accumulated to surface layer, and then froze to the deeper layer as the temperature reduced. The irrigation rates were the same in different treatments. The impacts of different nitrogen treatments on the soil moisture content was not significant. The soil moisture could meet the crop water demand. The soil salinities increased with the increasing nitrogen application rates during the growth period. A large amount of salt was leaching when water was applied in autumn. Soil salt was subjected to the combined effects of infiltration and evaporation during the water thawing, resulting in that the surface soil salinities were N₀(0.14%) < N₁(0.17%) < N₂(0.19%) < N₃ (0.45%). Secondly, during freeze-thaw period, soil nutrients were mainly concentrated in the surface soil layer of 0-20 cm. During the freeze-thaw period, the contents of total nitrogen, alkali-hydrolysis and organic matter in the soil showed a change pattern of first increasing and then decreasing. The maximum value occurred in the maximum freeze-thaw period, indicating that freezing helped the accumulation of total nitrogen, alkali-hydrolysis and organic matter. The last, soil fertility was comprehensively evaluated before the next spring sowing. Organic matter, organic carbon and total phosphorus on PC1 and PC2 had higher factor loads, contributing to soil fertility. Considering from the composite scores (N₃ < N₀ < N₁ < N₂), high nitrogen treatment led to the low soil fertility, and the highest scores were given in the medium nitrogen treatment, resulting in the highest soil fertility. Therefore, it is, recommended that the nitrogen application rate should be around 225 kg/hm² for the maize growth, and 20% for the basal, 40% for the jointing stage and 40% for the tasseling stage respectively. This fertilization will be beneficial for the improvement of the soil fertility in the following spring sowing and also for the agricultural sustainable development.

Abstract:In order to investigate the effect of biochar on dissolved organic matter (DOM) in soil, the anaerobic mud culture experiment of adding biochar to paddy soil was carried out to analyze the dissolved organic carbon (DOC) content, the composition of DOM, the fluorescence spectrum characteristics and the Fe (Ⅲ) reduction in anaerobic mud during different culture stages after adding biochar. The results showed that the addition of biochar could increase the content of DOC in paddy soil and impact the ultraviolet spectrum characteristic value (SUVA₂₅₄), resulting in the changes of the component and the relative content of DOM, and the changes among different soils were different, the role of biochar was more obvious in acid paddy soil. The reduction efficiency of Fe (Ⅲ) was promoted by adding biochar, and the initial soil pH was also impacted. The correlation analysis revealed that the addition of biochar could affect the nitrate reduction, iron reduction and methanogenesis in anaerobic paddy soils by adjusting SUVA₂₅₄, DOM composition and pH of the incubation system.

Abstract:In order to investigate the effects of saline-alkali on the organic carbon mineralization process, a method integrating field sampling and lab simulating experiment is used. In the study, exploring the saline-alkaline soil in Qianguo Irrigation District in Western Jilin Province, 4 paddy fields with different saline alkali degrees (P1, P2, P3, P4) were chosen as the experimental subjects. The experiment recorded the soil CO₂ emission flux on the 1st, 4th, 7th, 10th, 14th, 21st, 28th, 35th and 70th day of the incubation period. Combining the physical and chemical properties of soil to compare the dynamic changes of CO₂ flux in the progress of paddy field cultivation simulation among the subjects. The results showed that P1, P2 and P3 were weakly alkaline soils and P4 was strongly alkaline soil. The SOC content of each plot was significantly different and there was a surface enrichment, which was significantly negatively correlated with the degree of alkalization (r=-0.945). The accumulation process of SOC mineralization and culture time was consistent with the First order kinetic model C_t=C₀(1-e-^kt).In the initial stage of mineralization, the amount of CO₂ released was large, and the release intensity decreased rapidly. The mineralization rate decreased slowly with time and decreased to the minimum at the end of the culture period. The study interprets that the SOC mineralization process is affected by a variety of factors. In saline alkaline soils, ESP is the main influencing factors of this process. Salinization of soil inhibits the rate of soil C cycle, which has a greater impact on the C sink than the C source process. The intensity of SOC mineralization reaction, the accumulation of mineralization reaction and the completeness of mineralization reaction increase with the increase of SOC content, and decrease with the increase of ESP level.

Abstract:In order to understand the effect of coal accumulation on soil structure, three different levels of coal accumulation soils samples (low accumulation, moderate accumulation and high accumulation) were collected from the Jiaozuo mine-crop overlapped zone, and the coal-free soil was taken as the control. Soil samples were collected in the 0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm soil layers. Water-stable aggregate fractions were measured, and fractal dimension (D), mean weight diameter (MWD), geometric mean diameter (GMD) and macroaggregate destruction rate (PAD) were used as evaluation indicators to evaluate the effects of coal on the composition and stability of soil aggregates. The results showed that coal accumulation in the soils promoted the transformation of soil water stable microaggregates to macroaggregates, reduced the D value and increased soil aggregate stability. The increase amplitude of water stable macroaggregate content in deep soil layer (20-40 cm) was higher than that in surface soil layer (0-20 cm). Soil aggregate stability showed a trend of increase firstly and then decrease with the increasing of coal accumulation. It was also found that soil aggregate stability depended mainly on the content of water stable aggregates that greater than 2 mm. Our results suggested that coal accumulation in soils obviously improved soil structure. In addition, according to the results of this study, the "black soils" phenomenon due to long-term transportation, dumpling and washing of coal and mine water drainage and irrigation in the study area should not be considered as coal pollution.

Abstract:In order to accurately obtain the distribution information of soil potassium in the soil profile, and know well the regional migration of potassium and the need of reasonable precision fertilization, 134 soil profile (0-100 cm) samples were collected. Based on the sampling data, the distribution characteristics of soil available potassium in soil profiles of the western part of Chengdu Plain were studied through classical statistical and geostatistical methods, and the effects of parent material, soil type and land use on the available potassium distribution were compared and analyzed. The results found that the soil available potassium content had certain regularity in the horizontal direction, and its high value was concentrated in the Chongzhou, Qionglai and Dayi areas, which were south parts of the Jinma River, while the low value appeared in the Dujiangyan-Pixian-Wenjiang area. The area of the low-value-area accounted for more than 50% of the study area, and the overall showed a significant downward trend from the southwest to the northeast. In the vertical direction, the content of soil available potassium decreased with the increasing of soil depth in the range of 0 to 100 cm, and the available potassium content in top soil was significantly higher than that in the lower soil layer (P<0.05). The amplitude of soil available potassium content (the difference between the maximum and the minimum) in the lower soil gradually decreased with the increasing of soil depth. The nugget coefficients of different soil layers within 0 to 100 cm were between 25% and 75%, showing moderate spatial autocorrelation, which were affected by structural and random factors. The spatial distribution of available potassium in surface soil was affected by soil parent material, soil type and land use pattern, and the explanatory ability of soil type was the highest, which was 1.97 and 2.58 times that of soil parent material and land use pattern, respectively. The spatial distribution of available potassium in lower layer soil was mainly affected by the parent material and land use pattern, and the impact extents both increased with the increasing of soil depth, however the influence of parent material was more significant. The results showed that the parent material and land use pattern were the main controlling factors, which affecting the profile distribution of soil available potassium in the study area.

Abstract:A field experiment was conducted to study the yield of double cropping rice and its uptake of nitrogen (N), phosphorus (P) and potassium (K). The fertilizer utilization efficiencies and the relationships between the absorption and utilization efficiencies of P and K and N uptake and utilization were also measured under the different applications in N but the same in P and K. Our results showed that the rice yield was increased by moderate N application, however, high N showed negative effects on crop production. As for N application, 75%N treatment gained the highest yield for early rice, which was increased by 58.1% compared with CK without fertilizer application. And 100%N treatment had the highest yield for late rice, 67.6% more than CK. The accumulations of N, P and K in rice plants were significantly affected by N application levels. The accumulations of N, P and K in early and late rice grains were the highest under 100%N treatment, and their accumulations in rice plants were also higher than other treatments. Different nitrogen levels also had significant effects on N, P and K nutrient utilization efficiency. Our results showed a significant correlation between the accumulation of P and K and the accumulation of N in the early and late rice plants. The apparent use efficiencies and agronomy efficiencies of P and K were correlated positively with N accumulations in rice plants, respectively. Moderate N application could increase the yield of double cropping rice, promote the absorption of N, P and K by rice, and improve their utilization efficiencies. In this research, considering the yield effects of double cropping rice and the fertilizer utilization efficiencies, the suitable N application rate should be between 105 kg N/hm² and 146 kg N/hm².

Abstract:The effects of different phosphorus (P) fertilizers on the dynamics and distribution of soil P availability and the maize P uptake and yield were studied by the simulation experiments and field experiments. Both experiments included 4 P fertilizers application treatments respectively, which were control (no phosphate fertilizer), MAP (monoammonium phosphate), UP (urea phosphate), and AAP (water-soluble ammonium polyphosphate). In the simulation experiments, the available P contents in soil were increased by different P fertilizers, and the highest P content was observed in the APP applied soil of 10-15 cm. Under the general nutrient input and management level, soil acidification was found in all three P fertilizers treatments, of which UP gave the most significance. In the field experiment, the available P content in soil treated by APP was higher in deep soil at the late growing period of maize, and the pH value of soil treated by UP was lower, both of which were conducive to improving soil P supply capacity and improving soil available P content. The APP application had a significant promoting effect on root development, resulting in the highest P content and P absorption in maize tissues and the highest yield (14.40 t/hm²). Among the three P fertilizers, APP mobility was relatively better, resulting in the increased contents of available P in the deep soil, which could be conducive to root growth and nutrient absorption, and improving maize yield. Therefore, APP is a kind of P fertilizer suitable for maize water and fertilizer management.

Abstract:The effects of biochar addition on the physicochemical properties of coastal saline soil and the activity of the antioxidation system in maize seedlings were studied by pot experiment, and the typical coastal saline soil sampled from Yellow River Delta was taken as test soil. A total of six treatments were set up in the experiment, including non-fertilizing (CK), fertilizing without biochar (CFK) and fertilizing with different addition rates of biochar (the addition rate was 12.5, 25.0, 50.0 and 100 g/kg, respectively). The results showed that:(1) Compared with CK, with the increasing of biochar-addition rate, the electrical conductivity (EC), available potassium, available phosphorus, cation exchange capacity (CEC) and easily oxidized organic carbon (EOC) of coastal saline soil increased significantly. The pH and alkali hydrolysable nitrogen content of soil treated with biochar showed decreased trends compared with CK, but there was no significant different between the biochar treatments. However, biochar addition had no significant effect on exchangeable sodium compared with CK.(2) Moderate addition rate of biochar (12.5, 25.0 and 50.0 g/kg) increased the activities of antioxidant enzymes (SOD, POD and CAT) and root activity in maize seedlings, and reduced the production rate of superoxide anion and hydrogen peroxide content of leaves, thereby improving the physiological characteristics of maize seedlings. However, the higher addition rate of biochar (100 g/kg) exhibited a negative impact on the activity of antioxidant enzyme in maize seedlings, resulting in the higher accumulation of reactive oxygen in the plants. Therefore, moderate addition rate of biochar could improve the physical and chemical properties of coastal saline soil, and to a certain extent, effectively improve the physiological characteristics of maize seedlings under salt stress, but the higher addition rate could inhibit the antioxidant system of crops.

Abstract:In order to improve the soil fertility in arid mining area and enrich the theory of vegetation reconstruction and ecological restoration, through the potted experiment, three common herbaceous species (Medicago sativa, Elymus dahuricus Turcz and Agropyron cristatum) in dry ore fields were planted. Combined with different concentrations of microbial fertilizer treatments, two-factor variance analysis was used to reveal the effects of fertilization levels and plant species on soil biological, physical and chemical properties, and cluster and factor analysis were used to screen the best combination of plant species and fertilization level in soil improvement. The results showed that:(1) Compared with the control group, the soil bacteria, fungi, actinomycetes, total microbial quantity, microbial biomass carbon, nitrogen, organic matter, available nitrogen, phosphorus and potassium in the test group increased significantly (p<0.05), while the microbial biomass carbon-to-nitrogen ratio and pH decreased significantly (p<0.05). (2) Plant types and fertilization levels had significant interactions on some indicators, including bacterial quantity, fungi quantity, actinomyces quantity, total microbial quantity, microbial biomass nitrogen, the microbial biomass carbon-to-nitrogen ratio. (3) The results of factor analysis and cluster analysis were basically consistent. The best treatment for soil improvement in the arid mining area was planting M. sativa and applying 20 g/kg microbial fertilizer. The application of microbial fertilizer could effectively improve soils that was poor in moisture fertility in dry mining area. With the increasing of microbial fertilizer application amount, the effect of soil improvement was better.

Abstract:This study selected Picea crassifolia forest which lived at altitudes of 2 900~3 000 m in pailugou catchment of Qilian Mountains as objects. By field investigation and laboratory analysis, the distribution characteristics of soil physicochemical properties and enzyme activities along the altitudinal gradients were studied. The relationships between soil physicochemical properties and soil enzyme activities were also analyzed. The results showed that:(1) With the increased altitudes, soil water contents, as well organic matter, total nitrogen and available potassium contents increased gradually; but soil bulk densities, pH values and total potassium contents decreased gradually; total phosphorus contents decreased at first and then increased, available phosphorus contents had not significant variation. (2) With the increased altitudes, the activities of invertase and alkaline phosphatase showed an increasing trend generally, the activities of urease decreased at first and then increased generally, and the activities of protease changed a little and had no significant difference (P>0.05). (3) Soil enzyme activities were closely related to soil organic matter, nitrogen, phosphorus and potassium contents, among which sucrase, urease and protease activities were significantly correlated with soil total nitrogen, total potassium and available potassium contents (P<0.05). (4) There existed significantly correlations among four enzyme activities, indicating that enzymatic reaction had specificity and commonality.

Abstract:The pot buried experiments were conducted to study the effects of soil pH, nitrogen application, seasons and pakchoi planting on the degradation of bast fiber mulch film(BFMF) and the changes in soil microbial biomass and enzymes activities. The results showed that the degradation process of BFMF obeyed the Olson attenuation model (R²=0.689~0.996, P<0.05). The application of nitrogen and planting of pakchoi during the autum-winter season significantly inhibited the degradation of BFMF (P<0.05). Further, the degradation rate of BFMF was significantly higher during summer than autumn-winter season (P<0.05). While, limited effect of soil pH (5.80~8.34) on the degradation of BFMF was observed (P>0.05). Moreover, there were significantly positive relationships between the degradation rates of BFMF and the soil microbial biomass carbon, nitrogen (MBC, MBN), cellulose and catalase activities at the end of the experiments periods (P<0.05).These results indicated that the different degradation characters of BFMF might be due to the changes in soil microbial biomass and enzymes activities under different soil environment conditions.

Abstract:Taking the two year old "Rui pan 21/peaches" as test materials, the effects of molybdenum bag-controlled release fertilizer on soil enzyme activity, nutrient absorption and plant growth of potted peach tree were investigated by regulating the content of molybdenum in bag-controlled release fertilizer (0 g/bag:ordinary bag-controlled release fertilizer, 0.1 g/bag:molybdenum containing bag-controlled release fertilizer). The results showed that compared with ordinary bag-controlled release fertilizer, the activity of soil sucrose enzyme, urease, phosphatase and catalase in the soil treated by molybdenum containing bag-controlled release fertilizer increased by 6.99%, 7.61%, 12.27% and 22.86% after 30 days of fertilization, respectively, and increased by 6.31%, 11.58%, 9.05% and 32.41% after 60 days after fertilization, respectively, and the differences were significant. The molybdenum containing bag-controlled release fertilizer treatment increased the content of molybdenum in the soil and the number of lateral roots, the root activity, total root length, total surface area and total volume increased by 7.88%, 6.12%, 3.90% and 9.19%, respectively. The root shoot ratio increased by 6.92%, and the total dry matter increased by 9.99% compared with ordinary bag-controlled release fertilizer treatment. Compared with ordinary bag-controlled release fertilizer, the content of molybdenum ion, total nitrogen and total phosphorus in the leave, lateral branch and roots of the plant treated with molybdenum bag-controlled release fertilizer increased significantly, while the total potassium content in the plant increased slightly, and the difference was not significant. The content of calcium, magnesium, zinc and boron in leave, branches and roots also increased. The chlorophyll content and net photosynthetic rate of peach trees treated with molybdenum containing bag-controlled release fertilizer significantly increased. The study showed that, molybdenum containing bag-controlled release fertilizer could increase soil enzyme activity and root activity of peach saplings, and increase number of lateral roots, root shoot ratio and net photosynthetic efficiency of plant leaves, promote the absorption of nitrogen and phosphorus, thus promoting peach tree plant morphological construction.

Abstract:Based on the 25 categories of the major carbon resources from four aspects including agricultural land use, rice planting, livestock and poultry breeding and straw burning and the 17 categories of major crops carbon sink species, this study calculated the carbon emissions and carbon sink in Shandong Province from 2000 to 2015, and also calculated those of 17 prefecture-level cities in 2000, 2007 and 2015. Then, the agricultural net carbon sink and the intensity of net carbon sink were calculated, and the characteristics of spatial-temporal evolution were analyzed. The results showed that the amount of agricultural net carbon sink and net carbon sink intensity in Shandong province from 2000 to 2015 showed the upward trend, with the increase of 33.05% and 39.14% respectively. Carbon sink was the main carbon effect in agricultural development, and the effect of reduce emission on the increased carbon sink was obvious. The regional difference of agricultural net carbon sink was obvious and showed a trend of expansion with time, and there were four types of regions:"continuous increase", "fluctuant increase", "fluctuant decrease" and "continuous decrease". The regional difference of agricultural net carbon sink intensities was obvious and also showed a trend of expansion with time, and there were two types of regions:"continuous increase" and "fluctuant decrease". Based on spatial distribution features, the net carbon sink and net carbon sink intensities of each city were divided into five grades:lowest, lower, medium, higher and highest, from 2000 to 2015. The spatial distribution pattern of lowest net carbon sink area was relatively stable, while the other four grades of areas changed greatly. The highest net carbon sink areas were concentrated in the west of Shandong Province, and the higher net carbon sink areas in the southeast. The spatial distribution pattern of net carbon sink intensities changed greatly, the highest intensity areas of net carbon sink expanded from the middle to the west and southwest of Shandong Province, and the higher intensity areas from the middle to the southeast.

Abstract:In order to study the effects of nitrogen deposition on soil carbon and nitrogen fractions and enzyme activity in secondary forests, we took the moist evergreen secondary forests in rainy area of west China as the object. A simulated nitrogen deposition experiment in the field was conducted from January 2014. The addition levels of nitrogen included control (CK, +0 g/(m²·a)), low nitrogen (LN,+5 g/(m²·a)) and high nitrogen (HN,+15 g/(m²·a)). After 27 months of nitrogen deposition, soil samples of the humus layer and the surface of the leaching layer were collected to measure the contents of soil total organic carbon (TOC), extractable dissolved organic carbon (EDOC), readily oxidizable carbon(ROC), total nitrogen (TN), NO₃^--N, NH₄⁺-N as well as enzyme activities of sucrase, urease, acid phosphatase and polyphenol oxidase. The results showed that simulated nitrogen deposition significantly increased contents of TOC and NH₄⁺-N in the humus layer, and the contents of NO₃^--N in the humus layer and the surface of the leaching layer, and increased significantly the value of C/N in the humus layer of the secondary forest. The contents of TOC, NH₄⁺-N and C/N in the surface of the leaching layer and the contents of EDOC, ROC, TN and ammonium nitrate ratios in the two kinds of soil layers were not influenced by simulated nitrogen deposition. The polyphenol oxidase activity of the two soil layers decreased with the increasing of nitrogen addition, and the difference in surface of the leaching layer was significant. Simulated nitrogen deposition had no significant effect on the activities of invertase, urease and acid phosphatase. In the humus layer, there was a very significant positive correlation between the contents of NH₄⁺-N and NO₃^--N and the TOC. The polyphenol oxidase activities were significantly negatively correlated with the NO₃^--N content in the two soil layers. The results showed that the simulated nitrogen deposition further increased the TOC content in the humus layer of the secondary forest, and promoted the accumulation of soil inorganic nitrogen. The inhibition of simulated nitrogen deposition on polyphenol oxidase was more conducive to the accumulation of soil organic matter.

Abstract:In order to study the changes of soil water conservation ability after replacing evergreen deciduous broad-leaved mixed forest with Chinese fir plantation, the water retention characteristics of the litter and soil in the above two stands were studied by the indoor soaking method and the cutting ring method, respectively. The results showed that:(1) The average volume of litter in the evergreen deciduous broad-leaved mixed forest (3.42 t/hm²) was higher than that in the Chinese fir plantation (3.12 t/hm²), and the average litter thickness was Chinese fir forest (9.17 cm)>evergreen deciduous broad-leaved mixed forest (5.42 cm). (2) The maximum water-holding capacity was evergreen deciduous broad-leaved mixed forest (6.23 t/hm²)>Chinese fir forest (5.57 t/hm²), and the maximum water holding rate also showed the same rule, that was, evergreen deciduous broad-leaved mixed forest (184.40%)>Chinese fir forest(179.50%). The effective interception amount and the maximum amount of interception were both evergreen deciduous broad-leaved mixed forest (4.48 t/hm² and 5.41 t/hm²)>Chinese fir forest (4.13 t/hm² and 4.97 t/hm²). (3) The water absorption amount and soaking time of litter layer accorded with logarithmic function Q=aln(t)+b, while the water absorption rate and soaking time accorded with exponential function V=at^b, the water storage capacity of evergreen deciduous broad-leaved mixed forest was stronger than that of Chinese fir forest. (4) The maximum soil water holding capacity of evergreen deciduous broad-leaved mixed forest (43.58 mm) was higher than that of Chinese fir forest (41.88 mm), the soil in evergreen deciduous broad-leaved mixed forest could provide better water support for vegetation growth. The maximum retention of soil moisture was evergreen deciduous broad-leaved mixed forest (8.20 mm)

Abstract:In order to comprehensively evaluate the function of water conservation of litters in Robinia pseudoacacia forests and provide the theoretical basis for the function-oriented stand improvement in Gully Region on Loess Plateau, five stand densities (475, 900, 1 575, 1 850, 2 525 plants/hm²) were chosen as subjects in this study at Caijiachuan watershed in Ji County of Shanxi province from July to August, 2017. The comprehensive coordinate method was applied to evaluate the function of water conservation of litters in R. pseudoacacia forests. Results showed that the litters of R. pseudoacacia forests could become effective fully on water conservation when the stand density was 1 575 plants/hm². However, the ability of the litter to play the function of water conservation was significantly reduced when the forest density was too high (2 525 plants/hm²) or too low (475 plants/hm²). The forest density should be controlled at 1 500 plants/hm² so that its litters could play fully the function of water conservation in R. pseudoacacia forests. Therefore, it was advised that the existing forest of R. pseudoacacia should be improved accordance to this forest density.

Abstract:In order to investigate the seasonal dynamics of soil soluble nitrogen after returning farmland to forest in loess hilly region, the Hippophae rhamnoides forestland and Armeniaca vulgaris Lam. forestland in Yongning Town of Zhidan County were taken as the research object. Soil samples were collected in 0-10 cm, 10-20 cm and 20-30 cm soil layers, and seasonal dynamic variation of the density and proportion of soil soluble nitrogen component were analyzed. The results showed that the measures of returning farmland to forest significantly increased the density of soil nitrate nitrogen, ammonium nitrogen and soluble organic nitrogen, especially in the 0-10 cm soil layer. There were significant differences in the above indexes among different soil layers and between H. rhamnoides forestland and A. vulgaris Lam. forestland. On the whole, nitrate nitrogen density varied significantly with seasons, the value was the highest in March, declined from March to June, increased from June to September, declined from September to November, and was the lowest in November. The ammonium nitrogen content in 0-30 cm soil layer varied little. The soluble organic nitrogen content varied significantly with seasons, and the highest and lowest value was found in June and November, respectively, and the content increased from March to June, declined from June to September and rised from September to November. The seasonal variation of soluble organic nitrogen density was opposite to that of nitrate nitrogen. The content of soluble nitrogen in H. rhamnoides forestland was higher than that in A. vulgaris Lam. forestland. The soluble nitrogen content of sunny slope was higher than that of shady slope. In 0-30 cm soil layer, the soluble nitrogen was mainly soluble organic nitrogen, accounting for 73.3%~99.0%, followed by nitrate nitrogen accounted for 0.9%~24.3%, and the proportion of ammonium nitrogen was the least, which was below 2%. The conversion of farmland to forest significantly increased the density of soluble nitrogen in 0-10 cm soil layer. The soluble nitrogen density increased differently in different forestlands, the value in H. rhamnoides forestland was higher than that in A. vulgaris Lam. forestland.

Abstract:In order to understand the water conservation capacity of litters and soils in different forest types in the Huangpu River, and improve the protection and management level of water conservation forests, this paper took five typical artificial pure forests (the Cinnamomum camphora forest, Osmanthus fragrans forest, Koelreuteria paniculata foerst, Sapindus mukorossi forest and Taxodium ascendens forest) in the Pujiang Country Park on the east side of the middle reaches of the Huangpu River as the research object. Water conservation capacities of the litter layer and soil layer in different forest stands were studied by cutting-ring method, drying method and indoor immersion method. The water conservation capacities were also quantitatively compared by combining the modified interception amounts of the litters and the effective water storage capacities of the soils. The results showed that the modified interception amounts of the litters in the five forest stands were 7.74~27.90 t/hm², Taxodium ascendens forest > Sapindus mukorossi forest > Osmanthus fragrans forest > Koelreuteria paniculata foerst > Cinnamomum camphora forest. The effective water storage capacities of the soils in the five forest stands were 104.87~174.01 t/hm², Koelreuteria paniculata foerst > Sapindus mukorossi forest > Cinnamomum camphora forest > Taxodium ascendens forest > Osmanthus fragrans forest. The sum of the modified interception amounts of the litters and the effective water storage capacities of the soils were 116.79~184.17 t/hm². It showed that the litters and soils in Koelreuteria paniculata and Sapindus mukorossi forests had the stronger water conservation capacities, followed by Taxodium ascendens, Cinnamomum camphora and Osmanthus fragrans forests. Therefore, during the construction and management of water conservation forest in the future, it is suggested that deciduous broad-leaved tree species should be selected as a priority, and coniferous tree species and evergreen broad-leaved tree species be properly planted, and the protection of the surface litter layer could be strengthened, so that the forest could play better role in water conservation.

Abstract:Taking the Platycladus orientalis forest distributed widely in Beijing mountain area as research object, the evapotranspiration of the stand was quantitatively separated by two methods, which were hydrological measurement method (sap flow sluice combined with large-scale lysimeter) and stable isotope. The results showed that:(1) On the daily scale, the evapotranspiration and transpiration of the stand both showed "single peak" type curves. The total evapotranspiration and transpiration of the stand reached the maximum values around noon, which was 1.27 mm/h and 1.13 mm/h, respectively. (2) The proportion of transpiration to total evapotranspiration calculated by the measured method and the stable isotope method was 80.21%~89.63% and 79.10%~98.71%, respectively. Compared with the measured values, the error of the stable isotope method was(3.97±3.53)% on the hourly scale, and was (1.89±0.67)% on the daily scale. The evapotranspiration of this stand was mainly from the transpiration of vegetation, and the water consumption of forest transpiration was far greater than that of soil evaporation.

Abstract:In order to explore the influence of water and fertilizer coupling on the water consumption rule of drip irrigated grape in extreme arid area, the distribution of water use in each growth stage and the dynamic changes in the whole growth stage were investigated under different water and fertilizer combinations. Then the crop coefficient of drip irrigated grape was determined in the area using the water balance method and the Penman-Montes formula. The age-old seedless white grape in the test area was taken as a research object, and two factors of irrigation and fertilization were set, including four irrigation treatments:600, 675, 750, 825 mm (labeled W1, W2, W3, W4, respectively); three fertilization treatments:450, 750, 1 050 kg/hm² (labeled F1, F2, F3, respectively). The results showed that the average soil water contents increased with the increases of irrigation quota. The water contents of W3 and W4 were 13.35% and 14.04%, respectively, both of which were higher than 12.80% (80% of field water holding capacity), indicating the sufficient water supply. The effects of water and fertilizer coupling on yields and quality indicators reached the very significant level (P<0.01). The yield and soluble solids reached the highest value in W3F2, but the titratable acid and vitamin C performaned best in W4F2 and W4F3, respectively. There was no significant difference in W3F2 (P>0.05). Under different treatments, irrigation had significant effects on the total water consumption and water consumption and water consumption intensities during each growth period (P<0.05), but the corresponding effects of fertilization did not reach significant level (P>0.05). The water-fertilizer coupling had a significant effect on the water consumption intensity during each growth period (P<0.05). The total water consumptions were maintained between 665.96 and 902.90 mm under the different treatments. The water consumption and water consumption intensities of each treatment increased first and then decreased during the growth periods. There was a significant quadratic curve relationship between water consumption intensities and time. The mean water consumption modulus of each treatment in the berry growth period and berry ripening period was 27.01%~27.36%, which was the peak of grape water demand. The water consumption law under W3F2 could be regarded as the regional water requirement of grape. The grape crop coefficient generally increased first and then decreased during the growth periods showing a significant quadratic curve relationship with time. This study could provide a scientific basis for the promotion of water and fertilizer management and drip irrigation technology in the non-nuclear white grape farmland in similar areas of the Tuha Basin. It also could be of great significance for the efficient use of regional water resources and the realization of sustainable socio-economic development regionally.

Abstract:Taking the "Hutai No.8" grape variety widely planted in Shaanxi Province as the test material, the first berry (fruiting at bearing shoot)and the secondary berry (fruiting at axillary shoot) quality indexes (such as soluble sugar, soluble protein, vitamin C, soluble solids, titratable acid, resveratrol and procyanidine) in different summer pruning intensities were measured in greenhouse. The results were used to synthetically evaluate the response of fruit quality to different summer pruning intensities, and to provide guidance for greenhouse grape cultivation and management. The results showed that summer pruning intensity could obviously impact the quality of the first berry and the secondary berry, and there were obvious differences between the quality indexes. In the case of fruiting secondary berry, the middle shoot pruning improved the quality of the first berry, but reduced the quality of the secondary berry. In the case of prohibiting secondary fruiting, the grape quality with the long shoot pruning was better. Although the taste and flavor of the first berry treated by the short shoot pruning was poor, its healthcare value was higher. The healthcare value of the secondary berry was generally better than the first berry, but its flavor was generally poor.

Abstract:In this study, the optimal pattern for water-phosphorus coupling and its influences on Nitrogen (N), Phosphorus (P) and Potassium (K) uptake and accumulation of flue-cured tobacco were studied, which provided scientific basis for the rational use of water-fertilizer resources in Qiandongnan prefecture tobacco land, Guizhou province. Three irrigation rates:0.50 L/plant (W₁), 1.00 L/plant (W₂) and 2.00 L/plant (W₃), and three P fertilizer application rates:32 kg/hm² (P₁), 64 kg/hm² (P₂) and 96 kg/hm² (P₃) were set in this field plot experiment. The results showed that, at the same P application rate, N, P and K uptake and accumulation of tobacco plant were significantly increased by irrigation. The order of N, P and K uptake and accumulation of each treatment was as follows:W₃P_i > W₂P_i > W₁P_i > CK_i (i=1 or 2 or 3). At the same water irrigation level, N, P and K uptake and accumulation of tobacco plant increased as P application rates increased. The P application rate of 96 kg/hm² was beneficial for N, P and K uptake and accumulation. The order of N, P and K uptake and accumulation was as follows:W_iP₃ > W_iP₂ > W_iP₁. Under high P application treatment, irrigation rate of 1.00~2.00 L/plant, N, P and K uptake and accumulation were not significantly different between W₃P₃ and W₂P₃ treatment. The K uptake and accumulation of tobacco plant, leaf, stem and root were higher than N and P. The order of N, P and K distributed in root, stem and leaf was as follows:leaf > sti > root. The N, P and K uptake, accumulation and accumulation intensities of tobacco plant were different at different growth stages. Nutrients uptake and accumulation of tobacco plant occurred mainly at tobacco leaf and vigorous growth stages. The P application rate of 96 kg/hm² and irrigation rate of 1.00~2.00 L/plant were suitable for N, P and K uptake and accumulation of tobacco plant. The optimal application rates of N, P and K fertilizers and water and phosphorus coupling should be paid attention to adjust in fertilizer application of tobacco.

Abstract:Albic soil is one of the main farmland soils in the eastern part of Jilin Province and Heilongjiang Province. Studying the adsorption of humic acid by albic soil can provide a theoretical basis for exploring the carbon sequestration potential of albic soil. Batch balance method was applied to analyze the adsorption kinetics and isothermal adsorption characteristics of albic soil with different organic carbon content and its components (including de-organic soil, silt, clay) to humic acid. The results showed that with the prolongation of adsorption time, the amounts of humic acid adsorbed by albic soil and its components increased gradually; the whole adsorption kinetics process could be divided into fast reaction (0~30 min) and slow reaction (30~480 min) stage. At the reaction stage, the fitting effect of the pseudo second-order kinetic equation was better than that of Elovich, double constant and pseudo first-order kinetic equation. The amount of humic acid adsorbed by albic soil and its components increased with the increasing of the initial concentration of humic acid, and the fitting effect of the Langmuir equation was usually better than that of the Freundlich equation and the Temkin equation. With the increasing of organic carbon content of albic soil, the maximum adsorption amounts for humic acid were 26.9, 24.1 and 15.6 mg/g, respectively. For the different components of the albic soil, the maximum adsorption amount followed the order of clay > de-organic soil > powder, and the adsorption amount of clay was 2.15 to 3.88 times that of the original soil, 1.61 to 2.21 times that of the deorganic soil, 7.90 to 8.65 times that of the powder soil. The above results showed that the albic soil with low organic carbon content had stronger adsorption capacity to humic acid, and the albic soil with high clay content had greater adsorption potential to humic acid.

Abstract:In the present study, two biochars derived from Platanus orientalis Linn branches and leaves respectively were prepared by pyrolysis at the temperature of 500℃ under the oxygen-limited condition. The batch equilibration method was used to determine the effects of different factors, such as contact time, initial Pb²⁺ concentration and initial solution pH on Pb²⁺ adsorption capacity on the biochars. The characteristics of adsorption isotherms and adsorption kinetics were analyzed to reveal associated mechanisms. The results showed that the mineral elements and functional groups were more abundant in the leaf biochar than those in the branch biochar. The maximum adsorption of Pb²⁺ on both biochars occurred at the initial pH 5 after 24 hours, and the adsorption capacity of the leaf biochar was 25.6% greater than that of the branch biochar. The adsorption of Pb²⁺could be described well by the pseudo-second-order kinetics, indicating that the adsorption process was mainly controlled by precipitation. The adsorption isotherms demonstrated that the adsorption of Pb²⁺ to the biochars fitted Langmuir model better than Freundlich model. Therefore, monolayer adsorption was proposed as the dominant adsorption process, although the multilayer adsorption was also present. In conclusion, both biochars had good capacity for adsorption of Pb²⁺ in water, and the leaf biochar was more effective than the branch biochar.

Abstract:The effects of rapeseed cake compost (RSC) on Cd availability in soil and its accumulation in different rice tissues were investigated using a pot experiment in this study. In order to provide reference for the safe production of moderately Cd-contaminated fields, RSC was applied to a Cd contaminated paddy soils (Cd=0.72 mg/kg) with different rates of 0, 0.75%, 1.5%, and 3.0% respectively, and then rice plants (Xiangwanxian 12#) were cultivated. The results showed that:(1) The application of RSC resulted in a sharp decrease in the soil TCLP-extractable Cd concentration. Compared with CK treatment, the soil TCLP-extractable Cd concentrations decreased by 45.1%~68.7% after 0.75%~3.0% RSC application. However, the soil TCLP-extractable Cd concentrations in the amended soil gradually increased during the rice growing period. (2) RSC was an effective organic fertilizer for increasing rice yield, but the total Cd concentrations in rice grain were also increased. Compared with CK treatment, when the 0.75%~3.0% RSC was applied, the total Cd concentrations in rice grain were 0.04~0.14 mg/kg, which met the national limit of Cd in food (GB 2762-2012, Cd<0.2 mg/kg). The rice yield was increased by 3.6~4.3 g/pant, 1 620~1 935 kg/hm² approximately. (3) The application of RSC increased Cd transport from root to shoot and significant raised the amount of Cd accumulated in rice plant, especially in the aerial part. In general, in the present study, the application of RSC increased the total Cd concentrations in rice grain. And it still remained at a low level, could meet the safety production of rice in Cd moderately pollution area. However, if RSC was applied to soil with higher Cd pollution level or higher Cd bioavailability, the total Cd concentrations in rice grain might be higher than the national limit of Cd in food. Therefore, we suggested that the application of RSC should be more prudent for the Cd-contaminated fields for the premise of ensuring rice safety production.

Abstract:Effects of Cadmium (Cd) stress on the physiological indexes, rhizosphere soil indexes, and the bioaccumulation ability in Helianthus tuberous L. of Weifang and Xuzhou were studied by a soil culture experiment. Experimental treatments included CK (Cd²⁺ 0 mmol/L as control), T1 (Cd²⁺ 0.1 mmol/L), T2 (Cd²⁺ 0.5 mmol/L) and T3 (Cd²⁺1.0 mmol/L). The results showed that all of the root lengths, plant heights, leaf lengths, and leaf widths of two varieties of Helianthus tuberosus were inhibited to some extent under different Cd stresses after 21 days. The activities of antioxidant enzymes were decreased with the increasing of Cd concentrations. While the changes of MDA contents were different in two varieties. The MDA contents of Weifang H. tuberous were increased with Cd stress, but those of Xuzhou H. tuberous were increase only under T3 reaching the highest MDA content after 21 days, which was 3.52 times of CK. The rhizosphere soil pH decreased approximately linearly, and both values in Weifang and Xuzhou H. tuberous decreased the most after 20-day treatment of T3, with 3.85% and 3.41% respectively lower than those of CK. The organic matter contents were increased with the increasing Cd concentrations, with the largest increase of 38.60% and 36.01%, respectively in Weifang and Xuzhou H. tuberous after 20 days. As Cd concentrations became higher, it inhibited the uptake of alkali-hydrolyzable nitrogen (AN) in soil by Helianthus tuberosus. The overall inhibition was greater than that of Xuzhou H. tuberous. The destinations of Cd transfer were different in two varieties. With the increase of concentrations, Cd almost equally transferred to the leaves and stems in Weifang H. tuberous, while most of Cd in Xuzhou H. tuberous transferred from the roots to the stems. The results indicated that H. tuberous has a strong ability to accumulate Cd and a certain resistance under Cd stress, even more obvious for Xuzhou H. tuberous. Therefore, H. tuberous could be applied in Cd-polluted soils with both economic and ecological significance.

Abstract:The effects of different types of shell powder on different forms of cadmium in soil were investigated through indoor culture. Three proportions of natural scallop shell powder and ascarid shell powder were applied to the soil after the culture. The soil pH and cadmium forms were measured on the 1st, 5th, 15th, 30th and 50th days after the application of shell powder, respectively. The results showed that the addition of aragonite and calcite shell powder contributed to the increase of soil pH. After adding the two kinds of shell powder, the soil pH increased with the increasing of shell powder addition ratio. The pH value of soil treated with different kinds of shell powder was not different, and the difference in soil pH value was the most obvious among different addition ratios after 50 days. During the whole cultivation process, with the increasing of the culture days, shell powders could reduce the exchangeable cadmium content in the cadmium-contaminated soil, while the contents of carbonate-bound cadmium, iron-manganese oxides, organic-bound cadmium and residual cadmium increased gradually as a whole. Among them, the applying the aragonite shell powder as a passivating agent was more effective than the calcite type. As the proportion of shell powder increased, the exchangeable cadmium changed to other cadmium speciation was more. After 50 days of culture, the contents of available cadmium in soils treated with shell powder were significantly lower than that of CK. When the addition ratio of shell powder was 5%, the bioavailable cadmium accounted for the lowest proportion of total cadmium. The results showed that aragonite shell powder had better effect of reducing soil available cadmium activity than that of calcite shell powder.

Abstract:Based on the soil column simulation experiment, wheat was irrigated with different dilutions rural mixed wastewater (sewage:clear water as 1:0, 1:1 and 0:1), and then the effects of rural mixed wastewater irrigation (WG) on wheat growth and soil nutrients, enzyme activity and microbial diversity in rhizosphere soil were studied. The results showed that the content of sewage had a certain influence on wheat growth, soil nutrients, enzyme activity and microbial diversity in wheat rhizosphere soil. Compared with clean water irrigation (CK):(1) The plant height, diameter, fresh weight and dry weight of wheat treated with WG were significantly greater than those in CK treatment (P<0.05), and the contents of chlorophyll a, chlorophyll b and total chlorophyll in wheat leaves increased significantly (P<0.05). (2) In the WG treatment,the organic matter content in wheat rhizosphere soil increased by 16.42%, while soil pH, the contents of total nitrogen, total potassium, total phosphorus, available phosphorus, available potassium and alkali-hydrolyzable nitrogen as well as comprehensive fertility decreased (0.95%~16.79%), and available potassium content decreased significantly (P<0.05). (3) The activities of acid phosphatase, urease and invertase in wheat rhizosphere soil in WG treatment were significantly higher than those in CK treatment (P<0.05), but catalase activity significantly decreased (P<0.05). (4) According to Shannon, Ace, Chao, Coverage, Simpson index and microbial community structure distribution map of bacteria and fungi at genus level, the diversity of bacteria in wheat rhizosphere soil decreased in WG treatment, while the diversity of fungi increased. At the same time, WG changed the relative abundance of dominant species of bacteria and fungi at genus level in wheat rhizosphere soil, but the dominant species of bacteria did not change, and the fungi dominant species changed. This study provides a strong theoretical basis for the study of rural mixed sewage irrigation mode in demonstration area.

Abstract:In order to explore the effects of veterinary tetracycline on physiological characteristics of maize seedlings, pot experiment was conducted to study the effects of different substrates (single application of worm cast, fungal chaff, microbial inoculum, biochar and its combined application with microbial inoculum) on growth of maize seedlings under the stress of exogenous tetracycline pollution. The results showed that tetracycline inhibited significantly the maize biomass, and its inhibitory effect on root length was significantly greater than that on plant height. The inhibitory effect of tetracycline on maize plant height and root length could be alleviated by adding different substrates, and the effect of JK (fungal chaff) and JJ (fungal chaff + microbial inoculum) treatment was the most significant, with the increase of 17.29% and 30.08%, respectively. Tetracycline significantly increased SOD activity in maize by 3.34%, and inhibited CAT and POD activity by 10.98% and 46.68%, respectively. Among the treatments with different substrates, QY (worm cast) treatment had the most significant effect on promoting antioxidant enzyme system balance. Tetracycline could increase the content of proline, malondialdehyde, soluble sugar, soluble protein and total flavonoids in maize, among the treatments with different substrates, JK, JJ, QY, S and JK treatments had the most significant reduction effects, the decline rates were 29.09%, 50.88%, 42.01%, 50.23% and 35.79%, respectively. Correlation analysis showed that proline and malondialdehyde both were extremely significantly positively correlated with soluble protein and total flavonoids, POD activity had the strongest correlation with soluble sugar, malondialdehyde had the strongest correlation with total flavonoids. In conclusion, adding different substrates could effectively alleviate the toxic effect of tetracycline on maize seedlings. The general trend showed that JK, JJ and QY had the best effect. Through this study, we could select the best substrates and application methods which could effectively reduce the effects of tetracycline on plant growth, provide reference for the research of physiological toxicity of tetracycline to plants, and also provide scientific basis for the risk assessment of antibiotic on plants.

Abstract:Taking Cd contaminated rice soil as the research object, a pot experiment was conducted to study the effects of various combination application of selenium (Se, 0.5 and 1.0 mg/kg) and fulvic acid (FA, 0.6 and 1.2 g/kg) on the uptake and accumulation of cadmium (Cd) in rice and the mechanism, and to provide a scientific basis for the safe utilization of rice contaminated by Cd. The results showed that single application of Se increased soil pH by 0.08 to 0.23 units, reduced CaCl₂ extractable Cd in soil by 8.6% to 20.9%, decreased the concentration of Cd in aboveground organs of rice by 29.4% to 39.5%. Additionally, single application of Se could effectively reduce the accumulation of Cd in rice and inhibited the translocation of Cd to above ground tissues and rice grain. For the treatments applied FA only, soil pH was significantly decreased, while the concentrations of soil CaCl₂-Cd, the Cd and Se in rice organs (except the Cd concentration in leaves and brown rice treated with low amount of FA), and the Cd distribution in different organs were not significantly influenced. The effect of combined application of Se and FA on soil pH was related to the dosage of two. High amount of Se combined with FA significantly reduced the CaCl₂ extractable Cd in soil by 16.5% to 21.9%. Combined application of Se and FA significantly inhibited the translocation of Cd to aboveground organs and rice grain, and was more effectively in reducing the accumulation of Cd in brown rice. Compare with the control, Cd concentrations of rice in the two treatments applied with high amount of Se combined with FA were significantly decreased by 38.1% and 50.2%, respectively. In conclusion, the application of Se could effectively reduce the accumulation of Cd in brown rice, while the combined application of Se and FA had better effect.

Abstract:The effects of substrates size grading on the purification of black and odorous water by self-designed ecological media boxes and their effects on the accumulation and growth of N and P in aquatic plants were studied by artificial static simulation test. The results showed that with the prolongation of treatment time, the removal rate of each pollutant increased gradually. The removal effect of TP, TN and NH₄⁺-N in both progressively-graded groups, anti-graded group was better than that in single plant group and matrix group. The removal efficiency of TP in progressively-graded group was better than that in anti-gradation group, its removal rate reached 66.9%. The accumulation of TP in progressively-graded group was better than that in anti-gradation group and plant group. But the removal efficiency of TN and NH₄⁺-N in water in anti-graded group was better than those in progressively-graded group, the removal rates reached 69.1% and 87.4% respectively. The accumulation of TN in anti-gradation group was better than those in progressively-graded group and plant group. The plant factors in the ecological media boxes had a low contribution rate to nitrogen and phosphorus removal. The removal of N and P was mainly through non-plant factors (matrix, microbe). However, except for the blank group, there was no significant difference in the removal of COD_Mn between the groups, indicating that the direct removal of COD_Mn by substrates and plants is not obvious, and it depends more on the role of microorganisms attached to the substrate and plant carriers. The experimental group containing the mineral matrix (progressively-graded group, anti-gradation group, and matrix group) could raise the pH of water and effectively regulate the acidic water body. The way in which aquatic plants (Vallisneria natans (Lour.) Hara) were directly implanted into the sediment (plant group) is more suitable for plant growth. Therefore, the effect of repairing water bodies with different N, P pollution levels can be satisfied by replacing the substrates size gradations.

Abstract:Aiming at the poor physicochemical properties, the low fertilizer use efficiency and the weak crop growth in saline soils, a saline soil was ameliorated with different biochar fertilizers in this study. Brassica chinensis and cotton were used as research materials in this pot experiment. Five different treatments were conducted, i.e., non-fertilized control group (CK0), conventional fertilization (CK), conventional fertilization+biochar (C1), conventional fertilization + biochar + nitrification inhibitor (C2), conventional fertilization + biochar + Calcium sulphate (C3). The growth and photosynthesis of Brassica chinensis and cotton were measured. The results showed that C3 treatment was more effective in crop growth than that of CK. The plant height and weight of Brassica chinensis were increased by 32.7% and 112.0%, respectively, and the chlorophyll content and net photosynthetic rate were increased by 45.5% and 32.9%, respectively. The intercellular CO₂ concentration and transpiration rate were decreased by 15.0% and 59.2%, respectively. Spectral analysis indicated that the C3 treatment had higher reflectance and better leaf tissue. The experimental results also indicated that, compared to CK, biochar treatments promoted cotton growth, expressed as increase in chlorophyll content significantly, decreasing malon dialdehyde content and catalase activity in leaves, leading to the enhanced stress resistance and the reduced plant damage. At the same time, the intercellular CO₂ concentration in cotton leaves was reduced, and the water use efficiency was improved. Soil analysis suggested that the application of biochar significantly improved the physical and chemical properties of soil. Compared with CK, the organic matter content, available phosphorus content and alkali nitrogen content in C2 treated soil were increased by 57.3%, 22.9% and 40.8%, respectively. However, the influence on soil available potassium content and pH value was not obviously, and C3 treatment had an obvious increase in soil electrical conductivity. Therefore, when ameliorating the saline soil, it is necessary to pay attention to the reasonable application amount of the modifiers to prevent further accumulation of soil salinity.