Abstract:Based on the daily precipitation and runoff sediment yield data in 2016 and 2017 under different slope land measures (slope farmland and changing slope to terrace) in the test station, the law characteristics of runoff sediment yield under different slope land measures and rainfall intensities were studied. The impact of changing slope to terrace and slope farmland on runoff and sediment was quantitatively revealed. The results showed that: (1) In July, the average rainfall intensity I, the maximum rainfall intensity I₃₀ and the slope land runoff were the largest, and in August, the maximum rainfall intensity I₆₀ and the slope land sediment yield were the largest, indicating that the peak of runoff and sediment was the same as the peak of rainfall intensities. (2) The correlations between runoff and sediment yield in spring and summer and I, I₃₀ and I₆₀ were significant (more than 95% confidence test). The correlation coefficients in slope land were higher than those in changing slope to terrace land. In spring and summer, the sediment yields in slope land were 3.91 and 7.85 times of those in changing slope to terrace land. (3) The rainfall was mainly concentrated in I: 1~3 mm/h, I₃₀: 3~29 mm/h, I₆₀: 2~27 mm/h, and the runoff and sediment yield in slope land was positively correlated with the maximum rainfall intensity I₃₀ and I₆₀ at 95% confidence level. When I₃₀ reached 29.0 mm/h, I₆₀ reached 26.6 mm/h, the runoff and sediment yield in slope land reached the maximum. The peak values of runoff and sediment yield in slope land were 2.43, 7.52 times higher than those in changing slope to terrace land. The variation coefficients of runoff and sediment yield in the whole year were higher than those in changing slope to terrace land. Thus, changing slope land to terrace could prevent soil erosion to a certain extent, and reduce the variation of runoff and sediment yield.

Abstract:Based on indoor simulated rainfall test, this study compared the influence of intermittent rainfall and continuous rainfall on rill erosion on loess slope, quantified and compared the experimental errors of intermittent rainfall relative to continuous rainfall conditions, and evaluated the suitability of this experimental method in slope erosion simulation. The results showed that: (1) At low rainfall intensity (≤60 mm/h), for the intermittent rainfall test, the rill sediment production on the slope was significantly reduced with an error of -40.8%, and the error was between -33% ~ -45% along with the decreasing of ditch width, ditch depth and cleavage degree. The error of runoff production was small (0.4%). (2) When the rainfall intensity was high at 90 mm/h and 120 mm/h, the errors of various indexes of sediment and runoff production and rill morphology were all small, ranging from 3% to 12%, which had relatively little impact on the test results. (3) When the intermittent rainfall test method was used, it was suggested to adopt the high rainfall intensity test conditions (≥90 mm/h) to accurately simulate the rill erosion process of natural rainfall, and the rainfall duration of each stage of intermittent rainfall test should be controlled in case of high rain intensity, so as to avoid the continuous and rapid growth of accumulated sediment yield which leaded to the sharp development of rill erosion and further increase of error. Because of the difference of soil properties, the applicability of the test results in other areas needed further study. The results could provide technical support for the study of rill erosion process and mechanism.

Abstract:In order to explore the soil and water conservation benefit of different ecological restoration measures on sloping land under different rainfall conditions, this study analyzed the runoff and sediment under six ecological restoration measures (Ecological restoration grassland, ERG; Level terrace and preparation+fruit forest, LF; Fruit forest, FF; Sloping land, SL; Cultivated pastures, CP; Soil and water conservation forest, SWF) under the 104 erosive rainfalls. The observation data from 2014 to 2017 of runoff plots located in the Yunwu Water and soil conservation monitoring station, Guizhou province were used. The results showed that: (1) According to rainfall duration, rainfall intensity and rainfall, erosive rainfall could be divided into three types: A-type (medium duration, medium rainfall intensity and medium rainfall); B-type (long duration, light rainfall intensity and large rainfall); C-type (short duration, heavy rainfall intensity and small rainfall), and C-type was the main cause of regional soil erosion. (2) Compared with sloping farmland, the runoff reduction under the A-type and C-type showed the trend of LF > SWF > CP > ERG > FF, and the sediment reduction showed the trend of LF > CP > SWF > ERG > FF. The runoff reduction under the B-type showed the trend of LF > ERG > SWF > CP > FF, and the sediment reduction showed the trend of LF > ERG > CP > SWF > FF. Except ERG, the control effect of different measures on soil and water loss under A-type and C-type was better than that B-type. The control effect of different measures on slope sediment yield was better than that of runoff. ERG had good soil and water conservation effect under B-type. (3) The soil erosion of sloping land was the most serious. Compared with sloping farmland, the runoff reduction rate of LF was 62.7%, 53.0% and 63.2% under A-type, B-type and C-type respectively. The soil erosion modulus of LF was 3 t/(km²·a), which could reduce the soil erosion rate by 99.2% compared with the sloping farmland. (4) Slope runoff and rainfall were concentrated from May to August. Slope sediment and C-type were concentrated in May and June.

Abstract:As a direct reflection of human activities, land use cover deeply influences the surface vegetation and surface runoff, which leads to the change of soil conservation. Taking Chongqing as a case study, the soil conservation change trend was studied by the trend analysis method and the sensitivity of soil conservation to land use transition was analyzed by the cross-sensitivity coefficient method. The results showed that: (1) The land types in Chongqing were mainly forest land and dry land. From 2000 to 2015, the area of forest land, bare land, construction land, and water increased, while the area of dry land, grassland, and paddy field decreased. The construction land had the largest increase, mainly from dry land and paddy fields. The dry land had the largest decline, mainly converted into construction land and forest land. (2) From 2000 to 2015, the amount of soil conservation in Chongqing increased, but the growth trend was not linear. The soil conservation with extremely significant and significant increase accounted for 21.85% of the total increase area, respectively, while those with extremely significant and significant decrease were 0.10%, and the rest was not changed basically. The increased and significantly increased areas were mainly concentrated in the dry land and forest land with an altitude of 500~1 000 m, while the decrease and significant decrease areas were mainly in the dry land below 500 m above sea level. (3) The transitions of dry land to grassland and paddy fields to forest land were the most sensitive land conversion types with sensitivity coefficients of 11.01 and 6.73. The transitions of dry land to bare land, paddy fields, and water, forest land to water and bare land, and grassland to water, bare land, and forest land was sensitive, and their sensitivity coefficients were higher than 1.

Abstract:In order to quantitatively analyze the impact of land use changes on runoff in the Minjiang River basin, combined with the scenario setting method, SWAT model was constructed to simulate the runoff process under different land use scenarios in this study. The results showed that: (1) The parameterized SWAT model had good applicability to runoff simulation in the Minjiang River Basin with the evaluation indexes R²>0.9,NSE>0.8,|PBIAS|<10% at calibration and validation periods. (2) When the current land use was set as the reference, the annual runoff increased by 12.41%, 22.89% for the farmland reserve scenario and construction development scenario respectively, and decreased by 4.09%, 1.61% under the vegetation restoration scenario and zoning scenario, indicating that the forestland and grassland had the stronger mitigation effect on the runoff and reduced the inter annual variation of runoff, while farmland and construction land increased the runoff. (3) Combined with the value of conservation index and the simulation results of monthly average runoff in wet reason and dry periods, it was studied that the forestland and grassland had the stronger capacity of reserving water and regulating runoff, while that of farmland and construction land was weak, but the former was better than the latter. (4) Based on the "reasonable development of farmland and protection of forest in the north of West Fujian, and the promotion of ‘slope industry’ in the north of East Fujian", the zoning scenario could not only effectively decrease and regulate the runoff of the Minjiang River basin, but also ensure the grain safety and economic development, realize the unity of ecological and economic benefits, and provide reference for the scientific, efficient and sustainable land use planning of the basin.

Abstract:Taking the purple soil sloping farmland in the seasonal arid area of the lower Jinsha river as the research object, the PR2/6 soil profile moisture analyzer and tipping rain gauge were used to continuously observe the soil moisture content of 0—100 cm soil layers and rainfall during the rainy season, and the purple soil moisture dynamics and its response to rainfall were analyzed. The results showed that there was a significant difference in the monthly average soil moisture content. The soil moisture content of 0—20 cm was as follows: September > August≈July > June, showing an increasing trend throughout the rainy season. The amount of rainfall was the major factor affecting the depth of water supply in soil. Light rain (6.4 mm) only affected soil moisture content above 10 cm, which increased 12.35%; moderate rain (23 mm) affected soil moisture content above 30 cm, and 10, 20, and 30 cm increased by 21.16%, 17.77% and 8.22% respectively; heavy rain (49 mm and 112 mm) affected soil moisture above 60 cm, 49 mm increased by 7.18%~31.12%, 112 mm increased by 34.12%~49.18%. The increased amount of soil moisture in 0—40 cm was significantly correlated with the amount of rainfall and rainfall duration at the level of 0.01; meanwhile, the increased amount of soil moisture in 0—20 cm soil layers was significantly negatively correlated with the drought interval at the level of 0.05; the increased amount of soil moisture in 30—40 cm was significantly correlated with the accumulated rainfall in the previous 3 days. More than 70% of the soil water of purple soil was stored in 60 cm and 100 cm soil layers, accounting for 15.82% and 58.39% of the total soil water storage, respectively. The respond of soil water storage in different soil layers to rainfall was different. The soil water storage of 0—30 cm changed the most in June, the soil water storage of 60—100 cm was relatively stable, while the soil water storage of 60—100 cm changed more than that of 0—30 cm from July to September.

Abstract:Analyzing the temporal and spatial trends of climate change in Guizhou Province is of great significance for planning ecotourism development, environmental protection and disaster prevention in the region. Based on the monthly precipitation data from 17 sites in Guizhou Province during 1960 to 2018, methods of linear regression,moving average, ordered clustering, Mann—Kendall mutation test, and inverse distance weight interpolation were applied to analyze spatial and temporal characteristic of precipitation in Guizhou. The study showed that: In the past 59 years, Guizhou had a downward trend in precipitation, with a precipitation coefficient of -0.102. Although the annual precipitation in Karst valleys and non-karst areas was increasing, the trend was not significant. While other areas (karst troughs, peak-cluster depressions, Karst Plateau, and karst basins) showed all downtrend of precipitation, and the karst basin’s deceleration rate was -37.57 mm/10 a, which downtrend was the most significant, and it was 1.37~2.25 times of the other three regions. The annual precipitation descended at a rate of -16.50 mm/10 a, and annual precipitation tended to decrease from northeast to southwest in the space. The increase of precipitation in autumn and winter contributed the most to annual precipitation, while in spring and summer the precipitation showed a downtrend. Meanwhile the annual precipitation days and the maximum daily precipitation also showed a decreasing trend, the latter trend was most obvious after the 1980s so that the average maximum daily precipitation decreased to about 1/10 of that in the 1960s. In addition, the annual precipitation in non-karst areas and Karst Plateau changed abruptly from 1985 to 1986, and in karst basins the annual precipitation had a change in 2001 abruptly. There was no abrupt change in the annual precipitation in Karst troughs and peak-cluster depressions and Karst valleys.

Abstract:Based on the daily observation data of three runoff communities (tea, mulberry and red taro) in soil and water conservation test station of Huoshan county from 2016 to 2017, this study quantitatively analyzed the law and dynamic changing characteristics of runoff and sediment yield under the conditions of soil moisture content and natural rainfall. The results showed that: (1) April to July was the peak period of runoff, during which the yield of each community accounted for 76% (mulberry), 57% (tea) and 70% (red taro) of the annual yield. The inhibition effect of three crops on the runoff and sediment yield was ranked as tea > mulberry > red taro.(2) The changes of the soil moisture content under different crops were similar, showing a "W" type for the annual change. The average water contents of the surface soil were ranked as tea > mulberry > red taro, which was consistent with the effect of crop inhibition on runoff and sediment yield. The stability of soil moisture was the strongest in autumn and the weakest in summer. Mulberry trees stabilized soil moisture best throughout the year. (3) The grey correlation degrees between rainfall parameters and soil water content were as follows duration > mean rainfall intensity > I₃₀ > I₆₀ > rainfall. Rainfall erosivity had the greatest influence on runoff in crop plots. In terms of sediment yield, the maximum contribution variable of sediment yield in tea land and red taro land was I₃₀, and the maximum contribution variable of sediment yield in mulberry land was rainfall.

Abstract:Water resources are strategic resources that affect the high-quality development of the Yellow River Basin. Under the influence of human activities and climate, the runoff in the upper and middle reaches of the Yellow River has undergone changes greatly. Therefore, the variation characteristics of the runoff in the Yellow River and their prediction have great importance on the rational development, allocation and regulation of water resources. This study used the runoff data measured from 1950 to 2018 at the Tongguan station of the Yellow River to analyze the characteristics of runoff changes in the upper and middle reaches of the Yellow River by M-K and other methods. The change trends of runoff at different frequencies in the next 20 years were also predicted. The results showed that the runoff in the upper and middle reaches of the Yellow River decreased significantly from 1950 to 2018; the runoff changing point of the Tongguan station of the Yellow River was located in 1985, and the decreasing trend was significantly higher than before; through the optimized GM (1,1) model, 5% and 95% frequency runoff predictions indicated that the runoff change in the next 20 years would be 113.38 to 210.35 billion m³, and it would continue to decrease and stabilize; this optimized model had good simulation results for the Tongguan hydrological data of the Yellow River and was suitable for frequency optimized prediction of long sequences of low decreasing hydrology.

Abstract:Natural runoff reflects the effects of climate change and land surface variation, which is important for water resources allocation in the basin. Further understanding long-term variations in natural runoff is of great significance in water resources management. This study applied the empirical mode decomposition method (EMD), moving average method and anomalous accumulation method to reveal the temporal and periodical changes in natural runoff with long-term data from 1470 to 2018 in the Yellow River basin. The results showed that annual natural runoff had a significant random characteristic, showing wet-dry fluctuations within different periods. The annual natural runoff at 5% and 95% frequency were 33.70 billion m³ and 68.10 billion m³, respectively. The natural runoff of the Yellow River could be divided into two periods by the year of 1825. The EMD method showed that the natural runoff had a significant periodical cycle of 2.8 years, followed by 23.8 years, 47.3 years, 5.6 years and 11.3 years. The periodic feature was mainly influenced by the Sunspot activity, El Niño phenomenon and the amplitude changes factor of earth pole movement.

Abstract:Through simulated rainfall experiments, the experimental micro-plots were used to simulate different soil macropore structures (exposed type, shallow-buried type, and deep-buried type), and the totally soil filled micro-plots were used as a control to discuss the effects of soil macropore structure on karst soil and water loss processes. The results showed that: Compared with the totally soil filled micro-plots, the presence of soil macropore significantly accelerated the vertical water leakage, and different soil macropore structures had distinction runoff peaks (exposed > shallow-buried > deep-buried > totally soil filled). The soil macropores also exacerbated soil loss risk, and there were significant differences in soil loss between different soil macropore structure treatments (exposed > shallow-buried > deep-buried > totally soil filled). The soil loss amounts were relatively small (less than 10 g), and larger soil loss amounts only occurred under extreme conditions (exposed soil micropores with a rain intensity of 120 mm/h). Small-sized sediments less than 2 mm were dominated during soil loss processes for all treatments, and the sediments larger than 5 mm mostly occurred in the exposed soil macropore treatments. There were significant correlations between soil loss factors (soil loss amount and fine sediment content) and water leakage factors (water leakage initiation time and water leakage amount).The water leakage process was mainly affected by rainfall intensity, and the soil loss process was mainly affected by the soil macropore structures. The results of this study can provide scientific and technological support for the prevention and control of rocky desertification and groundwater pollution in karst areas.

Abstract:In this paper, the secondary forests of Populus and Quercus (hereinafter referred to as secondary forests), Robinia pseudoacacia forest, Platycladus orientalis forest, and Pinus tabulaeformis forest were selected as the research objects. Through sample survey and indoor immersion method, to compare and analyze the hydrological characteristics of litter (undecomposed layer, semi-decomposed layer), and study the hydrological and ecological characteristics of litter layer in typical forest stands. The results showed that: (1) The thickness of litter is 3.93 to 4.95 cm. The largest was R. pseudoacacia forest, and the smallest was P. tabulaeformis forest.The largest volume was secondary forest (19.28 t/hm²), followed by P. orientalis forest (18.03 t/hm²) and R. pseudoacacia forest (17.57 t/hm²), the smallest was P. tabulaeformis forest (14.73 t/hm²).The accumulation of undecomposed layers was less than that of semi-decomposed layers. (2) The maximum water holding capacity (rate) of litter was 30.92 to 61.31 t/hm² (197% to 320%), the secondary forest was the largest, followed by R. pseudoacacia forest, P. orientalis forest, and the smallest was P. tabulaeformis forest. (3) There was a significant difference in effective storage of litters (P>0.05), which was represented by secondary forest (31.29 t/hm²) > R. pseudoacacia (22.20 t/hm²) > P. orientalis (18.19 t/hm²) > P. tabulaeformis (13.94 t/hm²). The effective storage rate was 107% to 173%. (4) Within 2 hours of immersion, the water holding capacity and water absorption rate of litter in secondary forest and black locust forest changed most rapidly. The semi-decomposed layer changed faster than the undecomposed layer. In the process of holding water, the two had logarithmic function (R²>0.89) and power function relationship (R² > 0.99) with time. Among the four types of forest land, the hydrological potential of litter in secondary forests was the best, and that of pure P. tabulaeformis forest was the worst. The potential of hydrological characteristics was secondary forest > R. pseudoacacia > P. orientalis > P. tabulaeformis. R. pseudoacacia was the best forest species among the three plantations except secondary forest. It is recommended to reasonably optimize the restoration of tree species allocation in the study area to improve hydrological and ecological functions.

Abstract:Base on the measured data from 2014 to 2018 on runoff plots in Changting County of Fujian Province, the slope erosion characteristics of various land uses were studied. How the loss of soil and runoff were influenced by rainfall, soil and water conservation measures and vegetation was analysed, and the results showed that characteristics of the loss of soil and runoff are different on runoff plots of various land uses and with various soil and water conservation measures. The effect of annual rainfall on the annual loss of soil of runoff plots was not significant, whereas the effect of various soil and water conservation measures significant. Both the effect of annual rainfall and various soil and water conservation measures on the annual runoff of runoff plots were significant. The correlation coefficients between the annual loss of soil and the annual rainfall, the annual runoff and the annual rainfall were both related to the soil and water conservation measures and the species and growth of the plants in the runoff plots. There was a positive correlation between the annual loss of soil and annual runoff, which means the annual loss of soil increases with the annual runoff. This study can serve as a reference for water and soil loss control in Changting County.

Abstract:The objective of this study was to reveal the soil and water conservation effects of different straw returning patterns at croplands in the black soil region of China. Based on simulated rainfall experiments at field croplands in situ, effects of three representative straw returning patterns (deep application of straw, smashed straw turnover, and no-tillage with straw mulching) on the processes of runoff rates and soil loss rates, total runoff and soil erosion amount, runoff and sediment reduction benefits at 50 and 100 mm/h rainfall intensities were analyzed. The traditional up- and down slope tillage was used as the control treatment. The results showed that: (1) The runoff rates for treatments of different straw returning patterns increased as the rainfall amount increased. Both the runoff rates and soil loss rates decreased in the order of up- and down slope tillage (CK) > deep application of straw > smashed straw turnover > no-tillage with straw mulching. (2) The straw returning treatments delayed the runoff yield time for 14.0 min at 50 mm/h and 4.8 min at 100 mm/h compared with the traditional up-and down slope tillage treatment, which could reflect the soil and water conservation effects of these straw returning measures. (3) The mean runoff reduction benefits for deep application of straw, smashed straw turnover, and no-tillage with straw mulching treatments were 36.8%, 53.9%, and 65.8%, and their mean sediment reduction benefits were 84.9%, 90.3%, and 96.8%, respectively. Therefore, the pattern of no-tillage with straw mulching had the best soil and water conservation effect in this study, which was followed in descending order by the patterns of smashed straw turnover and deep application of straw.

Abstract:The soil erosion in hilly red soil region (HRSR) of southern China has a serious impact on the local ecological environment. The government has implemented a series of ecological projects to control soil erosion. However, there are few studies on the ecological effects of ecological projects such as the Grain for Green Program (GFGP) in the southern region. This paper selected the hilly red soil region of southern China as the research area. Based on the land use data in 2000, 2005, 2010, and 2015, we identified the spatial extent of the Grain for Green Program (GFGP) in HRSR. We also estimated the effect of soil conservation in areas where the GFGP actually occurred by the Revised Universal Soil Loss Equation (RUSLE). The results showed that from 2000 to 2015, the GFGP area in the HRSR was about 2 052.61 km². During this period, soil conservation quantity increased by 918 million tons, and the change in soil retention per unit area was 447 327.54 t/km². The overall soil conservation effect was significantly improved, but some areas still had negative benefits. In addition, the conversion of bare land into forest land was the most effective way of land use change for improving soil conservation services. The implementation of GFGP improved the regional soil retention function. This study has guiding significance for the implementation and management of the GFGP in hilly red soil region of southern China.

Abstract:Aimed to analyze the relationship between landslide distribution and vegetation types, typical landslide areas and tree species was chosen in this research. Pinus tabuleaformis, Pinus armandi, Larix kaempferi, and Quercus aliena are 4 typical tree species widespread in the study area, and their root distributions and mechanical characteristics among species were analyzed. The unmanned aerial vehicle images were used to obtain the landslide density in different vegetation areas according to different physiological characteristics of leaves. Root investigation within 100 cm depth soil by soil profile method was used to quantify root number and diameter distribution, indoor experiments were conducted to test the tensile strength of each single root for root additional cohesion evaluation. Finally, the safety factors of slopes with different vegetation types under different water conditions and slopes were calculated combining with forest survey results and the mechanical properties of rock and soil. The results showed that: (1) The P. tabuleaformis and P. armandi forests have higher landslide density than the L. kaempferi and Q. aliena forests in both high and low landslide density areas. (2) The root number, distribution depth, and tensile strength of single root of Q. alienawas significantly greater than those of P. tabulaeformis, P. armandi, and L. kaempferi. The root vertical distribution of Q. aliena was more than 100 cm, the root maximum tensile strength was (32.551±7.551) MPa, and the root average cohesion was 9.364 kPa in 100 cm depth. (3) When the rock and soil were in saturated extreme precipitation condition, the contributions of P. tabuleaformis, P. armandi, and L. kaempferito slope stability were negative, while Q. alienacould efficiently reinforce the slope and had good function of preventing and controlling the sallow landslide.

Abstract:In recent years, the influence of vegetation restoration on soil infiltration process in different ecosystems has been a hot topic. The purpose of this study was to explore the influence of different vegetation restoration strategies on the spatial change of soil infiltration characteristics. Through the analysis of soil bulk density, soil porosity, soil organic matter, and soil penetrability characteristics of natural grass shrub mixed forest, secondary forest land, natural grassland, mango land, nut land, and corn land in the experimental area of rocky desertification control in Guizhou, the results showed that: For different vegetation restoration strategies, there are significant differences in soil bulk density, porosity, and organic matter content, which are manifested in natural vegetation restoration (grass shrub mixed forest and secondary forest land) and straw returning planting mode can effectively reduce soil bulk density and increase soil porosity. With the increase of soil depth, soil bulk density increased, soil porosity and organic matter content changed in the opposite direction. Different vegetation restoration methods and soil depth significantly changed the soil water permeability characteristics, among which, the soil permeability of natural vegetation restoration (grass shrub mixed forest and secondary forest land) was higher than that of artificial vegetation restoration (mango land and nut land), mainly because under the condition of nature vegetation restoration, soil disturbance was small, plant roots and litter increased, which changes the physical properties of soil, reduces soil bulk density, and improves the comprehensive benefits of soil porosity. With the increase of soil depth, steady infiltration rate and cumulative infiltration amount decreased. By measuring the soil hydrological characteristics of different vegetation restoration methods, we can provide a scientific basis for the evaluation of vegetation restoration methods and soil infiltration performance in karst areas.

Abstract:In this paper, the spatial dynamic transfer process of soil organic carbon under hydraulic erosion was accurately described using geostatistics Kriging interpolation method to explore the relationship between erosion and carbon balance, and to provide scientific reference for effective control of soil erosion on the slope surface of Pisha sandstone area. The results indicated that: (1) Before and after the rainfall, the organic carbon of each soil layer decreased with the increase of soil layers, showing medium variation and positive spatial autocorrelation. The maximum autocorrelation occurred in the 0—10 cm soil layer. After rainfall, the organic carbon content of 0—20 cm soil layer decreased while that of 20—40 cm soil layer increased, and the variation degree of each soil layer was weaker than that before rainfall. (2) Before and after rainfall, soil organic carbon was fitted with Gaussian model and spherical model respectively, and the range increased with the increase of soil layers. Before and after rainfall, 0—10 cm soil layer showed strong spatial correlation and the nuggrt/sill increases after rain, while 10—40 cm soil layer showed moderate correlation and the nugget/sill decreased after rain. (3) After rainfall, the spatial heterogeneity weakened and the patch area became larger, which was generally manifested by the erosion in the same soil layer. Erosion occurred in the 0—20 cm soil layer, while sedimentation in the 20—40 cm soil layer. (4) Before and after the rainfall, soil organic carbon and clay contents showed a significant positive correlation. A very significant positive correlation was found in 0—10 cm layer before the rainfall, and the correlations increased after the rainfall, showing a very significant positive correlation in all soil layers. However, the correlation between soil organic carbon and silt contents before and after rainfall was weak and not significant, while the correlation between soil organic carbon and sand contents was basically negative.

Abstract:In order to deeply explore the temporal and spatial variation characteristics of soil moisture in dunes in semi-arid areas and its relationship with environmental factors, this study selected the Horqin Sandy Land, as the study area. Based on in-situ observation, numerical simulation, and redundant analysis, the temporal and spatial variation characteristics, variability, water balance and quantitative relationship of the environmental factors of soil moisture in dune were studied. The results showed that the soil moisture in the dune shows a trend of a gradual transition from a "mirror S" type of moving sand dunes to an "S" type of fixed dunes, and a "normal distribution" on the time scale. The soil water variability of the semi-flow, semi-fixed, and shady fixed dune gradually decreased with the increase of depth, and the half sun slope fixed dune showed an "S" type distribution with a maximum coefficient of variation of 75.45%, all of which were moderately variable. The water in the semi-flow and semi-fixed dunes was mainly consumed by deep leakage, accounting for 57.35% and 54.56% of the total water, respectively. The half sun slope fixed and shady fixed dunes moisture was mainly consumed in vegetation transpiration, accounting for 77.15% and 54.88% of the total water. The factors affecting soil moisture in dune were different. Bulk density, sand content, silt content, and saturated hydraulic conductivity were the main factors affecting soil moisture in semi-flow, semi-fixed, and shady fixed dunes. However, organic matter, sand content, silt content, and saturated hydraulic conductivity were the main influencing factors of soil moisture in the half sun slope fixed dunes. Study showed that the half sun slope fixed dunes are easy to consume the deep soil water, causing soil desiccation, and herbs and semi-shrubs are conducive to deep soil moisture retention.

Abstract:To investigate the effects of slope shapes and polyacrylamide (PAM) applications on runoff, soil erosion and nutrient loss, this study conducted the field artificial rainfall experiments with two PAM application rates and nine slope shapes. The results showed that the average amount of soil, ammonia nitrogen and phosphate losses from convex slopes increased by 25.12%,24.01% and 26.96%compared to the uniform slopes, respectively, while those of concave slopes decreased by 13.53%, 10.85% and 19.95%, respectively. Soil and nutrient losses were also increased with the increase of convexity in convex slopes. For runoff, there was little difference between concave and convex slopes, but the runoff amounts of both convex and concave slopes were greater than those of uniform slopes. After PAM application, the soil loss decreased by more than 90% and the nutrient loss decreased by 28.19%~68.13%. Application of PAM had the best effect on reducing soil erosion and nutrient loss in convex slopes.

Abstract:In order to illustrate the influence of changed tillage methods on the soil physical properties, field experiment was set up to monitor the variations of soil bulk density, water content, and soil penetration resistance after the change from rotary tillage (RT) to no-tillage (NT) and subsoiling (SS). Three treatments (RT, NT, and SS) were used to monitor the soil water content, bulk density, and penetration resistance in maize growing season, and quantitatively analyze the respond of soil penetration resistance to soil water content and bulk density changes. The results showed that soil bulk density was stable at 1.3 g/cm³ in NT during a maize growing season, and increased gradually with time from 1.0 g/cm³ to 1.3 cm³/cm³ at 0—15 cm depth in RT and SS. Compared with RT and SS, NT increased soil bulk density at 0—30 cm depth, water content at 0—45 cm depth, and penetration resistance at 0—15 cm depth, whereas NT reduced penetration resistance at 15—45 cm depth during the time of drought. An exponential model with soil bulk density and water content was developed to predict variation of penetration resistance (P<0.001, R²=0.77). Based on this model, if water content <0.13 cm³/cm³ and soil bulk density >1.4 g/cm³, penetration resistance was more than 2 MPa which is the threshold value of limiting root growth. If water content <0.2 cm³/cm³ and soil bulk density >1.2 g/cm³, the sensitivity of penetration resistance to the soil water content was greater than to the soil bulk density, this indicated that the increase in penetration resistance caused by drought in this area is more important than compaction. No-tillage could help to maintain soil water content in this area, reduced the soil compaction effect caused by the increased of bulk density, and avoid the impact of soil compaction stress on crop growth.

Abstract:To investigate the effects of ecological restoration project on variations of inorganic sulfur fractions in marsh soils during the growing season, the Phragmites australis marshes in un-restoration plot (R₀), restoration plot since 2007 (R₂₀₀₇), and restoration plot since 2002 (R₂₀₀₂) of the Yellow River estuary were studied. Results showed that the contents of inorganic sulfur fractions in marsh soils were greatly altered by the ecological restoration project. Compared with R₀, the levels of Water—soluble—sulfur (H₂O—S) in soils of R₂₀₀₂ and R₂₀₀₇ decreased by 46.7% and 44.7%, whereas those of Adsorbed—sulfur (Adsorbed—S) and HCl—Soluble—sulfur (HCl—Soluble—S) increased by 0.4%, 116.0% and 50.1%, 29.1%, respectively. By comparison, the contents of HCl—Volatile—sulfur (HCl—Volatile—S) in soils of R₂₀₀₂ decreased by 8.0% while those of R₂₀₀₇ increased by 19.7% compared to R₀. The contents of inorganic sulfur fractions in marsh soils of different restoration stages showed different variations during the growing season. There were two probable reasons. First, it was closely related to the growth rhythm of different marsh plants and the sulfur supply relationships between aboveground and belowground parts; Second, it was dependent on the variations of environmental factors (especially pH, EC, and nitrogen nutrient) caused by different ecological water supplement patterns. With increasing restoration years, both the total inorganic sulfur (TIS) content and its proportion in total sulfur (TS) content in marsh soils decreased greatly. Also, the TIS stocks in marsh soils generally decreased with increasing restoration years. The decline of TIS stock in marsh soils mainly rested with the contributions of H₂O—S, Adsorbed—S and HCl—Soluble—S, and H₂O—S was dominant (78%~80%). This study found that, with the gradual restoration of marshes in the Yellow River estuary and the implementation of reed harvest in winter every year, the inorganic sulfur nutrient in restoration marsh soils would gradually tend to be deficient, which might be unfavorable for the maintenance of stability and health of marshes in the long term.

Abstract:In order to explore the mechanism of plant roots on the soil shear strength of red soil layer in Benggang, an indoor direct-shear-test was taken to study the effect of Dicranopteris dichotoma roots on the shear strength of red soil layer under different water contents. The results showed that: (1) The shear strength of soil samples with different root weights generally decreased with the increasing water contents, and the shear strength of soil samples with roots was greater than that without roots. (2) Cohesion tended to increase first and then decrease with the increase of water contents, and increased with the increase of root weight density, but the increment gradually decreased. (3) There was a linear negative correlation between the internal friction angle and soil water content, but the internal friction angle had no obvious relationship with root weight density. (4) The influence of water content on shear strength was greater than that of root weight density. Water content and root weight density could be used to simulate the shear strength of the root-soil composite (NSE=0.84). In summary, plant roots could increase the soil shear strength of red soil layer on collapsing wall, but the strengthen effect of roots was reduced under high water content, and the stability of root-soil composite on collapsing wall could be increased by reducing the water injection.

Abstract:To study the effects of water-saving irrigation and phosphorus and potassium fertilizer reduction on wheat yield, quality,and water and fertilizer use efficiency, field experiments were conducted to study the effects of drip irrigation (W₁) and micro-sprinkler irrigation (W₂) on water-saving irrigation with constant fertilization as control (CK), four times of irrigation during the growth period (overwintering water, jointing water irrigation 600 m³/hm², reviving water, and grouting water irrigation 300 m³/hm²). Under W₁ and W₂, phosphorus and potassium fertilizer constant (R_PK) and reduced by 20% (R_PK-20), 30% (R_PK-30), and 40% (R_PK-40) were applied with 50% basal fertilizer, and 25% of water and fertilizer were applied in returning green stage and jointing stage respectively, yield and its components, quality characteristics and water use and fertilizer efficiency were investigated and analyzed in 11 treatments. The results showed that the yield of W₁ and W₂ treatments decreased with the increase of phosphorus and potassium fertilizer reduction, and the yield of drip irrigation increased significantly for R_PK-20, was 15.49% higher than that of CK, which was mainly related to the increase of panicle number and grain number per spike. The yield of W₂ was lower than that of W₁ under the same treatment. The protein content, sedimentation value, and settling time of W₁ and W₂ treatments were significantly higher than those of CK. The sedimentation value of R_PK and decreasing treatment was W₁>W₂. W₁ was 42.35%~105.24% higher than CK, W₂ was 36.06%~56.18% higher than CK. The water use efficiency of phosphorus and potassium fertilizer combined with bottom application and top application was higher than that of CK_相. The partial productivity of W₁ and W₂ were higher than that of CK. The same reduction of N, P, and K fertilizer was W₁>W₂. The partial productivity of nitrogen increased significantly by W₁R_PK-20. The effect of phosphorus and potassium fertilizer decreased on soil nutrient content was small in 0—40 cm soil, but the available P content was increased. Comprehensive analysis showed that in the wheat grow region in the south of Shanxi Province, drip irrigation was used for winter wheat, four times irrigation was used for growing period, and 50% basal application, and 25% of water and fertilizer application was integrated topdressing, and 20% reduction of phosphorus and potassium fertilizer yield and water use efficiency were the highest, it is a high-yield and high-efficiency water and fertilizer management mode. The 30% reduction of phosphorus and potassium was the best water and fertilizer management mode.

Abstract:Artificial moss biocrusts (moss-dominating biological soil crusts) have attracted attention as a new type of windproof and sand fixation method in recent years. In order to further optimize the existing breeding and propagation technology, this study used a 4 factor and 2 level orthogonal test design to discuss the effects of microorganism (Actinomyces bovis, Bacillus megaterium), algae (Chlorella, Microcolusvaginatus), artemisia gum (yes, no), and substrate type (sand soil matrix, formulation matrix) on the indoor propagation of sand-land moss biocrusts. The results showed that: (1) Among the four factors, only the substrate type significantly affected the coverage and plant density of moss biocrusts (P<0.01), which increased to 61.04% and 17.48 strains/cm², were higher than that of the formulation substrate treatment. (2) Algae, microorganism, and substrate types significantly influenced the physiological characteristics of moss biocrusts (P<0.01), while the effect of artemisiagum was not significant. The sandy substrates and the addition of actinomycetes and chlorella significantly increased the peroxidase (POD) activity and soluble protein content and reduced the content of malondialdehyde (MDA) of moss biocrusts. (3)The optimal treatment for propagation was sandy substrate + actinomycete (1 g/kg substrate) + chlorella (2 g/m²). Under the conditions of the incubator (set illumination, photoperiod, temperature, air humidity as 6 000 lx, 12 h/d, 20 ℃, 75%), we propagated 1 m² moss biocrusts (collected from the field and fragmented into provenance) to 4 m² moss biocrusts with a coverage of 97.14%, which achieved 4 times multiplication. This research would provide technical support for large-scale industrialization and efficient propagation of moss biocrusts in the future.

Abstract:Soil saturated hydraulic conductivity (K_s) is an important parameter reflecting soil infiltration performance and soil water holding capacity. Understanding the spatial distribution characteristics and influencing factors of soil K_s at the watershed scale is helpful to better comprehend soil hydrological processes and regulation mechanisms. Totally 70 soil samples were collected from different land use patterns in the horizontal gradients (upstream, midstream, downstream) of the Zhujiachuan watershed in the Loess Hilly Region of Northwestern Shanxi. The soil K_s was determined by constant-head method, the topographical factors and physical and chemical properties of the sample points were also measured to establish partial least-squares regression model of soil K_s, and then the main factors affecting the spatial distribution pattern of soil K_s were analyzed. The study showed that: (1) Soil bulk density and sand content showed a weak variation, but the other physical and chemical properties showed the moderate variations. The soil K_s performance in the horizontal gradients was upstream > midstream > downstream; (2) Soil K_s varied greatly with different land uses (P<0.05), the sequence was forest land > agricultural land > grassland; (3) Forest land (VIP=1.997), grassland (VIP=1.710), soil bulk density (VIP=1.548), soil organic content (VIP=1.323), macro-aggregates (VIP=1.266), silt content (VIP=1.062) and clay content (VIP=1.049) were the main factors influencing soil K_s, among which the use of forest land gave the greatest impact. Land use, soil properties and topographical factors were the main factors affecting the spatial distribution of soil K_s in the Loess Hilly Region and could be used to simulate and predict the spatial distribution of soil K_s.

Abstract:Regional ecological policy has a profound impact on regional ecological health and sustainable development. This study took the Shiyang River basin as the study area, and attempted to analyze the ecological effects of the Shiyang River Key Management Plan (SRKMP) implementation from three perspectives of surface vegetation dynamic change, land use, and ecosystem service value. Based on the remote sensing data, the MODIS-NDVI data from 2000 to 2018 and China’s Multi-period Land Use Land Cover Remote Sensing Monitoring Dataset (CNLUCC) were selected. By analyzing vegetation coverage trends, land use type conversion, and ecosystem service value changes before and after policy implementation, the policy-driven impacts on the ecological effects of the Shiyang River basin were obtained. The results showed that the vegetation coverage in Shiyang River basin had been improved significantly from 2000 to 2018. After implementing the SRKMP in 2007, the proportion of area where NDVI increased had risen from 27.41% to 41.44%, and the severely degraded area decreased from 37.86% to 12.14%. Water, cultivated land and construction land were increased significantly, while the area of forest and grassland decreased slightly. The ecosystem services value in the basin increased from 23.282 billion yuan to 23.689 billion yuan in the past 19 years, with the most significant growth trend from 2015 to 2018. These research results provide a reference for measuring the promoting effect of ecological protection policy on ecosystem restoration in Shiyang River basin.

Abstract:Vegetation coverage directly represents the characteristics and changes in eco-environment in arid regions. Under the background of accelerated climate change and intensified human activities, it is thus urgent to investigate the changes and attributions of vegetation; however, the contributions of different controlling factors have rarely been quantified. Take the Manas River basin as the study area, this study analyzed the temporal and spatial changes of vegetation coverage with NDVI and climate data during the period 1982—2015, and further differentiated the contributions of climate change and human activities to vegetation change. From 1982 to 2015, the spatial pattern of NDVI decreased from the east to the west and from the north to the south. During the past 34 years, the NDVI showed a significant upward trend (+0.60%/10 a), but exhibited interannual variations, and it changed abruptly in 1995. The NDVI increased/decreased significantly before\\after 1995 (+1.50%/10 a and -0.40%/10 a), respectively. Compared with 1982—1995, the vegetation change in 1996—2015 was the combined effects of climate change and human activities. The contributions of climate change and human activities to vegetation change were 52% and 48%, respectively. The method for contribution quantification effectively differentiated the impacts of different factors on vegetation change, and the results showed that it was urgent to implement land management to improve eco-environment in the Manas River basin.

Abstract:Based on the temperature, precipitation and runoff data of Lake Issyk-Kul in the past 70 years, the Mann—Kendall method, abrupt change test, and wavelet analysis were used to study the characteristics and differences of the temperature, precipitation and runoff in the typical watershed. On this basis, the effects of regional climate change on runoff were also discussed. The results showed that: (1) The temperature in the typical small watershed of Issyk-Kul basin in 1951—2012 tended to increase; the temperatures in Cholpon- Ata Station (central lake basin) and Kyzyl—Suu Station (eastern part) rised from 1975 and 1989 respectively. The increasing trend of temperature in autumn had a greater contribution to the temperature increase. The variation of precipitation was relatively complicated, and the overall trend was increasing. Among them, the precipitation in autumn had the largest increase. (2) The annual runoff changes of 4 typical hydrological stations in the study area were not the same due to the direct influence of temperature and precipitation. The runoff of Cholpon-Ata, Chong-Ak-Suu and Chong- Kyzyl-Suu station showed an obvious increasing trend While Karakol Station showed a significant downward trend. The trend of autumn in each station was significant, showing an increasing trend. From the runoff distribution in different seasons in a year, the increase of runoff in El Pont and Chong- Kyzyl-Suu station was obvious with the largest increase in summer. However, the decrease of summer runoff in Cholpon-Ata station was the largest. (3)Through Pearson correlation analysis and principal component analysis, on the inter-annual scale, there was a significant correlation between the runoff of each hydrological station and the temperature and precipitation. The increase in temperature and precipitation affected the runoff output. (4) From the analysis of cyclical changes, the cyclical changes of temperature, precipitation and runoff were obvious, and the fluctuations were basically the same, indicating that the response of runoff to temperature and precipitation was prominent.

Abstract:Stable and good water conservation functions are the foundation of regional development. The water conservation functions of ecosystems are the key areas of current regional ecohydrological research. Because of Qinling’s important ecological function and geographical environment characteristics, it has the dual meaning of scientific and practical guidance to grasp the information as the changes of its water conservation function, the spatial pattern of water conservation function and the sensitivity of influencing factors. In this paper, Qinling in Shaanxi was selected as the research area. Based on the In VEST water production module and water conservation model, the changes of water conservation in Qinling from 2000 to 2014 were calculated. The spatial pattern of water conservation was analyzed from the aspects of slope and elevation, and the sensitivity of factors such as precipitation, evapotranspiration, seasonal constants, root depth, and leaf area index were selected.The results showed that: (1) The annual average water conservation and annual average rainfall basically fluctuated synchronously, and the total water conservation in the Qinling Mountains increased from 2000 to 2014 with the average annual increase of 2×10⁹ m³, and the increasing trend was becoming more and more obvious. The average annual water conservation in the main watersheds of Qinling Mountains was Hanjiang River Basin > Danjiang River Basin > Weihe River Basin > Luohe River Basin > Jialing River Basin. (2) The water conservation function of Qinling was positively correlated with elevation, slope, and vegetation coverage. The water conservation capacity of the shady slope was greater than that of the sunny slope. The water conservation function of the sub-basin was mainly of medium importance and importance, but general importance and extreme importance were unfrequent. (3) The sensitivity of the key factors affecting the water conservation function was rainfall > potential evapotranspiration > leaf area index > seasonal constant > vegetable root depth.

Abstract:The alpine shrub meadow ecosystem in western Sichuan is of great significance to the water ecological security of the Yangtze River Basin, and its litter layer is one of the important components of the water conservation function in this ecosystem. The alpine shrub meadow litter in Zheduo mountain was chosen as study objective, the field investigation and laboratory analysis were used to study the litter accumulation, water holding and water loss process, in order to explore the difference of water conservation function of litter among different elevations and slope aspects. The results showed that: (1) The litter accumulation in the study area fluctuated between 4.02~4.77 t/hm², all of which showed a gradual decrease with the increase of altitude, and the rule of semi-shadow slope>semi-sun slope. The elevation had the extremely significant impact on litter accumulation (P<0.01); (2) The maximum water holding capacity and volume of litter in the study area showed the same law, the maximum effective storage capacity occurred in semi-sunny slope at 3 800 m (5.95 t/hm²), and the minimum occurred in semi-shady slope at 3 800 m (2.53 t/hm²); (3) The relationship between litter water holding capacity and immersion time was W_t=aln(t)+b; whereas the relationship between litter water absorption rate and immersion time was V=ktⁿ. Water loss amount and water loss time showed a significant logarithmic relationship (R²>0.95, P<0.01), whereas water loss rate and water loss time showed a significant power function relationship (R²>0.99, P<0.01). It could be seen that the water conservation function of shrub-meadow litter in this area had distinct characteristics under different altitudes and slope directions. Controlling grazing to reduce the meadow degradation and increasing the species diversity of this ecosystem could effectively improve the water conservation of litter in this area.

Abstract:Farmland non-point source pollution has become one of the main causes of water eutrophication. In order to reduce nitrogen loss and relieve the over loading of nutrients in the local water body of rice field, a pot experiment was carried out. The main plots were continuous flooding irrigation (I_F) and alternate wet and dry irrigation (I_A), and the subplots were a control (conventional nitrogen application, N1C0) and four different nitrogen and nitrogen-loaded biochar treatments (N3/4C1,N3/4C2, N1/2C1, N1/2C2), in which N3/4 and N1/2 represented that the nitrogen application amount was 3/4 times and 1/2 times of the local traditional nitrogen application amount (N1); C1 and C2 were respectively 10 t/hm² and 20 t/hm² nitrogen-loaded biochar. Results showed that: (1) The pH value of the surface water with the conventional nitrogen treatment was significantly increased by reducing the application of nitrogen fertilizer and nitrogen-loaded biochar; (2) The average concentration of NH₄⁺—N in the surface water of I_A was 8.0% higher than that of I_F, but the average concentration of NH₄⁺—N in the surface water of I_A was lower than that of I_F after adding 20 t/hm² nitrogen-loaded biochar; (3) In the later growth stage of rice, the nitrogen-loaded biochar had a significant slow-release effect on NH₄⁺—N, while in I_A, the reduction of nitrogen fertilizer combined with nitrogen-loaded biochar reduced the concentration of NO₃^-—N in the surface water compared with the treatment of N1C0. (4) The tillering rate of rice could be increased by reducing nitrogen application and adding nitrogen-loaded biochar, while the effective tillering rate of rice could be improved by adding 20 t/hm² nitrogen-loaded biochar when the amount of nitrogen application was less. In summary, reducing nitrogen application combined with adding nitrogen-loaded biochar could not only reduce the nitrogen content by about 30.8% in eutrophic water, but also significantly reduced the NH₄⁺—N concentration in surface water at the early stage of fertilization, reduced the risk of loss, prolonged the release time of NH₄⁺—N, reduced the nitrogen application amount by 25% and ensured the nitrogen demand at the end of rice growth, which was conducive to rice growth.

Abstract:In this study, the effects of irrigation and fertilizer coupling on production performance of Lycium barbarum L. were investigated and the irrigation scheduling was optimized based on water and nitrogen coupling. The study adopted two factors of drip irrigating water quota (W) and amount of nitrogen application (F). W included 225 (LW), 300 (MW) and 375 m³/hm² (HW), respectively, and F included 480 (LF), 629 (MF), and 777 (HF) kg/hm². There were 9 treatments combined by W and F with three levels for each: T1 (LW, LF), T2 (LW, MF), T3 (LW, HF), T4 (MW, LF), T5 (MW, MF), T6 (MW, HF), T7 (HW, LF), T8 (HW, MF) and T9 (HW, HF). The field experiments were conducted in Zhongning county, Ningxia Hui Autonomous Region, Northwest China in 2014 and 2015.The results showed that the yield increased with the increasing irrigation water quota with maximum yield of 1 335.7 kg/hm² of HW for four-year-old tree under the same fertilizer condition, the yields of MW and LW were 1 174.2 and 1 066.5 kg/hm², respectively. The maximum yield was MW by 2 556.1 kg/hm² for the five-year-old, and the yields of HW and LW were 2 463.7 and 2 394.5 kg/hm², respectively. Under the same irrigation level treatment, the yield was the highest in the MF treatment and lowest in the LF treatment for 2 years experimental results. The yields of HF, MF and LF were 2 595.5, 2 758.0 and 2 407.0 kg/hm², respectively for the four-year-old, and 3 652.3, 4 113.9 and 3 532.1 kg/hm², respectively for the five-year-old. The results of 2 years experiments showed that yield climbed up from LF to MF and declined from MF to HF. There was no consistency of yield with irrigation water quota in 2 years experiments. We optimized the irrigation scheduling with the methods of this study, the results showed that the total ET_a of the one-year-old Lycium barbarum L. was 166.0~198.8 mm, and 194.7~252.5, 196.6~227.2, 173.5~221.6 and 179.3~196.6 mm, respectively for the two-, three-, four- and five-year-old tree. This attributed to the consumption of fertilizer and fertilizer use efficiency increased with tree-age increase, as well as the increased irrigation or fertilizer couldn’t promot yield of Lycium barbarum L.. It is necessary that water and fertilizer should get perfect coupling. This study would be as reference of optimized irrigation scheduling of ideal yield for ‘Ningqi No.1’ with 1 to 5 years tree-age.

Abstract:Crop straw is rich in phosphorus (P), potassium (K) and other nutrient elements, but the optimal combined application of phosphorus and potassium on late japonica rice under crop residue incorporation is still unclear. A two-factor (P and K) experimental design was adopted in the field experiments, four levels of P and K fertilizer application rates were set up, which P₂O₅ were 0, 63.75, 127.50, 191.25 kg/hm² (denoted by P0, P1, P2, P3) and K₂O were 0, 102, 204, 306 kg/hm² (denoted by K0, K1, K2, K3), respectively. The yield, quality, and milled rice nitrogen accumulation of japonica rice were investigated and analyzed at rice harvest stage. Both P and K fertilizer could significantly enhance the yield, dry matter weight and harvest index of late japonica rice, and the significant interaction effect between them was found in our study. The reasonable combined application of P and K fertilizers had synergetic effect on the yield of late japonica rice, the high yield was achieved when the application rates of P and K fertilizer were 62.45 kg/hm²and 206.08 kg/hm², respectively. At the same time, the milled rice nitrogen accumulation was significantly increased by the reasonable combined application of P and K fertilizers. The brown rice rate, milled rice rate, head milled rice and gel consistency were improved by the reasonable combined application of P and K fertilizers, but the chalkiness rate, chalkiness degree, amylose content and protein content were also increased. Except that the peak viscosity, hot viscosity and cool viscosity had significant differences among the amount of K fertilizer, there were no significant differences in the rice RVA profile characteristics in P, K fertilizer and interaction of both. And the peak viscosity, hot viscosity and cool viscosity were first increased and then decreased with the increased amount of K fertilizer applied. In practices, optimizing the combined application of P and K fertilizers on japonica rice should be concerned during the late-rice cropping seasons in Southern China. The synergy effect of K and P was best under P1K2, which simultaneously achieved the high yield, high efficiency and high quality production of late japonica rice under upper-middle soil fertility and total rice straw incorporation.

Abstract:Analysis of the regional changes of soil organic matter (SOM) and its relationship with pH and bulk density (BD) in agricultural areas of China were conducted. That would provide support for improvement of cultivated land fertility and soil structure. The characteristic of SOM changes were analyzed based on 913 national long-term monitoring sites which were carried out in 7 regions (Northeast, NE; North China, NC; Northwest, NW; Middle of Yangtze River, MYR; Yangtze River Delta, YRD; South China, SC; and Southwest, SW). Soil pH and bulk density were also evaluated. The results showed that the averaged SOM content in the agricultural cultivation areas were between 22.4 and 24.8 g/kg., and 72.5% of total monitoring sites were with SOM content grade <30.0 g/kg (grade 3~6). There were significantly difference of SOM content in soil cultivated layer among regions (p<0.05). Soil organic matter content in MYR was significantly higher than that in other regions. Soil pH and BD in the agricultural cultivation areas were (6.90±1.20), and (1.30±0.15) g/cm³. Soil utilization patterns affected SOM content, pH, and BD. The SOM content in paddy fields were significantly higher than that in upland. The pH and BD in upland were significantly higher than that in paddy fields. The Adams equation and exponential equation were recommended to fit response relationship between BD and SOM (R²=0.09, RMSE=0.17, n=759), pH and SOM (R²=0.16, RMSE=1.24, n=886).The SOM content was generally low in plowed layer in the agricultural areas, and that showing a decreasing trend from southeast to northwest of China. Soil pH and BD showed significant negative correlation with SOM. The Adams and exponential equation could well fit the responses relationship between soil BD and pH to SOM, and that could be used for nonlinear interpolation to supplement BD and pH missing values.

Abstract:In order to identify the effects of paddy rice cultivation history on wheat production, three rice-wheat rotation fields with different paddy rice cultivation years (2 years, 18 years, and >100 years) were selected for study in the Jianghan Plain. Soil samples and wheat plants were collected in different wheat growth periods to measure the moisture, nitrate nitrogen (NO₃^-—N) and ammonium nitrogen (NH₄⁺—N) contents in soils, and even the wheat yield. The results showed as follow: (1) With the increase of paddy rice cultivation years, soil moisture, NO₃^-—N and NH₄⁺—N contents increased significantly. The highest average soil water content was observed in the >100 years field (0.42 cm³/cm³), followed by the 18 years field (0.39 cm³/cm³) and the 2 years field (0.36 cm³/cm³). NO₃^-—N and NH₄⁺—N were enriched in the 0—20 cm soil layer, and the average NO₃^-—N content and NH₄⁺—N content in this soil layer was 12.26 and 6.01 mg/kg, 12.74 and 8.33 mg/kg, and 14.88 and 11.69 mg/kg for the 2 years, 18 years, and >100 years paddy fields, respectively. (2) The wheat yields decreased with the extending paddy rice cultivation years, which was 4 068, 3 080 and 2 469 kg/hm² for the 2 years, 18 years, and >100 years paddy rice fields, respectively, and were characterized by the decreasing of number of available tillers and ears per plant. (3) Water logging in the plough layer was the main reason for the reduced wheat yield, rather than the differences in nitrogen content. It is necessary to enhance soil water drainage rate to reduce the risk of water logging on wheat growth in the fields with long paddy rice cultivation years.

Abstract:In order to reveal the law of phosphorus loss on a slope of karst valley under natural rainfall conditions, the migration process of different forms of phosphorus through the two transport pathways (slope runoff and erosion sediment) was analyzed, and the influence of rainfall conditions and land use patterns on phosphorus loss was emphatically discussed. Three standard runoff plots (20 m×5 m) of cultivated land, forest land, and orchard land were set up in Longfeng trough valley to monitor the phosphorus loss for one year. The results showed that: (1) Phosphorus loss was strongly dependent on the process of runoff and sediment generation. (2) In general, the total loss of phosphorus decreased in the order: cultivated land > orchard land > forest land. The total loss of phosphorus in cultivated land was 0.17 kg/hm², which was about 1.76 times that of orchard land and 4.68 times that of forest land. (3) The change of phosphorus concentration in slope runoff was controlled by the rainfall intensity. The significant form of phosphorus loss in slope runoff was dissolved phosphorus (TDP) at the beginning of the rainy season, while in other rainfall runoff events particulate phosphorus (PP) was the primary form which accounted for 63.92%~96.97% of the total amount of phosphorus runoff loss. (4) The change of phosphorus concentration in sediment was less affected by the rainfall intensity, and the sediment had the enrichment effect of phosphorus, there was no obvious correlation between the enrichment ratio of total phosphorus (ER_STP) and rainfall intensity.

Abstract:In view of the problems of large fertilizer application rate, low fertilizer utilization rate, poor fruit quality soil environment in facility vegetable fields, a field experiment was conducted to study the yield, quality, nutrient utilization, and soil of facility cucumber under different soil conditioning measures. The impact of the improvement would provide a scientific basis for the realization of safe vegetable production and protection of soil environmental quality. The results showed that compared with the conventional fertilization of local farmers, the recommended inorganic fertilizer combined with biological bacterial fertilizer, medium and micronutrients, and zeolite-treated N, P and K inorganic fertilizers were all reduced by about 40%, but cucumber yield was increased from 6.3% to 8.7%, and net income increase from 18 663 to 19 958 yuan/hm². The nitrogen and potassium accumulation in the whole plant treated by inorganic fertilizer and biological bacterial fertilizer were increased by 13.3% and 22.7%, respectively. And the population of soil bacteria and actinomycetes and the ratio of bacteria/fungi were increased by 3.2, 1.7 and 7.7 times. The phosphorus accumulation in the whole plant treated by inorganic fertilizer and zeolite was increased by 31.7%. The surface soil NH₄⁺—N content was increased by 31.6%. The contents of VC, soluble protein and soluble sugar under the application of biological bacterial fertilizer and medium and micronutrient treatment increased from 14.0% to 18.6%, 22.2% to 34.6%, 7.8% to 10.0%, and nitrate decreased by 15.8% to 21.7%. Compared with the recommended fertilization, the three soil conditioning measures increased the production efficiency of N, P and K fertilizers by 6.2% to 8.5%, and increased the agronomic efficiency of N, P and K fertilizers by 26.1% to 35.9%. All the three soil conditioners promoted cucumber nutrient absorption, increased yield, improved the fruit quality, reduced soil nitrogen residues, and increased the population of beneficial microorganisms in the soil. Among them, the recommended inorganic fertilizer combined with biological bacterial fertilizer were used to stabilize production and improve the quality of organisms and soil. With the better environmental benefit, it was recommended in facility cucumber production.

Abstract:In agricultural production, nitrification inhibitors and microbial agents are often used as fertilizer synergist to coordinate soil nutrients and promote crop growth. In order to solve the problem of nitrogen utilization in facility melon production, two kinds of nitrification inhibitors, 3,4—dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD), and microbial agent were selected as test materials to study the effects of their single application or combination of inhibitors and microbial agent on melon growth and soil nitrogen utilization through a field experiment. The results showed that the addition of nitrification inhibitors and microbial agents could promote melon’s growth. During the growth period of melon, the application of synergist regulated the supply state of soil nitrogen and reduced the pH of rhizosphere soil. Among all treatments, C+DMPP+J treatment had the most significantly positive effect on melon growth and soil nitrogen utilization. Compared with conventional fertilization treatment, C+DMPP+J led to that melon production was increased by 21.7%;during the growth period, the plant height and stem diameter were increased by 13.6% (40 days after transplanting) and 8.9% (65 days after transplanting) at most, and the ammonium nitrogen was increased by 96.9% (90 days after transplanting, 20—40 cm), the nitrate nitrogen in soil decreased. It significantly improved the partial productivity of nitrogen fertilizer (21.6%), agronomic efficiency of nitrogen fertilizer (60.7%) and physiological utilization rate of nitrogen fertilizer (40.3%).The combination of nitrification inhibitor and microbial bacteria agent with chemical fertilizer showed obvious inhibition effect on soil nitrogen transformation, the content of ammonium nitrogen was higher during the growth period of melon, which extended the supply time of soil nitrogen. It could be seen that nitrification inhibitors and microbial agents combined with chemical fertilizers could prolong the nitrogen release cycle, which should be of great significance for reducing nitrogen loss and increasing crop yield.

Abstract:Coastal saline-alkali land is an important land reserve resource, as well as an important way to ease the pressure on agricultural land. Soil amendments are widely used in soil improvement. Grasping its effect on water movement and salt transport is the first problem for amendment application. In order to explore the effects of humic acid on soil water movement and salt transport characteristics and infiltration parameters, one-dimensional vertical infiltration experiments were performed at five application rates (0, 1, 3, 5, 7 g/kg). The results showed that when the infiltration time was same, the cumulative infiltration amount and wetting front of each treatment decreased with the increase of humic acid application; for the same infiltration depth, the infiltration time required with the increase of humic acid application, cumulative infiltration and average water content in the profile increased significantly. Compared with CK, the cumulative infiltration and water contents increased by 8.0% and 10.0% respectively when the application rate was 7 g/kg when infiltration finished; the application of humic acid could promote the migration of salt from the soil profile to the deep soil layer and effectively reduce soil pH, compared with the CK application rate of 7 g/kg, the average desalination rate of 0—20 cm increased by 10.2%. The results showed that Philip and algebraic models could better describe the characteristics of water infiltration under the condition of humic acid application. The permeability (S) decreased with the increase of the amount of humic acid applied, and the overall shape coefficient α increased with the increase of the amount. Between the model parameters and the amount of humic acid had a follow linear relationship. In addition, the root mean square error and the average absolute error were 0.005~0.018, 0.004~0.014 cm³/cm³, indicating that the algebraic models could better describe the distribution of water content. The above research results provide a certain reference for the application of amendment in the improvement of coastal saline-alkali land.

Abstract:In order to investigate the impact of biochar on the tea garden soil organic carbon, tea residue was made into biochar at 500 ℃. In this study, a 112-day incubation experiment was conducted to study the impact of biochar input on soil organic carbon contents and stability in three typical tea garden soils (purple soil, paddy soil, and yellow soil) of Ya’an. The study included five kinds of carbon soil ratio (CK, 0.5%, 1%, 2% and 4%), fifteen treatments in total, and samples were taken at 1, 2, 7, 30, 60, and 112 days of culture. Research showed that: tea residue biochar input can significantly increase the content and stability of total organic carbon (TOC) in purple soil, paddy soil, and yellow soil, and increases with the addition ratio, at the end of the cultivation period, the increasing ranges of total soil organic carbon in the three soils were 15.97%~96.64%, 13.01%~72.36%, and 15.29%~321.43%, respectively. Among them, the effect of increasing the TOC content of yellow soil was the best. After the addition of biochar, the contents of microbial biomass carbon (MBC), water-soluble organic carbon (WSOC), and readily oxidized organic carbon (ROC) in the three tea garden soils had also been significantly increased. By the end of the cultivation period, the largest change in MBC content in the three soils was purple soil, with an increase range of 12.97%~40.35%, and the largest changes in WSOC and ROC contents were in yellow soil, with increases ranging from 12.50% to 50.00% and 5.66% to 54.72%, respectively. Tea residue biochar significantly improved the oxidation stability of three types of soil organic carbon, and increased with the addition ratio. The improvement range of oxidation stability coefficient was 28.07%~146.66%, 44.79%~225.66% and 447.18%~1 941.19%, respectively.

Abstract:In order to study the stability of soil aggregates and the distribution of organic carbon and other nutrients in alpine grassland and alpine meadow on the Qinghai Tibet Plateau, in this study, soil samples were collected from the alpine region of the Qinghai Tibet Plateau, the changes of soil aggregates and nutrient factors were measured and analyzed in the laboratory. The results showed that: >0.25 mm percentage of water-stable aggregates (WSA), mean weight diameter (MWD), and geometric mean diameter (GMD) in the alpine soil of the Tibetan plateau were meadow>grassland, the fractal dimension (D) and the aggregate processing damage rate (PAD) were grassland>meadow. Therefore, on the Qinghai Tibet Plateau the stability of soil aggregates in the alpine meadow was higher than that in the alpine grassland. The soil stability and nutrient content of alpine meadow decreased significantly with the increase of soil depth (P<0.05), while the soil stability and nutrient content of grassland showed no significant change trend with the increase of soil depth. The soil stability and nutrient content of alpine grassland decreased with the increase of altitude, while that of alpine meadow decreased firstly and then increased with the increase of altitude. There was a significant correlation between soil agglomeration degree and nutrient content in alpine meadow (P<0.01), while there was no significant correlation between soil agglomeration degree and nutrient content in alpine grassland. Aggregates of >4, 4~2, and 2~1 mm were the main factors that affect the content of soil nutrients, and the stability of soil aggregates was mainly affected by macro-aggregates. The results of the study have important scientific significance for soil quality evaluation and ecological environment protection in the Qinghai Tibet Plateau.

Abstract:The biologically-based soil phosphorus (BBP) fractionation method assesses soil P availability by considering plant rhizosphere mediated P acquisition mechanisms: root interception, organic acid complexation, enzyme hydrolysis and acidification caused by proton excretion, and is a convenient method to reflect soil P status. This study examined the effects of straw incorporation and water management on biologically-based soil P fractions and rice P uptake in a double rice cropping system in subtropical China. Four treatments were set up, that was (i) no straw incorporation with intermittent irrigation (S0W1), (ii) rice straw incorporation with intermittent irrigation (S1W1), (iii) no straw incorporation with continuous flooding (S0W2), and (iv) straw incorporation with continuous flooding (S1W2). Four kinds of biologically-based soil P fractions were measured using the BBP fractionation method, which are the P fractions extracted by CaCl₂ solution (CaCl₂—P), citric acid solution (Citrate—P), phytase and phosphatase solution (Enzyme—P), and HCl solution (HCl—P). The results showed that straw incorporation treatments significantly increased the contents of soil CaCl₂—P, Enzyme—P, and Citrate—P, compared with the corresponding no straw incorporation treatments, while continuous flooding increased CaCl₂—P and Citrate—P, compared with intermittent irrigation in the early rice season. Straw incorporation treatments significantly increased the contents of Enzyme—P and Citrate—P, compared with the corresponding no straw incorporation treatments, and continuous flooding increased CaCl₂—P, compared with intermittent irrigation in the late rice. HCl—P was reduced in rice straw incorporation with intermittent irrigation and no straw incorporation with continuous flooding, compared with the corresponding rice straw incorporation with continuous flooding and no straw incorporation with intermittent irrigation, irrespective of the early and late rice season. The main sources of available P in paddy soil were Enzyme—P and Citrate—P because of soil available P being positive correlation with Enzyme—P and Citrate—P. Straw incorporation treatments significantly reduced rice grain P uptake, compared with the corresponding no straw incorporation treatments in the early rice season, and the rice P uptake was the lowest in straw incorporation with continuous flooding. In the late rice season, straw incorporation significantly increased both grain and straw P uptake of rice, compared with the corresponding no straw incorporation treatments, and water managements had no significantly difference in P uptake of rice. Except for HCl—P, soil biologically-based phosphorus was positively correlated with total P uptake, and was negative correlation with total P uptake in the early rice season, while was positively correlated with rice P content in the late rice season. Soil Citrate—P content was the second among the four kinds of BBP fractions (only lower than HCl—P), so Citrate—P played a major role in rice P uptake. Straw incorporation is beneficial to improve soil P availability and rice P utilization in the double rice cropping system.

Abstract:Based on the total nitrogen content data of 600 samples in Longxi County, the spatial distribution characteristics of soil nitrogen in Longxi County were studied by geostatistics and the nitrogen reserves were calculated. The results showed that the total nitrogen content in Longxi County was (0.734±0.306) g/kg, and the coefficient of variation was moderate. The average nitrogen density was 0.091 kg/m², and the nitrogen reserves were 7.6×10⁶ kg. The nitrogen reserves in the 0—10, 10—30, and 30—50 cm soil layers accounted for 35.97%, 7.06%, and 56.97% of the nitrogen reserves in the 0—50 cm soil layer respectively. The spatial distribution of total nitrogen content and nitrogen reserves in Longxi County was similar, mainly distributed in patches. The high-value area was mainly concentrated in Shouyang town and Heping Township in the south of the study area, while the low-value area was mainly concentrated in Guanjiawan Township in the east of the study area. From the vertical distribution, the total nitrogen content of soil decreased with the increase of soil depth. The total nitrogen content of 10 cm in the soil surface was extremely significantly or significantly correlated with latitude, elevation, slope direction, slope, rainfall, ground temperature, and air temperature. Principal component analysis showed that longitude, latitude, rainfall, ground temperature, air temperature, relative humidity, and evaporation could be considered as important environmental factors affecting the total nitrogen content of soil. Through clustering analysis can divide the Longxi County soil into five types. The total nitrogen content of class IV soil was significantly higher than the other four types of soil, and no extreme significant difference was observed among the rest four types of soil total nitrogen content. Soils contain total nitrogen content belong to the fifth class standard accounted for 70.35% of the total sample area.

Abstract:Field positioning experiments with split-plot design were conducted for five consecutive years on winter wheat which was used as the test crop in the dryland of Northwest China. The main treatment was five nitrogen application rates (N 0, 75, 150, 225, 300 kg/hm²), while the secondary treatment was mixed with or without organic fertilizer (30 t/hm²). After harvesting in June 2019, we took samples of soil layers of 0—10, 10—20, and 20—40 cm to measure and analyze soil physical properties such as soil bulk density, saturated hydraulic conductivity, and water stable aggregates. The results showed that the combined application of organic and inorganic fertilizer significantly increased the winter wheat yield compared with the single application of chemical fertilizer, with an average increase of 13% in five years, and the best effect was N150+M treatment. After the application of organic fertilizer, the bulk density of the tested soil decreased. In the 0—10, 10—20, and 20—40 cm soil layers, the bulk density of treatments received organic fertilizer respectively decreased by 4%, 2%, and 4%. In the 0—10 cm soil layer, the combined application of organic and inorganic fertilizers reduced the saturated hydraulic conductivity of each treatment compared with the single application of chemical fertilizers, but failed to reach a significant difference. Compared with N0 treatment, the water-stable aggregates of >2 mm respectively increased by 224%, 105%, and 3% in the 0—10, 10—20, and 20—40 cm soil layers under N0+M treatment. The MWD and GMD values of the soil aggregates in the 0—40 cm soil layer did not change significantly when the organic and inorganic fertilizers were combined with chemical fertilizers. But the nitrogen application rate of 150 kg/hm² had a stable effect on the water-stable aggregates of the tested soil and had a certain promoting role. To sum up, the application of N 150 kg/hm² with organic fertilizer 30 t/hm² is beneficial to the increase of winter wheat yield and the stability of the soil structure in the northwest dryland.

Abstract:In order to find a reasonable and efficient mode of carburizing and reduce the loss of organic carbon in alkalized soil, the effect of different organic materials addition on the capacity of dissolved organic carbon in saline-alkali soil of Hetao Irrigation District in Inner Mongolia had been studied. Taking mild and moderate saline-alkali soil in Hetao Irrigation District of Inner Mongolia as the objects to carry out field trials, the three treatments of biochar (BC), goat manure (GM), and CK were used to compare and analyze the changes of soil organic carbon (SOC), dissolved organic carbon (DOC), and soil physio-chemical properties after adding different organic materials. The results showed that: (1) compared with CK, the DOC capacity treated by BC and GM in mild alkalized soil has increased by 3.28% and 20.66%, the SOC capacity has increased by 5.40% and 10.30%, respectively. The capacity of dissolved carbon treated by BC and GM in moderate alkalized soil had increased by 41.32% and 74.10%, and the SOC capacity had increased by 60.24% and 79.16%, respectively. (2) There was a negative correlation between DOC capacity and SOC capacity treated by BC and GM in mild alkalized soil, and a positive correlation between DOC capacity and SOC capacity treated by BC and GM in moderate alkalized soil. (3) The capacity of SOC and DOC in saline-alkali soil was mainly related to the change of soil pH and conductivity, compared with the treatment of GM, the conductivity of BC was about 1.93%~29.15% lower, while the soil pH and alkalinity of GM was 0.31%~1.53% and 7.10%~24.63% lower than that of BC, respectively. In general, the addition of organic materials could increase the capacity of SOC and DOC in the soil, and reduced the degree of soil alkalization, and the addition of GM was slightly better than that of BC. Therefore, compared with BC, GM was more effective to improve the carbon capacity of alkalization soil in Hetao Irrigation District, the effect of soil amendment was better, and the improvement of soil physio-chemical properties was more obvious.

Abstract:In order to improve the nitrogen fertility and wheat yield of saline soil, achieve the purpose of improving fertilizer, increasing yield and efficiency, a field experiment was conducted in coastal saline soil test site to study the reasonable fertilizer management suitable for coastal saline soil. The split plot experiment was conducted from 2017 to 2019, with three mixing ratio of available and slow-released nitrogen fertilizer (N: 225 kg/hm²), 100%∶0 (F1), 50%∶50% (F2), 30%∶70% (F3), were used as the main plots. Three organic fertilizer rates were set as sub plots: 6 t/hm² (O1), 12 t/hm² (O2), and 15 t/hm² (O3), and no nitrogen application was the control (CK).The results showed that compared with other nitrogen and organic fertilizer treatments, the F3O3 treatment effectively reduced the salt content in the surface of saline soil by 0.7%~9.5%, reduced the content of nitrate and ammonium nitrogen in 20—100 cm soil layers by 1.3%~42.3% and 3.8%~44.3% respectively, which effectively reduced the nitrogen leaching out of the plough layer, increased the contents of available nitrate and ammonium nitrogen in plough layer by 16.6%~59.8% and 21.5%~60.4% respectively from the turning green stage to mature stage. And the F3O3 treatment significantly increased wheat grain yield, increasing by 5.9%~47.0% in 2018 and 8.3%~46.6% in 2019 compared with other nitrogen and organic fertilizer treatments. To sum up, in the coastal saline soil, the treatment of 70% slow-released urea and 30% available urea combined with organic fertilizer 15 t/hm² could effectively reduce the soil salinity and nitrogen leaching, maintained the available nitrogen nutrients, and improved the nitrogen supply capacity of the surface soil and wheat yield. It was the reasonable fertilizer operation mode of nitrogen fertilizer combined with organic fertilizer in coastal saline soil which can be widely used to improve fertilization and soil fertility.

Abstract:With soda saline-alkali paddy soil as the test soil, 5 treatments of 0, 3.0, 7.5, 12.0, 16.5 t /hm² were set to investigate the effects of continuous biochar returning on nutrients of soda saline-Alkali paddy soil and fungal community structure through pot experiment. The results showed that: (1) The soil pH, organic matter, available potassium, available phosphorus and total phosphorus were increased and the total nitrogen and total potassium showed a trend of increasing at first and then decreasing with the different amounts of biochar returning, which amended the saline-alkali soil. (2) Illumina MiSeq sequencing results showed that relative abundance of Aphelidiomycota, Basidiomycota and Alternaria under 7.5 t/hm² was significantly higher than that of control and the relative abundance of Ascomycota, Mucoromycota and Mortierella under 12.0 t/hm²was significantly higher than that of control. Correlation analysis indicated that soil physicochemical characteristics were closely related to the relative abundance of fungal phyla and genus, suggesting that biochar affected the relative abundance of fungi by regulating the physicochemical properties of soil. (3) Biochar returning treatment had little influence on fungal α diversity, while had a certain impact on the structure of soil fungal community, especially at a higher biochar returning level. Redundancy analysis (RDA) that further analyzed the environmental factors affecting the change of community structure, indicated that the total potassium content had the greatest impact on the community structure.

Abstract:Taking 0—100 cm soils from the farmlands (not reclamation formation) and reclamation areas of 1, 2, 3, 4, 7, 8, 9 years old in the Yellow River Delta as study objects, the spatiotemporal distribution and stoichiometry characteristics were analyzed through analyzing the soil organic carbon (SOC), nitrogen (TN), and phosphorus (TP), meanwhile the soil physiochemical and enzyme activities properties were exanimated and the C, N, and P storage were calculated. The results showed that the average values of SOC and TN in different soils of reclamation years were lower than the national average level. The TP level was lower than the national average level in the reclamation soil of 1 and 2 years, and was the same or slightly higher than the national average level in the reclamation soil of 3, 4, 7, 8, and 9 years. With the increasing of the reclamation years, the content of SOC, TN, and N/P decreased firstly and then increased, but C/N increased firstly and then decreased, C/P showed increasing trends after 7 years of reclamation, C, N, and P storage were increasing in 0—20 cm soil layer of different reclamation years, while the change rule of TP was fluctuating. With the increase of soil depth, the content of TP and TN, except in the first year, after reclamation increased firstly and then decreased in soil profiles, C/N increased and N/P decreased, the SOC contents and C/N showed significant vertical variation in the 0—40 cm soil layer. The values of SOC, TN, and TP showed significant negative correlations with soil conductivity and extremely significant or significant positively correlations with soil urease, alkaline phosphate, and invertase activity in 0—20 cm and 20—40 cm soil layer. C storage was extremely significantly correlated with C/N and C/P. The correlation analysis also showed that soil SOC and TN were the main factors regulating the soil eco-stoichiometry ratio of reclamation soils.

Abstract:Corn straw was added to low, medium, high, and removal organic soil for indoor culture test to study the influence of straw addition amount on soil acidity and buffer performance of soil with different organic matter contents. The results showed that after 150 days of constant temperature culture at 15 ℃, the contents of soil pH value, exchangeable salt-base, CEC, and salt-base saturation all increased with the increase of straw addition, while the contents of exchangeable H⁺ and exchangeable Al³⁺ decreased with the increase of straw addition. Among them, when the addition amount of straw was between 10 g/kg and 15 g/kg, the increase of soil pH value and the content reduction of exchangeable Al³⁺ and exchangeable H⁺ were the largest in the LSOM treatment. When the adding amount of straw was between 15 g/kg and 20 g/kg, the increase of soil pH value and the content of soil exchangeability Al³⁺ and exchangeability H⁺ decreased the most in the MSOM treatment and HSOM treatment. Moreover, adding straw to the HSOM treatment had the best effect on reducing soil acidity. Adding straw to the soil can obviously improve the buffer capacity of soil acid-base, and the buffer capacity of soil to the alkali side was more obvious than that to the acid side. The buffer capacity of soil increased with the increase of straw addition, and the acid and alkali buffer capacity of treatment was HSOM > MSOM > LSOM > RSOM.

Abstract:Through soil column simulation test, the effect of phosphogypsum and its combined application with acidic materials on soil water and salt transport in alkalize solonchaks of Ningxia was studied under leaching with different quality water. In this study, the Yellow River water, low-salinity farmland backwater, and high-salinity farmland backwater were used as leaching water sources, and humic acid, furfural residue and aluminum sulfate were used as acidic materials. The results showed that: (1) Under the leaching with different quality water, there was a linear relationship between the depth of vertical wetting front or cumulative infiltration and the square root of infiltration time. Under the leaching of the Yellow River water, the "phosphogypsum+furfural residue+aluminum sulfate" treatment was the best, while under the leaching of high-salinity farmland backwater, the single application of phosphogypsum was the best.(2) The application of amendments reduced the electrical conductivity of 0—50 cm soil layer under the leaching of the Yellow River water and low-salinity farmland backwater. Under the leaching of the Yellow River water, the "phosphogypsum+aluminum sulfate" treatment had the lowest soil electrical conductivity. Under the leaching of high-salinity farmland backwater, the "phosphogypsum+furfural residue+aluminum sulfate" treatment had the lowest soil electrical conductivity. (3) With the increase of leaching water salinity, the pH value of soil increased. The application of amendments reduced the pH value of 0—30 cm soil layer. Under the leaching of the Yellow River water, the "phosphogypsum+aluminum sulfate" treatment was the best. Under the leaching of low-salinity farmland backwater, the "phosphogypsum+ furfural residue+aluminum sulfate" treatment was the best. Under the leaching of high-salinity farmland backwater, the "phosphogypsum+ furfural residue" treatment was the best. (4) Under the leaching of the Yellow River water, the application of amendments increased the soil water content at different depths. Under the leaching of different quality water, the application of amendments increased the water content of 0—70 cm soil layer, and there was not large difference among the treatments. For the improvement of alkalize solonchaks, it was suggested that under the leaching of the Yellow River water and high-salinity farmland backwater, a combination of "phosphorgypsum+aluminum sulfate" should be used to improve the soil, while under the leaching of low-salinity farmland backwater, the combined measures of "phosphogypsum + furfural residue + aluminum sulfate" should be used.