Abstract:The economy of China has been developing very fast since the 20th century, and large numbers of construction projects have been carried out, which have intensified the contradiction among people, land, and resources. Unreasonable disposal and dumping of residues in development construction projects not only wastes a lot of soil and stone resources, but also invades a large amount of land. At this situation, environmental pollution and disasters are usually induced. China is vigorously promoting the construction of ecological civilization at present. The action plan for soil pollution prevention-control and the pilot project of waste free city construction have been carried out successively. The resource utilization of residues is an important content of the soil and water conservation law, so characteristic analysis and evaluation of resource utilization potential are of great significance. Based on the available data, it is predicted that the amount of residues currently available in China is close to 40 billion tons. Because of the material composition of residues are mainly soil, sand and stone, the methods and materials for resource utilization are easier to realize and low in cost, and have the potential for resource utilization. However, so far, the management and research on residues is mainly based on policy guidance. The methods, materials, and potential evaluation of residues to achieve resource utilization are still weak. This paper summarized and analyzed the types, material composition, and utilization potential of residues, and further points out the importance and feasibility of residues resource utilization. This research could provide scientific guidance for production and construction units and relevant administrative departments to effectively reduce the occurrence of residues and realize resource utilization.

Abstract:The alpine shrub meadow soils in Zheduo Mountain, Kangding, were studied by the combination of field investigation and indoor analysis, and the principal component analysis method was used to comprehensively evaluate the erosion durability of soil, in order to explore the differences of soil physical, chemical properties, and erosion durability of soil under different elevations and slope aspects. The results showed that:(1) The variations of soil physicochemical properties in leaching layer were more severe than that of the sedimentary layer, and this change was not affected by the elevation and slope direction. The difference in soil properties between different slopes aspects was mainly dominated by climatic factors. (2) There were significant correlation among soil physical, chemical properties, and erosion durability of soil, erosion durability of soil was mostly affected by agglomerate content and stability; (3) The erosion durability of soil followed the order:3 800 m semi-sunny slope > 4 200 m semi-shady slope > 3 800 m semi-shady slope > 4 200 m semi-sunny slope > 4 000 m semi-sunny slope > 4 000 m semi-shady slope. The three indicators that >0.25 mm air-dried aggregate content, aggregate GMD value, and aggregate fractal dimension D were the best indicators for evaluating soil corrosion resistance in this area. It can be seen that there were obvious differentiation characteristics of soil erosion durability under different elevations and slope aspects. Increasing the content and stability of soil aggregates were the key processes in strengthening erosion durability of soil in this area.

Abstract:Through the simulation of indoor wind, hydraulic and freeze-thaw conditions, the combined experiments of single hydraulic erosion, freeze-thaw hydraulic erosion, and freeze-thaw wind hydraulic erosion were carried out. The law of runoff and sediment production of Pisha sandstone under the condition of composite erosion was revealed. The results showed that:(1) Under the same rainfall conditions, the runoff of freeze-thaw hydraulic erosion and freeze-thaw wind hydraulic erosion test is 1.2 times of that of hydraulic erosion test, and the sediment yield is 2.4 and 2.8 times of that of hydraulic erosion test respectively. Freezing and thawing could increase the runoff and sediment yield of Pisha sandstone, while wind erosion had little effect on the increase of erosion and sediment yield. (2) The peak value and variation amplitude of runoff and sediment yield process of Pisha sandstone increased with the increase of the types of operating forces, and the runoff and sediment yield process of single hydraulic erosion had a significant flat feature compared with the water and sediment yield process under the effect of compound operating forces. (3) The composite erosion increased the initial infiltration rate and decreased with the rainfall. The initial water content was larger and the later was smaller with the increase of the operation force. (4) The relationship between the cumulative yield and the cumulative yield was power function. The effect of freeze-thaw erosion on the relationship between water and sediment was greater than that of wind. This experiment shows that the increase of the combined erosion force will aggravate the erosion process of the Pisha sandstone slope and increase the sediment yield.

Abstract:This was the first attempt to investigate the sediment yields of karst environment at the time scale of 100 a, and expected to improve our understanding of the evolution karst rocky desertification impacted by human activity. Taking Changjiawa depression and its watershed in Karst trough-valley area as the research object, the ¹³⁷Cs and ²¹⁰Pb_ex techniques were applied to calculate sediment yield intensity over the past 100 a. The results indicated that:(1) The average sediment deposition rate in the depression was 1.00 cm/a (1917-1963) and 0.25 cm/a (1963-2017), the average specific sediment yield (SSY) in the basin was 609 t/(km²·a) (1917-1963) and 152 t/(km²·a) (1963-2017); (2) The high values during 1917-1963 were related to the intense human activities in the region from the Republic of China to the early period of New China, especially the large-scale deforestation in the 1950s; (3) The sharp decreased values of 1963-2017 were due to the fact that the previous erosion had led to less soil and exposed local bedrock, combined with the vegetation recovery, the decrease of human activity intensity, and conservation measurements; (4) The intensity of sediment yield in Changjiawa basin was larger than that in other karst areas in southwest China, which was mainly related to lithology and human disturbance. Karst rocky desertification was not only the result of human disturbances in the last 50 years, but also related to human activities with nearly 100 years and even longer.

Abstract:In order to reveal effects of seasonal freeze-thaw cycles and soil properties on soil erodibility in the black soil region of Northeast China, the effects of freeze-thaw cycles and soil properties on soil shear strength were analyzed through indoor freeze-thaw cycle simulation and direct shear tests in laboratory. Two different tested soils were collected from top soil (0-20 cm plough layer) at typical thin-layer black soil region (BX) in Binxian County and typical thick-layer black soil region (KS) in Keshan County of Heilongjiang Province. The results showed that:(1) Freeze-thaw alternations reduced soil shear strength, cohesion and internal friction angle for both tested soils (BX and KS). After one time of freeze-thaw cycle, soil shear strength of BX and KS tested soils decreased by 3.9% and 9.2%, the soil cohesion decreased by 15.2% and 29.4%, and internal friction angle decreased by 1.4% and 3.6%, respectively. After seven times of freeze-thaw cycle, soil shear strength of the two tested soils decreased by 9.1% and 15.1%, soil cohesion decreased by 40.7% and 74.5%, and soil bulk density decreased by 6.7% and 9.2%, respectively. Due to the differences in the contents of soil organic matter, soil water stable aggregate and clay content, the decreasing extent of shear strength, cohesion and internal friction angle of KS tested soil were all greater than those of BX tested soil. (2) Soil shear strength decreased gradually and then tended to be stable with the increasing of freeze-thaw cycles for both tested soils. Moreover, the first freeze-thaw cycle had the greatest damage to soil shear strength, the decrement of soil shear strength after the first freeze-thaw cycle for both BX and KS soils occupied 43.4% and 61.0% of the total decrement of soil shear strength after seven freeze-thaw cycles, respectively; the decrement of soil cohesion after the first freeze-thaw cycle accounted for 37.3% and 39.4% of the total decrement of soil cohesion after seven freeze-thaw cycles, respectively. (3) Soil shear strength had significant positive correction with soil bulk density and mean weight diameter of soil aggregates (MWD), while it had significant negative correction with freeze-thaw cycles.

Abstract:Taking the Jialu River Basin of the Loess Plateau as the study area, this study collected the hydrometeorological data from 1966 to 2006, meanwhile selected 60 flood data to analyze the flood process line, runoff characteristic value, and runoff generation mechanism. Combined with the changes of forest and grass vegetation in Jialu River Basin in the past 30 years, the response relationship between vegetation coverage and watershed runoff mechanism was analyzed comprehensively, which revealed the reason for the dramatical water and sediment reduction in the Yellow River Basin. The results showed that in the past 30 years, the volume of runoff and sediment in the Jialu River Basin decreased sharply. Compared with the 1960s, the annual average volume of runoff was abated by about 75.0%, the vegetation coverage rate increased from 8.0% to 35.0% and the watershed storage capacity of the basin had the same growth trend with the vegetation coverage. The proportions of floods dominated by runoff formation in excess of infiltration in the three stages(1966-1975,1976-1996,1997-2006) was 72.8%, 65.0% and 60.0%, respectively; however, compared with the period of 1966 to 1975, the proportions of floods dominated by runoff formation at the natural storage were increased by 8.4%, 4.3% respectively during 1997 to 2006. The research results would help to realize the runoff law of the main water and soil loss areas in the Yellow River Basin, reveal the mechanism of water changes in the Yellow River, and provide a scientific basis for ecological construction in the area.

Abstract:In order to explore the effect of different sediment concentrations on infiltration characteristics of muddy water in layered soil, using the indoor free infiltration test of film hole irrigation, the cumulative infiltration, the wetting front migration law and the distribution of soil water in the wet body of clear water and different sediment concentrations (2%, 5%, 7% and 9%) of muddy water in layered soil with 5-10 cm sand layer were studied. The relationships of the cumulative infiltration volume, the wetting front migration distance and the infiltration time were established. The cumulative infiltration volume model of per unit film hole area under different muddy water sediment concentrations was proposed based on clear water infiltration. The results showed that there was a consistent trend for the cumulative infiltration under different sediment concentrations. The larger the sediment concentration was, the smaller the cumulative infiltration was, resulting in the more obvious of infiltration reduction force with muddy water. The smaller the infiltration coefficient was, the larger the infiltration index was. The wetting front migration distance decreased with the increasing of sediment concentrations. When the water infiltrated into the loam-sand interface, the wetting front had a significant stagnation in the vertical direction, which advanced with the infiltration time only in the horizontal direction. The soil moisture in the wet body mainly concentrated above the sand layer, and the soil water contents decreased with the increase of the muddy water sediment concentrations. These results could provide a theoretical reference for further research of muddy water film hole irrigation technology in layered soil.

Abstract:The contents of total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC) in 16 sampling points of the Weihe River and its tributary channels were studied, and the possible sources of sediments were studied by C/N and N/P ratio methods. The status of sediment pollution is evaluated by the organic pollution index method. The study shows that the TN content in the sediment is between 0.069~3.839 g/kg, 66.1% of sample content is below the average 0.639 g/kg; the TP content is between 0.453~1.841 g/kg, 62.7% of sample content is below the average. 0.713 g/kg; TOC content is between 0.772~25.221 g/kg, 62.3% of sample content is below the average value of 5.609 g/kg. The organic matter in the sediments of the Weihe River in Shaanxi Province is mainly affected by endogenous sources, and is dominated by algae and phytoplankton. The source of phosphorus in sediments is mainly external input. The N/P values of all sampling points from 2014 to 2016 were less than the Redfield ratio, which may be related to the biogeochemical processes of carbon, nitrogen and phosphorus in sediments. In November 2016, there were external sources of organic matter in partical rivers such as Linjia Village, Wolongsi Bridge, Changxing Bridge, Xingping, Caotan and Qingjiang River. In 2015, the organic index and the organic nitrogen index changed in the same period, namely before the flood

Abstract:Typical soils (i.e., red soil, yellow soil, brown soil and dark brown soil) under different elevations and typical land use types (cultivated land and forestland) were selected to investigate the variations in the vertical zonality of soil erodibility in dry-warm valley of China. AV-shape simulation flume was used to estimate rill erodibility in the erosion process. A series of rill erosion-based scour experiments were conducted, using water discharge of 150, 300, 450, 600, 750, 900 mL/min and hydrological conditions of drainage, saturation and seepage conditions. Results showed that the composition of soil particle composition had no obvious vertical zonality. The content of sand in forestland soil was relatively high, and the difference of particle composition in each soil was within 9%. All soils were silt loam. However, an obvious difference in soil organic matter appeared among different vertical zones. A vertical zonality of the rill erodibility (K_r value) could be find. As the elevation increased, K_r value of forestland soil decreased, and K_r value of dark brown soil was 47.74% less than that of red soil for forestland. For cultivated land, K_r value of yellow soil was slightly larger than that of the red soil, which could be ascribe to different human activities and soil maturity. Soil K_r of forestland was significantly higher than that of cultivated land with an average increase of 22.63%, which might be relate to the improved anti-erosion ability by soil organic matter. Soil erodibility was highest under seepage condition among different hydrological conditions, and soil erodibilitywas higher under saturation condition than that under drainage treatment. This result indicated that the difference of hydraulic gradients would also affect soil erodibility. Meanwhile, the critical shear stress was also highest under seepage condition among different hydrological conditions, and the critical shear stress was higher under saturation condition than that under drainage treatment. No obvious variation trend appeared among different vertical zonalities and land use types.

Abstract:The spatiotemporal variations and influencing factors of erosion gully in the last 50 years in Wangmaogou Watershed were studied by extracting some information like shoulder line, land use, soil and water conservation measures, vegetation coverage and LS from the three high-resolution remote sensing images of 1968, 2004 and 2018. The results showed that:(1) The information collected by remote sensing could basically satisfy the analysis of medium and long-term change in the erosion gully. (2) Gully erosion in Wangmaogou Watershed was developing all the time, but this change tempered gradually in the past 50 years. Specifically, the average advance rate of gully head were 0.30 m/a and 0.27 m/a respectively in early stage and the late stage, and the average expansion rate of gully wall were 0.009 m/a and 0.004 m/a. Spatially, the proportion of the variation density of erosion gully above 200 m/(km²·a) in the two periods were 26.89% and 7.07% respectively, which mainly distributed in the middle and lower reaches of the watershed. (3) In 1968-2004, the dominant factors affecting the development of erosion gully were land use changes and increased soil and water conservation measures, while erosion gully changes were mainly affected by the further improvement of vegetation coverage and land use diversity in 2005-2018. The study could help to quantify and analyze the development of erosion gully and its influencing factors for many years in the management process, and could also provide an important reference for ecological benefit evaluation of erosion gully before and after the implementation of "Grain-for-Green Program".

Abstract:In order to reveal the effect of surface land fluctuation on the overland flow under the micro-scale conditions, through the field artificial rainfall simulation experiment, the influence of five micro topography types on the overland flow were analyzed under 60, 90 and 120 mm/h rainfall intensity for 90 min. The five micro topography types were smooth, single mound, single depression, intervals mound and depression, continuous mound and depression. The results showed that:(1) Compared with the smooth group, the single mound, single depression and mixed fluctuation mode all delayed the initial flow generation time, and the time followed the order of smooth group < single mound group < single depression group < intervals mound and depression group < continuous mound and depression group. (2) The existence of mounds and depressions reduced the average flow velocity, among which the average flow velocity of continuous mound and depression group was the smallest. (3) Under the three kinds of rain intensity, there were three kinds of catchment form of overland flow on slope (branch shape, parallel shape and feathery shape) in five kinds of microtopography, among which catchment forms of the smooth group and the intervals mound and depression group were both branch, the catchment forms of the single mound group and the single depression group were feathery and branch, while it was mainly feathery shape in single mound group and branch in single depression group. The catchment forms of the continuous mound and depression group were mainly parallel shape. (4) Under the three kinds of rainfall intensity, the confluence density and runoff frequency showed the same change rule, which was the confluence density and runoff frequency of smooth group and single mound group decreased at first, and then increased with the increasing of rainfall intensity, meanwhile, the confluence density and runoff frequency of single depression group and combination of mound sand depressions groups increased with the increasing of rainfall intensity. The differences in the confluence density and the runoff frequency among the five microtopography were the smallest under the rainfall intensity of 90 mm/h. The results of this study revealed the influence of different surface fluctuation types on the overland flow of sloping farmland, which was helpful to further study the mechanism of soil erosion.

Abstract:By studying the land use change in the ecological barrier area of the Three Gorges Reservoir dam area in the past 25 years, the temporal and spatial variation characteristics and driving mechanisms were revealed, which could provide a scientific basis for the rational development and utilization of land resources and local ecosystem management. The Landsat remote sensing images of 1993, 2006 and 2018 were processed using RS and GIS techniques to obtain the distribution map of land use types. Combining the spatial analysis tools of geographic information system and the analysis method of transfer characteristics, this study analyzed the land use change in the ecological barrier zone of the Three Gorges Reservoir dam area from 1993 to 2018. The results showed that since 1993, the land use structure of the ecological barrier zone in the dam area of the Three Gorges Reservoir has changed significantly, showing an increase in forest land, garden plot and water area, and a significant reduction in cultivated land. The increase in water area was as high as 183.0%, while the reduction in cultivated land area was 68.9%. The transfer characteristics of land use indicated that the increase of both water area and garden plot were mainly from cultivated land and forest land. The increase of forest land and construction land were mainly from the conversion of cultivated land, and unutilized land was transformed into different types of land use. The water area in the ecological barrier zone of the Three Gorges Reservoir dam area from 1993 to 2006 was much larger than that in 2006-2018, while the other types of land use change were similar. In general, the construction of the Three Gorges Project, the development of urbanization, the structural adjustment of agriculture and forestry industry and ecological protection were the main reasons for the land use changes in the ecological barrier zone of the Three Gorges Reservoir dam area.

Abstract:The Gushanchuan Basin of the Loess Plateau was selected as the study area. The interannual variation of flow-sediment relationship and the mutation year were analyzed using the Mann-Kendall and the Pettitt test. The results of the runoff and sediment yield of Gushanchuan showed a significant decrease trend (p<0.01) from 1965 to 2014, and the mutation year was 1979 and 1996, according to which the study period was divided into the reference period (1965-1979), the transition period (1980-1996), and the benefit period (1997-2014). Compared with the reference period, the average annual runoff depth and sediment modulus decreased by 34.11 mm and 401.48 t/km² in the transition period, respectively, and decreased by 65.05 mm and 213.09 t/km² in the benefit period. When the runoff depth was less than 10 mm, the flow-sediment relationship was discrete. When the runoff depth was more than 10 mm, the flow-sediment relationship was relatively stable. The contribution rates of human activities for runoff and sediment reduction during the transition period were 79.12% and 86.45%, and the contribution increased to 86.45% and 87.45% in benefit period, respectively.

Abstract:The particle size distribution of sediment reflects the basic information of soil erosion. Researching the characteristics of sediment separation will improve better understanding to the process and mechanism of soil erosion on the slope. Field scouring experiments were conducted in four different shrub-grass patterns at three different flow rates (15 L/min, 20 L/min and 30 L/min) on the 8° slope in the Pisha sandstone area. This study taken the shrub grassland on the upper slope (SU), shrub grassland on the middle slope (SM), shrub grassland on the lower slope (SL) and grassland without shrub (GL) as the research objects, and bare land was taken as contrast in the Pisha sandstone area. The results showed that:(1) Vegetation could affect the distribution of sediment particles by affecting the hydrodynamic parameters. The sediment particles in different vegetation patterns tended to coarsen with the increasing of scouring time and flow. Silt and sand were the main particles of erosion sediment in this area. (2) The flow shear force, flow power and unit flow power all were negatively correlated with sediment D_V, and positively correlated with D₀ and D₁.The mean D_V of sediment was 2.422, 2.381 and 2.348 under three flow rates, respectively. The D_V under different vegetation patterns followed the order of GLD₀ and D₁ wasopposite to D_V. (3) The relationship between fractal dimension of sediment and hydrodynamic parameters could be described by exponential function and logarithmic function. Regression analysis showed that flow power was the best hydrodynamic parameter for describing sediment distribution characteristics, and using flow power and unit flow power could better simulate the sediment separation characteristics on slope of Pisha sandstone area. This study provided a theoretical basis for further improvement of soil erosion model on slope in Pisha sandstone area in the future.

Abstract:In order to explore the impact of rainfall and land use on the slope soil erosion characteristics of lateritic red soil in South China, the runoff and erosion sediment characteristics of different land use types (slope farmland, orchard, artificial pasture and abandoned land) were analyzed quantitatively through the observation experiment of natural rainfall, and the impact of rainfall types and land use on the erosion and sediment yield of slope, as well as the relationships of rainfall parameters and slope water and sediment were discussed. The results showed that the rainfall in 2018 was mainly from May to September, and the monthly rainfall was constituted by one or several rainstorms and heavy rainstorms. (2) The annual runoff and erosion of slope farmland were the largest, and the runoff amount of farmland was about 3.4, 8.0 and 6.0 times of orchard, artificial pasture and abandoned land, respectively, and the sediment yield of slope farmland was about 340.5, 1 605.3 and 1 720.3 times of orchard, artificial pasture and abandoned land, respectively. (3) Runoff amount on the slope surface kept a stable level during the early period of the year, then the fluctuation increased during the late period of the year, while the trend of sediment yield was opposite to that of runoff amount, and the erosion and sediment yield were mainly concentrated in the early period. (4) Runoff generated by heavy rainstorm and large heavy rainstorm accounted for more than 75% of the annual runoff for all land use types, while the erosion generated by heavy rainstorm and large heavy rainstorm accounted for 99.1%, 71.8%, 52.3% and 51.6% of the annual erosion for slope farmland, orchard, artificial pasture and abandoned land, respectively. (5) Rainfall amount and maximum rainfall intensity in 30 min were the most important parameters for soil erosion, and rainfall duration and vegetation coverage also significant affected runoff amount for orchard, artificial pasture and abandoned land. The results were helpful to clarify the soil erosion characteristic of lateritic red soil under different land use status and provide reference for regional water conservation of South China.

Abstract:Soil anti-scouribility and anti-erodibility were measured by undisturbed soil washing flume method and static water disintegration method. The gap and canopy stand of Picea koraiensis-Abies nephrolepis-Pinus koraiensis forest (PA) and Tilia amurensis-Pinus koraiensis forest (TP) were taken as contrasts to analyze the effects of different pit and mound microsites formed by uprooted trees and soil properties on soil anti-scouribility and anti-erodibility in Xiaoxing'an Mountains, and reveal the relationship between them. The results showed that in the pit and mound microsites of the two forests, the soil sand content was higher and the soil erosion resistance was weaker, but the trends were opposite in the contrast. There was no significant negative correlation between soil bulk density and soil anti-scouribility and anti-erodibility (P>0.05) in the two types of microsite of the two forests, while there was no significant positive correlation between soil bulk density and soil anti-scouribility and anti-erodibility in the gap of the PA (P>0.05). In the TP, the soil bulk density was extremely significantly positively correlated with soil anti-scouribility and anti-erodibility in the gap, while in the canopy stand, the soil bulk density was extremely significantly negatively correlated with them (P<0.01). There was no significant positive correlation between soil organic matter and soil erosion resistance in the two types of microsite, but there was an extremely significant positive correlation between them in the contrast stand. Soil erosion resistance varied with forest types and microsite types, the soil erosion resistance of TP pit and mound microsites was not significantly higher than that of PA. But the soil erosion resistance of PA contrast was significantly higher than that of TP contrast. It can be concluded that the formation ofpit and mound microsites would lead a significant decline in soil erosion resistance, resulting in the loss of soil nutrients, the reduction of soil clay content, and the process of soil restoration was difficult.

Abstract:Soil erosion is one of the important environmental problems in the Dianchi Lake Basin. It is helpful for the implementation and improvement of water and soil conservation to grasp the temporal and spatial characteristics of soil erosion sensitivity in Dianchi basin. Taking rainfall, DEM, soil type and Landsat Image as data sources, four factors including rainfall, soil, slope length and steepness, and vegetation coverage were selected to establish a soil erosion sensitivity evaluation system which apply to basin, such as Dianchi Lake Basin. The results showed that the sensitivity of soil erosion in Dianchi Lake Basin was mainly mildly and moderately sensitive. In the spatial distribution, the mildly sensitive areas were mainly distributed around Dianchi Lake. The moderately sensitive areas were mainly distributed in the mountainous areas with steep terrain. In terms of the temporal change, the sensitivity of soil erosion in the Dianchi Lake Basin declined during 1999-2014. The area of mildly sensitive areas increased by 20.18%, the area of moderately sensitive areas decreased by 20.31%, and the increase of mildly sensitive areas originated from the transformation of moderately sensitive areas, which were distributed in the northwest and southeast of Dianchi Lake Basin. Among the soil erosion sensitivity impact factors, rainfall was a key factor affecting soil erosion sensitivity in Dianchi Lake Basin. The spatial-temporal changes of soil sensitivity in the Dianchi Lake Basin were studied, and the areas prone to soil erosion in the Dianchi Lake Basin were identified, which contributed to the implementation of soil and water conservation measures, ecological management and land use optimization in this area.

Abstract:Based on the field monitoring data of runoff plot in erhugou small watershed from 2014 to 2016, under the condition of the surface soil (0-20 cm) in the pisha sandstone area, the soil parameters of the model were calibrated by the cumulative error method; at the same time, the model validity coefficient (ME) and the decision coefficient (R²) were used to verify the model validity, and WEPP model was used to simulate the runoff and sediment conditions of different erosion control measures. The ecohydrological effects of runoff and sediment reduction were compared and analyzed. The results showed that:(1) When the effective hydraulic conductivity, critical shear force, and erodibility of rill soil are 4.73 mm/h, 1 Pa and 0.01 m/s respectively, the simulation effect of the model is the best. (2) The R² and ME of WEPP model to simulate runoff and erosion of no measure (bare land) plot were 0.722 3 and 0.616 0, 0.702 5 and 0.616 7 respectively, and the runoff and erosion of WEPP model to simulate measure (grassland) plot were were 0.711 6 and 0.674 1, 0.844 7 and 0.690 3, respectively, and the simulation effect of the model with measures was better than that without measures. (3) Under different rainfall types, the effects of scenario a (herbage with low coverage on sunny slope), scenario b (shrub with low coverage on sunny slope), scenario c (shrub with medium coverage on sunny slope), scenario d (shrub with high coverage on cloudy slope), scenario e (shrub with high coverage on cloudy slope), and scenario f (shrub with low coverage on cloudy slope) on runoff reduction were 13.04%~91.28%, and the effects of sediment reduction were 44.46%~99.98%. In general, the effects of different scenarios were:scenario d > scenario e > scenario c > scenario f > scenario b > scenario a.

Abstract:The runoff data was collected from Sunshuiguan hydrological station located in Sunshuihe river basin, Liangshan Prefecture, Sichuan Province, China. The runoff distribution and its tendency as well as the effects of precipitation and human activities on runoff since the last six decades were analyzed by application of the methods of Mann-Kendall trend method, cumulative departure curve inspection method, and double mass curve method. The results showed that:(1) The annual average flow had an obvious but insignificant decrease with a rate of 0.116 3 m³/s per year and a mutational point was observed in 1997. (2) The distribution of runoff was relatively uneven in each year, and the runoff was mainly contributed by the summer and autumn. The runoff significantly decreased in the spring and winter with a rate of 0.028 8, 0.070 9 m³/s per year, while the decrease was not significant in the summer and autumn. The flow mutation occurred in the summer of 1995. (3) The decrease of flow in the Sunshuihe river basin was mainly caused by precipitation and human activities, and the effects of the two factors on the flow varied in different periods. The decrease after 1975 was largely caused by human activities, with the highest impact rate reaching 89.16%. The research results could provide a theoretical basis for the runoff rule study, flood control and drought prevention, and water resources utilization in the mountainous areas of southwest China.

Abstract:Aiming at the low irrigation efficiency of farmland irrigation and drainage system layout in Hetao Irrigation District, this paper explored the suitable design scheme of border irrigation under changing environment. This paper analysed the state of water flow movement, irrigation performance, and cost-effectiveness by carrying out the fine horizontal irrigation field experiment under different widths. The results showed that:(1) Different widths have great influence on soil infiltration depth and irrigation performance. When the width of the border was large, the water flow advancement time was prolonged, and the water depth of the furrow head infiltration increased, resulting in poor overall irrigation effect. By 10~15 m, the effective water use efficiency and irrigation uniformity increased by 11.96%~20.61% and 2.49%~5.95%, respectively, and the irrigation performance was significantly improved. When the width was reduced to 5 m, the relative flow rate of the single inlet increased. Irrigation water accumulated in the furrow tail, which increases the depth of the infiltration of the furrow tail, and the infiltration of the furrow head was insufficient, which leads to a decrease in the performance of irrigation. (2) By analysing the composition of each treatment cost and the yield benefit, it could be found that the most expensive expenditure in agricultural production is still other costs such as fertilizer, seeds, and films, accounting for more than 70% of the total plant cost. After the increase in the number of ridges, the mechanical cost increased by 0.3~4.6 times compared with the local traditional level. Although the water fee decreased slightly, the total cost T_c increased by 2.72%~9.98%. (3) When water-saving experiments were carried out, the water-saving benefits and economic benefits were usually contradictory. The water-saving and good-efficiency schemes tend to have poor economic benefits, while the schemes with poor water-saving benefits had improved economic benefits, it is recommended to increase the enthusiasm of farmers by granting water-saving subsidies to farmers in accordance with the subsidy standard of 1 095~1 665 yuan/hm² when promoting new water-saving technologies in irrigation districts. (4) In this paper, by analysing the comprehensive benefit function under the combination of different weights of economy and water saving benefits, it is preliminarily determined that when the optimization of each treatment scheme is made, if the water saving benefit is prioritized, the width should be appropriately narrowed, and if the economic benefit is prioritized, the width should be appropriately enlarged.The results should provide theoretical support for water saving reform design and sustainable development of agriculture.

Abstract:In order to reveal the effect of the reclaimed water irrigation modes on tidal soil structural properties and water conductivity, an indoor simulated soil column infiltration experiment with four treatments as:fresh water irrigation (CK), reclaimed water irrigation (RW), mixed irrigation of fresh water and reclaimed water (RW-2), and alternative irrigation of fresh water and reclaimed water (ARW) was conducted to assess the effect of irrigation modes on soil bulk density, total porosity, aggregate stability, infiltration rate, and saturated hydraulic conductivity. The results showed that compared with CK, the bulk density of each treatment showed a decreasing trend and the total porosity increased, but the difference was not significant. Reclaimed water irrigation promoted the transformation of >1 mm aggregates to <1 mm aggregates in tidal soil. Compared with CK, the content of <1 mm aggregates in each treatment increased by 11.51%~31.22%, respectively. The water stability of tidal soil aggregates decreased, the content of >0.25 mm aggregates decreased by 2.92%~9.75%, the mean weight diameter decreased by 11.30%~38.38%, and the geometric mean diameter decreased 3.93%~12.78%, among which RW was the most significant. The correlation analysis showed that the higher the percentage of water-stable aggregates particle size bigger than 1 mm, the more stable of the soil structure. The soil water infiltration rate of tidal soil increased by 80.00%~260.00% under three irrigation modes of reclaimed water. The effective water conductivity of ARW increased by 22.68%, while RW and RW-2 reduced by 14.47% and 42.36%, respectively. The best capacity of improving the structural properties of tidal soil was RW-2, while ARW was the most significant treatment for improving hydraulic conductivity of tidal soil.

Abstract:In order to explore the soil water conservation function of abandoned rare earth mining area in southern Jiangxi, the water storage function of litter and soil layer of the mining site were studied through the ring knife method. The results showed that the average soil water content of 0-30 cm soil layer in different mining sites followed the order of natural forest land (180.37 g/kg) > stacked ground (170.67 g/kg) > mining land (86.36 g/kg). The average value of soil bulk density followed the order of stacked ground (1.54 g/cm³) > mining land (1.31 g/cm³) > natural forest land (1.20 g/cm³). The average value of soil capillary porosity followed the order of natural forest land (44.08%) > stacked ground (37.89%) > mining land (35.82%). The average value of soil capillary storage followed the order of natural forest land (440.77 t/hm²) > stacked ground (378.94 t/hm²) > mining land (358.20 t/hm²). The trend of soil maximum water storage was similar to that of soil capillary storage. The natural forest land had the strongest water conservation capacity among the different mining sites, and the water storage capacity per unit area was (561.34±44.32) t/hm², and that in the mining area was the worst with the value of (431.65±53.66) t/hm². The water conservation of natural forest land was stronger than that of other mining sites, and the mining operations in the rare earth mining area had a great influence on the water storage of litter and soil layer.

Abstract:In this experiment, the wolfberry field under different ditch and ridge measures in Delingha wolfberry production area of Qinghai Province was used as the research object, and the uncovered flat wolfberry field was used as a control (CK). Based on the analysis of rainfall characteristics in the area, the effect of furrow-ridge mulching with different furrow-ridge ratios (30:32 cm, 24:32 cm, 18:32 cm, 12:32 cm) on soil moisture content, yield, and water use efficiency of Chinese wolfberry was studied. The results showed that:(1) In the test area with annual rainfall less than 300 mm, the soil moisture content, yield, and water use efficiency of the plantations with different furrow-ridge ratios were significantly higher than those of the uncovered flat planting. Compared with CK, the best treatment GLBc (furrow-ridge ratio 18:32 cm) in improving yield and saving water increased yield by 60.14%, reduced water consumption by 7.47%, and increased water use efficiency by 72.46%. (2) As the decrease of furrow width, the soil moisture content, yield, and water use efficiency all firstly increased and then decreased, and maximized when the furrow-ridge ratio was 18:32 cm. When the furrow width was 18 cm, the water use efficiency of Chinese wolfberry was 40.0%, 8.5%, and 9.2% higher than those when furrow width was 30, 24, and 12 cm, respectively. (3) Regression analysis of furrow width and wolfberry yield showed that when the furrow-ridge ratio was 17:32 cm, the yield of wolfberry reached a maximum of 1 503 kg/hm². Therefore, in the main wolfberry production areas of Qinghai, furrow-ridge mulching could significantly increase the yield and water use efficiency of wolfberry compared with traditional planting. At the same time, in combination with the current status of the local furrow-ridge ratio, reduce the furrow width to 17 cm which is the furrow-ridge ratio of 17:32 cm, would achieve the highest output, the smallest evapotranspiration, and the highest water use efficiency. The results of this study have guiding significance for improving the water use efficiency and yield of Chinese wolfberry, and provide scientific reference for the efficient utilization of agricultural water resources in arid areas.

Abstract:A field experiment was conducted to understand the effect of reducing irrigation amount and urea on summer maize yield and soil water, taking summer maize as the research object in Yangling of Shaanxi Province. The organic fertilizer with high organic matter content and strong water retention performance developed by the research group was selected, combined with two levels of irrigation (full irrigation W1 and deficit irrigation W2). According to the principle of equal nitrogen, the organic fertilizer and inorganic fertilizer were mixed with different ratios (F1:100% inorganic fertilizer, F2:24% organic fertilizer+76% inorganic fertilizer and F3:48% organic fertilizer+52% inorganic fertilizer), and the effects of irrigation amount and organic and inorganic fertilizers on water use efficiency and yield of summer maize were studied. The results showed that under W1, the grain yields of F2 and F3 treatments increased by 4.8%~6.3% compared with F1; under W2, the grain yield of organic fertilizer treatment increased by 1.8%~2.3%. Under the same irrigation level, organic fertilizer treatment significantly increased soil water storage at harvest stage (P<0.05), providing a certain humidity for winter wheat germination and growth. The application of organic fertilizer had a significant effect on the plant height at the three-leaf stage and the small trumpet stage, but had no significant effect on the plant height at other stages. The results of this study showed that the treatment of deficit irrigation (W2) and organic fertilizer (F2) was better, which was an effective scheme for summer maize planting. This findings could provide a scientific basis for the optimal management of irrigation and fertilization in the Guanzhong Plain and other similar areas.

Abstract:In order to study the effects of different materials returned to field on soil microbial biomass carbon, nitrogen and microbial entropy of 0-20 cm and 20-40 cm soil layers in summer maize silking and harvesting period, a field experiment was conducted on the purple soil in Sichuan Hilly area. This study was expected to provide a theoretical reference for the comprehensive utilization of agricultural waste organic materials and the improvement of soil quality in hilly areas of Sichuan. Four treatments with different materials returned to field were designed in this experiment, including control (no material returned to the field), faba bean straw, rape straw and pig manure. The results showed that:(1) Although the organic materials were returned to the 0-20 cm soil layer, the soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (SMBC), microbial biomass nitrogen (SMBN) contents in both 0-20 cm and 20-40 cm layers were significantly affected. The contents of SOC, TN, SMBC and SMBN in the 0-20 cm soil layer were significantly higher than those in 20-40 cm. Soil SOC, TN, SMBC and SMBN in both soil layers appeared as silking stage>harvest stage during the growth period. (2) In the two growth periods, the three materials returned to the field could increase the SOC, TN, SMBC and SMBN contents of 0-20 cm and 20-40 cm soil layers. Compared with the control, the contents of SOC, TN, SMBC and SMBN in the treatments with materials returned were increased by 2.6%~141.2%, 1.9%~33.0%, 5.1%~114.7% and 41.5%~98.7%, respectively. The contents of SOC, SMBC and SMBN in both soil layers appeared as rape straw > faba bean straw > pig manure > control, while TN contents as faba bean straw > pig manure > rape straw > control. (3) In this study, SMBC/SMBN, qMB and SMBN/TN varied from 3.74 to 10.53, 0.86% to 2.19% and 1.01% to 3.41%, respectively. The materials returned to the field reduced SMBC/SMBN and improved soil qMB and SMBN/TN values. Correlation analysis indicated that there were significantly positive relationships between SMBC, SMBN, SOC and TN. Therefore, we could improve the contents of SMBC, SMBN, SOC, TN and qMB value by returning materials to the field in agricultural production, and then we could maintain high farmland productivity so as to improve soil quality. However, during returning the specific types of materials, the balance among higher soil fertility, maize production and environmental benefits should also be considered.

Abstract:In this paper, the 0-40 cm soil in the hydro-fluctuation belt of the Pubugou reservoir was collected in the study area according to different land use and land cover (LULC), elevation, topography and time. The sampling time was April 25, 2017, July 5, 2017 and April 25, 2018, the influence of summer and annual cycle on soil total nitrogen and alkali-hydrolyzed nitrogen content was analyzed. The results showed that:(1) The contents of total nitrogen and alkali-hydrolyzed nitrogen decreased with the increase of soil depth. (2) The contents of soil total nitrogen and alkali-hydrolyzed nitrogen in low altitude area was higher than that in high altitude area. (3) The average contents of soil total nitrogen and alkali-hydrolyzed nitrogen was:sludge > grassland > dry land > bare land. (4) The contents of soil total nitrogen and alkali-hydrolyzed nitrogen was inversely proportional to the terrain factor LS. (5) The contents of total nitrogen and alkali-hydrolyzed nitrogen in soil samples collected in summer were significantly lower than that in April. This study explored the distribution characteristics of soil total nitrogen and alkali-hydrolyzable nitrogen contents in the hydro-fluctuation belt of the Pubugou reservoir from time and space, which could provide scientific data support for the ecological environment management of the Pubugou reservoir.

Abstract:In order to reveal the effects of different organic fertilizers on nitrogen mineralization characteristics in a coal mining reclamation soil, a pot experiment was conducted by using a subsidence reclamation soil, which collected from Shuiyu Coal Mining in Xiaoyi City, Shanxi Province. The nitrogen mineralization dynamic characteristics of 0~161 days after application of three organic fertilizers (chicken manure, pig manure, cattle manure) were studied by indoor aerobic incubation method under 40% water content and 30℃ incubation conditions. The nitrogen supply characteristics of different organic fertilizers in the reclaimed soil of the mining area could be predicted, which could provide a scientific basis for the rational application of organic fertilizers for the fertility improvement of low-yield farmland. The results showed:(1) The dynamic trend of NH₄⁺-N content in each treatment was basically same. The NH₄⁺-N contents decreased rapidly with incubation time at 0~14 days, which were significantly negative correlation with the incubation time (P<0.01). The NH₄⁺-N contents remained at the low level at 14~161 days. At the end of incubation, the content of NH₄⁺-N in each treatment was lower than 1.31 mg/kg. (2) The dynamic trend of soil NO₃^--N content, NO₃^--N accumulation amount and mineral nitrogen accumulation showed an increased S-shaped curve in the whole incubation period, which slowly increased at 0~56 days, quickly increased at 56~84 days, and basically unchanged at 84~161 days. At the end of incubation (161 days), the NO₃^--N content, NO₃^--N accumulation amount and mineral nitrogen accumulation varied among different treatments, with a sequence of chicken manure > pig manure > cattle manure > CK, and chicken manure treatment was significantly higher than pig manure treatment and cattle manure treatment, meanwhile pig manure treatment and cattle manure treatment were significantly higher than CK (P<0.05). (3) The time of nitrogen net mineralization in different fertilization treatments was different. The net mineralization of chicken manure occurred at 14 days, while the net mineralization of pig manure and cattle manure occurred after 28 days. (4) Although the accumulation rates of NO₃^--N and mineral nitrogen of different fertilization treatments at different periods of incubation were different, their trends were totally consistent, which showed that the soil mineralization rate fluctuated greatly at 0~84 days, peaked at 56~84 days, decreased steadily at 84~161 days. In a word, the application of organic fertilizer could effectively promote the nitrogen mineralization of reclaimed soil in coal mines, thereby improved soil nitrogen availability. Among three organic fertilizers, the application of chicken manure was better than pig manure and cattle manure in improving the available nitrogen in the reclaimed soil in the mining area. The effects of nitrogen mineralization varied with four treatments, with a sequence of chicken manure > pig manure > cattle manure > CK.

Abstract:Based on long-term experiment of Black soil in Gongzhuling, ¹³C labeled corn straw was incorporated to the field and incubated in-situ. The turnover of straw C in soil and its contribution to total SOC in different fertilization treatments with mulching were investigated, in order to provide a reference for soil fertility improvement and C sequestration in the Black soil region. The results showed that after straw returning to soil under no-mulching, the δ¹³C values of SOC was significantly higher (P<0.05) in the treatments of no fertilizer (CK) and chemical fertilizer (NPK) than that in the treatment of combination of organic manure (MNPK) and chemical fertilizer. The δ¹³C values of SOC after straw returning to soil under mulching ranged from -18.27‰ to -17.19‰ and were not significant different (P>0.05) among different fertilization treatments on the 360^th day. Content of straw C in SOC (¹³C-SOC) was significantly higher (P<0.05) under mulching than that under no-mulching. Especially, the content of ¹³C-SOC under mulching treatment was 1~3 times that under no-mulching treatments on the 60^th day, which indicated the soil moisture and thermal conditions under mulching promoted the accumulation of straw C in soil. The average contribution percentage of straw C to SOC in the treatments of CK, NPK, and MNPK under no-mulching was 1.28%, 1.32%, and 0.46%, and was 0.81%, 1.51% and 0.97% in those treatments under mulching, respectively. The results implicated that the supply of chemical nutrients of nitrogen, phosphorus and potassium promoted the accumulation of straw C in soil, which played a positive feedback for soil C sequestration.

Abstract:In order to study the effect of different organic materials on the distribution of micro-aggregates in native saline soils and the adsorption capacity of different fractional micro-aggregates on organic carbon, the native saline-alkali soils were used as test objects. The field experiment included the control treatment (CK), granular straw treatment (GW), normal corn straw treatment (CS), forage treatment (GS) and sheep manure treatment (SM). Combined with laboratory analysis, the particle size distribution of soil micro-aggregates and the content of organic carbon between different size micro-aggregates were studied. The results showed that the application of organic materials increased the contents of micro-aggregates of 2~0.25 mm in soil compared with CK, with an increase of 9.02%~20.37% and an order of GW > SM > GS > CS > CK. There were some differences in the effects on the micro-aggregates with other particle sizes. In general, organic material application increased the large particle size soil micro-aggregates and reduced the soil micro-aggregates with small particle size. The application of different organic materials could increase the organic carbon content of soil micro-aggregates of various particle sizes. At the same time, the application of organic materials increased the stability of soil micro-aggregates. The regression model analysis, correlation analysis and redundant analysis and principal component analysis were used for factor analysis. The results showed that the application of granular straw was more beneficial to increase the stability of soil microaggregates.

Abstract:In view of the problems of improper straw treatment and increased fertilizer application in rice production, taking Saint Rice 18 under the rice-wheat rotation system in Jining City, Shandong Province as the research object, three treatments were set up through field experiments:conventional fertilization, wheat straw non-return (CK); conventional fertilization + wheat straw full return (T1); 85% of the conventional fertilization + wheat straw full return (T2). The rice growth, photosynthetic parameters and yield at different growth stages were studied to provide theoretical basis for working out the reasonable rice planting measures. The results indicated that straw returning to field under rice-wheat rotation system was adverse to the early growth of rice, however, it could significantly improve rice growth in the middle and late growth stages, and enhance the absorption of nitrogen, phosphorus, potassium and other nutrients in the middle and late growth stages. The chlorophyll content, net photosynthetic rate and spectral reflectance of T2 were the highest in the middle and late growth stages, and the SPAD value and net photosynthetic rate increased by 4.4% and 37.5%, respectively, compared with CK. During the filling stage, both F_v/F_m and PI_abs were higher than the previous periods. The experiment also showed that T2 had the highest yield, which increased by 13.1% compared with CK. The direct reason for yield increasing was the increase of effective panicle per unit area. In summary, straw returning to the field combined with fertilizer reduction is helpful to achieve high yield and efficiency in rice cultivation production, which is worth popularizing and applying.

Abstract:The physiological characteristics and salt tolerance mechanism of two genotypes of alfalfa (Medicago sativa L.) Adrenalin (salt-stress tolerant) and Peru (salt-stress sensitive) under salt stress were explored by using 150 mmol/L NaCl to deal with two genotypes of alfalfa seedlings. Catalase (CAT), malondialdehyde (MDA), peroxidase (POD), relative water content (RWC), Chlorophyll (Chl), and proline (PRO) were respectively determined before and after 2, 4, 6, 8, 16 hour of salt stress. The result showed that the catalase activity, the peroxidase activity, and the malondialdehyde content of two genotypes of alfalfa showed a trend of increase under salt stress, while the proline content and the relative water content showed an opposite trend. The chlorophyll content significantly decreased. In addition, it was found that the variation of the relative water content and the chlorophyll content corresponded to the change of plant phenotype. Principal component analysis showed that the catalase and the malondialdehyde contributed the most, which could provide a theoretical basis for the research on salt tolerance mechanism and molecular breeding of alfalfa.

Abstract:In order to clarify the effect of fulvic acid application on cotton in garlic-cotton intercropping production and realize high-yield, high-quality and high-efficiency fertilization of cotton, a two-season field experiment was conducted. The experiment consisted of no fertilization (CK), conventional fertilization (BF), conventional fertilization combined with low, medium and high rates of fulvic acid microbial agents (FA20, FA30, FA40), conventional fertilization combined with fulvic acid foliar fertilizer (BFL50), conventional fertilization combined with low amount of fulvic acid microbial agent and fulvic acid foliar fertilizer (FA20L50). The effects of different fulvic acid fertilizers combined with conventional fertilizers on yield, fiber quality and soil nutrients of cotton-garlic intercropping were studied. The results showed:(1) Compared with conventional fertilization, the yield of cotton lint increased with the increase of the fulvic acid microbial agents application rates. The average lint yield in FA30 and FA40 treatments increased significantly by 12.07% and 22.41% respectively in comparison with BF treatment. Meanwhile, FA30 and FA40 treatments significantly increased soil nitrate nitrogen, ammonium nitrogen and available potassium contents during seedling and full bloom, FA40 also increased soil available phosphorus contents. (2) The cotton lint yield of conventional fertilization combined with fulvic acid foliar fertilizer increased by 7.19% on average compared with conventional fertilization, and the SPAD of leaves increased by 7.78% during flowering stage, which significantly increased stomatal conductance and net photosynthetic rate, and decreased intercellular CO₂ concentration. (3) Compared with FA20 and BFL50, FA20L50 increased lint yield by 7.68%~27.51%, significantly increased fiber length, evenness index and breaking strength. Moreover, FA20L50 increased soil ammonium, nitrate, available phosphorus and available potassium contents. Soil phosphatase activity in FA20L50 was significantly higher than other treatments. The total amounts of nitrogen, phosphorus and potassium in cotton stems and leaves in FA20L50 treatment were significantly higher than other treatments, besides FA40 treatment. FA20L50 increased the total nutrient contents by 8.96%~47.35% in the bell shell in comparison with other treatments, and significantly improved the net photosynthetic rate compared with treatments without fulvic acid foliar fertilizer. In conclusion, conventional fertilizer combined with 300 kg/hm² fulvic acid microbial agent and 750 mL/hm² fulvic acid foliar fertilizer had the best application effect, which could improve the available nutrient supply of soil at all growth stages of cotton and facilitate the accumulation of nutrients in reproductive organs, thus promote the net photosynthetic rate of cotton leaves and improve the yield and quality of cotton.

Abstract:The purpose of this study was to screen out the appropriate mixing ratio of slow-controlled-release urea (CRU) and common urea (U) suitable for Zhangqiu onion-wheat, and to realize the high efficiency of one-time application of slow-controlled-release fertilizer. Field experiments were conducted to investigate the effects of different mixing ratios of CRU and U on yield, apparent utilization rate of nitrogen fertilizer, economic benefits and soil nitrogen of Zhangqiu onion-wheat. The results showed that compared with conventional fertilization, the total yields of onion and wheat in two seasons increased by 2.2%~6.0% and 4.3%~5.2% respectively in 50% CRU+50% U and 70% CRU+30% U treatments, and the nitrogen apparent efficency of 50% CRU+50% U and 70% CRU+30% U in spring onion season increased by 3.44~8.48, 2.74~3.77 pecentage point respectively, 50% CRU+50% U and 100% CRU in wheat season increased by 6.41~6.96, 3.00~6.98 pecentage point respectively. In spring onion season, 50% CRU+50% U and 70% CRU+30% U increased 10 783.93 and 5 823.04 yuan/hm² respectively; in wheat season, 50% CRU+50% U and 70% CRU+30% U increased 2 035.33 and 1 448.24 yuan/hm² respectively. The nitrate nitrogen content in 0-20 cm soil under 100% CRU and 70% CRU+30% U was higher than that in conventional application. The accumulation of nitrate nitrogen in 20-100 cm soil layer with slow-contrdled slow-release fertilizer was higher than that of conventional fertilization, and the higher the mixing ratio of slow-controlled-release fertilizer, the higher the retained nutrient content. Considering all the factors comprehensively, 50% CRU+50% U was the best ratio applied in Zhangqiu onion-wheat, followed by 70% CRU+30% U. These two ratios could achieve one-time application of slow-controlled release fertilizer, at the same time, improve the apparent efficiency of nitrogen fertilizer, increase economic benefits, and prolong the ability of soil to provide nitrogen.

Abstract:To explore wind erosion law of farmland and effects of planting spring wheat and pasture on soil and nutrient loss, the experiment took bare land (CK), planting Triticum aestivum and Medicago sativa/Bromus inermis farmland as research objects. We measured indexes of vegetation characteristics, soil wind erosion, and physical and chemical properties. The results showed that soil loss showed a 'U' curve pattern, with more loss in late autumn and early winter, less loss in winter, and significantly increased loss in spring. There were two peak periods of wind erosion (September to November and March to May) from September to June of the following year. The average annual soil loss of bare land was up to 1.7 kg/m², that was, as 1.3 mm thick topsoil was blown away by wind, resulting in the loss of land organic matter up to 236.2 kg/hm². When wheat and pasture were planted, the soil mass loss reduced by 20.1% and 52.3%, and the organic matter loss reduced by 12.2% and 50.7% under the influence of surface vegetation (stubble). Due to the higher coverage, height, and surface biomass of pasture vegetation (stubble) than those of wheat in wind erosion season, the surface roughness, humidity, and water content of topsoil (0-5 cm) of grassland were higher than those of wheat field, resulting in less soil and organic matter loss than that of wheat field. Correlation analysis showed that there were a significant positive correlation between vegetation characteristics and surface roughness and soil moisture content, while there were a significant negative correlation between vegetation characteristics and surface soil and organic matter loss. Regression analysis showed that every 1% increase of vegetation coverage would reduce topsoil and organic matter loss by 4.1 g/m²and 59.3 mg/m². Every 1 g/m² increase of surface biomass would reduce topsoil and organic matter loss by 2.3 g/m² and 34.0 mg/m². The amount of topsoil loss of wheat fields sowed in spring was the same as that of bare land, while planting perennial legume-grass mixtures could significantly reduce the loss of topsoil and organic matter. On the whole, crops sowed in spring in irrigated areas of Gansu would likely cause soil degradation, while planting perennial legume-grass mixtures could fulfill the farmland ecological conservation, improve quality of cultivated land and regional environment.

Abstract:In order to detect the dynamic changes of soil fertility and salt alkali and their effects on wheat yield, the newly reclaimed farmland (10, 20, 30, 40 and 50 years) in the south margin of Tarim Basin were taken as the research object, and the uncultivated desert natural soil was taken as the control, the soil properties, such as organic matter, nutrient and salt alkali of the surface soil (0-40 cm) were measured. The results showed that the organic matter content in the surface soil (0-20 cm and 20-40 cm) increased linearly with the extension of cultivation time, but the change range of organic matter content in 20-40 cm soil layer was relatively small. In the 0-40 cm soil layer, the changes of the total nitrogen, available nitrogen and available potassium content with time extension were all significantly positively correlated with organic matter content, which increased by 88.8%, 213.4 and 37.5% in 50 years of reclamation respectively compared with that of the native desert soil. Available phosphorus content increased linearly in the initial 30 years after cultivation and then decreased. However, it increased by 1 201.2% in 50 years after cultivation compared with the uncultivated soil. The nature desert soil was mildly salinized soil dominated by Na⁺ and Cl^-. The total salt content decreased sharply after cultivation, and the difference between different years was not obvious, and the average value of which was 0.8 g/kg in 0-40 cm soil layer. The dominate cation and anion of the cultivated oasis farmland changed to be Na⁺ and HCO₃^-. The pH value increased by 13.4% in the initial 30 years (pH 8.85) compared with the desert soil, and then decreased significantly. The change of pH was positively related with accumulation of CO₃^2- and K⁺. The average wheat yield in the new reclaimed farmland was 4.79 t/hm², and which was negatively related to the content of Na⁺ and Cl^-, but was not related to the content of soil organic matter, nutrients and total salt as well as pH value. In conclusion, continuous cultivation significantly improved soil fertility and salinization degree. However, the wheat yield was closely related with the content of Na⁺ and Cl^- in 0-40 cm soil layer. The results suggested that fertilizing oasis farmland soil and taking effective measures to reduce Na⁺ and Cl^- content from rising again were important to achieve stable and high yield of wheat in the study area.

Abstract:The bark and wood of the apple branches were separated and then made them into carbonized bark and wood in low oxygen at 450℃.The ultrastructural and adsorption to NH₄⁺-N and NO₃^--N of them were investigated. The results showed that the cellulose content in carbonized bark was higher than that in carbonized wood, and there were more microscopic holes and gullies in the carbonized bark, and the longitudinal gullies and pores were more developed after carbonization. The saturated adsorption capacity of the carbonized bark to NH₄⁺-N and NO₃^--N was 24.11 mg/g and 12.93 mg/g, respectively; while the corresponding parameter of the carbonized wood was 22.24 mg/g and 11.99 mg/g, respectively, and carbonized bark had stronger adsorption capacity to NH₄⁺-N and NO₃^--N than that of carbonized wood. The adsorption capacities of these two kinds of materials to NH₄⁺-N were greater than those to NO₃^--N. Freundlich and Langmuir isothermal adsorption models, pseudo second-order kinetic model and Elovich model could be used to fit the adsorption processes. Carbonized bark had stronger adsorption capacity, which was related to its higher cellulose content and more developed microscopic gullies.

Abstract:In order to explore the optimum additive formula that promotes straw decomposition and soil carbon sequestration, the effects of additives on the straw decomposition and its surrounding soil environment were studied. We chose corn stalks as test materials to carry out the burial bag in-situ decomposition experiment for 150 days. The effects of three types of additives (urea, biological bacteria decomposition accelerator and trace element conditioner) on the decomposing process of 15 cm and 30 cm depth returning straw and the soil environmental factors were studied. The results showed that:(1) Additives significantly affected the amount of carbon loss (p<0.01), directly affecting the degree of straw decomposing and the release of carbon in the soil. The depth of returning to the field affected the weight loss by affecting the water content, and the water content was significantly negatively correlated with the weight loss (r=-0.51). SOC and carbon loss were close to a linear negative correlation (r=-0.94), and SOC was significantly positively correlated with C/N (r=0.72), and C/N was significantly negatively correlated with carbon loss (r=-0.53). (2) The trace element additive not only improved soil water content in the early stage, but also slowed the loss of water in the later stage. However, the additive had the tendency to accelerate soil acidification. The effect of trace element additive was more obvious at the depth of 15 cm, but the biological additive worked better at 30 cm depth. (3) The additives accelerated the decomposition of the straw but reduced the carbon loss. After 150 days, the average carbon loss of 15 cm and 30 cm depth returning to the field were reduced by 3.4% and 4.8%, respectively, which was conducive to soil carbon sequestration. Among them, the biological bacteria additive was more conducive to the decomposing of 15 cm returning straw, and the nitrogen additive was more conducive to the decomposing of 30 cm depth returning straw. (4) The additives slowed down the loss of the straw decomposing products, especially the biological bacteria additives and trace element. When the 15 cm depth returning field was used, the biological bacteria additive was more conducive to soil carbon sequestration, and the trace element additive was more conducive to the renewal of organic carbon, while the 30 cm depth returning was the opposite.

Abstract:According to the requirements of organic agricultural production, through field experiment, we studied the effects of organic drip irrigation on the yield, quality of wine grape, as well as the soil chemical and biological properties of vineyard in the alluvial fan area at eastern foot of Helan Mountain in Ningxia. And the way of high-efficiency utilization of water and fertilizer in barren coarse bone gray ash soil developed from parent material of high mountain in semi-arid area was explored. The results showed that the yield and quality of wine grape treated with different amounts of organic drip irrigation were significantly different (p<0.05), and the yield of the treatment of 3.6 t/hm² was the highest, which was 8.29 t/hm². T_4.5 treatment had the heaviest single fruit and the largest fruit grain. Compared with CK, 3.6 t/hm² treatment significantly increased the contents of soluble solids, soluble sugar, total phenols and anthocyanins in wine grape (p<0.05). The analysis of the relationship between wine grape quality index and fertilization treatment showed that 3.6 t/hm² treatment had the highest score. In 0-20 cm, 20-40 cm and 40-60 cm soil layers, soil organic matter, alkali nitrogen, available phosphorus, available potassium and other chemical properties as well as biological indicators such as urease, alkaline phosphatase, invertase, catalase and so on all increased with the increasing of fertilization amount, and 4.5 t/hm² treatment had the maximum value (p<0.05). The results of this study were great importance to the efficient utilization of limited soil and water resources in the ecologically fragile area of the Helan Mountain alluvial fan area in Ningxia, the production of the most high-end organic wine grape and wine, promote the organic combination of soil and water conservation and economic benefits, and the increase of farmers' income and agricultural efficiency.

Abstract:In order to study the growth and water conservation capacity of typical plantations in southern hilly areas, six forest stands of Huaying City were selected as research objects. By measuring the characteristics of litter layer and soil layer under forest, the water holding capacities of litter and soil in different forests were analyzed and compared. The results showed that the litter of Chinese fir pure forest (close-to natural management) had the largest accumulated stock, and the water holding capacities of litter was as follows:Chinese fir pure forest (close-to-nature management) > Chinese fir pure forest > Pinus massoniana and Loropetalum chinense mixed forest (close-to-nature management) > Chinese fir and Populus alata mixed forest > Cypress pure forest > Pinus massoniana and Chinese fir mixed forest; the total soil porosity, capillary porosity and available water holding capacities of pure Chinese fir forest were optimal, reaching 67.67%, 60.39%, 138.11 t/hm².The available water holding capacities of the six forest stands soils were:pure Chinese fir forest > pure Chinese fir forest (close-to-nature management) > Pinus massoniana and Chinese fir mixed forest > Chinese fir and Populus alata mixed forest > Cypress pure forest > Pinus massoniana and Loropetalum chinense mixed forest (close-to-nature management). Combined with the water holding capacities of litter layer and soil layer, it could be found that the Chinese fir pure forest (close-to-nature management) gave the best water conservation capacity, 309.77 t/hm², but the Pinus massoniana and Chinese fir mixed forest gave the weakest.

Abstract:In order to improve the utilization rate of urea nitrogen and promote the research and development of new slow/controlled release nitrogen fertilizer, a pot experiment, which including five treatments as control (CK), common urea (U), U + common urease inhibitor HQ (SRU1), U + coated HQ (SRU2), and U + 30% common HQ+70% coated HQ (SRU3), were conducted to study the effect of partially or completely coated HQ mixed with urea on wheat growth, soil nitrogen, and urease activity. The results showed that compared with SRU1, coated HQ can promote wheat growth, improve wheat yield components, increase wheat yield, and improve nitrogen utilization rate. SRU2 and SRU3 respectively increased the yield of wheat by 34.71% and 56.54%. Compared with SRU2, SRU3 treatment of common HQ mixed with Coated HQ could effectively inhibit the hydrolysis of urea at the early stage, maintain the appropriate concentration of NH₄⁺-N in soil, and increase the content of NH₄⁺-N at the later stage, so as to ensure the continuous supply of available nitrogen in the soil, reduce the loss of nitrogen, and maintain the urease activity of soil at a low level for a long time in the whole growth period of wheat. SRU3 treatment had the strongest nitrogen supply capacity and the highest nitrogen utilization rate in soil, and had the most significant effect on the growth of wheat.

Abstract:Investigating the effects of mixed application of biochar and polyacrylamide (PAM) on water infiltration and evaporation of coal gangue matrix can provide a basis for the regulation of soil moisture in coal gangue mountain in mining area. The water retention capability, infiltration and evaporation characteristics of coal gangue matrix with different ratios of coal gangue to soil (1:2, 1:1 and 2:1) under the mixed application of different proportion of biochar (1%, 2% and 4%) and PAM (0.5‰ and 1‰) were studied by using a simulated soil column method. The results indicated that:(1) The influence of biochar on the infiltration performance of coal gangue matrix was greater than that of PAM and ratio of coal gangue to soil.With the rate of biochar addition increased, the saturated water content and infiltration rate of matrix increased. Whereas the rate of PAM addition increased, the saturated water content and infiltration rate of coal gangue matrix declined. (2) The cumulative evaporation of with addition of 1‰ PAM was lower than that of 0.5‰ PAM.The effects of ratio of coal gangue to soil on moisture evaporation of coal gangue matrix were greater than that of biochar and PAM. (3) Cluster analysis showed that the water retention capacity and infiltration rate of coal gangue matrix were high under the mixed addition of 4% biochar and 0.5‰ PAM, while the mixed application of 2% biochar and 1‰ PAM could weaken soil water evaporation when the ratio of coal gangue and soil was 2:1. In a word, increasing the addition of biochar would be beneficial to the water infiltration and increasing the proportion of PAM could restrain the evaporation of water in coal gangue matrix.

Abstract:The purposes of this study were to understand the water conservation capacity of litter of Cryptomeria fortunei plantation with different forest ages, and to provide basis for the determination and implementation of forest soil and water conservation measures. Five age groups of C. fortunei plantation in Pingba Dapo Forest Farm of Guizhou Province were chosen as object in October 2018. The water holding capacity of litter was studied by drying method and laboratory immersion method, and the water conservation function of litter in five age groups was evaluated comprehensively by entropy weight method. The results showed that:(1) With the growth and development of C. fortune plantation, litter reserves and water holding characteristics showed a trend of first increasing and then decreasing, showing that mature forest was the largest and young forest was the smallest. The litter thickness, volume, maximum water-holding capacity, maximum water-holding rate, effective storage capacity and effective storage rate of mature forest were 7.40 cm, 2.21 t/hm², 6.46 t/hm², 265.14 t/hm², 3.94 t/hm², and 175.74% respectively. (2) The water conservation capacity of litter in five age groups was calculated by the method of entropy weight, which was:mature forest (11.46) > near-mature forest (10.79) > over-mature forest (8.26) > middle-aged forest (4.83) > young forest (3.94). The mature forest had the largest water conservation capacity.

Abstract:To investigate the effects of biochar as a salt-isolation layer in soil, the effect of biochar as a salt-isolation layer was evaluated by comparing the flow rate of subsurface pipe, the conductivity of leachate, the rate of soil desalination, and the efficiency of leaching of the biochar salt-isolation layer to the conventional gravel salt-isolation layer. The results showed that the flow rate of subsurface pipe of the biochar treatment was 16.1% higher than that of the gravel treatment. The leachate conductivity of 0.83 mS/cm could be treated as the theoretical end point of the leaching. Both treatments reached the theoretical end of leaching during the second leaching process, and the time consuming of the biochar treatment reached the theoretical end of leaching was 13.3% shorter than that of the gravel treatment. The soil leaching efficiency of the two treatments were almost the same. The soil resalinization preventing effect of the biochar salt-isolation layer was better than that of the gravel salt-isolation layer. To sum up, the application effects of the biochar salt-isolation layer were better than that of the traditional gravel layer. The research results provided a reference for the engineering application of the biochar salt-isolation layer in saline-alkali land improvement.

Abstract:In order to explore the effects of bio-organic fertilizer combined with reduced fertilizer on nutrient utilization and yield of continuous cropping cucumber, a field plot experiment with nine treatments (T1~T9) was conducted, and cucumber was taken as the test crop. The nine treatments (T1~T9) were divided into three treatment groups, which were CK treatment group with 0 t/hm² bio-organic fertilizer addition (T1 reduced fertilizer 0%, T2 reduced fertilizer 10% and T3 reduced fertilizer 20%), Y1 treatment group with 10 t/hm² bio-organic fertilizer addition (T4 reduced fertilizer 0%, T5 reduced fertilizer 10% and T6 reduced fertilizer 20%) and Y2 treatment group with 20 t/hm² bio-organic fertilizer addition (T7 reduced fertilizer 0%, T8 reduced fertilizer 10% and T9 reduced fertilizer 20%). The results showed that compared with CK treatment, the cucumber yield of Y1 and Y2 treatment groups increased by 1.48%~38.88% and 15.31%~50.91%, respectively, the nitrogen utilization ratio of Y1 and Y2 treatment groups increased by 1.51%~10.07% and 6.41%~18.71%, the phosphorus utilization ratio of Y1 and Y2 treatment groups increased by 2.07%~5.38% and 5.67%~8.90%, and the potassium utilization ratio of Y1 and Y2 treatment groups increased by 9.50%~16.31% and 16.95%~28.43%, respectively. Under the condition of applying the same amount of bio-organic fertilizer, with the decreasing of chemical fertilizer application, the cucumber yield in CK treatments group (T1, T2 and T3) was significantly different. In Y1 group, the cucumber yield of T4 and T5 was significantly different from that of T6. In Y2 group, the cucumber yield of T8 was significantly different from that of T9. Among the nine treatments, T8 had the highest yield of cucumber, while the utilization rate of nitrogen, phosphorus and potassium of each treatment in Y1 (T4, T5 and T6) and Y2 group (T7, T8 and T9) all showed increase trends. The results could provide scientific basis for improving nutrient utilization rate and reducing crop continuous cropping obstacles.

Abstract:Sedum plumbizincicola is a hyperaccumulator of Cd and Zn, and commonly used for the remediation of Cd-contaminated soil. Organic acids can increase the availability of heavy metals in soil, and enhance the accumulation of heavy metals in plants, and thus increase the plant remediation efficiency of heavy metal-contaminated and influence microbial quantity in soil. In this study, alluvial soil and reddish clay soil were used as test soils, and the effects of EDTA, citric acid, oxalic acid on remediation efficiency of Sedum plumbizincicola and soil microbial quantity were discussed. The results showed that organic acid could significantly increase the soil available Cd content, with the best effect given by citric acid. The available Cd contents in alluvial soil and reddish clay soil increased by 72.73% and 12.99% respectively compared to SCK (P<0.05). Sedum plumbizincicola in planted in two soils treated with EDTA had the highest shoot Cd content, which increased by 99.24% and 33.32% in the alluvial soil and reddish clay soil, respectively. The remediation efficiency of Sedum plumbizincicola cultivated in two soils treated with organic acid increased significantly compared with SCK. The application of organic acids increased significantly the quantity of microorganisms in soil compared with SCK, in which citric acid increased the quantity of bacteria and fungi in alluvial soil by 34.38% and 68.42% (P<0.05) respectively, and oxalic acid treatment increased the quantity of actinomycetes in reddish clay soil by 150.00%. This study could provide theoretical support for plant enhancement remediation technology used in heavy metal contaminated soils.

Abstract:The effects of aluminium sulphate (0, 300, 500, 900 and 1 400 kg/hm²) application on the rapid amelioration and fertility improvement of newly reclaimed soda saline-alkali paddy field were studied through a field experiment. Compared with the control treatment without aluminium sulphate, the pH value, total salt content, exchangeable sodium, cation exchange capacity, alkalinity, CO₃^2-, Ca²⁺, K⁺, Na⁺, water soluble organic carbon (C), aromatic C, carbonyl C, ratios of alkyl carbon/O-alkyl C and hydrophobic C/hydrophilic C, proportions of >2 mm water-stable aggregates and <0.053 mm silt plus clay fractions, and mean weight diameter of water-stable aggregates in soil generally declined, while SO₄^2-, (CO₃^2-+HCO₃^-)/(Cl^-+SO₄^2-) ratio, total organic C, humic acid C, fulvic acid C, humin C, organic C associated with various water-stable aggregate size fractions, alkyl C, O-alkyl C, aliphatic C/aromatic C ratio, proportions of 2~0.25 mm and 0.25~0.053 mm water-stable aggregates increased after the application of aluminium sulphate. The above effects were generally more obvious with the increase of aluminium sulphate application rates, but the differences between 900 and 1 400 kg/hm² application rates were generally not statistically significant. The above results suggested that the application of aluminium sulfate could decline soil alkalinity and salinity, increase soil organic C contents and improve its quality, which was thus an effective way for the rapid amelioration and fertility improvement of soda saline-alkali soil. However, it is noteworthy that the application of aluminium sulfate alone is not beneficial to the improvement of soil structure, and it is necessary to combine aluminium sulfate with other amelioration measures.

Abstract:The surface sediments in wetland along the lower reach of the Dazhang Stream were sampled in July 2018 and the concentrations of six heavy metals (Cr, Ni, Cu, Zn, Pb and Cd) in samples were determined to evaluate their distribution characteristics and ecological risks according to the geoaccumulation index (I_geo) and the potential ecological risk index (RI). Results showed that the average contents of heavy metals in sediments generally followed the sequence of Zn > Pb > Cr > Cu > Ni > Cd and their variations along the lower reach were consistent, which mainly depended on the distributions of grain composition, magnetic parameters, pH, EC, and organic matter along the lower reach. The levels of six heavy metals in sediments of Taohuazhou, Gengjiaoting, Fangzhuangcun and Aolaishidai were very low, which might be due to the sand mining activities at the four sampling sites. The sand mining activities could alter the conditions of flow and sediment in river, resulting in the coarsening of sediments in wetland. Significantly positive correlations were observed among the six metals in sediments (P<0.01), indicating that they might have similar source which represented a combination of sand mining/quarrying wastes and construction/living wastes. The Pb in sediments of most sampling sites was in an unpolluted to moderately polluted status, while Cd was in a moderately polluted status. The average single potential ecological risk indices (E_rⁱ) of six heavy metals in sediments generally followed the order of Cd > Pb > Ni > Cu > Cr > Zn, and Cd showed a high ecological risk. The average RI value of heavy metals in all sampling sites was 228.62, implying that the wetland along the lower reach, as a whole, was in a moderately ecological risk. The study found that although the levels of heavy metals in sediments of wetland along the lower reach of the Dazhang Stream were much lower compared with the other branches in the upper reach of the Min River and the main stream of middle and lower reaches of the Min River, the pollution of Pb and Cd (particularly Cd) and their ecological risks were still very serious. Thus, in the next step, more attentions should be especially emphasized to strengthen the management of wetlands along the lower reach of the Dazhang River.

Abstract:Soil salinization is the most important factor that restricts the soil quality in the newly coastal reclamation area, which seriously inhibits the growth and yield of crops. Six treatments including control treatment (CK), organic fertilizer (OM), polyacrylamide+organic fertilizer (PAM+OM), straw mulching+organic fertilizer (SM+OM), buried straw+organic fertilizer (BS+OM), and bacterial fertilizer+organic fertilizer (BM+OM) were set up to study the effects of different amelioration on soil salinization in coastal saline-alkali soil, and to identify the main factors controlling the variation of soil salinization degree. The results showed that the salt content, sodium adsorption ratio, and exchangeable sodium percentage of surface soil gradually increased, while the pH decreased gradually with the growth stage of oats. Compared with CK treatment, PAM+OM, SM+OM, BS+OM, and BM+OM treatments could significantly reduce soil salinity, pH, sodium adsorption ratio, and exchangeable sodium percentage at 0-20 cm depth. Among them, SM+OM treatment had the best inhibition effect on soil salinity, reaching 68.0%~73.6%, while BM+OM treatment had the best inhibition effect on pH, sodium adsorption ratio, and exchangeable sodium percentage, which decreased by 4.5%~8.2%, 61.5%~80.8%, and 55.5%~79.4%, respectively. The analysis of key influencing factors showed that the effects of soil bulk density, soil water content, and evaporation on the salinization degree of surface soil reached an extremely significant level (P<0.01), while the effects of wind speed and precipitation reached a significant level (P<0.05).

Abstract:In order to better understand the effects of electrodialysis and acid leaching treatments on the acidification process of purple soils, an acid purple soil with the pH value of 5.00 and a neutral purple soil with the pH value of 7.06 collected in Chongqing were treated by electrodialysis and acid leaching treatments for different days (1, 2, 5, 7 and 10 days, respectively). The variation of soil acidity and exchangeable base cations during these treatment processes were analyzed. The results showed that the pH values of both acid purple soil and neutral purple did not change significantly. This could be attributed to the high acid buffering capacity. The purple soils could not be acidified in a short-term acid rain leaching. Differently, after 10-day electrodialysis treatment, the pH values of acid purple soil and neutral purple soil decreased by 3.4 and 1.1, respectively. In the electrodialysis process, the soil exchangeable acidity increased significantly and the content of exchangeable base cations decreased greatly. It was indicated that electrodialysis could be used to rapidly acidify purple soil. The acidification degree of neutral purple soil after electrodialysis treatment was higher than that of acid purple soil. This was because the amount of negative surface charge of neutral purple soil was higher than that of acid purple soil, which caused that more acidic ions (H⁺ and Al³⁺) were adsorbed on the surface of neutral soil, correspondingly, resulting in the increased acidified degree of neutral purple soil. Therefore, compared to acid leaching treatment, electrodialysis treatment was a more effective way to acidify the purple soil in a short time. It also could help us to reveal the acidification mechanism of purple soil. After taking the feasibility of electrodialysis and acid leaching treatments into account, it was concluded that electrodialysis was an effective technique to study the acidification of purple soil.

Abstract:In this study, a polluted farmland in eastern Zhejiang province was selected. Four treatments, including straw returning, straw non-returned, straw returning+lime, and straw non-returned+lime were set up. The dynamic monitoring of heavy metals in soil, straw, cereals, and vegetables was carried out for nine years. The results showed that the accumulation of heavy metals in rice straw, grain, and vegetable was significantly reduced by applying lime in polluted farmland, but the effect of applying lime on the content of total heavy metals in soil was not obvious. The effect of applying lime on the reduction of heavy metals in rice straw, grain, and vegetable was gradually weakened with the experimental time. Compared with straw non-returned, straw returning had less effect on the accumulation of heavy metals in soil, rice straw, and vegetable in a short time. However, the accumulation of cadmium and mercury in soil and the accumulation of cadmium, lead, and mercury in rice straw and vegetable after 4~5 years were significantly lower in straw non-returned farmland than that in straw returning farmland, and the effect on the accumulation of lead in soil was less. With the increase of test time, the difference of heavy metal accumulation in soil, rice grain, and vegetable between straw returning farmland and straw non-returned farmland gradually increased. The content of soil organic matter and available potassium in straw returning farmland was higher than that in straw non-returned farmland. It was concluded that long-term application of straw returning in cadmium and mercury polluted farmland was not conducive to the improvement of agricultural product quality, and the heavy-polluted rice straw returning should be controlled.

Abstract:In order to investigate the effects of biochar on the adsorption and desorption characteristics of cadmium (Cd) elements, the adsorption kinetics, isothermal adsorption and desorption of Cd²⁺ in red soil paddy soils amended with biochar were studied by a primary equilibrium method. The results showed that after applying biochar of CK (0 t/hm²), A10 (10 t/hm²), A20 (20 t/hm²), A30 (30 t/hm²) and A40 (40 t/hm²), the adsorption of Cd²⁺ in red paddy soil was dominated by chemical adsorption and heterogeneous multi-surface adsorption. The maximum contents of adsorption and desorption of each treatment were between 2 933~3 346 mg/kg and 171~192 mg/kg, respectively. The biochar enhanced the adsorption and fixation capacity for Cd²⁺ in red paddy soil and improved the buffer capacity for Cd²⁺. The improvement of adsorption and desorption capacity in red paddy soil amended with biochar was shown as follows:A30 > A40 > A20 > A10. High addition of biochar could saturate the soil adsorption point. Therefore, the adsorption capacity of biochar was relatively low. In conclusion, addition of 30 t/hm² biochar was the most reasonable measure.

Abstract:In order to ascertain the input and output characteristics and variation of Cadmium (Cd) in the typical paddy soils in southern China, this study took the certain rice fields of Xiangxiang City in Hunan Province as research targets to discuss the connection between three input pathways (fertilizer, irrigation water and atmospheric deposition) and two output pathways (surface runoff water and rice straw removal) and the Cd content of soil. The results showed that the net fluxes of Cd between 2017-2018 and 2018-2019 were 3.259 and -1.246 g/(hm²·a) respectively, and the total change of Cd in two years was 2.013 g/(hm²·a). Atmospheric deposition was the main input pathway. The net fluxes in two years were 8.68 and 5.75 g/(hm²·a) respectively and the average contribution rate was higher by 94%. Rice straw was the main output pathway. The net fluxes in the two years were 5.73 and 7.32 g/(hm²·a) respectively, and the average contribution rate was higher by 97%. Through the input-output equilibrium analysis, the soil Cd content showed an increasing trend within two years. Therefore, it was necessary to adopt agricultural management measures such as "straw out from field" to improve the safe use efficiency of the soil. The research results could provide theoretical basis and method for the prevention and control of soil Cd pollution sources in this region.

Abstract:Pot experiment was conducted to study the tolerance and remediation effect of Napier grass to cadmium (Cd) in purple soil and granitic sandy soil using Fourier infrared and X-ray diffraction analysis methods, and the exogenous Cd was added with gradients of 0, 0.5, 2.0, 10.0, 20.0 mg/kg. The results showed that Napier grass had a good tolerance to Cd, the tolerance index was 0.65~0.79. When the concentrations of Cd were 0, 0.5, 2.0 mg/kg, the bioconcentration factors were more than 1, showing a good ability of enrichment to Cd. Napier grass was not hyper accumulator of Cd because of transfer factors ranged from 0.60 to 0.84, but its restoration efficiency on Cd-contaminated soil was considerable when no exogenous Cd was added resulted from its enormous above ground biomass. And it was the most significant in granitic sandy soil, i.e., 2.48%. In addition, the differences in soil physicochemical properties such as pH, CEC and organic functional groups could also lead to the differences in Cd enrichment in Napier grass. Comprehensive analysis showed that Napier grass was more suitable for the remediation of moderately Cd-contaminated soil, and the remediation efficiency of granitic sandy soil was better than that of purple soil.

Abstract:A pot experiment was conducted with three levels of biochar addition (0, 2.5% and 5% (w/w)), to investigate the effect of biochar on the uptake of Cd and Pb by ratoon rice (Oryza sativa L.). The results indicated that biochar addition decreased the accumulation of Cd and Pb both in the main crop and ratoon crop. This could attribute to the following reasons:Biochar addition increased the soil pH and the content of soil organic matter, which consequently promoted Cd and Pb transformation from acid soluble fraction to reducible fraction. The CaCl₂-extraction Cd and Pb concentrations were also reduced in soil, resulting in the decreased uptake of Cd and Pb by rice root. Biochar addition decreased the transfer factors (TF) of Cd from leaf to brown rice both at main crop and ratoon crop, and also reduced the TF_stem-leaf and TF_stem-rice of Pb; therefore, the concentrations of Cd and Pb in brown rice were decreased. The Cd content in brown rice was 0.15 mg/kg inratoon crop with 5% biochar addition, which was below the hygienic standard for rice in China (0.2 mg/kg). And 5% biochar addition reduced Pb concentration in brown rice of ratoon crop by 68.18% compared with the control. What is more, this research also found that Cd and Pb concentrations in brown rice of ratoon crop were lower than those in the main crop. In a word, biochar addition could reduce the Cd and Pb transfer from soil to ratoon rice.