Abstract:This paper oriented to study hydrodynamic characteristics of steep loess slopes (25°~50°), in an attempt to lay down a foundation for elucidating the in-depth relationships of the hydrodynamic characteristics of shallow water flow on slopes with soil erosion. An indoor experiment was carried out to simulate rainfalls on steep loess slopes. The experiment was designed to have only one soil type (loessal soil), three rainfall intensities (1.0 mm/min, 1.5 mm/min and 2.0 mm/min) and six slope gradients (25°, 30°, 35°, 40°, 45° and 50°). Results showed that:(1) Soil erosion rate increased with rising rainfall intensities on slopes with the same gradient, and under the same rainfall intensity, the effects of slope gradients on soil erosion rate exhibited a critical point in gradient, that was, between 40° and 45°. On slopes with gradient lower than the critical point, soil erosion rate increased with rising slope gradients, whereas on slopes with gradient higher than the point, soil erosion rate decreased with rising slope gradients. (2) Flow shear stress, stream power and unit energy of water-carrying section were increased with the rising rainfall intensities and slope gradients, while stream power had the best regularity. (3) The increasing power functions were found between soil erosion rate with flow shear stress, unite stream power and unit energy of water-carrying section, with the determining coefficient of R²(ω)>R²(τ)>R²(E). So stream power was the best one of all the hydrodynamic parameters tested to describe the soil erosion process on the steep loess slopes.

Abstract:The resistance coefficient is one of the hydrodynamic parameters of the slope surface and also is an important eigenvalue that reflects the hydraulic characteristics of the slope surface. In order to explore the variations of surface runoff resistance coefficient of grassland in loess region with different rainfall intensities (0.7, 1.0, 1.5, 2.0, 2.5 mm/min) and slope gradients (7°, 10°, 15°, 20°, 25°), indoor artificial rainfall simulation was adopted in this study. The results showed that:(1) The sheet flow resistance coefficient of grassland slopes decrease firstly, and then gradually stabilized with the rainfall duration under different rainfall intensities and slope gradients. The relationship between resistance coefficient and rainfall duration could be described by a quadratic polynomial equation, and the correlation was significant, also the coefficient of determination was above 0.5. (2) The sheet flow resistance coefficient of grassland slope increased gradually with rainfall intensity, and the relationship could be described by a exponential equation with the coefficient of determination was above 0.8; while the sheet flow resistance coefficient of grassland slope decreased with the increase of slope gradient, and the relationship could be described by a logarithmic equation with the coefficient of determination was above 0.6. (3) The integrated response of the average flow resistance coefficient of the grassland slope could be described by a binary exponential function with the coefficient of determination was 0.923. Through comparative analysis, it was found that the influence of rainfall intensity to average sheet flow resistance coefficient was greater than that of slope gradient. This study provides a theoretical basis for the reference of grassland flow hydrodynamics and the flow control mechanism of grassland vegetation. It is of great significance for us to deeply understanding the erosion dynamics of grass slope and ecological construction in the loess area.

Abstract:Through indoor simulated rainfall experiment and water balance methods, the rainfall infiltration law of slope during thawing period was studied. The experimental treatments included 4 initial thawing depths (0, 2, 4 and 6 cm) and 3 rainfall intensities (0.6, 0.9 and 1.2 mm/min). The results showed that:(1) The infiltration process varied from high to low with the increase of rainfall duration. (2) The initial infiltration rate of slope surface was greatly affected by rainfall intensity. The initial infiltration rate under rainfall intensity of 0.9 mm/min was significantly higher than that of 0.6 mm/min (p<0.05), and the steady infiltration rate at different initial thawing depths was smaller than that at different initial thawing depth. The change trend of average infiltration rate and the steady infiltration rate decreased firstly and then increased with the increase of initial thawing depth and the critical thawing depth was 4 cm. The cumulative infiltration amount at the initial thawing depth of 6 cm was significantly larger than that at 0 cm, 2 cm and 4 cm, and the cumulative infiltration amount increased with the increase of thawing depth under the rainfall intensity of 0.6 mm/min. However, under the rain intensity of 0.9 and 1.2 mm/min, the critical thawing depth was 2 cm and 4 cm, which decreased first and then increased. (3) By using the Kostiakov,Horton, Jiang Dingsheng and Philip models to simulate the experimental results, it was found that Horton model could best reflect the characteristics of rainfall infiltration on slope during thawing period. These findings were expected to reveal the change mechanism of runoff production and soil erosion during the thawing period.

Abstract:In order to study the response process of different soil types in desert steppe to precipitation, the sierozem, aeolian sandy soil, and bedrock weathered residual soil were selected as the research objects in Wanjigou village, Yanchi country, Ningxia. The infiltration process was determined by double-ring sampling method, and the infiltration characteristics of the three were analyzed and compared. The models were used to fit the soil infiltration process. The results indicated that three types of soil infiltration process can be divided into three stages. The first stage was from 0 to 5 minutes, in which the infiltration rate decreased rapidly; during 5 min to 10 min, the infiltration rate brought a gradual decreased and tended to be stable, and reached a relatively stable state after 30 min. By comparing the initial infiltration rate, stable infiltration rate and cumulative infiltration rate of 60 minutes in different soils, it was found that the infiltration characteristics of different soil types were different. Soil infiltration of the aeolian sandy soil was the best, followed by bedrock weathered residual soil, while sierozem was the worst. The differences in soil infiltration characteristics were caused by the differences in soil structures. The analysis of the differences in soil physical properties showed that the mechanical composition and non-capillary porosity were the main factors affecting soil infiltration in the study area. Using four soil infiltration models to fit the infiltration process of different types of soil, the universal empirical model was more suitable for describing the change of soil infiltration rate with time in the study area.

Abstract:The characteristics of runoff and sediment yield on the red soil slope nested gravel-sand were studied through artificial simulated rainfall, and the differences of runoff and sediment yield between nested gravel red soil slope and no gravel slope under the conditions of rainfall intensity (60,120 mm/h) and slope gradient (10°, 15°, 20° and 25°) were analyzed. The results were as follows:(1) The start time of production runoff (T) on the nested gravel slope was less than that on the no gravel slope, and compare with no gravel slope, the runoff production time on the nested gravel slope was delayed 4.20, 2.95, 2.23 and 1.03 min, respectively, when the slope gradient was 10°, 15°, 20° and 25° under the rainfall intensity 60 mm/h. (2) When the slope gradient was the same, the runoff rate of the nested gravel-sand slope was less than that of no gravel slope obviously, but the increase of rainfall intensity could cover up the influence of nested gravel-sand on the decrease of runoff rate. (3) When the rainfall intensity was 60 mm/h and the slope was 10°, the average runoff rate of nested gravel-sand slope was the lowest, while the average runoff rate was 4.5 times higher than the lowest value when the rainfall intensity was 120 mm/h and the slope gradient was 25°. When the rainfall intensity was 120 mm/h and the slope gradient was 25°, the average runoff rate of no gravel-sand slope was 4.8 times higher than the lowest. (4) The sediment yield intensity and the amount of sediment yield increased with the increasing of rainfall intensity and slope gradient. When the rainfall intensity was 60 mm/h and the gradient was 10° and 25°, the average sediment yield intensity of nested gravel-sand slope was 6.0% and 28.4% of the no gravel slope, respectively. When the rainfall intensity was 120 mm/h, the value was 33.9% and 25.3%, respectively.

Abstract:To explore the mechanism of surface runoff and sediment yield of evergreen broad-leaved forest in the middle subtropical region, the natural rainfall and raindrop characteristics from May to September in 2016 and 2017 were observed by field observation and indoor test analysis Also, the leading environmental factors were selected by RDA sequencing and the Forward analysis of CANOCO. The results showed that:(1) Sediment yield was positively correlated with rainfall outside forest and throughfall in forest area. When runoff was greater than 0.064 mm in the study area, sediment occurred. The buffer effect of canopy layer on rainfall kinetic energy was more obvious when rainfall intensity was small. (2) Canopy buffering energy, leaf area index and stemflow and sediment yield had a negative correlation, rainfall duration, rainfall outside the forest, forest rainfall, average rainfall intensity, raindrop number, raindrop diameter, raindrop velocity, rainfall kinetic energy and rainfall kinetic energy on runoff sediment produced positive influence. (3) Through the screening of the leading factors of 12 environmental factors, we got the most significant influences of total rainfall, total rainfall, average rainfall intensity, canopy buffer kinetic energy and rainfall duration on the runoff and sediment yield of 12 environmental factors. The results from canonical eigenvalues analysis showed that choosing only 5 main environmental variables could explain 73.2% of the information content of the relationship between environmental factors and runoff and sediment yield, which was only 16.8% less than that explained by 12 variables.

Abstract:Under natural rainfall conditions, a field plot experiment (2014-2015) was conducted to study the effects of different fertilization modes (i.e. conventional fertiliser application, T1; reduced fertiliser application, T2; optimized fertiliser application, reduced fertiliser application and wheat straw biochar application, T3) on nitrogen (N) loss by surface runoff, the apparent N balance, and vegetable yield in the vegetable field of cabbage (Brassica Oleracea L.) in Taihu Lake Basin, China. The results showed that total volume of surface runoff reached up to 1 729.20 m³/hm² during the vegetable growing season, which showed a significant positive linear correlation with rainfall capacity. In T1 treatment, total nitrogen (TN) loss by surface runoff reached up to 47.66 kg/hm² during the vegetable growing season. Compared with T1, T2 and T3 significantly reduced TN losses by 13.95% and 23.68%, respectively. Compared with T2, TN loss decreased significantly by 11.31%, after application of wheat straw biochar (T3). The lost N was mainly nitrate nitrogen (NO₃^--N), which accounted for 81.11%~85.94% of TN loss. Meanwhile, N surplus amount in the vegetable field of cabbage reached up to 158.24 kg/hm² under T1 treatment. With decreasing N application in the vegetable field, N surplus significantly decreased. Compared with T1, N surplus decreased significantly by 29.03%~39.81%. Furthermore, T2, T3 significantly reduced cabbage head yield by 16.12%~19.11%, but the sphericity index increased significantly by 6.17%~7.41%, and the partial factor productivity of nitrogen (PFPN) for cabbage head increased significantly by 24.39%~28.98%. And, compared with T2 treatment, after application of wheat straw biochar (T3) in the vegetable field, cabbage head yield and PFPN increased slightly, but no significant difference was found.

Abstract:Large-scale roughness element plays an important role in soil erosion control, but few studies have been performed to quantify the effects of large-scale roughness element on hydraulics of overland flow. Laboratory flume experiments were conducted to investigate the potential effects of large-scale roughness element on flow velocity, water depth, Froude number, and hydraulic resistance of overland flow. The plastic hemispherical were glued onto the flume bed to simulate the large-scale roughness element, and a sand cloth bed was used as control. The flow discharges varied from 2.81 L/min to 84.43 L/min and the slope gradients ranged from 2° to 10°. Results showed that:(1) The mean flow velocity, mean water depth and Froude number had power function relationships with the flow discharges and slope gradients. However, the resistance coefficient decreased as Reynolds number increased. (2) The variation trend of water depth around the large-scale roughness element was water depth in front of the large-scale roughness element (h₁)>water depth on both sides of the large-scale roughness element (h₂)>water depth behind the large-scale roughness element (h₃). At a smaller slope gradient, h₁-h₃ increased first and then became stable with the increasing flow discharges. At a larger slope gradient, h₁-h₃ increased first and then decreased with the increasing flow discharges. (3) Compared with the sand cloth bed surface, the large-scale roughness element had a function of reducing flow velocity, increasing resistance, and changing flow regime. (4) The total resistance on large-scale roughness element was partitioned into grain resistance and form resistance, and form resistance accounted for 29%~77% of the total resistance. In a word, the large-scale roughness element cloud retards the flow, reduce soil erosion and have obvious effect on soil and water conservation.

Abstract:In this study, the reservoir deposits were used to compare the effect of dam construction on sediment interception from two representative small catchments underlain by granite and limestone, namely the Jiangzhuang and Quananzi catchments, respectively, over the past 50 years in the Yimeng Mountain Region. Three cores were collected from reservoirs in the both catchments. The activities of ¹³⁷Cs and ²¹⁰Pb_ex at different depths, clay contents, and dry sediment bulk densities in cores from the two reservoirs were analysed with reference to human activity and environmental change in the catchment over the past 50 years. The chronologies of the cores were established by ¹³⁷Cs and ²¹⁰Pb_ex dating methods. The mean annual sediment interception for different time periods since dam construction were estimated from each core by referring to the original reservoir capacity curve, which could be generally used to represent the sediment interception effect of the reservoir. The sediment interception effects estimated from the three cores in the Jiangzhuang and Quananzi reservoirs ranged between (394±142)~(121±43) t/year, and (22±7)~(59±21) t/year, with mean values of (208±75) and (41±15) t/year respectively. The total sediment interceptions since the dam construction were about 10 475 and 2 097 t for Jiangzhuang and Quananzi reservoirs, respectively. Overall, the temporal trends of sediment interception associated with the two reservoirs reflect the different patterns of sediment yield response to the environmental change influenced by human activity in the two contrasting lithological small catchments over the past 50 years.

Abstract:Preferential flow is a non-equilibrium flow which presents the rapid movement of water and solute transport in soil. It has become a significant soil water movement type in special geological conditions of karst area. This paper concentrated on typical farmland of sugarcane field with smash-ridging and no-tillage types in the karst area of Southwest China, using the methods of brilliant blue dye, image analytics and the soil moisture layer evaluation to present the soil preferential flow features of two tillage types. The results showed that under the same water supply condition, the wetting front curve of sugarcane field with smash-ridging was more gentle than no-tillage field. The average infiltration depth of sugarcane field with smash-ridging was 0.05 times lower than that of no-tillage type, which presented homogeneous infiltration pattern. The preferential flow staining pattern of sugarcane field with two tillage types was scattered clumps (smash-ridging type) and dendritic patterns (no-tillage type), respectively. At the same external condition, the occurrence of preferential flow was faster in sugarcane field with no-tillage, which the rate of preferential flow was 1.45 times higher than the sugarcane field with smash-ridging. The average preferential flow fraction of sugarcane field with smash-ridging was 82.89%, which was lower than the no-tillage (88.61%). There was significant difference between them (P<0.05). Along with soil depth, the occurrence and change degrees of preferential flow in sugarcane field with smash-ridging changed from secondary active, active, secondary active, relatively stable, and to secondary active, while the change degrees of preferential flow in no-tillage type was higher, which changed from secondary active, active, secondary active, and to relatively stable. The occurrence of preferential flow in no-tillage type was mainly at depths of 5-35 cm, which was deeper than the smash-ridging type (10-30 cm). Compared with the no-tillage type, the smash-ridging type reduced the occurrence and change degrees of preferential flow in sugarcane field of karst area. The soil abilities of water and fertility retention were improved to a certain extent.

Abstract:In this study, Dalateqi County in Inner Magnolia which stands for highly intensity human activity and Chengduo County in Qinghai Province which is for low intensity human activity were selected as study areas. The data on land use and remote image in 2014-2015 and 2017 were collected. The soil loss was calculated using Chinese soil loss equation. The variation of land use and soil loss was analyzed. The differences in soil loss and land use were compared based on the two period land use results (LUR) and on the two period remote image variation results (IVR). The results showed that variation of soil loss based on the LUR was more obvious than that on the IVR. The area variation of soil loss based on the LUR was 64 times (Chengduo) and 94 times (Dalateqi) of that on the IVR. The area variation of soil loss based on the IVR was more reasonable, which reflected the true variation. The area variation of soil loss was far smaller than that of land use. The results will provide the technique support for the evaluation method on the incoming annual variation of soil loss according to the "soil loss inventory plan in China (2018-2022)".

Abstract:Based on DEM digital elevation model, RUSLE model combined with GIS, GeoDa, GS+ and other software, the evolution of spatial pattern of soil erosion and its influencing factors in 25 years in Chongli District, Zhangjiakou City, Hebei Province were analyzed. The results showed that:(1) From 1990 to 2015, the soil erosion was severe in the central, western, and southwestern regions of the study area. The intensity of soil erosion was mainly mild and moderate. The amount of soil erosion firstly decreased and then increased. (2) From 1990 to 2000, the change of soil erosion intensity was dominated by mild transformation. Soil erosion was alleviated. From 2000 to 2010, it was mainly slight erosion turning to high-level erosion, and showed aggravate trend. From 2010 to 2015, the overall transformation was in the form of slight erosion, mild erosion turned to high erosion levels, but the area of increased erosion decreased, and the erosion slightly improved. (3) Soil erosion's Moran's I>0, the spatial distribution was positive correlation, showing aggregation state, with high-level aggregation mainly in central and western and southwest. Soil erosion modulus met index model and spherical model, R² was 0.943~0.979. The range of soil erosion reduced from 3 870 m to 860 m and then increased to 1 470 m, indicating that the change of soil erosion was firstly fast and then slow down from 1990 to 2015, the spatial distribution of spatial correlation expanded and the spatial heterogeneity increased firstly and then decreased. The fractal dimension of soil erosion ranged from 1.922 to 1.971. Spatial heterogeneity of soil erosion was mainly caused by stochastic factors such as vegetation cover, land use types, and water and soil conservation measures in a small spatial scale. (4) The contribution rate of the first, second, and third principal components to the soil erosion factors accounted for 89.215 0%. In the first principal component load, the projection length of vegetation cover factor was the largest, which was 0.976 4. In the second and third principal component loads, the projection length of soil and water conservation measures factor and soil erodibility factor were large. Therefore, the influencing factors of soil erosion in Chongli District were in order of vegetation cover factor, soil and water conservation measures factor, soil erodibility factor, rainfall erosivity factor, and slope length slope factor. The results can provide theoretical basis for soil and water management and sustainable development of Qingshui River Basin in Chongli District.

Abstract:In order to explore the quantitative relationship between different undergrowth vegetation and moisture migration in Southwest China, and the impact of different undergrowth vegetation on water retention, three common shrubs, Sarcandra glabra Nakai, Maesa japonica Moritzi and Orixa japonica Thunb, were selected in the Simian Mountain. And the artificial rainfall method was used to study the interception characteristics of single shrubs and litters under different rainfall intensities, and the interception characteristics of compound structure. The results showed that:(1) The interception of single shrubs, the interception of litter and the interception of shrubs and litter assemblages were all divided into three stages, its were rapid trapping phase, saturated and stable phase, and a post-rainfall drainage phase. (2) The maximum and minimum interception rates of the studied three typical shrubs increased first and then decreased with the increase of rainfall intensity. (3) There was a positive correlation between the maximum interception of litter and rainfall intensity. The unit area quality of the litter with the mean maximum and minimum interception of the litter also showed a positive correlation. (4) Compared with single shrubs and litter alone test, the maximum interception of composite structure showed a positive correlation with rainfall intensity, and gave the longer rapid trapping phase and the larger maximum interception. When the rainfall intensity was 35 mm/h, the maximum interception of the composite structure of Sarcandra glabra Nakai and Maesa japonica Moritzi were larger than the sum of maximum interception of single experiment, but the maximum interception of the composite structure of Orixa japonica Thunb was less than the sum of maximum interception of single experiment. And the maximum interception of all the composite structure were less than the sum of the maximum interception of individual shrubs and litters when the rainfall intensity was 70 and 95 mm/h. Undergrowth shrubs and litters all played an important role in the process of water transport. Litters had a greater contribution to water interception. Therefore, rationally constructing and arranging the undergrowth vegetation could effectively retain water, which had a certain positive effect on reducing soil erosion in forest land.

Abstract:Using the space-for-time substitution experimental design, three apple orchards with different ages but the same species and management (i.e. 5-year old young orchard has not yet borne fruit, 8-year old orchard has borne fruit for two years, and 13-year old mature orchard, respectively) were selected on the Loess Plateau in Changwu County, Shaanxi Province. On July 12th and August 19th, 2015, soil samples were taken at 0.2 m intervals from the surface to 5 m depth of a profile, and the corresponding apple tree branches were taken at each site. The stable oxygen and hydrogen water isotopes of the soil and branch samples were measured and the Bayesian mixing model was used to quantify the contribution of soil layers from different depths to apple water uptake and their responses to precipitation. Results showed that:(1) The depth of the primary water source for apple trees before and after precipitation differed with stand ages. During the dry season, the main water absorbing depth of 13-year old trees was deeper than that of 5- and 8-year old trees. At the peak growing season, rainfall in the rainy season could only increase the soil water storage in 5-year old young orchards that has not borne fruits, thus young orchards were free of deep soil water deficit. For the 8- and 13-year old mature apple orchards that has borne fruits for several years, the deep soil water could not be replenished even under the large precipitation. (2) For 5- and 8-year-old apple trees, the contribution of 0-100 cm shallow soil layer to the plant transpiration was more than 50% during the drought period. However, 50% of tree water came from 100-300 cm depth for the 13-year-old apple orchard. After precipitation, the main water source of trees was 100-300 cm for the 5- and 8-year-old orchards, and the resulting contribution was about 40%. For the 13-year-old apple orchard, the main water contribution layer was 0-100 cm soil layer, with nearly 50% of the total contribution. (3) The contribution of soil water in 300-500 cm layer showed very weak response to precipitation for all the three orchards, maintained around 30% consistently.

Abstract:The characteristics of vegetation community and soil nutrient content were measured by 4 different degrees of desertification around the Saline Lake of Jartai. The characteristics of vegetation communities, vertical distribution characteristics of soil nutrient contents and correlation between vegetation communities and soil nutrient contents were analyzed. The results showed that:(1) With the intensification of desertification, Shannon-Wiener diversity index, Simpson dominance index and Margalef richness index decrease, and vegetation community structure tends to be simplified. (2) With the intensification of desertification, the content of soil organic matter and available nutrients decreased in general. (3) Soil organic matter, available phosphorus and available potassium all had significant positive correlations with Shannon-Wiener diversity index, and there was a significant negative correlation between available potassium and Pielou evenness index. There was a significant positive correlation between alkali hydrolyzed nitrogen and Margalef richness index. The study of vegetation characteristics and soil nutrients in different desertification degree provides scientific basis for the restoration and reconstruction of natural vegetation and in Saline Lake area of Jartai and high-yield of Saline Lake.

Abstract:In order to clarify the source and sedimentological significance of the climbing dunes on the Qinghai-Tibetan Plateau and reveal its formation mechanism, the climbing dunes section samples were collected in the Tola Hai River, and the grain size and geochemical characteristics of the different terrain parts of the climbing dunes were analyzed. The results showed that the grain size of the climbing dunes of Tola Hai River mainly consisted of very fine, fine and medium sand with an obvious aeolian sedimentary characteristic. The characteristic of particles varied in different terrain; the mean grain size became coarser from the riverbed to upwind slope, meanwhile, the sorting trended to be better, but the opposite trend was observed from the upwind slope to the leeward slope. The geochemical evidence indicated that in the climbing dunes of Tola Hai River, Si, Al and Ca were the dominant elements. Compared with the upper continental crust (UCC), all the elements except Co, As, CaO and SiO₂ appeared to a depletion status. The distribution of chemical elements in different terrain was similar, and there was a good correlation between constant oxides, indicating that they had similar sedimentary environment. The A-CN-K ternary diagram and the CIA index showed that chemical weathering of the surface sediments in the climbing dunes was in a low degree, most of the chemical elements had no significant weathering or migration, and the whole was in the stage of early Na and Ca. Moreover, A-CNK-FM ternary diagram showed that the spatial distributions of Fe and Mg were different in the whole section and the loss of Fe and Mg was mainly caused by sorting action of wind. All the chemical weathering index, including CIA, A-CN-K and A-CNK-FM, presented that different topographic parts were in different weathering degrees, the weathering degree of the river bed was the weakest, the weathering degree of the upwind slope was the strongest. The source of the riverbed and river terrace was diverse, while the source of windward slope and leeward slope was relatively single, which may be caused by ancient dunes activated and local sand source or local accumulation. Therefore, we preliminarily believed that the formation of the climbing dunes in the Tola Hai River has undergone two stages:the first was the formation of the ancient dunes and the second was the formation of modern climbing dunes. On different spatial scale, the physical and chemical characteristics of the surface sediment of climbing dunes were related to the difference between power of wind and hydrodynamic force, reflecting the response of the sediment to the interaction of wind and water.

Abstract:In 2016 and 2017, two drip irrigation frequencies (the low frequency W1:one irrigation every 7 days, the high frequency W2:one irrigation every 2 days) and two nitrogen levels (suitable N1:375 kg/hm², high nitrogen N2:565 kg/hm²) were conducted in a solar greenhouse of squash in the northern cold and dry land, with the same irrigation quota of 269.87mm. The soil water and nitrate distributions and the yield of squash in solar greenhouse were studied. The results showed that:(1) W2 increased the soil water contents of 0-40 cm and reduced the deep seepage. (2) The soil nitrate contents were higher in all layers under N2, suitable nitrogen treatment combined with high frequency drip irrigation could maintain the nitrate contents at a relatively suitable level at 0-40 cm in the root zone, so the nitrate content in the 40-80 cm soil layer was relatively lower. The improved frequency of drip irrigation could reduce the leaching risk of nitrogen. (3) Under N1, squash yield was sensitive to irrigation frequency, however, for N2, the increasing irrigation frequency had no significant effect on yield, which indicated that the sensitivity of squash yield to irrigation frequency was low. (4) For a given fixed irrigation quota, the effect of drip irrigation frequency on water use efficiency of squash was greater than that of nitrogen fertilizer on water use efficiency of squash. (5) Taken together, W2N1 was more conducive to the growth of squash and the increase of yield. So, it is recommended that the nitrogen level in greenhouse drip irrigation was 375 kg/hm², and the irrigation frequency was 2 days.

Abstract:In order to compare and analyze the impacts of stand density on hydrological and ecological functions of litter layer, the Robinia pseucdoacacia plantations with 6 different densities (475, 900, 1 200, 1 575, 1 825 and 2 350 trees/hm²) in Loess region of Western Shanxi Province were chosen as the object. By the methods of field survey and laboratory experiment, the hydrological characteristics of litter layer, such as the litter total storage capacity, the maximum water holding capacity and modified interception capacity and their relationships with soaking time, were studied, aimed to propose the reasonable density of the Robinia pseucdoacacia management in this area and provide scientific basis for giving full play to soil and water conservation functions as well as achieving function-oriented vegetation regulation and optimal allocation. The results showed that:(1) The litter total thickness of Robinia pseucdoacacia plantations with 6 densities ranged from 28.67 mm to 54.33 mm in the studied area. The total volume was about 2.98~10.65 t/hm², and in a certain stand density, the litter total storage capacity increased first and then decreased with the increase of densities, showing an order of 1 575 trees/hm² > 1 825 trees/hm² > 1 200 trees/hm² > 900 trees/hm² > 2 350 trees/hm² > 475 trees/hm². (2) The maximum water holding rates varied from 295.35% to 427.84% with no obvious regularity. The maximum water holding capacity was 11.16~37.01 t/hm² and had significant differences among some plantations with different densities, which achieved the best (37.01 t/hm²) at 1 575 trees/hm². The water holding capacity in half-decomposed litter layers was higher than that in un-decomposed litter layers, but different stand densities had little effects on water absorption rates. (3)The modified interception capacity was about 7.22~23.64 t/hm² in different stands and the maximum was found in 1 575 trees/hm², reaching 23.64 t/hm². (4) Water holding capacity of litter had a logarithmic correlation with immersion time (Q=aln t+b, R²>0.95), and water absorption rates showed a power function with soaking time (V=ktⁿ, R²>0.99). In summary, within the scope of this study, the litter layer showed better hydrological and ecological function under plantation with around 1 575 trees/hm². When the density was lower than 1 200 trees/hm², it tended to drop sharply. From the perspective of litter hydrological function, it is recommended to maintain the rational stand density range of 1 200~1 800 trees/hm² in future Robinia pseucdoacacia plantation management of this area.

Abstract:Based on the concept of natural storage, natural infiltration, natural purification for rainwater advocated the sponge city, infiltration and seepage-proof rainwater gardens were designed and built according to the rainfall characteristics in Xi'an. We monitored the runoff regulating effects in 33 rainfall events from 2015 to 2017. The results showed that:(1) Seepage-proof rain garden filled with undisturbed soil reduced runoff volumes by 11.2%~100% (medium=69.14%). (2) The results of pollutant concentration exceedance probability analysis showed that the probabilities of concentrations of total nitrogen, ammonia nitrogen, total phosphorus and chemical oxygen demand exceed the limit standard IV of the surface water quality decreased by 58.57%, 2.71%, 20.57% and 29.71%, respectively, in the rainwater flows through the garden system, compared with the exceedance probabilities of inflow concentration. (3) The correlation coefficient between the runoff reduction rate and the pollutant load reduction rate was more than 0.857 for 33 rainfall events. (4) Through monitoring the precipitation, water qualities of inflow and outflow, we estimated that the annual pollutant concentration removal was 11.93%~60.97%, and the annual load of pollutants reduced more than 70% in the rainwater garden.

Abstract:To improve the water use efficiency of slope, cracks on slope, surface runoff, bottom leakage and soil storage were measured by the method of soil spraying, and the water distribution on slope was analyzed under irrigation and rainfall conditions. The results showed that the distribution of soil cracks on slope was not uniform, and the soil cracks tended to decrease from the top slope to the bottom. The total area of cracks on sunny slope was greater than that on the shady slope. Water distribution characteristics under irrigation condition varied from different slope directions. On the sunny slope, 0.02% of the water was dissipated through evapotranspiration, 7.00% of the irrigation water moved along the slope forming surface runoff, 10.00% of water turned into the bottom leakage and 53.00% of the irrigation water was stored in soil. The ratios of evapotranspiration, surface runoff, bottom leakage and soil moisture were 0.01%, 35.00%, 0.25% and 39.00% on the shady slope respectively. With the growth of vegetation coverage, the surface runoff formed by irrigation decreased and the soil water storage increased. Rainfall intensity had a significant effect on water distribution characteristics. About 95.00% of the rainfall was stored in the soil under the light rain, and the amount of bottom leakage and surface runoff reached the maximum under moderate and heavy rain conditions respectively. With various rainfall intensities, surface runoff on shady slopes was 1.1~3.0 times higher than sunny slopes. The sunny slopes had a higher water use efficiency with greater amount of bottom leakage than the shady slopes. These results could provide a scientific reference for the effective use of water in the highway slope greening.

Abstract:Taking the grassland, the Xanthoceras sorbifolia, the Hippophae rhamnoides and the Caragana korshinskii shrub in Lijiabao, the hilly-gully region in the Loess Plateau, as the research objects, the field sampling and the indoor analysis were used to study the soil physical characteristics and infiltration characteristics under four vegetation types. The results showed that with the increase of soil depth, soil bulk density increased generally, while soil porosity and aeration decreased. In the four vegetation types, the soil bulk density of grassland was the largest, with the smallest porosity and aeration, while the soil bulk density of Caragana korshinskii shrub soil was the smallest, with the highest porosity and aeration. The physical characteristics of soil water were the largest in Caragana korshinskii, the following was in Xanthoceras sorbifolia and Hippophae rhamnoides, and the lowest in grassland. The maximum water holding capacity, capillary holding capacity, minimum water holding capacity, maximum water storage capacity and drainage capacity of 0-40 cm soil layers in Caragana korshinskii shrub were 23.00%, 22.51%, 15.02%, 12.76% and 61.28% respectively higher than those in grassland, and the variance analysis showed significant difference. The logarithmic relationships were found for the soil moisture infiltration processed under the four vegetation types, the R² of soil permeability coefficient were between 0.937 9 and 0.986 9, and the F test reached the extremely significant level (P<0.001). The infiltration rate and water conservation capacity of Caragana korshinskii shrub were significantly higher than those of grassland, which could improve soil physical characteristics and increase the construction of Caragana korshinskii forest.

Abstract:Influenced by vegetation types, there are significant differences in the distribution and water holding characteristics of litter. This study selected four typical vegetation plots of Robinia psendoacacia, Caragana intermedia, Artemisia gmelinii and Bothriochlo aischaemum in the hilly area of the Loess Plateau, and studied the changes of litter volume, water holding capacity and storage capacity. The results showed that:(1) The surface litter volume (0.14~0.83 kg/m²) and soil litter volume (0.18~0.66 kg/m²) were both followed the order of forest land>shrub land>grassland, while the proportion of soil litter to total litter volume (44.1%~73.5%) was grassland>shrub land>forest land. Surface litters and soil litters in both R. psendoacacia and C. intermedia forest lands showed an alternate cycle of increasing and decreasing along the slope. However, the surface litter and soil litter increased with the increasing of slope length. (2) The water holding capacity of the litter was a logarithmic function of soaking time (R² ≥ 0.89, p<0.01). The water holding capacity of the surface litter of B. aischaemum was the highest, and the water holding capacity of the soil litter of R. psendoacacia forest was the highest. The maximum water holding capacity of soil litter was higher than that of surface litter in varying degrees, which was 1.9~2.5 times higher than that of surface litter. (3) The correction coefficient of effective interception of soil litter was 0.34~0.48, which was generally less than that of surface litter. The effective storage capacity of ground litter and soil litter was 2.4~12.5 t/hm² and 1.6~5.8 t/hm², respectively. The effective storage capacity of soil litter was lower than that of surface litter in forest land, while the opposite trend was found in the grassland. In general, the total effective interception of litter in R. pseudoacacia plot was the maximum (16.4 t/hm²), which was 1.5~4.1 times that of other plots. The results provided an important basis for evaluating the water-holding characteristics of litter in typical vegetation and understanding the hydrological effects of vegetation restoration on the Loess Plateau.

Abstract:Throughfall, stem flow and canopy interception of three types of forest (Pinus tabulaeformis forest, Larix principis-rupprechtii forest and Populus davidiana forest) were studied in Liaoheyuan Natural Reserve, Hebei province, through a field investigation from May to September in 2013 and 2014. The results showed that:(1) Throughfall rates of P. tabulaeformis forest, L. principis-rupprechtii forest and P. davidiana forest were 78.8%, 81.1% and 83.8%, respectively. Throughfall amounts of three forests all showed positive linear correlation with rainfall amounts outside the forests. The monthly variations of throughfall were consistent with the monthly trend of rainfall outside the forest. Throughfall happened when rainfall exceeded 1.5 mm for P. tabulaeformis forest, 0.9 mm for P. davidiana forest and 1.2 mm for L. principis-rupprechtii forest. Stem flow rates in the three types of forests were 0.8%, 1.0% and 3.7%, respectively, and the regression analysis showed that stem flow amounts of the three forests had positive linear relationship with rainfall amount. (2) The capacity of canopy interception ranked from higher to lower as P. tabulaeformis forest (20.4%)>L. principis-rupprechtii forest (17.9%)>P. davidiana forest (12.4%). The canopy interception of P. tabulaeformis forest was significantly greater than that of the P. davidiana forest, which was more obvious under small rainfall events, and the rainfall characteristics and canopy structure had an influence on the canopy interception.

Abstract:The characteristics of groundwater in Sara Wusu Formation and its effects on the eco-environment were studied by using the data of drilling and pumping test, and remote sensing data and vegetation survey. The results showed that the aquifer thickness was the main controlling factor of the groundwater accumulation, and there was a positive correlation between the two above; in the distribution area of the basement depression, aquifer thickness was greater, which was the enrichment area of the groundwater; the buried depth of 3 m was the constrained water level for groundwater exploitation in the beach area. Excessive exploitation of groundwater might cause the succession or degradation of the vegetation on the beach to the sandy land, or even disappear, and speeding up the desertification process. Groundwater mining had no significant effect on the growth of drought-tolerant vegetation species on sandy and dune lands. These research results provided the basic theory and data for the site selection, rational exploitation and utilization of the groundwater, water and soil conservation and ecological environment protection and in the desert.

Abstract:A well-developed ephemeral gully, which located in Pinus massoniana forests, was selected as study slope. Then, the spatial distribution characteristics of soil particle size in surface layer (0-5 cm) were studied. The results showed that:(1) The gravel content was higher in topsoil, which texture belonged to sandy. The water erosion led to the coarse soil surface. (2) Soil particle size distributions varied with the different topographic position of ephemeral gully, the content of gravel (>2 mm) showed that the groove P<0.01). All the Extremely coarse sand, coarse sand, fine sand, silt and clay contents were characterized by groove>gully slope>gully edge, and the contents in groove were significantly greater than the gully slope and edge (P<0.01). The difference between soil particle contents in gully slope and edge were not significant (P>0.05). (3) With the gully length direction from head to mizoguchi, the coarse particle contents decreased in groove, but the fine particle contents increased. And the opposite results were found in gully slope and edge. (4) All the optimal semi-variance functions for different graded soil particles were gaussian model, the largest nugget coefficient of soil particles content is only 0.36%, far less than 25%, showing a strong spatial correlation.

Abstract:The distribution of soil humus was studied under three soil types (yellow soil, purple soil and paddy soil) and four patterns of land use (paddy fields, dryland, orchard and tea garden), samples were collected in Mingshan River watershed. The results showed that the carbon content of three types of soil humus was between 9.74 and 21.66 g/kg, and the content of the surface soil (0-20 cm) was greater than that of the lower soil (20-40 cm), and the content followed the order of paddy soil>purple soil>yellow soil. The carbon content of paddy soil was significantly greater than those of purple soil and yellow soil. The carbon content of each humus component was significantly positively correlated (P<0.01). From the way of land use, the carbon content of paddy humus was significantly larger than that of orchard, tea garden and dry land, and it was significantly correlated with HA (P<0.01), and the degree of humification of soil was yellow soil>purple soil>paddy soil. The content of the recombinant carbon in different utilization modes was paddy field>orchard>tea garden>dry land. The ratio of the loose humus to the tight humus in the tea garden was the maximum (1.37), which was 2.14 times as high as that of the lower soil of the paddy field. The content of HA in the three types of soil aggregates was between 0.02 and 4.57 g/kg, and the content of the humic acid content decreased first and then increased with the decreasing of the particle size. Except for 2~5 and <0.25 mm aggregates, the aggregates with the sizes of >5, 1~2, 0.5~1 and 0.25~0.5 mm were positively correlated with HA content (P<0.05). In conclusion, soil humus composition was affected by soil types and artificial cultivation management activities. Paddy field soil fertility was the highest, and the content of HA was most affected by aggregates larger than 5 mm.

Abstract:In order to explore the effects of different straw returning methods on soil carbon and nitrogen cycle, soil hydrothermal processes and winter wheat yield, field experiments were conducted to study the effects of different treatments including no straw returning (T0), straw mulching (T1), straw plowed into the soil (T2), and ammoniated straw plowed into the soil (T3), on soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil organic carbon (SOC), total nitrogen (TN), soil temperature, water use efficiency (WUE) and wheat yield in Guanzhong Plain. The results showed that straw returning increased MBC and MBN in the early growth stage and reached the highest levels at jointing stage. Straw returning greatly increased SOC and TN in 0-10 cm soil layer as compared to 10-20 cm depth. Compared to control, T1, T2 and T3 treatments increased the average soil temperature in the early growth stages with the highest value in T2, while slightly decreased after overwintering stages. T3, T1 and T2 increased the grain yield by 23.48%, 20.17% and 13.17%, respectively, while the aboveground biomass increased by 19.41%, 5.63% and 11.19%, respectively. WUE of T3, T2 and T1 increased by 28.73%, 15.36% and 18.83% compared with that of T0. Among them, T3 showed better performances on crop grain yield and aboveground biomass than other straw returning methods. Our findings suggest that T3 is more suitable for dry land agriculture farming, in terms of improving the soil quality and crop yield in this region.

Abstract:In order to reveal the spatial and temporal variations of soil microbes in alpine grassland in Eastern Qilian Mountains, three species of grassland soil microbes (fungi, bacteria and antinomycete) were collected from the same study area (perennial cultivated grassland, inside the fence grassland, annual cultivated grassland and outside the fence grassland) in 2003, 2011 and 2017 usingplatelet count method. The results showed that:(1)At the same time, three types of soil microbes and nitrogen physiological populations were significant (p<0.05) in different disturbance habitats, and they decreased gradually with the increase of the soil depth; (2)In different time and different disturbance habitats, three types of soil microorganisms and the number of nitrogen physiological groups were significant (p<0.05; specifically, the ranks of soil bacteria, actinomycetes, nitrifying bacteria and aerobic nitrogen fixing bacteria distribution were 2003 > 2011 > 2017; and the ranks of fungi, denitrifying bacteria and anaerobic nitrogen fixing bacteria quantity distribution were 2017 > 2011 > 2003; (3) The total number of microorganisms in different disturbance habitat performance were 2003 > 2011 > 2017. Compared with 2003, the total number of microbes in 2011 and 2017 decreased by 1.65 and 2.86 times. The perennial grassland decreased by 3.12 and 5.12 times respectively, the grassland within the enclosure decreased by 3.05 and 4.09 times, and the grassland decreased by 2.11 and 3.26 times respectively. In conclusion, with the unreasonable grazing and artificial utilization, the number of soil microorganisms in the alpine grassland of East Qilian Mountains gradually decreased with time. Therefore, we should pay enough attention to grassland utilization and protection in this area.

Abstract:In order to reveal the changes of organic carbon and nitrogen content of reclaimed soil aggregates in coal mining subsidence areas under long-term fertilization measures, we examined the characteristics of soil aggregates distribution and the changes of organic carbon and nitrogen contents in 4 years and 8 years of reclamation soil under five fertilization measures, which were non-fertilizer (CK), single application of manure fertilizer (M), single application of chemical fertilizer (CF), manure fertilizer and chemical fertilizer (MCF), biological organic fertilizer and chemical fertilizer mixed fertilizer (MCFB). The results showed that the content of reclaimed soil aggregates first decreased and then increased with the decreasing of grain size, in which the content of aggregates with the size of 3~2 mm was the lowest, accounting for 2%~3% of the total aggregates, and the content of aggregates with the size of 2~1 mm was the highest, accounting for 25%~31%. There was no significant difference in the distribution characteristics of soil aggregates between the 4 years and 8 years of reclaimation under different fertilization measures, but the contents of 7~5 mm and >7 mm aggregates significantly decreased compared with unreclaimed raw soil. The mean weight diameter (MWD) and geometric mean diameter (GMD) of the 8 years reclaimation soil were both higher than those of 4 years, while the fractal dimension (D) value was lower than that of 4 years. The MWD and GMD values of M treatment were the highest, but the D of it was the lowest. The contents of organic carbon and nitrogen in soil aggregates increased with the decreasing of soil aggregate size in reclaimed soil. The aggregates with the size of 0.5~0.25 mm were the highest, while the organic carbon and nitrogen storages in the aggregates with the size of 2~1 mm were the highest, accounting for 24.2%~33.8% and 17.0%~33.1%, respectively. Organic carbon and nitrogen contents were the highest in M treatment, but there was no significant difference in the storages of organic carbon and nitrogen between different treatments. Thus, there was no significant change in the distribution characteristics of soil aggregates and carbon and nitrogen reserves in the 4 years and 8 years reclaimed lands of coal mining subsidence area. The application of manure fertilizer could increase the organic carbon and nitrogen content and the stability of the reclaimed soil aggregates.

Abstract:In order to study the effects of cultivation and irrigation on soil aggregation and organic carbon, the study subjects were selected from the irrigation zone in Ningxia province, and selected the control and irrigated soil. Through the combination of dry and wet methods, we got the proportion of large macroaggregates (>2 mm), small macroaggregates (0.25~2 mm), microaggregates (0.25~0.053 mm) and silt + clay (<0.053 mm), and measured the content of organic carbon in each aggregate fraction and analyzed the relationship between organic carbon and total organic carbon. The results showed that aggregate distribution changed significantly (P<0.01) after irrigation, large macroaggregates and small macroaggregates proportion raised, microaggregates and silt + clay mass proportion decreased, the distribution trend was microaggregates>silt+clay>small macroaggregates>large macroaggregates. Irrigated soil aggregate stability was greater than that of the control soil, different types of irrigated soil had the same stability, and showed difference between control soils. In addition to <0.053 mm, the aggregate distribution of organic carbon after irrigation had significant difference (P<0.05), the organic carbon content had a "V" distribution with the size of the granule. Soil organic carbon in aggregate was higher in irrigated soil than that of the control soil, Irrigated-silted soil and Fluvo-aquic soil showed higher aggregate organic carbon content. There was a significant positive correlation between organic carbon in aggregate and total organic carbon in non-cultivated and non-irrigated natural soils, soil total organic carbon increase mainly depended on increment of >0.053 mm aggregate organic carbon. Cultivation and irrigation with sediment laden Yellow River water was significantly beneficial to increase the proportion of large scale aggregate, the stability of the aggregate, and the organic carbon content.

Abstract:Based on chemical fertilizer application, we studied effects of combining application biochar and organic fertilizer on crops planting and nutrients loss in dryland, which aimed to further explore the effective ways of rational fertilization, high yield and high efficiency planting and the optimal utilization of resources in dry land crops under the conditions of high temperature and precipitation in the hilly region of southern China. Field plot experiments were conducted to investigate the effects of biochar and organic fertilizer on maize yield, nitrogen-phosphorus loss derived by surface runoff and fertilizer utilization efficiency, and five fertilization treatments were set up, which were non fertilization (CK), only chemical fertilizer application (CF), chemical fertilizer combined with biochar (CF+B), chemical fertilizer combined with organic fertilizer (OF+CF) and chemical fertilizer combined with biochar and organic fertilizer (OF+CF+B). The results showed that compared with CF, the application of biochar or organic fertilizer could significantly increase the yield of 8.2%~11.1%, but the combination of organic fertilizer and biochar was the best, and the yield increased by up to 13.7%. Compared with the CF treatment, the treatment of CF+B could significantly reduce the runoff losses of nitrogen and phosphors by 15.9% and 24.2%, respectively, and significantly increase the aboveground accumulation of nitrogen and phosphorus by 26.3% and 11.8%, respectively. The OF+CF treatment could significantly reduce the runoff losses of nitrogen and phosphorus by 17.5% and 25.0%, respectively, increase the nitrogen and phosphorus accumulations by 36.5%(P<0.05) and 8.2% (P>0.05), respectively. The runoff losses of nitrogen and phosphorus were significantly reduced by 33.3% and 35.2% in the treatment of OF+CF+B, respectively, and aboveground accumulations of these two nutrients were increased by 52.1% (P<0.05) and 29.0% (P>0.05), respectively, and this treatment presented the highest fertilizer utilization efficiencies of nitrogen and phosphorus, up to 49.1% and 26.4%, respectively. On the one hand, OF+CF+B could promote the growth of spring maize, increase vegetation coverage and enhance erosion resistance of the soil, significantly reduce the volume of surface runoff; on the other hand, this treatment could reduce runoff loss of soil nitrogen and phosphorus including the dissolved and particulate, increase soil fertility. Therefore, comprehensive considering the economic and environmental benefits, applicating biochar and organic fertilizer combined with partial chemical fertilizer is the most reasonable way of fertilization, and it is worth promoting and applying in the region.

Abstract:The soil carbon evolution was studied under a complete reclamation cycle in the Ji'ning coal mine area with the high groundwater level. The stratified sampling and laboratory anlaysis of the soil were carried out under the different reclamation cycles, including Land subsidence (M1), reclaimed land for 0 and 3 years (M2, M3) and normal cultivated land (M4), to study the total carbon (TC), soil organic carbon (SOC), soil organic carbon density (SOCD), organic carbon components (WDOC, POC, MOC, LFOC, HFOC and MBC) and stable isotopes (δ¹³C). The results showed:(1) The contents of TC, SOC, SOCD and organic carbon components in the subsided area were lower. After the reclamation, the SOCD returned to the level of normal cultivated land in the first year, and the TC and SOC contents were increased with the reclamation period. The recovery rates of components such as WDOC, POC, LFOC and MBC were faster, but the MOC and HFOC recovery periods were longer. (2) The recovery rates of TC, SOC, SOCD and organic carbon components gradually decreased with the increase of soil depth. (3) After reclamation, the δ¹³C mean difference was small at different soil depths, and the standard deviation and coefficient of variation were larger, indicating that the layers were not obvious in the reclaimed soil and the soil sources might be confused in the same layer. In conclusion, the reclamation work could promote the role of "carbon sinks", but it could cause damage to soil layer. It was suggested that the reclamation method that disturb the soil layer as little as possible should be adopted, and the topsoil stripping and backfilling process should be optimized so as to achieve better recovery effect.

Abstract:The ¹⁵N-label technique was employed in the maize field to quantify the nitrogen fertilizer utilization and its fate.The experiment was designed with three nitrogen fertilizer application rates (0, 120, 240 kg/hm²), and three replications were set up in each treatment. Results showed that soil residual ¹⁵N increased significantly with the increasing of nitrogen fertilizer application (P<0.05). For the spatial distribution, soil residual ¹⁵N showed a trend of decreasing first and then rising, and the accumulation of ¹⁵N in 40-60 cm and 60-80 cm soil layers were the maximum in both high nitrogen treatment (240 kg/hm²) and low nitrogen treatment (120 kg/hm²), and the residual ¹⁵N in these two soil layers accounted for 37.55% and 18.99% of the total input amount, respectively. Compared with the control, application of nitrogen fertilizer significantly improved the dry matter, grain yield and total nitrogen uptake rate of different parts of maize. Although the nitrogen application rate of high nitrogen treatment increased by 1 times compared with the low nitrogen treatment, the grain yield increased only 0.14 times. The agronomic efficiency and the apparent utilization rate of nitrogen fertilizer decreased significantly with the increasing of nitrogen application rate. The utilization rates of nitrogen fertilizer labeled by ¹⁵N, the soil nitrogen residual rates, the proportion of leaching loss into groundwater and the other loss rates were 28.86%, 50.42%, 4.27% and 16.45% in the high nitrogen treatment, respectively, while these values of low nitrogen treatment were 31.15%, 36.52%, 0.68% and 32.33%, respectively. All these results showed that the nitrogen application of 120 kg/hm² would be favorable to improve grain yield and nitrogen use efficiency, and reduce residual nitrogen rate in soil. Therefore, this nitrogen application rate was suggested to lighten the environment pollution risk.

Abstract:To investigate the effects of controlled-release urea on vertical distribution and migration of nutrients in the profile of double-rice cropping field, a long-term field experiment was conducted to compare common urea (U) and reduction of controlled-release urea (CRU) in nutrient accumulation and distribution of paddy field profile. Results showed that with the increase of soil depth, total N, NO₃^--N, organic matter, total P, available P and total K content in soil decreased; NH₄⁺-N content first decreased and then increased; available K content increased; soil pH increased to be stable. Fertilization could reduce pH and available K content in 0-20 cm soil. Compared with U treatment, total N content in 0-20 cm soil under CRU treatments increased by 7.72%~19.45%, and increased with the increase of N fertilizer rate; soil NH₄⁺-N content in 40-60 cm under CRU treatments reduced by 6.99%~19.23%. Application of CRU could effectively reduce soil NH₄⁺-N leaching, and increase total N and NO₃^--N content in 0-40 cm soil, to prevent soil N loss. Application of CRU had no significant effect on organic matter, available P, total P, available K, total K and pH in different depths of soil, but more reduction of CRU resulted in the decrease of organic matter. Reduced of CRU by 10%~20% treatments significantly increased N, P, K uptakes of double-cropping rice at maturity. Correlation analysis showed that N, P, K uptakes at maturity by different rates of CRU treatments was significantly positively related with grain yield in early- and late-rice. In conclusion, CRU treatments can effectively reduce N leaching and the potential non-point source pollution by N fertilizer application, and can improve soil nutrient levels and fertility, and finally promote nutrients accumulation, to realize win-win situation of ecological and economic benefits.

Abstract:In order to improve the soil condition after the reclamation of hollow village, and to resume the agricultural production quickly, seven different returning materials were selected, and their effects on soil water storage, soil nutrition, water use efficiency and crop yield were analyzed. The results revealed that the soil water storage (0-105 cm) of different returning materials were significantly higher than the control in the summer maize growing season (P<0.05). The average soil water storage was increased by 10.2 mm to 32.9 mm than control. Different returning materials could effectively increase temperature and conserve soil moisture. After reclamation in the seasons, the organic matter, total nitrogen, available phosphorus and available potassium of the reclaimed soil using the different returning materials were respectively increased by 12.50%~66.44%, 15.15%~20.00%, 6.58%~64.62% and 18.24%~26.82% compared with the control. The nutrients contents were significantly different from the control (P<0.05), there was significant difference in nutrients contents except the total nitrogen using the different returning materials(P<0.05). The average height of maize using the different returning materials was significantly higher than that of the control, which increased by 13~29 cm. Compared with T0, TFC, TF, TSC, TSF and TFC treatment significantly increased the yield of maize, by 18.40%~48.50%, TF, TSC and TSF treatment significantly increased the water use efficiency of summer maize, by 12.52%~44.47%. In the loess hilly region in the hollow village renovation, the composited application of organic fertilizer and fly ash could obviously improve farmland soil water, heat and nutrients contents, improve the summer maize plant height, yield and water use efficiency. These two should be the most suitable returning materials for the loess hilly hollow village renovation, and have an important significance for the improvement of soil quality in the reclaimed hollow village.

Abstract:In order to reveal the characteristics of nitrogen mineralization in reclaimed soil of coal mining subsidence area with different fertilization measures, this experiment used the method of intermittent leaching and aerobic culture to study the effects of five kinds of fertilization measures, such as no fertilizer application (CK), single application of chemical fertilizer (CF), single application of organic fertilizer (M), chemical fertilizer combined with organic fertilizer (MCF), and chemical fertilizer combined with biological organic fertilizer (MCFB) on the changes of mineral nitrogen and soluble organic nitrogen in reclamation soil for 4 years and 8 years, and the characteristics of nitrogen mineralization were also studied. The result showed that:As the years of reclamation increases, the accumulated NO₃^--N production in 8 years of reclamation is 2.63%~26.83% higher than that of 4 years, the cumulative production of NH₄⁺-N increases 12.50%~32.14%, the accumulative production of soluble organic nitrogen (SON) reduced by 31.59%~62.50% under CF and M treatments, and the other treatments increased 3.44%~34.69%. Under the same reclamation years, the accumulative production of NO₃^--N, NH₄⁺-N, and SON were the highest in MCFB. According to the mineralization parameters, the mineralization potential of the five fertilization measures was higher in 8 years than that in 4 years, and the increase range were MCFB(26.9%) > CK(15.9%) > CF(15.0%) > M(12.7%) > MCF(4.8%); Under CK and CF treatments, the potential mineralizable organic nitrogen (N₀/N) decreased with the increase of reclamation years, with the decrease rates being 9.4% and 13.8%, while the other three fertilization measures (N₀/N) showed an increasing trend, with the increase rate of MCF(13.2%)>MCFB(7.5%)>M(2.8%). Under MCF treatment, the mineralization rate (N_t/N) increased with the increase of reclamation years, and the increase rate was 13.2%, the mineralization rate of the other four fertilization measures was lower in 8 years than that in 4 years, and decreased by CF (12.1%) > CK (9.4%) > MCFB (7.5%) > M (2.7%). The values of N₀, N₀/N, and N_t/N in different treatments were the highest in 8 years of reclaimed soil with MCFB treatment. On the whole, after 8 consecutive years of reclamation, the biomineralization parameters of chemical fertilizer combined with biological organic fertilizer were improved to a greater extent than those of other fertilization measures. However, with the increase of reclamation years, the increase of N₀, N₀/N treated with chemical fertilizer and organic fertilizer was the largest, the reduction rate of N_t/N was the lowest in the treatment of chemical fertilizer combined with biological organic fertilizer, and the potential mineralizable organic nitrogen content decreased by (N₀/N) in long term single application of chemical fertilizer.

Abstract:In order to reveal the influence of the mix ratio between slow released urea (SRU) and ordinary urea on the nitrogen (N) translocation and soil mineral nitrogen accumulation of post-anthesis wheat, the effect of N managements of control (CK), conventional (Ncon), optimized (Nopt), different mix ratios of SRU to urea (SRU1、SRU2、SRU3), and only urea (SRU4) on post-anthesis N translocation, yield, nitrogen use efficiency (NUE), soil NO₃^--N and NH₄⁺-N accumulation of wheat was investigated via field experiments between the mixed soil and yellow-brown soil corresponding to the wheat-maize and wheat-rice rotation distributed over Anhui province. Results showed that the yield, the amount of post-anthesis N accumulation and translocation in mixed soil were higher than those in yellow-brown soil under the same treatment, which increased by 71.8%, 199.1% and 25.8% on average, respectively. However, N translocation rate and apparent surplus amount of soil mineral N decreased by 16.1% and 49.7% on average in mixed soil than those in yellow-brown soil, respectively. Compared to the Ncon, yield showed no obvious differences, but NUE was significantly higher under the treatments of SRUs, which increased by 43.7%~91.9% and 6.6%~26.9% between mixed soil and yellow-brown soil. The highest NUE was under the treatment of SRU2 (ratios of SRU to urea 2:1). Compared to the Nopt, NUE increased at significant level only under the treatment of SRU2 in mixed soil. There was more soil NO₃^--N and NH₄⁺-N accumulation in 0-30 cm soil layer in Ncon than in SURs in post-anthesis of wheat, while the accumulation soil mineral N showed similar trend. The results showed it decreased accumulation soil mineral N under the treatments of SRUs in the late growth period of wheat with higher wheat yield and NUE. Therefore, one-time applying of the mix of SRU to urea could improve wheat yield, and reduce environmental pollution risk.

Abstract:A wheat pot experiment was conducted to study the effects of different fertilization layers on soil nutrients and crop growth. The local farmer's customary fertilization (tillage after topsoil fertilization) was taken as control, and the following treatments was set:no fertilizer application, controlled-release bulk-blend fertilizer topsoil fertilization then tillage, one layer fertilization and topdressing of common fertilizer, common fertilizer layered fertilization and controlled-release bulk-blend fertilizer layered fertilization. The fertilization layers treatments included:one layer (5 cm), two layers (5 and 10 cm) and three layers (5, 10 and 15 cm). The aim was to select the optimal fertilization layers of common fertilizer and controlled-release bulk-blend fertilizer respectively, and to provide the theoretical support for the technology of layered fertilization, especially for the technology of sowing and fertilization at the same time which is popularized now. The results showed that compared with the topsoil fertilization of common bulk-blend fertilizer, the wheat yield was increased by 14.02% and 15.83% significantly under one layer and two layers fertilization of common fertilizer, respectively, and the biomass was significantly increased by 13.44% under two layers fertilization of common fertilizer. Compared with controlled-release bulk-blend fertilizer fertilization, the yield of two layers and three layers fertilization of controlled-release bulk-blend fertilizer was significantly increased by 7.47% and 5.55% respectively, but the biomass was increased insignificantly. The nitrogen supplying of one layer and two layers of common fertilizer fitted better with every wheat growing stage than other treatments, and two and three layers fertilization of controlled-release bulk-blend fertilizer better than other controlled-release bulk-blend layered fertilization. The contents of available phosphorus and available potassium were not significant among different treatments. Compared with the topsoil fertilization of common fertilizer, the nutrient use efficiency of common fertilizer layered fertilization was significantly increased by 44.4%, 40.7% and 62.9% (nitrogen), 35.7%, 64.3% and 42.8% (phosphorus) and 16.7%, 33.3% and 53.3% (potassium), respectively. But compared with the topsoil fertilization of controlled-release bulk-blend fertilizer, only the phosphorus use efficiency of controlled-release bulk-blend fertilizer layered fertilization was increased significantly by 35.0%, 35.7%, and 35.0% respectively. So, it was suggested that two layers (5 and 10 cm) fertilization of common fertilizer, two layers (5 and 10 cm) or three layers (5, 10 and 15 cm) fertilization of controlled-release bulk-blend fertilizer should be practiced in agricultural production.

Abstract:Dynamics of soil microbial biomass nitrogen, potentially mineralizable nitrogen and particulate organic nitrogen during crop growing stages are important to understand the nitrogen cycling responding to mulching practices in dryland cropping systems. Based on a long-term mulching experiment in the Losses Plateau, this study investigated the dynamics of soil nitrogen fractions at different crop growth stages under straw and plastic film mulching conditions. Three treatments as straw mulching at a rate of 9 000 kg/hm² (SM), plastic film mulching (PM) and no mulching (CK) were included. The results showed that:(1) The contents of soil total nitrogen, microbial biomass nitrogen, potentially mineralizable nitrogen, particulate organic nitrogen and mineral nitrogen showed a tendency of decreasing at seedling stage, increasing at jointing stage, decreasing again at belling-heading stage and recovering at filling and harvest stages, except for nitrate nitrogen and ammonium nitrogen which increased at seedling stage. (2) Compared with CK, straw mulching effectively increased the contents of soil total nitrogen and nitrate nitrogen in 0-40 cm soil layer and soil ammonium nitrogen in 0-20 cm soil layer at most growth stages of spring maize, and increased soil microbial biomass nitrogen, potentially mineralizable nitrogen, and particulate organic nitrogen in 0-40 cm soil layer at nearly all growth stages. (3) Compared with CK, plastic film mulching improved soil nitrate nitrogen in 0-40 cm soil layer and ammonium nitrogen in 0-20 cm soil layer at most growth stages of maize, and decreased soil total nitrogen in 0-20 cm soil layer and particulate organic nitrogen in 0-40 cm soil layer at the later growth stages, and decreased microbial biomass nitrogen in 0-40 cm soil layer and potentially mineralizable nitrogen in 10-20 cm soil layer at most stages of maize. (4) Soil microbial biomass nitrogen, potentially mineralizable nitrogen and particulate organic nitrogen under mulching all had an important contribution to the dynamics of total nitrogen, except for the ratio of particulate organic nitrogen to total nitrogen in 20-40 cm layer under plastic film mulching. In conclusion, straw mulching in the Loess Plateau has a significant role in increasing the contents of soil nitrogen and its fractions in spring maize field, which is conducive to improve the soil fertility and nitrogen fixation levels as well as crop production. While plastic film mulching would reduce soil nitrogen fractions at the later growth stages of maize. Higher soil nitrate nitrogen level with plastic film mulching would increase the nitrogen leaching risk in maize field.

Abstract:To investigate the effects of tillage and straw management methods on spring maize yield, soil water and nutrient contents and root distribution, field experiments including two factors of tillage (rotary tillage, tilling) and straw management (straw returning to the field and straw removed) were conducted during two consecutive years. Spring maize yield, water use efficiency, soil nutrient and root distribution were analyzed. The results showed that two tillage treatments had the same yield and water use efficiency, and rotary tillage increased the root length density, root surface area density and root dry density of the 0-30 cm soil layers in the drought year (2015), while tilling significantly reduced bulk density and soil penetration resistance of the 10-30 cm soil layer, and reduced soil moisture content, soil available phosphorus content and soil available potassium content of the 0-40 cm soil layer, increased the root length density, root surface area density and root dry weight density of 30-60 cm soil layer in drought year and those of 0-60 cm soil layer in wet year (2016). The straw returning treatment increased spring maize yield by 9.5% and water use efficiency by 7.3%, and it promoted root length density of 0-60 cm soil layer in 2015, and increased root length density, root surface area density and root dry weight density of 30-60 cm soil layer in 2016. Meanwhile, straw returning increased the contents of soil water, nitrate nitrogen, available phosphorus and available potassium in the 0-60 cm soil layer. Overall, rotary and tilling tillage with straw returning can improve the distribution of soil water and fertilizer, and promote root growth in deep soil layers, increase yield and water use efficiency of spring maize.

Abstract:A pot experiment was conducted to investigate the effects of different stalk-derived biochar added (20, 40 g/kg soil), different chicken manure added (20, 40 g/kg soil), combination of stalk-derived biochar and chicken manure (20 g/kg soil, respectively) applications on the growth and physiological characters of maize under lead stress. Results showed that all treatments with stalk-derived biochar or/and chicken manure addition significantly increased plant height and fresh weight of maize, photosynthetic pigment contents, photosynthesis characteristics and antioxidant enzyme activities. Amending soil with stalk-derived biochar and chicken manure together produced the largest increment in maize growth and physiological characteristics. This effect was additive, with 69.9%, 50.0% greater fresh weight and plant height, 50.0%, 97.9%, 126.5%, 132.6% higher chlorophyll b content, net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s), 68.4%, 69.4%, 115.3% higher activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), 88.6%, 48.6% higher proline and soluble sugar, respectively. The combination of stalk-derived biochar and chicken manure treatment played the best effective role on promoting the growth of maize, improving leaf photosynthetic and antioxidant capacity under lead stress. This study provides a cost-effective way for improving the soil quality of Pb-contamination and crop growth.

Abstract:In order to explore the effects of PPMn type water soluble fertilizer mixed with humic acid of cottonseed meal fertilizer on soil properties and cotton yield, the functional and appearance characteristics of two novel water soluble fertilizers were studied by infrared spectroscopy and scanning electron microscopy analysis. The field experiments were also conducted to study soil physical properties, cotton yields and fertilizer use efficiency. The results showed that application of humic acid fertilizer of cottonseed meal (H), PPMn type water soluble fertilizer (P) and two new types of water soluble fertilizer (HP) had the better effects on improving soil physicochemical structure and enhance the cotton yield than the conventional water soluble fertilizer (S) and no fertilizer (CK), and HP gave the best. Under HP, soil bulk density was decreased by 8.15%, soil porosity was increased by 7.49%, the proportion of <0.25 mm soil aggregate was reduced effectively, the agronomic efficiency of nitrogen phosphorus and potassium was improved significantly, and the cotton yield was increased by 7.5%~41.0% compared with other treatments.

Abstract:Based on 40 field experiments carried out in Yongji, Jiutai, Lishu and QianGuo counties of central Jilin province from 2013 to 2016, the application effects and applicability of two recommended fertilization methods (i.e. soil testing and formulated fertilization (ST), and nutrient expert system (NE)) were compared by investigating grain yield, plant nutrient uptake, fertilizer use efficiency and apparent nutrient balance in one-season rice area. The results showed that the average rice grain yield was 9.17 t/hm² in the farmer practice fertilization (FP) treatment, the average grain yield was 9.21 and 9.24 t/hm² in ST and NE treatment, respectively, which were higher than that of FP, but there were no significant difference. The agronomic efficiency of nitrogen fertilizer in NE treatment was higher than that in ST treatment, and agronomic efficiency of phosphorus fertilizer in ST treatment was higher than those in FP and NE treatments, while there was no significant difference in agronomic efficiency of potassium fertilizer. Overall, no significant difference was observed in plant nutrient uptake and fertilizer recovery efficiency among the FP, ST and NE treatments. For the apparent balance of nutrients, soil nitrogen in three treatments all showed evident surplus, and the value followed the order of FP > ST > NE, while soil phosphorus and potassium showed slight and dramatical deficit, respectively. There were differences in the performance between different regions, the grain yield, plant nutrient uptake and fertilizer agronomic efficiency were relatively lower in ST treatment than those in NE treatment in Qianguo county, and this was different from the other three regions. In conclusion, both ST and NE methods showed well application effects on reducing fertilizer rate, maintaining high grain yield and increasing fertilizer use efficiency in the one-season rice area of central Jilin Province. The applicability of two methods were both well in semi-humid region (i.e. Yongji, Jiutai and Lishu), however it was relatively better for NE than ST in semi-arid region (i.e. Qianguo).

Abstract:The objective of this long-term positioning experiment was to study the effects of biochar addition on soil physicochemical properties, heavy metal concentrations and microbial biomass in the red paddy soil polluted by heavy metals. Biochar was added once at rates of 0, 10, 20, 30, and 40 t/hm², and the topsoil samples (0-15 cm) were collected in September 2017. The results showed that biochar addition had signification effects on soil physicochemical properties, heavy metal concentrations and microbial biomass. Soil pH, electrical conductivity (EC) and soil organic matter (SOM) were observed significantly increased under biochar addition as compared to the control, ranging from 5.11% to 18.43%, 37.62% to 104.31%, and 1.72% to 22.41%, respectively. However, the available phosphorus and ammonium nitrogen content were firstly increased and then decreased with the biochar addition rate increment, and the highest available phosphorus and ammonium nitrogen content were in the 10 t/hm² and 30 t/hm² treatments, respectively. As for the changes of heavy metals, the available content of Cd and Pb decreased with the biochar addition rate increment, whereas the available content of As increased firstly, and then decreased with biochar amendment rate increased, and the highest content of As was in the 40 t/hm² treatment. Soil microbial biomass carbon, nitrogen and microbial quotient firstly increased and then decreased with the addition rate of biochar increment, they maximum value of them were all in the 20 t/hm² treatments. Correlation analysis showed that the biochar addition was significant negative correlated with the available content of Cd and Pb (P<0.01). The path analysis indicated that the available content of Cd in soil was mainly affected by biochar addition through the direct impact, whereas the soil pH, EC, SOM, microbial biomass carbon, nitrogen, and available phosphorus content could mainly affected the available Cd content by indirect impact. In conclusion, biochar addition can not only improve status of soil heavy metal pollution and soil physicochemical properties, but also improve the soil biological properties. This study can provide a scientific basis and support for improving the soil fertility and remediating the heavy metal contamination.

Abstract:To reveal the driving effect of rice on form transformation of Zn in soda-saline-alkali soil and its mechanism, Tessier continuous extraction method was used to study the content of Zn in different forms in soda-saline-alkali soil and its distribution characteristics in soil profile in Songnen Plain under different planting years. The results showed that the improvement of saline-alkali soil by planting could significantly enhance the contents of available Zn, exchangeable Zn and organism combined Zn, and other bio-available Zn in all soil profile, but reduce the contents of carbonate combined Zn, oxide combined Zn, residual Zn and other non-bio-available Zn. The effect was the most significant in the first year after planting, and then entered the gentle rising stage after the fifth year. The promoting effect of planting on the contents of available Zn, exchangeable Zn, organism combined Zn and other bio-available Zn weakened with the deepening profile level. Correlation analysis showed that exchangeable Zn and organism combined Zn had a significant negative correlation with pH, but a significant positive correlation with organic matter content respectively. Carbonate combined Zn and oxide combined Zn showed a significant positive correlation with pH but a significant negative correlation with the organic matter content, indicating that after saline-alkali soil improvement by planting, the decrease in soil pH and increase in organic carbon contents were the main factors for driving the transformation of Zn in different forms.

Abstract:Tub experiment was carried out to investigate the influence of conditioners on the soil pH, cation exchange capacity (CEC), the distribution and migration of soil Cd concentration, and soil Cd fraction when exposed to high Cd pollution (40 mg/kg). Four conditioners were organic-inorganic composite conditioner, inorganic polymer compound conditioner, polyacrylate compound conditioner, and organic polymer compound conditioner. The results showed that:(1) Four conditioners increased the soil pH and CEC,and the inorganic polymer compound conditioner worked the best in the 0-20 cm soil layer, increased by 0.43 units and 4.43 cmol/kg respectively. (2) The use of four conditioners improve the transformation of exchangeable Cd to other forms. Correlation analysis showed that there was a significant negative correlation between carbonate and exchangeable Cd (P<0.01), and showed particularly prominent effect at 0-20 cm and 20-40 cm soil layer. The use of inorganic polymer compound conditioner showed the best reduction of the soil exchangeable Cd, reduced 3.61 mg/kg. (3) Soil pH and CEC were negatively correlated with the concentration of soil exchangeable Cd in all soil layers and positively correlated with other forms. That is, the conditioners affect the soil cadmium distribution and migration by changing the soil pH and soil CEC, thereby reducing the effectiveness of cadmium, and improving the soil environment.

Abstract:In this study, elution method was used to determine the retention quality amounts of TSP (larger particles) and PM_2.5 (smaller particles) per unit leaf area of 15 common afforest plant species. The retentive capacities of TSP and PM_2.5 for leaves from different plant species were analyzed and compared, and the location-variation law was investigated. Results showed:(1) There were significant differences in the retention amounts of TSP and PM_2.5 per unit leaf area among plant species, ranging from 3.68 to 5.94 g/m² for TSP, and from 0.47 to 0.92 g/m² for PM_2.5, respectively. The largest difference of retention amounts for plant species reached up to 2 times. (2) In the same location, the retention capacities of TSP and PM_2.5 for different plant species varied as the variations of canopy height, blade surface roughness and specific leaf weight. Specifically, the sequence of retention capacities from high to low was hedge plants, bush plants and arbor plants, and the species with larger specific leaf weight had stronger retention capacity. For the factors of surface roughness, the retention amount of particles increased as the increase of groove depth, and a leaf with neither too wide nor too narrow groove width was proved to have good retention capacity. (3) For the retention amount of TSP in varied locations, the sequence from high to low was Industrial Area (IA), Transportation Area (TA), Open-pit Mine (OP), and Clean Area (CA). In the case of PM_2.5, there were little difference at those locations. The particle retention amounts per leaf area or per plant of P.albavar.pramidalis and Syringa oblata were higher than those of other examined species. Thus, those two species could be chosen as the priority species for urban afforestation for cities in Northwest of Liaoning Province with much dust weather.

Abstract:In order to comprehend the acidity characteristics of mountainous soils planted tobacco for many years, the characteristics of soil acidity index and their relations were studied in Xiangxi Autonomous Prefecture, as well as the effects of planting years, soil types, organic matter and clay on soil acidity were studied. The results were as follows:(1) The effect of tobacco planting years on soil acidity in Wuling mountain area was greater than that of soil types, and with the increasing of planting years, the soil pH, the exchangeable base cations, cation exchange capacity and base saturation of yellow-brown soil decreased, while the potential acidity increased. (2) The relationship between soil pH and exchangeable acid was a power function, and exchangeable Alex was the main body of exchangeable acid in soil, the strength of soil exchangeable acid increased with the increasing of exchangeable Alex and its relative proportion. (3) The relationship between soil pH and exchangeable base cations, cation exchange capacity and base saturation was a quadratic curve, and when the soil pH was less than 6, the exchangeable base cations and cation exchange capacity decreased with the increasing of soil pH, while the base saturation increased; when soil pH was more than 6, the exchangeable base cations and cation exchange capacity increased with the increasing of soil pH, while base saturation fluctuated slightly. (4) Soil exchangeable base ions were mainly exchangeable calcium, followed by exchangeable magnesium, and the exchangeable calcium was the most important factor influenced soil pH. (5) Soil organic matter and clay mainly affected the soil pH, cation exchange capacity, exchangeable base cations and exchangeable calcium.

Abstract:In order to study the relationship between the mineral composition and the acidity of the purple soil under the microtopography, the typical purple soil in the hilly area of Hechuan, Chongqing, was collected to simulate acidification by electrodialysis, and the mineral composition and acidity before and after the electrodialysis were analyzed by the X ray diffraction spectrum. The results showed that with the decreasing of topography, the proportion of the soil primary mineral decreased gradually, and the development degree of soil was higher and higher. The pH value of purple parent rock and its developed soils followed the order of parent rock > stony sub-soil > half sand half mud > purple yellow mud. There had a clear correlation between the change of soil pH value and the contents of calcite, albite and potassium feldspar in soil. The pH values of stony sub-soil and half sand half mud decreased 4.3 and 3.8 units respectively after electrodialysis, while the primary minerals of soil decomposed and weathered, indicating that the soil primary minerals such as feldspar minerals could buffer the acidification of purple soil.

Abstract:A novel superfine phosphorus-potassium fertilizer was developed to reduce the soil fixing and leaching of phosphorus-potassium fertilizer, improve the nutrition efficiency, reduce the fertilizer application rate, reduce non-point source pollution, and increase crop yield. The potted pakchoi experiment was conducted to study the effects of this new fertilizer on the yield and quality of pakchoi, soil nutrients and fertilizer use efficiency. Nine treatments were designed in this study, with common phosphorus-potassium fertilizer plus Humic Acid and common phosphorus-potassium fertilizer as the control. The phosphate-potassium fertilizer was grinded and mixed with Humic Acid, zeolite powder, diatomite activator respectively in different proportions, which were used to produce the superfine phosphorous-potassium activator fertilizer. The results were as follows:The superfine phosphorus-potassium activator fertilizer significantly increased the pakchoi yield by 13.22%~35.14%. The superfine phosphorus-potassium-Humic Acid-zeolite powder fertilizer, the superfine phosphorus-potassium-Humic Acid-diatomite fertilizer and superfine phosphorus-potassium-Humic Acid-zeolite powder -diatomite fertilizer reduced the nitrate contents in pakchoi by 30.46%~74.31%, and increased the soluble sugar contents by 41.70%~150.00%. The available phosphorus contents of soil increased 23.15% in average. For the superfine phosphorus-potassium activator fertilizer, the utilization rates of phosphate fertilizer were increased by 47.58%~238.62%. The agronomic utilization rates were increased by 114.14%~303.46%. The partial factor productivities of potassium fertilizer were increased by 13.22%~35.15%. The results indicated that the superfine phosphorus-potassium activator fertilizer could contact enough with the activating agent, which improve the fertilizer efficiency. Thus, it was recommended to select the superfine phosphorus-potassium-Humic Acid-zeolite-activated fertilizer in fertilizer production and application.

Abstract:To study the photosynthetic characteristics and antioxidative enzyme system of cucumber in calcareous soil under cadmium (Cd) stress is important for the control of Cd in plants. This paper explored the photosynthetic parameters such as net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), and intercellular CO₂ (C_i) of cucumber in Cd-contaminated soil under the intervention of silicon, Chlorophyll content, changes in antioxidant enzyme systems such as MDA, SOD, POD, and CAT. The results showed that:compared with the control, Cd alone, P_n, G_s, T_r and chlorophyll content decreased, but C_i increased. However, after silicon intervention, the total amounts of P_n, G_s, T_r and chlorophyll significantly increased, and the content of C_i was reduced. For example, when the Cd content was 5 mg/kg, and the silicon application amount was 100~200 mg/kg, P_n, G_s, T_r, and chlorophyll increased, and C_i decreased, compared with the control. However, the difference between 100 and 200 mg/kg of silicon was not obvious, and the effect of 300 mg/kg of silicon was best. For the antioxidant enzyme system, compared with the control, when the soil Cd content was 3~5 mg/kg, the activities of the three antioxidant enzymes were significantly inhibited. But, the introduction of 200~300 mg/kg of silicon couldsignificantly increase the activity of SOD, POD, CAT, but decrease the MDA value. It could be concluded that application of silicon can significantly improve the photosynthetic characteristics and antioxidant enzyme system of cucumber leaves under Cd stress. Application of a small amount of silicon fertilizer has obvious application prospects to relieve Cd toxicity in plants.

Abstract:In order to study the influence of urea and controlled-release urea combined with plant inducer on the wheat (Triticum aestivum L.) yields, nitrogen use efficiency and soil nutrients, a field experiment was designed with five treatments, which were controlled-release urea (CRU), controlled-release urea combined with plant inducer (CRUR), urea added plant inducer (UR), urea (U) and no nitrogen (CK) treatments as the control. The results showed:(1) Wheat yield of UR was significantly increased by 23.6%, the nitrogen use efficiency was improved by 10.1%, and the net income was significantly increased by 3 269 Yuan per hectare, compared with U. (2) Wheat yield of CRUR was significantly increased by 14.5%, the nitrogen use efficiency improved by 12.4% and net income was significantly increased by 2 361 Yuan per hectare, compared with UR. Wheat yield of CRUR was significantly increased by 16.3%, the nitrogen use efficiency was improved by 11.9% and net income was significantly increased by 2 446 Yuan per hectare, compared with CRU. (3) During the maximum nitrogen use efficiency period of wheat growth, soil nitrate content of CRUR was significantly increased by 29.5% compared with CRU, but increased by 88.2% compared with UR. Soil ammonium content of CRUR was significantly increased by 34.4% compared with UR. These findings indicated that CRUR could achieve synergistic effects, increase the wheat yield, nitrogen use efficiency, net income and soil available nutrient supply intensity. Then, the research results could provide reference for the development and application of slow and controlled-release fertilizer combined with plant inducers.

Abstract:In order to study the application effect and safety of the titanium gypsum with harmless treatment as a soil conditioner, we employed a systematic test of ingredients identification, soil column leaching, and potted experiment to study the content of harmful elements in titanium gypsum and titanium gypsum leaching solution, and to study the effect of gypsum on the growth, yield and leaf photosynthetic rate of rape seedlings simultaneously. Results showed that the main elements in leachate were calcium sulfate and iron oxide, all content of heavy metals in titanium gypsum were below the national safety standards, the presence of elements in the leachate did not contaminate the soil and groundwater after application. With the increase proportion of titanium gypsum, rape seedlings production increased firstly and then decreased, excessive titanium gypsum could inhibit the growth of rape seedlings. Titanium gypsum showed the best effect at the ratio of 1:4 to the soil. The leaf transpiration rate increased by 11.86% after 20 days of seedling emergence as compared to that of conventional soil cultivation. Thirty days after seedling emergence, the plant photosynthesis, plant height, and biomass increased by 4.33%, 12.97%, and 14.08% than those of the conventional soil cultivation, respectively. Correlation analysis showed that the relationship between yield (y) of rape seedlings and the addition ratio (x) of titanium gypsum was y=0.0001x³-0.0212x²+0.6966x+41.815 (R2=0.999 4). In actual production, the application of 300 tons of titanium gypsum per hectare should be the best application dose to improve the crop productivity.

Abstract:In order to understand about the impact of pore scale on colloid migration more deep, migration processes of colloid in acid-washed glass beads/quartz, Milli-Q-washed glass beads/quartz were compared under different pH and ionic strength. Results showed that the pore scale of glass beads with the same shape (porosity 0.38) was smaller than that of quartz sand with various shapes (porosity 0.45), although the glass beads and quartz sand had a uniform particle size (0.45~0.60 mm). The surface components of glass beads changed at a very small range from 0 to 0.6% after acid washing and Milli-Q washing. The acid-washed media could provide more favorable adsorption sites. The colloid retention of quartz sand increased after the acid washing or Milli-Q washing(72.1% and 69.2%, respectively) when the pH of the solution raised to 10. The enhancement of adsorption was induced by pore scale retention mechanism, such as retention in particle contact points, non-flowing area or low velocity area and eddy current area, which could not be explained by the DLVO theory. The retention of colloid in the acid-washed quartz sand was about 16.3% and 28.0% higher than that of the acid-washed glass beads under the environments of ion strength of 0.001 mol/L and 0.05 mol/L, respectively, which implied that increased pore scale enhanced colloid retention in particle contact points, non-flowing area or low velocity area and eddy current area. However, occurrence of preferential flow in soil columns impaired the retention of colloid in pores greatly. In addition, only a small parts of colloids (<3.9%) was desorbed from eddy zones in the glass beads and the quartz sand after using ultra-pure water, indicating that the colloid retention in the eddy zones wasn't the dominant mechanism.

Abstract:To better understand the responses of soil carbon and nitrogen to the nitrogen addition, this paper revealed the response processes and mechanisms of soil carbon and nitrogen to exogenous nitrogen addition through a short-term simulated nitrogen deposition experiment in artificial Pinus tabulaeformis Carrière plantation in Ziwuling Mountain of the Loess Plateau. From 2015 to 2016, four nitrogen addition levels, including control (0 kg/(hm²·a), N0), low nitrogen (50 kg/(hm²·a), N50), medium nitrogen (100 kg/(hm²·a), N100), and high nitrogen (200 kg/(hm²·a), N200), were set up to study the responses of soil organic carbon(SOC), total nitrogen (TN) and soil carbon and nitrogen storage (C_S and N_S) in different soil depths to the simulated addition nitrogen. The results showed that soil layer had significantly influence on SOC, TN, C_S and N_S. SOC, TN, C_S and N_S in the surface layer were significantly higher than those in the deeper soil layers. Nitrogen addition level had no significant impact on the SOC and C_S, while significantly affected the TN and N_S. In addition, SOC, TN, C_S and N_S, and C_S/N_S were significantly affected by the carbon nitrogen ratio (C/N) of belowground biomass. Therefore, short-term nitrogen addition had no significant influence on soil carbon, but it could significantly affect soil nitrogen, and C/N of belowground biomass was the important factor affecting soil carbon and nitrogen.

Abstract:A pot experiment was carried out in apple-Trifolium repens Linn. (M1) and apple-Lolium perenne L. (M2) intercropping system to investigate the effects of root interaction on the growth and ¹⁵N-urea absorption, utilization, loss and residue of apple trees under different root barrier method (N1, N2 and N3 were equivalent to solid barrier, mesh barrier and no barrier, respectively), using the ¹⁵N-labeled tracer technique. Results showed that, at new shoot growing stage, the growth index of apple trees displayed an order of N3 > N2 > N1 in M1 intercropping system, while the opposite tendency was observed in M2 intercropping system. Compared with N1 treatment, the ¹⁵N utilization rate of apple trees increased by 11.91% and 18.96% in M1 intercropping system under N2 and N3 treatment, but decreased by 5.76% and 8.99% in M2 intercropping system. The plant total N content and ¹⁵N absorption amount showed the same tendency. The effect on ¹⁵N abundance and total N content in the soil of apple trees were the most significant in N1 treatment, and the least in N3 treatment. At leaf fall period, the growth index of apple trees was obviously the highest in N3 treatment, and the lowest was found in N1 treatment. In comparison with N1 treatment, the soil ¹⁵N abundance of apple trees under N2 and N3 treatment increased by 22.33% and 34.15% in M1 intercropping system, and the rate of increase in M2 intercropping system were 13.73% and 21.44%, the total N content in the soil of apple trees showed the same tendency. There were significant differences in plant total N content,¹⁵N absorption amount and Ndff value among the treatments, which was in a trend of N3 > N2 > N1 in M1 and M2 intercropping system. The ¹⁵N utilization rate of apple trees under N2 and N3 treatment were 19.11% and 42.66% higher than that of N1 treatment, with the ¹⁵N loss rate were 13.55% and 27.12% lower than that of N1 treatment in M1 intercropping system, the same trend was showed in M2 intercropping system. Overall findings showed that it mainly showed a competitive effect in apple-Lolium perenne L. intercropping system and a relatively minor positive effect in apple-Trifolium repens Linn. intercropping system during early stages of apple growth. While in the later period of apple growth, the root interaction in forage grasses and apple trees reduced nitrogen loss and consequently improved the absorption, utilization of nitrogen nutrition and the growth of apple trees by a certain degree, and Trifolium repens Linn. played a better effect than Lolium perenne L.