Abstract:Sediment sources information has considerably enhanced our knowledge of patterns of soil erosion, sediment delivery and deposition in a watershed. It also has great significance for the development of effective sediment and nonpoint source pollution control strategies. Sediment fingerprinting technique has been widely used as a reasonable and reliable means for investigating sediment sources in different watersheds in the world. In recent two decades, rapid progresses have been made in methods improvement, such as fingerprints selection and unmixing model optimization, and also in application range, such as different spatial-temporal scales and different sources classifications. Even more, sediment fingerprinting technique is now transforming from a research tool to a management tool. This paper reviewed the development of fingerprinting technique in aspects of research scales, fingerprints selection, source contribution apportionment and uncertainty analysis. This review also examined the current problems associated with the methodology and identified some research needs for further investigation in the future.

Abstract:Based on thoroughly review of the past 70 years development of soil and water conservation in China, the authors outlined the methodical advance that from qualitation to quantitation and the progress of framework that from incompleteness to more perfect, and then summarized the three stages of regionalization of soil and water conservation’s evolution. Statistical analyses were employed to determine to what extent these regionalizations have influenced soil and water conservation both theoretically and practically. Moreover, three main problems of the existing regionalization schemes were proposed which are absence of economics and management science, flaws of indicator system and lack of implementation, and their corresponding solutions were raised by scenario simulation and case study. Considering the trend of regionalization, two topics, the balance between quantitative and qualitative studies and the more attention paid on practice, were discussed in the end with the hope that it could present some inspired thoughts for further development of regionalization.

Abstract:In order to study the influence of different rainfall intensity on the erosion, artificial rainfall simulation experiment and indoor analysis were connducted to analyze the effects of three rainfall intensity (0.5,1.0,1.5 mm/min) on runoff and sediment yield in purple soil. The results showed as follows. Under 50% and 75% vegetation coverage, (1) The greater the rainfall indestiny, the more the runoff production rate and the runoff volume in the purple soil. In the same time, under the three kinds of rainfall intensity, the surface runoff accounted for 18%, 30%, and 52% of the total runoff volume, respectively. (2)The greater the rainfall intensity, the more the sediment yield and erosion rate occured. In the same time, under three kinds of rainfall intensity the sediment yield in purple soil accounted for 13%,33%, and 54% of the total sediment yield, respectively. (3) The particle size of water-stable aggregate in erosion sediment was mainly concentrated in < 0.25 and > 3 mm. The total amount of the two particle size accounted for 74% and 67% of the total sediment, respectively, while water-stable aggregate particle size of 0.25~3 mm accounted for 30% and 26%, respectively. (4) There was a significant positive correlation between rainfall intensity and the yield of runoff and sediment in the purple soil (P < 0.01). The linear equation was synthesized by rainfall intensity and sediment yield. The correlation coefficients were 0.96 and 0.97, respectively. A linear equation and a quadratic equation were synthesized by rainfall intensity and runoff yield, respectivelly, and the correlation coefficients were 0.89 and 0.94, respectively. The results can provide references for controlling soil erosion in purple soil and revealing related erosion mechanism.

Abstract:Quantitatively assessing the effects of ridge cultivation methods on slope soil erosion can provide important theoretical guidance for prevention slope erosion. Based on the long-term field monitoring data of runoff plot in Harbin city from 2012 to 2015, the effect of longitudinal ridge, contour ridge and flat tillage on runoff and sediment were discussed. The relationships between runoff and sediment under different ridge tillage were analyzed. The results showed that there were significant differences in runoff and sediment yield between different ridge tillage methods, showed the orders of runoff and soil loss was of flat tillage > longitudinal ridge tillage > contour ridge tillage. Compared with flat tillage, contour ridge tillage reduced the runoff and sediment yield by 92.4% and 98.3%, and longitudinal ridge tillage reduced the runoff and sediment yield by 66.4% and 72.2%. When the slope gradient increased from 3° to 5°, the soil loss increased by 0.8, 8.2, and 5.5 times, respectively under flat tillage, longitudinal ridge tillage and contour ridge tillage. The result also showed the significant correlations between runoff and sediment under three tillage methods. The increasing range of soil loss under longitudinal ridge tillage and flat tillage treatment was much larger than that under the contour ridge tillage slope. When the slope runoff was greater than 10.0 mm, soil loss under borth treatments of longitudinal ridge tillage and flat tillage increased sharply.

Abstract:The objective of this study was to understand the influence of precipitation and land use change on water and sediment yield in Luoyugou watershed in the loess hilly gully region, which based on the annual precipitation data, runoff and sediment yield data and land use change data collected from 1986 to 2010. The results indicated that during 1986 to 2010, the annual precipitation and precipitation of flood season were basically stable, and there was no obvious increase or decrease trend, while the annual runoff and annual sediment discharge in Luoyugou watershed were fluctuating and decreasing during this period. The precipitation and runoff correlation analysis showed that the runoff and sediment yield in the flood season had the greatest significant influence on the annual runoff and annual sediment discharge in the watershed. Through analyzing the change of water and sediment in different periods, we found that the change of land use mode, mainly the change of soil and water conservation measures such as terraced fields and forest grass, had limited effect on water reduction and sediment reduction in the watershed. The increase in the area of terraced fields and forest grass did not significantly change the relationship of water and sediment in the watershed, and the engineering measures such as silt dams played important role in reducing the water and sediment in the hilly and gully region of the Loess Plateau. The results could provide some theoretical basis for soil erosion management and dispose of soil and water conservation measures in loess hilly and gully region.

Abstract:Soil detachment process provides material for soil erosion, which is importance for understanding soil erosion process and building soil erosion model. In this study, the Brown soil was selected as the research object. Six soil moisture contents (3%, 6%, 9%, 12%, 15% and 18%), three slope gradients (5°, 10° and 15°), and three flow discharges (8, 12 and 16 L/min) were designed. The effects of soil moisture content, slope gradient and flow discharge on soil detachment capacity were explored. The results showed that: (1) As soil moisture content increased, soil detachment capacity decreased, and the differences of soil detachment capacity decreased; the detachment capacity was almost 0, when soil moisture content was 18%. There was a quadratic polynomial function between soil detachment capacity and soil moisture content, and soil detachment capacity was the highest when soil moisture content was 3%. (2) Soil detachment capacity increased with increasing of slope gradient when soil moisture content were 6%, 9%, 12% and 18%,respectively, and a quadratic polynomial relationship exsited between soil detachment capacity and slope gradient. When the slope gradient was 15°, soil detachment capacity reached the maximum. (3) Soil detachment capacity increased with increasing of flow discharge when soil moisture content was 3%~12%, and had a quadratic polynomial relationship with flow discharge. When flow discharge was 16 L/min, soil detachment capacity had the maximum value. (4) If only considered the influence of two factors, the contribution rate of the error was the largest. With three factors included, the contribution rate of slope gradient to the variation of soil detachment capacity was the largest (29.64%), followed by soil moisture content (22.29%) and flow discharge (19.72%). The simulation accuracy of soil detachment capacity could be increased from 0.550, 0.638 and 0.498 to 0.995 by including soil moisture content, flow discharge and slope gradient.

Abstract:To reveal the characteristics of runoff and sediment yield on the slope of the desert steppe for long-term grazing, taking the grazing desert steppes (Inner Mongolia area) with four different intensities as the research object, and all steppe were grazing for 15 years. Indoor artificial simulated rainfall was conducted to explore the effects of grazing intensity and rainfall intensity on coupling process of runoff and sediment production on the steppe slope. The results were as follows: (1) Under the different rainfall intensities, the initial runoff time of different grazing steppe advanced with the increasing of grazing intensity, and runoff yield rates increased first and then showed a state of stability. The runoff yield rate and its fluctuating range both followed the order of heavy grazing (HG) > moderate grazing (MG) > control (CK) > light grazing (LG). The influence of rainfall intensity on runoff yield rate was greater than that of grazing intensity. The cumulative runoff yield of desert steppe was linearly related to rainfall duration and the fitting degree was higher. (2) The change of sediment production rate in desert steppe was characterized by multi-valley and multi-peak. Rainfall intensity, grazing intensity and their interaction had a significant effect on sediment production rate. Under different rainfall intensities,the sediment production rate and its fluctuating range followed the order of HG > MG > CK > LG. The relationship between total amount of sediment loss and rainfall duration fit a quadratic curve.

Abstract:For exploring the effects of contour hedgerows on the migration of atrazine residues in soil, the features of migration and distribution of atrazine residue those were influenced by hedgerow system under different slope gradients (15% and 20%) were studied by simulated rainfall experiment. The results showed that the vertical migration of soil atrazine remained dominant after rainfall. Grass hedges significantly reduced atrazine residues compared with the control. The residual levels of atrazine did not differ among 3 soil depths inside the grass hedges, whereas atrazine residues were markedly higher in topsoil than those in subsurface soil, and decreased with increasing soil depth in areas without hedges. Atrazine residues in the surface layer (0—10 cm) were significantly higher than those in other layers. Soil atrazine residues at different areas in the hedgerow system were significant different, and the ranks showed as: Hedgerow zone < deposition zone < crop zone. The optimal scaling regression analysis showed that the degree of influence of various factors on the atrazine residues in the soil was in descending order: Grass hedge > soil depth > soil water content > slope area > slope gradient > slope position, and the role of grass hedge was more important than that of the other factors. In general, the hedgerow can significantly affect the horizontal and vertical migration of the soil atrazine in sloping farmland, which is the primary factor to control the loss of agricultural pesticides.

Abstract:The leaching of soil nitrogen and phosphorus in the citrus orchard of Zigui County of the Three Gorges Reservoir Area were studied in August 2017 by using the original soil column simulated experiment, and the effects of different fertilization treatments on soil nitrogen and phosphorus leaching were discussed, which provided a theoretical basis for the prevention and control of agricultural non-point pollution in this region. The results were as follows: (1) The leaching concentration of total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO₃^-—N) and ammonium nitrogen (NH₄⁺—N) in the filtrate of citrus orchard under different fertilization treatments were 37.16~163.07, 0.61~6.69, 27.54~79.38 and 2.37~7.10 mg/L, respectively. (2) Both the amount of fertilizer and the type of fertilization were the factors affecting the leaching of nitrogen and phosphorus in soil. Under the same fertilization treatment, the soil nitrogen and phosphorus leaching concentration increased significantly with the increase of the amount of fertilizer, and then the increase reduced. Under the same nitrogen application rate, the leaching of nitrate nitrogen was most affected by the type of fertilizer, while the leaching of ammonium nitrogen was the smallest. (3) In soil filtrate, nitrate nitrogen was the main leaching form of soluble nitrogen, and the ratio of leaching loss and total nitrogen leaching was 29.72%~46.18%, and the proportion of NH₄⁺—N leaching loss was 1.09%~2.05%. The finding indicate that the treatment of constant compound fertilizer is more beneficial to the conversion of fertilizer nitrogen to soluble nitrogen for plant absorption and to reduction the accumulation of nitrogen in soil after fertilization.

Abstract:By the methods of space instead of time, the erosion process and characteristics of different vegetation method under simulated rainstorm condition in typical red soil region were explored. In the experiment, 1.5 mm/min rainfall intensity was designed. The reconstruction of inefficient forests (R1), the shrub-grass structure(R2), the natural restoration(R3), with different recovery years were selected, and the contrcl plots(DZ) was selected field simulated rainfall experiments were carried out to analyze the characteristics of initial runoff time, runoff rate, erosion rate, cumulative yield discharge and infiltration rate. The results showed that: (1) The order of the initial runoff production time of the three recovery models was R2 > R1 > R3, which was prolonged with the increase of the governance years; (2) The runoff rate, erosion rate and cumulative sediment yield of the three restoration models all showed R3 > R1 > R2, and the runoff rate, erosion rate and cumulative sediment yield of R1 and R2 showed decreasing trends with the increase of treatment years; (3) Within the same recovery period, the initial infiltration rate, cumulative infiltration rate, and runoff and sediment reduction benefits of the three restoration plots all showed R2 > R1 > R3; (4) The effects of the three restoration methods and the recovery years on the erosion process were shown as R1 > R2 > R3. The relationship between cumulative sediment yield and cumulative runoff was a power function. The results provide references for revealing erosion processes under different governance methods and scientific basis for soil erosion control in typical red soil regions.

Abstract:Phosphorus was the main limiting factor of eutrophication. Previous studies have shown that the pollution load of phosphorus in surface water mainly comes from agricultural non-point source pollution. This paper collected four main cultivated soils, i.e., black soil, fluvo-aquic soil, red soil and paddy soil, and a soil column simulation experiment was conducted to study the spatial distribution characteristics of phosphorus in four soil profiles, as well as TP, TDP contents, dynamics and loss characteristics of soil leakage. The results showed that: (1) The contents of total phosphorus and available phosphorus in different soils were significantly different: Paddy soil > fluvo-aquic soil > black soil > red soil. The contents of total phosphorus and available phosphorus in black soil, red soil and paddy soil all showed the decreasing trends with the increase of soil depth, but the profile of fluvo-aquic soil presented the distribution pattern that upper and lower lawyer was high, and middle was low. (2) The dominant forms of phosphorus in the four soils leakage were inconsistent. The fluvo-aquic soil was dominated by MRP, black soil and paddy soil were dominated by DOP, while red soil by PP. In terms of the dynamics of soil phosphorus, the contents of TP in fluvo-aquic soil decreased first and increased next, and then decreased, while the TDP content increased first and then decreased. Black soil showed that TP content increased first and then decreased, while continuous decline in TDP content. TP and TDP contents in red soil and paddy soil did not vary significantly. (3) The correlation between Olsen-P in soil and TP in leachate was analyzed. It was found that there was an exponential relationship between Olsen-P and TP in leachate in four soils. (4) The highest TP and TDP leaching loss was observed in fluvo-aquic soil, followed by the black soil and paddy soil, the smallest loss was in red soil. The largest proportion in phosphorus loss was TDP.

Abstract:Through the water discharge scour test in field simple runoff plot, soil and water conservation benefits of different vegetation types in the riparian of Beijing mountain area were explored. 3 kinds of flow discharge and 6 different vegetation types were designed, and the test lasted 31 min. Runoff and sediment samples during the experiment were cllocted to analyze the characteristics of runoff and sediment production in different runoff plots. The results showed that: (1) The average total amount of runoff and sediment (43.29 L/m²,0.71 kg/m²) were significantly lower than those on the bare slope (65.86 L/m², 3.21 kg/m²) (p < 0.05). Vegetation was benificial for reduction runoff and sediment production, and the benefits of sediment reduction (78.66%) were significantly greater than runoff reduction (36.16%); (2) Soil and water conservation benefits were significant difference among different vegetation types. Specificially, the average flow rate (6.16 L/min) and the average sediment production rate (55.50 g/min) of bermudagrass slope was the smallest among different vegetation slopes, and the benefits of soil and water conservation was the best.(3) Stable infiltration rates were significantly difference among different vegetation types (p < 0.05), both were larger than the stable infiltration rate under bare slope conditions. Among them, the stable infiltration rate of bermudagrass was the highest (129.0 mm/h). In summary, vegetation had obvious soil and water conservation benefits, and there were significant differences among different vegetation types. The results provide a theoretical basis for the construction of ecological environment and the ecological restoration of riparian in Beijing mountain area, and also provide a reference for species selection for vegetation restoration.

Abstract:With global warming, the effects of freeze-thaw on soil properties have been increasingly emphasize. Taking saline and alkali soil in Shenzhou city of Hebei province as research object, the impacts of freeze-thaw on the physical and chemical properties of 0—20 cm deep saline and alkali soil were investigated by analyzing the changes of soil water content, water-holding capacity, bulk density, saturated hydraulic conductivity, electrical conductivity, pH and organic matter content. The results showed that freeze-thaw increased moisture content of the soil in 0—20 cm depth but had no apparent effect on water-holding capacity. For the 0—10 cm deep, freeze-thaw increased soil bulk density and pH, but reduced the electrical conductivity and permeability. The water and salt migration of the soil in this layer was special, the soil moisture content and conductivity showed the opposite trend. For the 10—20 cm deep, freeze-thaw increased soil permeability and organic matter content. Soil bulk density was very significantly negatively correlated with the water-holding capacity (P< 0.01), and significantly negatively correlated with soil moisture content (P< 0.05) in the 0—20 cm deep soil. The organic matter and saturated hydraulic conductivity had no significant correlation with other properties. The pH had very significant correlation with soil bulk density and moisture content, and it had significant correlation with water-holding capacity in the 0—10 cm deep soil. There were significant negative correlation between electrical conductivity and soil bulk density, and a significant positive correlation between electrical conductivity and water-holding capacity in 10—20 cm deep soil. These results will provide a scientific basis for the study of the influence of freeze-thaw on saline-alkali soil and the improvement of saline-alkali soil.

Abstract:Snowmelt erosion is an important part of soil and water loss in seasonal snow cover area. It is important for preventing and controlling erosion gully to understand the effect of snowmelt on gully development. Based on the field observation and measurement, snowmelt erosion processes and rill erosion morphology of gully slope were analyzed in the northeast black soil area, and the prevention and control effect of soil and water conservation measures on snowmelt erosion was investigated. The results showed that there was no runoff in G2, and the runoff rate and sediment concentration of G1 and G3 in middle stage of snowmelt period was greater than those in last stage and initial stage of snowmelt. The daily dynamic changes of runoff rate and sediment concentration were both increased first then decreased. During the snowmelt period, for the three gullies, mean rill width was ranged from 6.7 to 9.4 cm, mean rill depth was ranged from 3.3 to 4.3 cm. The number of rill, rill density, degree of rill dissection, rill tortuosity complexity and average rill erosion depth on sunny slope were all greater than those on shady slope, which indicated that the degree of rupture and rill erosion on sunny slope was greater than that on shady slope. The rill was dominated by type of wide-shallow, and the ratio of width to depth was ranged form 1.91 to 2.18. Effect of soil and water conservation measures was obvious during snowmelt period. The benefits of soil and water conservation measures on water and sediment blocking in erosion gully G2 was 100%, and for G1 and G3, most of the sediment eroded by snowmelt was also deposited in the gully.

Abstract:In order to investigate the mechanism of non-homogeneous soil air permeability in reconstruction soil and provide a theoretical basis for further studies of the characteristics of complex heterogeneous soil, the effects of coal gangue composition and topsoil texture on air permeability of reconstruction soil were studied. The coal gangue was mixed with different particle size gravel to change its composition, the soils were reconstructed by using three different soils in the soil column, and the air permeability was measured by one-dimensional transient method. The results showed that the influence of particle size and mass fraction of different gravel on saturated mass water content of mixed matrix was different. The saturated mass water content was increased gradually from 7.29% to 12.9% with 2~5 mm particle size gravel increasing. The saturated mass water content was increased first and then decreased with the mass fraction increasing of 5~10 mm particle size gravel, which were 7.28%, 8.5% and 6.9% respectively. The air permeability of coal gangue was much larger than that of soil, and the sensitivity of coal gangue to mass water content was increased with the mass water content increasing, while the sensitivity of soil was decreased with the mass water content increasing. The presence of gravel created an advantage for the formation of large pores and reduced the soil ventilation section to block the air transmission channel. The air permeability of reconstruction soil was influenced by topsoil texture and bottom filling matrix. The air permeability of reconstruction soil depended on topsoil permeability, and the air permeability of bottom filling matrix determined the influence coefficient of filling matrix on the air permeability of reconstructed soil (S_ka). S_ka had a significant correlation with the filling matrix permeability, which could be fitted by an exponential function (R²=0.93). The air permeability of reconstructed soil could be estimated by topsoil and filling matrix air permeability, which simplified the air permeability determination process of reconstruction soil.

Abstract:To study the variation of hydraulic parameters of unsaturated zone in the coal mining subsidence cracks region, the soil particle size distribution, soil water characteristic curves (SWCCs) and unsaturated hydraulic conductivity curves (UHCCs) were measured and analyzed in PanJi coal mining subsidence area in Huainan compared with the no-Subslihen cearea. The results showed that the hydraulic parameters of unsaturated zone chagend continuously in the coal mining subsidence in steady phase, and subsidence fissures had reduced the slope of the SWCCs and the SWCCs air entry value, and then resulted in higher water-holding capacity. Under the same matrix potential, the UHCCs of subsidence area soil significantly is lower than that of the non-subsidence area. This was due to the precedence flow in subsidence fissure, which would produce non-water-conductive fissure zone and resulted in the decrease of moisture content and hydraulic conductivity. All the results above will provide significant basis for experimental studies in water movement process of unsaturated zone in coal mining subsidence region.

Abstract:Many factors such as the types of forests influence snow processes in forest ecosystems, but the effects of forest cover on snow hydrology are not well defined in Xiaoxing’an Mountains of northeastern China. The objective of this study was to investigate the effects of forest types on snowpack properties by measuring snow depth, snow density and snow water equivalence (SWE) during snowpack accumulation and snowmelt. The results indicated that the noticeable differences in the mean snow depth and the mean SWE were found between the mixed spruce-fir Korean pine forest and the opening site. The degree of heterogeneity in SWE variations in the mixed spruce-fir Korean pine forest was higher than the white birch forest and the opening. The Maximum snow water equivalence (MSWE) was reduced by 26.08% in the mixed coniferous forest and 5.43% in the white birch forest compared with the opening site. The mean ground snow densities in the three sites were not significantly different. The mean ablation rate was 1.52 mm SWE/day (76% of the opening) in the mixed coniferous forest and 2.05 mm SWE/day (94% of the opening) in the white birch forest. But, the differences of the mean daily melt in the three sites were not significant. The mixed coniferous forest and the white birch forest intercepted 24.02 mm SWE/27.27% of snowfall and 5.43 mm SWE/6.16% snowfall, respectively. The mean interception in the mixed coniferous forest was significantly greater than the white birch forest. Our results demonstrated that the mixed coniferous forest cover could have a remarkable effect on snow accumulation and interception.

Abstract:In order to research the effect of forest types on the distribution pattern of soil water stable aggregate, its stability, the organic carbon component and their relationships, the distribution pattern of soil water stable aggregate, the average aggregate diameter, percentage of aggregate disruption, macroaggregate proportion and the content of organic carbon component were determined in the Eucalyptus grandi plantation, Cunninghamia Lanceolata plantation and Pinus massoniana secondary forest in Southwest Edge of Sichuan Basin, the results showed that: (1) The soil water stable aggregates in the three forests were mainly macroaggregates (> 0.25 mm). The water stability of aggregate distribution pattern was different in the three forests, the water stable aggregates of > 5, 0.5~0.25 mm in 0—20 cm soil layer, and < 0.25 mm of 20—40 cm soil layer were dominant for Eucalyptus grandi plantation, and Cunninghamia Lanceolata plantation was focused by > 5, 0.5~0.25 mm in 0—20 cm soil layer, and 1~0.5, 0.5~0.25 mm in 20—40 cm soil layer, and ≤ 0.25 mm in 0—20 cm soil layer, and >5 mm in 20—40 cm soil layer for Pinus massoniana secondary forest. The difference of soil aggregate stability was significant for different forest types in 20—40 cm soil layer, the MWD, R_0.25, PAD of Pinus massoniana secondary forest were highest. According to the Bissonnais and international soil aggregate stability classification standard, the soil aggregates could not reach the stable level (0.4 ≤ MWD < 0.8) for the three forests. (2) The content of HUC in the Pinus massoniana secondary forest was significantly higher than Eucalyptus grandi plantation, and the soil humification degree of Pinus massoniana secondary forest was the highest in 0—20 cm soil layer, while Cunninghamia Lanceolata plantation was the highest in 20—40 cm. (3) The relationships between aggregate stability and organic carbon components in three forests was different, and a significant correlation was found among MWD, SOC, FAC, and HUC. Soil organic carbon could promote soil agglomeration process and its stability, and FAC, FAC and HUC played the significant roles. In short, the soil aggregate stability, organic carbon contents and their relationships in the Eucalyptus grandi plantation, Cunninghamia Lanceolata plantation and Pinus massoniana secondary forest were significant differences, the influencing mechanisms were different. These results could provide theoretical basis for the accurate evaluation of the ecosystem function of different forest types in this region.

Abstract:In order to compare the effects of different amounts with straw returning in different soil layers on the composition and stability of micro-aggregates, organic carbon and the humus components of micro-aggregates, situ-simulation experiment using nylon bag was conducted. In the experiment, four levels of R0 (0), R1 (0.44%), R2 (0.88%), R3 (1.32%) and three different returning depths of 0—15(S1), 15—30(S2), 30—45(S3) cm designd. The results showed that the micro-aggregates of 0.25~0.02 mm were the predominant class, and the aggregates of 0.25~0.02 and >0.25 mm content in the soil layers increased with the straw returning, while the aggregates of 0.02~0.002 and <0.002 mm were reduced, and the largest change among the particle content occured in the S1 layer. By incorporating the straw into the soil, the mean weight diameter (MWD) of different size micro-aggregates in different soil layers increased compared with those without straw. At the same time, different amounts of straw returning to the soil could increase the content of humic acid and fulvic acid in each fraction of micro-aggregates, and in the same soil layer, the content of organic carbon and humic acid increased with the decrease of particle size, while in different soil layers, the content of organic carbon and humic acid showed as S1 > S2 > S3. The ratio of humic acid to fulvic acid showed different trends for different micro-aggregates in different soil layers. As a result, it can be seen that straw returning can promote the transformation of soil micro-aggregates to larger aggregates, thus increase the soil fertility and improving the structure of the soil.

Abstract:In this study, a 3-year fixed-site field experiment was conducted to investigate the influence of different tillage practices and straw incorporation on soil aggregates, retention of organic carbon, and crop yields. Six treatments were set up: plough + chemical fertilizer (T1), plough + straw incorporation + chemical fertilizer (T2), rotary tillage + chemical fertilizer (T3), rotary tillage + straw incorporation + chemical fertilizer (T4), no-tillage + chemical fertilizer (T5), no-tillage + straw incorporation + chemical fertilizer (T6). The results showed that, compared to plough tillage, the macroaggregates (> 2mm, A1) in surface soil (0—20 cm) under no-tillage increased by 35.79%, the medium-aggregates (2~0.25 mm, A2) increased by 30.81%, and the microaggregates (0.25~0.106 mm, M1) increased by 25.80%. Soil aggregates of T6 had the highest capability to hold organic carbon, the contents of soil organic carbon in A1, A2 and M1 under T6 were 25.04%, 28.55% and 18.12% higher respectively than those under T1. The sub-surface soil (20—40 cm) showed the similar trend with surface soil. The difference was that the proportion of aggregated carbon retained in sub-surface soil layer was higher than that in surface soil. The crop residue was brought into deep soil by plough, which increased the accumulation of organic carbon in deeper soil. The results also showed that the increase of carbon in soil profile mainly came from the import of crop residue carbon. Deep plough was beneficial to raise the retention of organic carbon in deep soil profiles. In terms of crop yield, the equivalent rice yield under the conventional tillage was higher compared with the conservation tillage. The main reason should be that the conservation tillage not only hindered the growth of seedlings, but also reduced the effective panicle number for the mature rice and wheat.

Abstract:For exploring the effect of natural vegetation restoration of abandoned farmland in the loess hilly region on soil water environment, this paper took five natural vegetation restoration (10, 20, 30, 40 and 50 years) abandoned farmlands as the research object in Ansai County,Yanan. And the changes of soil characteristic in different natural restoration stages and its effects on soil water-storage capacity were studied using the method of substituting temporal serial with spatial serial . The results showed that: In the process of natural vegetation restoration of abandoned farmland, the soil bulk density of the surface layer (0—20 cm) was lower than that of the lower layer (20—40 cm) in different soil layers at the same natural recovery stage. At different stages of natural restoration, the soil bulk density of surface soil decreased first and then increased with a minimum at 30 years of natural restoration, indicating that natural vegetation restoration could lead to decrease soil bulk density of surface soil. Reaching the maximum at 30 years, the total capillary porosity and non-capillary porosity of surface soil increased first and then decreased, while capillary porosity decreased initially and increased afterwards. Reaching the maximum at 30 years, soil total water-storage capacity and non-capillary water-storage capacity increased first and then decreased at different stages of natural restoration. The changing trends of soil physical characteristic showed that with the increase of soil bulk, soil gravel content and capillary porosity, and with the decrease of non-capillary porosity, the soil water-storage capacity was reduced, and vice versa.

Abstract:Through the field survey and laboratory analysis, this paper studied the impact on soil aggregate and infiltration capability after forestland converted into tea garden. The results showed that the water-stable aggregates of the forestland and 30 years-tea garden (30 years) were dominated by macro-aggregates (> 5 mm), and the soil micro-aggregates (< 0.25 mm) was the highest in newly-reclaimed young tea garden (3 years). After the conversion from forestland into tea garden, in 0—20 cm depth, the soil R0.25 (water-stable aggregate > 0.25 mm), mean weight diameter (MWD), geometric mean diameter (GWD), initial infiltration rate, average infiltration rate, stable infiltration rate, cumulative infiltration in 30 min and cumulative infiltration significantly decreased by 10.59%~19.38%, 30.32%~65.60%, 44.04%~72.08%, 49.97%~76.62%, 51.04%~73.90%, 51.90%~55.66%, 55.61%~78.82% and 59.65%~69.23% (P< 0.05) respectively, and the fractal dimension (D) significantly increased by 4.61%~7.52% (P< 0.05). The soil R0.25, MWD, GWD, initial infiltration rate, average infiltration rate, stable infiltration rate, cumulative infiltration in 30 min and cumulative infiltration were in the order of forestland > 30 years-tea garden > newly-reclaimed young tea garden, and D varied as the opposite trend simultaneously. Pearson correlation analysis showed that soil infiltration properties in different plots had a extremely significant positive correlation with R0.25, MWD, GWD and >5 mm macro-aggregates, and a significant or extremely negative correlation with D, 1~2, 0.5~1, 0.25~0.5 and <0.25 mm micro-aggregates. The eigenvalues of soil aggregate and infiltration capability (except the D) had extremely significant positive correlation with soil organic carbon, available nitrogen, available potassium, soil porosity and field capacity, and showed extremely significant negative correlation with soil bulk density, but not significant correlation with soil pH and available phosphorus. In summary, soil water-stable aggregate (especially the >5 mm macro-aggregates) contents were decreased dramatically after forestland converted into tea garden, consequently reducing the soil aggregates stability and also the soil infiltration capability. With the increasing tea plantation age, the soil organic carbon and available nutrients were also improved, which could increase the soil macro-aggregates content, leading to the improved soil aggregate and infiltration capability, but still not reach the level of forest.

Abstract:By comparing to the crop land (CL), the effects of two typical restoration measures (Zenia insignis Chun+Napiergrass (ZN) and Natural restoration (NR)) on soil hydraulic properties at three depths (surface layer 0—10 cm, subsurface layer 10—30 cm, underlying layer > 30 cm)were investigated in a typical peak-cluster depression area in northwestern Guangxi, based on in situ infiltration experiments and numerical inversion methods. The results showed that, the order for K_s was CL < ZN < NR. The two restoration measures had more obvious impacts on K_s both in the surface and underlying layer. Compared to the CL, the K_s increased by 49.0% (ZN) and 51.9% (NR) in the surface layer, and by 33.1% (ZN) and 21.1% (NR) in the underlying layer, respectively. The order for parameter α and n were CL < ZN < NR and CL > NR > ZN, and the rank for water-retaining property (calculated based on residual water content θ_r, saturated water content θ_s, α and n) was CL < NR < ZN. These results indicated that the two ecological restoration measures could improve soil hydrological functions. However, the statistical analysis showed that the differences among the soil hydraulic parameters in CL, NR and ZN were not significant (P> 0.05). There might be ascribed to the slow impacts of ecological restoration on soil hydraulic properties, and the high heterogeneity of soil hydraulic properties.

Abstract:Through field investigation and laboratory experiment, this study quantitatively evaluated the water holding capacities of ground covers (litter and moss) and soils among three forest types (Picea likiangensis coniferous forest, Picea likiangensis coniferous forest-Salix oritrepha shrub and Sibiraea angustata shrub) in an ecotone of the source area of Minjiang River. The results showed that the reserves of ground covers was significantly different among the three forest types, which was following the order of forest-shrub (72.67 t/hm²) > coniferous forest (43.87 t/hm²) > shrub (11.00 t/hm²). The reserves of moss was 27.00 t/hm² and 44.71 t/hm² in coniferous forest and forest-shrub, respectively, which accounted for more than 61.5% of the ground cover reserves. The maximum water holding capacity of ground covers followed the order of forest-shrub (21.23 mm) > coniferous forest (11.33 mm) > shrub (2.45 mm). The maximum water holding capacities of litters was 7.45 and 12.12 mm in coniferous forest and forest-shrub, respectively, which were both larger than those of moss layers. Moreover, the maximum water holding capacity of litter and moss was 4.3~4.4 and 1.4~2.0 times larger than those of their reserves in coniferous forest and forest-shrub, respectively. The soil bulk density increased and the maximum water holding capacity of soil decreased with the increasing of soil depths. The maximum water holding capacity of soil in 0—20 cm depth was in the order of forest-shrub (153.70 mm) > shrub (132.28 mm) > coniferous forest (128.25 mm). Combined considering the water holding capacity of ground covers and soils, the water holding capacity of the ecotone ecosystem was significantly different among the three forest types, following the order of forest-shrub (174.93 mm) > coniferous forest (139.58 mm) > shrub (134.73 mm). Moreover, the soil layer was the dominant component of the water holding capacity of ecosystem, accounting for more than 87.9% of the total water holding capacity of the whole ecosystem. These results would increase our comprehensive understanding of the eco-hydrological effects in the source region of Minjiang River.

Abstract:Studying the effects of rotational grazing on the physicochemical properties of grassland soil is of great significance for scientific utilization of grassland and ecological protection of grassland. Taking the desert grassland with the largest area in Ningxia as the research object, the effects of enclosure, continuous grazing, and rotational grazing on the physical and chemical properties of 0—40 cm soil were studied in the second, fourth and sixth districts through grazing experiments. Grassland health status was also evaluated by using evaluated method. The results showed that: (1) The silt content and moisture content of rotational soil in Sixth District and Fourth Region were higher. And the rotational grazing method had little effect on soil bulk density and porosity. The rotational grazing in Area IV and Region VI was prone to form soil physical crusts, lichen-algae Crust maintenance. (2) Continuous grazing had the lowest content of organic matter in the soil, and the total nitrogen content was the lowest in the grazing prohibition. The available nitrogen content was the highest in the four-area rotational grazing, and the available phosphorus and potassium contents were the highest in the six-area rotational grazing. (3) There were significant correlations between soil properties, but the correlation between grassland plant biomass and most soil properties was not obvious. (4) The health index of the six-region rotational grazing was the highest, and that of continuous grazing was the lowest. According to these findings, the grassland in the study area is suitable for rotation in six districts.

Abstract:Drip irrigation and straw returning affected the accumulation of salt in the surface soil by affecting the amount of salt input and the migration of irrigation water, and irrigation and salt washing are important measures to reduce the accumulation of salt in soil. The effect of long-term drip irrigation mode and soil management on salt content were analyzed by measuring the change of salt content in soil plough layer during summer fallow under the model of long-term drip irrigation and flooding irrigation and different straw treatments. The results showed that after the harvest, the total salt content of the drip irrigation mode and the flood irrigation mode was 2 402 and 1 713 mg/kg, respectively. The increase of the total salt content under the drip irrigation mode was mainly from the increasing of Ca²⁺, SO₄^2- and NO₃^- ions, which accounted for 12.9%, 63.4% and 23.6% of the total salt increase, respectively. The addition of wheat or maize straw significantly increased the content of soil salt by 5.8%~23.4% under the drip irrigation, but it had no effect on the soil salt under flood irrigation mode. The single flood irrigation during summer fallow significantly decreased the content of Mg²⁺、Na⁺、K⁺ and NO₃^- by 58%~69%, 61%~63%, 37%~50%, and 37%~45% under drip irrigation mode, respectively, and significantly decreased the content of Mg²⁺ and NO₃^- by 38%~44% and 5%~12% under flood irrigation mode, respectively, while it had no significant effect on the other cations under this mode. HCO₃^- changed greatly during the summer fallow, and the trend of change was opposite to that of NO₃^-. The soil salt content significantly decreased by 29% and 8.7% under drip and flood irrigation mode during the summer fallow, respectively. In general, the drip irrigation mode and straw addition under this mode significantly increased the soil salt content, and the soil management during summer fallow played an obvious role in declining the soil salt. After the flood irrigation and the high temperature shed during summer fallow, the salt content decreased obviously, but it was still slightly higher than that in the flood irrigation mode, the amount of nitrogen, potassium and sulphur based water soluble fertilizers should be further reduced in production.

Abstract:In this paper, four sampling plots with different slope directions and different densities were selected as the research object in the Caijiachuan watershed of the loess area in western Shanxi Province. An observation point was placed at the center of each plot, and the soil volumetric water content from January 2016 to December 2016 were determined by the TRIME-TDR soil moisture analyzer. The soil moisture in each 0—200 cm soil layer was determined stratified with every 20 cm respectively in the early, middle and late of each month. Four sampling plots were studied about the seasonal variation of soil moisture, the vertical variation in soil profiles, and the effects of slope directions and densities on soil moisture. The results showed that: (1) Seasonal changes of soil moisture could be divided into four periods including stationary period, consumption period, fluctuation period and recovery period, the annual maximum soil moisture was in the same month of the maximum rainfall in the year, and the seasonal distribution of precipitation had effect on soil moisture. (2) Soil layers could be divided vertically into three layers, including severe-changing layer, weak-changing layer and relatively stable layer. With the increasing soil depth, soil moisture increased first, decreased next, and then leveled off. (3) The slope directions and densities had significant effects on soil moisture. Soil moisture on shady slopes was significantly higher than that on sunny slopes (P<0.01). Low-density soil moisture was significantly higher than the high-density (P<0.01).

Abstract:In order to investigate the effect of groundwater depth on maize growth and yield under mulched drip irrigation, selecting the maize of Zhengdan 958 in the case of Shenyang region as test material, five different groundwater depths of 1.0 (D1.0), 1.5 (D1.5), 2.0 (D2.0), 2.5 (D2.5) and 3.0 m (D3.0) were set up by the simulation system. The growth index, photosynthesis, yield and water consumption of maize were analyzed. The results showed that the specific performance of plant height, stem thickness and leaf area index which reached the peak value under different groundwater depths was D1.0 > D1.5 > D2.0 > D3.0 > D2.5. Besides, D1.0 and D1.5 treatments could shorten time after planting when plant height and stem thickness reached the peak by 10~20 days. Compared with other treatments, the net photosynthetic rates and transpiration rates were increased under D1.0 by 18.05%~32.89% and 18.50%~137.24% respectively. Maize yield decreased with the increasing groundwater depths, and the yield of D1.0 was the largest, reaching 17 100 kg/hm². And maize yield increased with the increasing groundwater recharge and water consumption during the whole growth period. Through the path analysis between maize yield factors and yield,it turned out that groundwater depth improved maize yield by increasing leaf area index and grain numbers. In conclusion, groundwater depth of 1.0~2.5 m could shorten the process of maize growth, increase maize yield by increasing the maize leaf area index, then improve the photosynthesis capacity, promote the formation of maize grain in the filling stage,and finally increase grain numbers. These findings could provide scientific guidance for maize planting and water-saving irrigation under different groundwater depths in the middle area of Liaoning Province.

Abstract:Nebkhas are the fast pathways for hydrological processes of shrub vegetation in arid regions, and also the key points for regulating soil water balance. Taking the degraded artificial Caragana intermdia in desert grassland asobject, the dynamic responses of hydrological processes and hydrological effects of Nebkhas by artificial sand buried were explored for five consecutive years (2012-2016). The results showed that the sand burial intervention did not significantly change the main hydrology physical indicators of 0—10 cm in the surface layer, but significantly increased soil moisture infiltration rate of 5—10 cm, while infiltration rate of the 0—5 cm was significantly reduced. The instant water capacity of 0—5 cm soil surface was significantly improved by the sand burial intervention. After the precipitation, the decay process of moisture content in surface soil showed a strong seasonal change. The relative storage effects of 0—100 cm soil with sand burial at the end of the growing seasons in 2012—2016 were 11.3%, -6.5%, 4.5%, 4.3%, and 15.7%, and the increase of 0—60 cm was the most obvious. In general, the sand burial intervention had no significant effects on the hydrophysical characteristics of the surface soil. Water infiltration rate of soil 5—10 cm layer was significantly improved, but infiltration rate of the 0—5 cm was reduced. However, the enhancement of local infiltration performance did not increase the depth of water recharge, while the hydrological connections between the upper and lower layers were weakened.

Abstract:To investigate the effects of different proportions of chicken manure and nitrogen fertilizer on the fractal characteristics of soil water stable aggregates and the carbon pool management index in the forage triticale/maize rotation, a field experiment was conducted from 2010 to 2017 (successive eight years) with five treatments: C₀N₀ (no fertilizer, CK), C₀N₁₀ (chicken manure nitrogen:urea nitrogen=0:10), C₂N₈ (chicken manure nitrogen:urea nitrogen=2:8), C₄N₆ (chicken manure nitrogen:urea nitrogen=4:6), C₅N₅ (chicken manure nitrogen:urea nitrogen=5:5). Soil water stable aggregate composition and organic carbon (SOC), total organic carbon (TOC), active organic carbon (AOC), soil mass fractal dimension (D_m) and soil carbon management index (CPMI) were assayed in triticale/maize rotation. The results showed that different fertilization measures had significant influence on the composition of soil water stable aggregates in triticale/maize rotation. The soil water stable aggregate composition was less than 0.25 mm particle size, its content was the highest in C₀N₀ treatment, followed by C₀N₁₀, C₂N₈ and C₅N₅ treatments, and C₄N₆ treatment was the lowest. Compared with CK, aggregate SOC content of each treatment were significantly increased (p< 0.05), and the increase order from large to small was C₄N₆ > C₅N₅> C₂N₈ > C₀N₁₀, and SOC of C₄N₆ treatment was significantly higher than those of other treatments (p< 0.05), the D_m of soil water stable aggregates from large to small was C₀N₀ > C₀N₁₀ > C₂N₈ > C₅N₅ > C₄N₆. Soil TOC, AOC and CPMI of each treatment in order was C₄N₆ > C₅N₅ > C₂N₈ > C₀N₁₀ > C₀N₀, and the AOC, CPMI and TOC contents of the same treatment decreased gradually with the increasing soil depth. The pearson correlation analysis showed that D_m had a very significant negative correlation with TOC, AOC and aggregate SOC (p< 0.01), and CPMI was significantly positively correlated with TOC, AOC and aggregate SOC (p< 0.01). Comprehensively, the combined application of chicken manure with nitrogen fertilizer was not only beneficial to improving the stability of the soil structure, but also to enhancing soil fertility in triticale/maize rotation system, which C₄N₆ was the best treatment.

Abstract:The growth condition of crop trees as well as the entire forest carbon storage can be affected by thinning. Studying the long-term effects of thinning on the carbon sequestration of plantations contributes to accurately evaluate the carbon sink function and the scientific management of plantations. The Pinus tabulaeformis plantations constructed in 1962 on the Loess Plateau forest area, were thinned to 4 different densities: 800 (Heavy), 1 500 (Medium), 2 200 (Light) and 2 900 (Unthinning) stem/hm² in 1985. In August 2016, the effects of thinning on different vegetation layers, leaf litter, coarse wood debris and soil organic carbon pools were studied. The results showed that the total carbon storages of the Pinus tabulaeformis plantations under Light and Medium thinning were significantly increased by 28.54% and 21.33% respectively compared with the control, but no significant difference observed between the Heavy (154.66 t/hm²) and the control (169.26 t/hm²). The arbor layers were the main carbon pools of plantations, accounting for 64.85%~74.62% of the total carbon storage. Under different treatments, the carbon storage of stems in the arbor layers was the highest (52.05%~56.43%), followed by the roots and branches (22.27%~22.60% and 17.73%~18.32%), and the lowest in leaves (3.56%~7.01%). While Medium and Heavy thinning improved the diversity of shrubs and herbs, the total carbon storages of shrubs and herbs under those were 24.27% and 25.24% respectively higher than that of the control. Thinning significantly reduced leaf litter, which under heavy thinning declined to 48.15% of the control. The changes of soil carbon pool were mainly caused by the disturbance of topsoil 0—20 cm. The surface carbon storages under Medium and Heavy thinning fell by 17.68% and 33.76% respectively compared with the control, while the difference between Light thinning (51.23 t/hm²) and the control (50.96 t/hm²) was not significant. There was a significant negative correlation between soil surface carbon storages and plant diversities and basal respirations. In conclusion, Light and Medium thinning could increase carbon sequestration in forest ecosystems, and Light thinning was not only conducive to carbon sequestration in above-ground vegetation but also contributed to the maintenance of soil carbon pools.

Abstract:Using the brown soil as the tested soil, pot experiment was conducted to investigate the effects of biochar derived from rice husk on soil nitrogen content, rape yield, nitrogen contents of aboveground and underground of rape, and the loss of N₂O gas under two consecutive cropping seasons using ¹⁵N tracing method. Nitrogen utilization efficiency of nitrogen fertilizer and the proportion of different fate were calculated to study the effect of biochar addition on uptake and transport of nitrogen in rape. Biochar was applied at four rates (0, 0.5%, 1% and 2%) to the soil. The results showed that biochar application significantly increased the yield of rape in the first and the second cropping seasons. Compared with no biochar addition, the ratio of soil nitrogen uptake by rape was increased by 2% in the first season in the treatment of 0.5% biochar application, and it was increased by 0.8%, 2.4% and 3.2% in the second cropping season, in the treatments of 0.5%, 1% and 2% biochar application, respectively. The nitrogen contents of leaves and roots increased with the increasing of biochar application. Compared with no biochar addition, biochar application significantly decreased N₂O gas emission of rape in the two seasons, and the N₂O gas emission reduced amount was 0.30 and 0.10 mg/kg in the first season and the second season, respectively, in the treatment of 2% biochar application. Compared with no biochar addition, nitrogen utilization efficiency of rape increased by 16.3% in the treatment of 2% biochar application. The average nitrogen utilization efficiency of two seasons increased by 0.42%, 0.72% and 5.3% in the treatment of 0.5%, 1% and 2% biochar application, respectively. Thus, 2% biochar application should be considered as a suitable soil amendment.

Abstract:In order to analyze the rainfall redistribution in forest canopy and the spatial variation of the throughfall in phyllostachys edulis stands, a total of 72 gauges were randomly set up within a 30 m×30 m sample plot of a phyllostachys edulis stand, which was located in the Jinyun Mountain National Nature Reserve at Chongqing, and 6 standard trees were selected to observe the stem flow. Altogether 18 rainfall events were monitored from May to August, 2017. The results showed that the total volume of interception, throughfall and stem flow of all the rainfall events was 32.76, 208.1 and 10.97 mm respectively, accounting for 13.00%, 82.64% and 4.36% of the total rainfall, respectively. A logarithmically increasing function was fitted between throughfall ratio and rainfall depth. The coefficients of spatial variability of throughfall showed a power function relationship with both rainfall volumes and rainfall intensities. The impacts of leaf area index (LAI) on throughfall ratio decreased with the rising rainfall depth. A significantly negative correlation was found between the throughfall ratio and LAI when rainfall was less than 10 mm. The coefficients of variance of throughfall among all the 18 rainfall events (CV_T) at different gauges changed from 19.2% to 47.7%. The spatial distribution pattern of CV_T was in accordance with the spatial distribution pattern of phyllostachys edulis densities, but showed no significant relationship with the distribution of LAI. The monitoring points with larger throughfall tended to be located at the edge of Pyllostachys edulis canopy.

Abstract:In order to reveal the changing characteristics of soil organic carbon and nitrogen of light and heavy fractions in reclaimed soil as affected by different reclamation years and fertilization measures, the variation of carbon and nitrogen contents and C/N ratio of light and heavy fractions were studied under five fertilization modes by the density fractionation (no-fertilizer control, CK; single fertilizer, CF; single organic manure, M; fertilizer combined organic manure, MCF; and biological organic fertilizer and chemical fertilizer mixed fertilizer, MCFB). The results showed that TOC (total organic carbon), TON (total organic nitrogen), carbon and nitrogen of light fraction and heavy fraction all increased with the increasing ages. Single organic manure showed significant increase in TOC, TON, LFOC, HFOC, LFON and HFON compared with other treatments after 8 years of reclamation, and the corresponding contents were 148.10%,68.09%,163.68%,129.51%, 35.00% and 92.59% higher than those of raw soil, respectively. The sequence of C/N was Light Fraction C/N > Heavy Fraction C/N. The light fraction C/N in all treatments increased with the increasing reclamation ages, being the highest (25.48) in CF, and the heavy fraction C/N in all treatments decreased with increasing time, being the lowest (6.44) in CF. Fertilization measures had a significant effect on the management index of soil C and N stocks. Treatments of MCFB could improve CMI and NMI more effectively than other treatments. On the whole, under same nutrient inputs condition, single organic manure was more conducive to the accumulation of soil total organic carbon and nitrogen pools and carbon and nitrogen contents of light and heavy fractions in the reclaimed soil of coal mining subsidence areas. Single fertilizer promoted the increases of light fraction organic carbon and heavy fraction organic nitrogen to a greater extent.

Abstract:The limited rainfall and low water use efficiency are the main causes of the low and unstable crop productivity in arid agricultural area of the Loess Plateau in Long Zhong. Developing conservation tillage practices is an important way to protect water and soil resources and improve water use efficiency. The aim of the study was to determine the underlying mechanisms of different tillage practices in improving yield and water use efficiency. The effect of different tillage practices on soil evaporation, field water consumption, crop transpiration, ratio of evapotranspiration to evaporation, yield and water use efficiency were studied from 2015 to 2016. The study was conducted in a long-term tillage experimental field located in the arid farmland of Long Zhong. The experiment included six treatments, which were conventional tillage with no straw (T), no-till with straw cover (NTS), no-till with no straw cover (NT), conventional tillage with straw incorporated (TS), conventional tillage with plastic mulch (TP) and no-till with plastic mulch (NTP), all the fields were used for the rotation of spring wheat and pea. The results showed that: (1) Compared with T treatment, the evaporations of spring wheat and field pea in NTS, TP and NTP treatments significantly reduced by 6.52%~50.81% during the whole growth period, and the effect of NTS to reduce the evaporation was mainly after the flowering of wheat and the pod of the pea, and the plastic mulching could significantly reduced the evaporation in each growth period. (2) NTS treatment had no significant effect on water consumption during the whole growth period, and the water consumption in NTS treatment was significantly higher than that in T treatment in wheat fields. Compared with traditional tillage, NTS treatment significantly increased the amount of water consumed and the proportion of total water consumption in the stages of wheat flowering to harvest and pea podding to harvest. (3) NTS, TP and NTP significantly increased the transpiration of spring wheat and pea, reduced effectively the proportion of evaporation to evapotranspiration in the field, and the ineffective loss of water. (4) Compared with T treatment, the yield of spring wheat and pea in NTS, TP and NTP treatment increased by 7.64%~62.79% in each year, and the water use efficiency increased by 0.43%~50.88%. Therefore, the conservation tillage measures, such as no-tillage straw mulching and plastic mulching, could improve the water use efficiency and yield of wheat and pea in the arid agricultural area of the Loess Plateau in Long Zhong. No-till with straw cover could improve the water use efficiency and yield of spring wheat and pea by reducing the evaporation and increasing the water consumption in the later period of crop growth, and reducing the ratio of evaporation to evapotranspiration. The plastic mulching was mainly to reduce the evaporation during the whole growth period, increase the total transpiration of the crop and reduce the proportion of evaporation to evapotranspiration, so as to realize efficient use of water and increase crop yield.

Abstract:In order to clarify the reasonable application amount of nitrogen fertilizer in late japonica rice in the southern double season rice area, an field experiment was conducted in 2016—2017 during the late-rice cropping seasons in southern China, the six nitrogen levels including N1 (0 kg/hm²), N2 (165 kg/hm²), N3 (210 kg/hm²), N4 (255 kg/hm²), N5 (300 kg/hm²) and N6 (345 kg/hm²) were set, and the effects of different nitrogen application rates on the japonica rice yield, quality and nitrogen use efficiency were studied. The results showed that the yield of late japonica rice showed a parabolic trend with the increasing of nitrogen application. Compared with the yield of N4 plots, the grain yield of the N1, N2, N3, N5 and N6 plots decreased by 29.2%~34.9%, 10.1%~11.8%, 5.5%~5.7%, 1.2%~4.4% and 2.3%~9.0%, respectively. The grain yield of the N4 plots was significantly higher than those of the N1 and N2 plots in two years. The main reason for the increase of late japonica rice yield was the increase of productive panicle number and seed setting rate. With the increasing of nitrogen application, the total nitrogen accumulation of rice increased, while the nitrogen dry matter production efficiency, nitrogen physiological efficiency, nitrogen factor productivity for applied nitrogen, nitrogen agronomic efficiency and nitrogen harvest index were all decreased, and the nitrogen uptake and utilization efficiency first increased and then decreased. With the increasing of nitrogen application, the industrial quality, appearance quality and nutrition quality of the late japonica rice were all improved, the content of amylose content in eating and cooking quality decreased and the gel consistency increased. The peak viscosity, hot viscosity, cool viscosity and breakdown of RVA spectrum decreased gradually with the increasing of nitrogen application, while the setback and consistence increased. To sum up, it is advisable to apply nitrogen to N4 (255 kg/hm²) of japonica rice under the experimental conditions during the late-rice cropping seasons in southern China, which can reach the high yield, quality and efficiency.

Abstract:Taking reclaimed soil of the subsided land resulting from coal-mining as the research object in Jincheng, Shanxi province, the experiment studied the effects of organic manure (M), inorganic fertilizer (NPK) and organic+inorganic fertilizer (NPK+M) application for 3 years on soil physical and chemical properties, phosphorus fractions. The results showed that: there was no significant difference in soil pH, bulk density, total nitrogen and total phosphorus among different fertilization treatments, and the content of organic matter in M treatment was significantly higher than that of single fertilizer treatment, and the content of soil available phosphorus in NPK+M treatment was higher than that in the rest treatments, but the difference was not significant. NPK+M treatment could significantly increase Ca₈-P content of the soil inorganic phosphorus fractions, and all fertilization treatments significantly improved the content of Fe-P, while the difference was not significant. The growth of O-P and Ca₁₀-P was not obvious in all treatments. The contents of different inorganic phosphorus components in the control treatment generally declined, and Ca₈-P and Fe-P declined more obviously. M treatment had significant effect on active and medium active organophosphorus, NPK+M treatment impacted active and medium stable organophosphorus more obviously, and NPK treatment had no significant effect on organophosphorus. The correlation analysis showed that Ca₂-P, Ca₈-P, Al-P, Fe-P, medium activity, medium stable organophosphorus and available phosphorus had significant positive correlation, and Ca₈-P, medium active organophosphorus and available phosphorus were very significantly correlated.

Abstract:The present study investigated the photosynthetic characteristics (net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), internal water use efficiency (WUE)), transpiration rate (T_r) and leaf water potential (Ψ_w) of Amygdalus pedunculata Pall and Salix psammophila under drought stress in soils with different textures (sandy soil and loamy soil) on the Loess Plateau through water control pot experiment. The results showed that P_n, G_s, WUE and T_r of A. pedunculata Pall and S. psammophila in soils with different textures increased firstly and then declined under the drought stress, while C_i and Ψ_w showed a trend of rising and decreasing, respectively. Soil texture significantly affected the sensitivity of A. pedunculata Pall and S. psammophila to the water deficiency. Under the same drought degree, the P_n and G_s of A. pedunculata Pall in the loamy soil were significantly higher than those in the sandy soil, while an opposite trend was observed for the S. psammophila (p < 0.05) (except the severe drought treatment). A significant difference in WUE of A. pedunculata Pall and S. psammophila was observed between the soils with different textures when the soil moisture was reduced to moderate and severe drought (p < 0.05). The growth of A. pedunculata Pall in the loamy soil was better than that in the sandy soil, while S. psammophila showed an opposite trend. Therefore, during the vegetation restoration and ecological construction on the Loess Plateau, the tree species should be chosen not only according to the soil water condition, but also considering the different responses of vegetation to drought stress in soils with different textures.

Abstract:In order to study the effects of basal/topdressing nitrogen fertilizer on nitrogen utilization and soil nitrogen apparent loss under water saving cultivation, this study took the cultivar Jimai 22 as the experimental material, and set up five treatments with different basal/topdressing nitrogen (0:10(N1), 3:7(N2), 5:5(N3), 7:3(N4) and 10:0(N5)). And the preconditions of the experiment were that the total nitrogen application rate was 240 kg/hm², and the relative water content of the 0-40 cm soil layer was maintained up to 70% at the joining and anthesis stages. The results showed that the nitrogen accumulation amounts and nitrogen accumulation in grain of the N3 treatment were significantly higher than those of other treatments, while the nitrogen accumulation in vegetative organs, loss of mineral nitrogen, apparent residual rate of nitrogen fertilizer and apparent loss rate of nitrogen fertilizer were significantly lower than those of other treatments. Compared with N1, N2, N4 and N5 treatments, in the N3 treatments, the nitrogen utilization ratio increased by 33.22%, 12.60%, 11.54% and 98.14%, respectively, and grain nitrogen recovery efficiency increased by 148.65%, 56.48%, 59.63% and 229.29%, respectively, nitrogen agronomic efficiency increased by 96.52%, 34.86%, 37.64% and 204.98%, respectively, apparent budget of nitrogen decreased by 35.04%, 13.82%, 30.36% and 29.30%, respectively. According to the correlation coefficient analysis of different basal/topdressing nitrogen fertilizer, nitrogen accumulation amounts, nitrogen accumulation in grain, nitrogen utilization ratio, grain nitrogen recovery efficiency, nitrogen agronomic were significantly negatively correlated with NO₃-N content and total amount of residual mineral nitrogen in the 0-200 cm soil layer of mature period. In conclusion, the treatment with base/topdressing nitrogen fertilizer of 5:5 was the best treatment under the experimental conditions.

Abstract:Unreasonable cultivation is one of the main causes of soil degradation. In order to reveal the effect of cultivation on the change characteristics of soil organic nitrogen in alpine grassland, this study took alpine meadows of northwestern Sichuan after cultivation for 1, 3, 10, 16, 27 and 40 years as research objects and the uncultivated natural grassland as the control. The effects of cultivation on total acid hydrolysable nitrogen (TAHN), acid solution of ammonium nitrogen (ASAN), amino sugar nitrogen (ASN), amino acid nitrogen (AAN), acid hydrolysable unknown nitrogen (AHUN) and acid insoluble nitrogen (NAHN) were studied through soil sampling and analysis. The results showed that the contents of TAHN, ASAN, ASN, AAN, AHUN and NAHN decreased significantly (P < 0.05) with the increasing of cultivation years in the alpine grassland in northwestern Sichuan, especially in 0—20 cm soil layer, which decreased by 72.15%, 62.72%, 66.08%, 63.44%, 94.00% and 51.78%, respectively. The AHUN was the most significant decrease among the organic nitrogen components. The decrease of TAHN, ASAN, ASN, AAN, AHUN and NAHN mainly occurred in the first ten years of cultivation, and the annual average reduce rate decreased with the increasing of reclamation years. Therefore, reducing the reclamation of alpine grassland is important to promote the ecosystem balance and sustainable development of alpine grassland in the northwest Sichuan Plateau.

Abstract:In order to explore stoichiometry characteristics of carbon, nitrogen and phosphorus in maize and influencing factors under different water and fertilization conditions, pot experiments with different soil water contents and total nitrogen contents were conducted, and the effects of different treatments on maize growth traits and stoichiometry characteristics of carbon, nitrogen and phosphorus were discussed, meanwhile the correlation analysis was carried out. Three moisture gradients including 90% (W1), 70% (W2) and 50% (W3) of field capacity, respectively, three nitrogen levels (150% (N1), 100% (N2) and 50% (N3) of normal nitrogen application in the field, respectively) were set up, and there were nine treatments in the experiment. The results showed that the dry biomass of maize root, stem and leaf diminished as the decreasing of nitrogen amount, increased with the increasing of soil moisture content. When the soil moisture was in high and middle level, plant height of maize increased with the increasing of nitrogen application rate. When maize was under drought stress, nitrogen application rate had little effect on plant height. Stem diameter under low moisture was significantly lower than those under high and medium moisture. There was no significant difference in carbon content among maize root, stem and leaf. Nitrogen contents of maize root, stem and leaf in N3 treatment were significantly lower than those in other two treatments. N1 and N2 treatments had different effects on nitrogen content of maize root, stem and leaf. The difference of stem nitrogen content reached significant level, while the difference in leaf nitrogen content was significant after tasseling stage. The ecological stoichiometric characteristics of C/N: P were different with the change of water and fertilizer, in which the average nitrogen and phosphorus ratio (N/P) was 6.01, and it increased with the increasing of nitrogen application, decreased with the increasing of soil water content. Carbon and nitrogen ratio (C/N) was 0.31, and decreased with the increasing of nitrogen application, but it was not sensitive to moisture factor. Carbon and phosphorus ratio (C/P) was 1.62, which showed strong stability, and did not change with the change of external biological and abiotic environment.

Abstract:In order to solve the problems of low capacity of water and nutrients retention, drought stress, low potato yield and rainfall utilization rate in the hilly area along the Great Wall of Inner Mongolia, a two-year field experiment with different plastic mulching and ridge tillage planting was conducted. The soil enzyme activity, soil water content, soil temperature, pH and potato growth and yield was studied under five planting treatments, which were full-film mulching with double ridge planting (A1), full-film mulching with single ridge planting (A2), full-film mulching with single ridge micro furrow planting (A3), full-film with flat planting (A4) and traditional planting (CK). The result showed that in different growth stages of potato, full-film mulching and ridging planting densities had different effects on soil water content and soil temperature. Compared with CK, the soil water content of A1, A2, A3 and A4 treatments was increased by 32.76%, 23.60%, 42.92% and 17.58%; the soil temperature of A1, A2, A3 and A4 treatments was increased by 11.51%, 9.41%, 6.87% and 4.83% respectively. Meanwhile, the activities of soil enzymes (soil catalase activity and soil urease activity) was increased and soil pH was decreased under different plastic mulching and ridge tillage treatments, and result in the increase of the potato bud fresh weight, root fresh weight, bud diamete and root activity, and the decrease of malonaldehyde content (MDA) accordingly. Compared with CK,the tuber yield significantly was increased by 48.62%, 34.22%, 52.85%, 21.70% in A1, A2, A3 and A4 treatment respectively, and the rainfall utilization rate and fertilizer biased productivity were also significantly increased. In conclusion, full-film mulching with ridging tillage could significantly improve soil quality and increase crop yield and rainfall utilization rate, and the effect of A1 and A3 treatments A3 and A1 was more optimal,which could be a water saving cultivation practice in the rain-fed and hilly area along the Great Wall of Inner Mongolia.

Abstract:The aim of the experiment was to explore the accurate management mode of water and fertilizer supplies for greenhouse cabbage in Hexi Corridor oasis irrigation area. Greenhouse cabbage plot experiments were conducted to analyze the effects of fertilizer amount and irrigation frequency on cabbage growth, yield, quality, nutrients absorption and water and fertilizer use efficiency. Three fertilizer levels (F₁: N 320-P₂O₅ 160-K₂O 210 kg/hm², F₂: N 260-P₂O₅120-K₂O157.5 kg/hm², F₃: N 200- P₂O₅ 80-K₂O 105 kg/hm²) and two drip irrigation frequencies (H₁: 6 days, H₂: 9 days) were set. The results showed that contents of total nitrogen, phosphorus and potassium consistently increased with the increasing of fertilizer in H₁ treatment. The contents of total nitrogen and phosphorus increased at first and then decreased with the increasing of fertilizer application in H₂ treatment, but the content of potassium increased gradually. Under the same irrigation condition, the partial productivity of fertilizer increased with the decreasing of fertilizer amount. Under the same fertilization level, the contents of nitrogen, phosphorus and potassium and the absorption amount per plant in high irrigation frequency treatment were higher than those in low irrigation frequency treatment, but the partial factor productivity was opposite. The leaf height and diameter, biological yield and dry biomass reached the highest value in the treatment of H₂F₁. The leaf ball compactness, ratio of dry and fresh weight, single head weight, economic yield and economic coefficient were the maximum in H₂F₂ treatment, while the center column, midrib and leaf ratio were the minimum in H₂F₃ treatment. The effects of fertilizer amount and irrigation frequency on the quality of cabbage were significant, and the interaction of two factors reached a significant level. The content of nitrate, soluble sugar and vitamin C was the maximum in the treatment of H₁F₁, H₂F₁ and H₂F₂, respectively. The contents and absorption efficiency of total nitrogen and phosphorus were the maximum in H₂F₂ treatment, and the maximum of potassium content and absorption rate were observed in H₂F₁ treatment. With the increasing of fertilizer amount, water use efficiency also increased gradually, and it was significantly higher in H₂F₁ than that in other treatments. Integrated analysis implied that both the fertilizer amount and the irrigation frequency had significant effects on growth, yield, quality, nutrients absorption and water and fertilizer use efficiency of the greenhouse cabbage, and effect of irrigation frequency was greater than that of fertilizer amount. Thus, H₂F₂ treatment (9 days of irrigation frequency, N 260-P₂O₅ 120-K₂O 157.5 kg/hm²) was the best water and fertilizer application combination for getting the best agronomic traits, yield, quality, nutrient absorption and water and fertilizer utilization efficiency of the greenhouse cabbage in Hexi oasis.

Abstract:The Suaeda salsa marsh in high tidal flat of the northern Yellow River estuary were selected as study object, and the variations of inorganic sulfur fractions during the growing season were investigated by conducting an in situ experiment of nitrogen (N) import which included four treatments (N0, no N input; N1, low N input; N2, middle N input; and N3, high N input). Results showed that the inorganic sulfur contents in soils under different treatments generally followed the order of H₂O-S > Adsorbed-S > HCl-Soluble-S > HCl-Volatile-S, and the total inorganic sulfur (TIS) contents accounted for 34.52%~39.58% of the total sulfur (TS) in the four treatments. The contents of H₂O-S, Adsorbed-S, HCl-Soluble-S and HCl-Volatile-S in wetland soil was changed by exogenous N enrichment in varying degrees, and the effects reached significant levels in some periods of the growing season (P<0.05). Compared with N0, the contents of H₂O-S increased by 6.12% and 7.07% under N1 and N2 treatments, respectively, and decreased by 0.98% under N3 treatment. The content of Adsorbed-S increased by 11.73% under N1 treatment, but decreased by 23.53% and 13.77% respectively under N2 and N3 treatments. The contents of HCl-Soluble-S and HCl-Volatile-S showed a decreasing trend under N1, N2 and N3 treatments, and the decline were 5.21%, 19.63%, 59.59% and 0.28%, 16.10%, 6.44% respectively. Soil nutrient condition, water salinity, and acid-alkali conditions under different N enrichment treatments were the key factors that affected the amount of TIS, but the effects of pH and EC on the dynamics of different inorganic sulfur fractions were especially obvious. This study found that the exogenous N enrichment could affect the absorption and utilization of inorganic sulfur fractions by altering the growth rhythm of plants and the acid-base status of soils, which consequently changed the contents of inorganic sulfur fractions and the stock of TIS in marsh soils.

Abstract:In order to explore the changing law of soil properties in different degraded alpine meadows, we measured and analyzed the soil nutrient content and ecological stoichiometric characteristics of different degraded alpine meadows (mild degraded grassland, moderate degraded grassland and severe degraded grassland) located in Kangle, Huangcheng and Tianzhu experimental plots in the Qilian Mountains. The results showed that: (1) The soil pH, electrical conductivity, water content and organic matter content decreased with the increasing of soil depth. In the 0—20 cm soil layer, the soil pH showed an upward trend, and the electrical conductivity increased first and then decreased. In the 20—40 cm soil layer, the soil pH increased first and then decreased, while the electrical conductivity showed the opposite trend. Soil waters and organic matters in 0—20 and 20—40 cm soil layers decreased gradually as the degree of degradation intensifying. (2) The contents of organic carbon, total nitrogen, total phosphorus and total potassium in different grassland soil decreased gradually with the increasing of degradation degree and soil depth, and the differences among plots were significant (p< 0.05). (3) In different soil layers of different degraded grasslands, the variation range of C/N was 19.10 to 40.48, the change range of C/P was from 87.85 to 121.97 and the range of N/P changed from 4.10 to 6.76. (4) As the intensifying of grassland degradation degree, the soil cellulase activity increased first and then decreased, urease and neutral phosphorus acid enzyme, dehydrogenase, invertase and oxidoreductase showed a decreasing trend. (5) The results of correlation analysis between soil physicochemical, enzyme activity and ecological stoichiometric ratio and principal component analysis showed that the soil physicochemical index, enzyme activity and ecological stoichiometric ratio could reflect the soil quality of different degraded grasslands. In conclusion, the soil of degraded alpine grassland had deteriorated gradually in Qilian Mountains. The rational utilization and scientific management of grassland in this area should be strengthened.

Abstract:Based on the 4 029 soil samples data obtained from the cultivated land, the spatial distribution of soil nutrients (organic matter (OM), available nitrogen (AN), available potassium (AK) and available phosphorus (AP)) in Taihe county and its influencing factors were analyzed by means of semi variation analysis, autocorrelation analysis and regression analysis. The results showed that the contents of OM, AP, AK and AN were 4.40~58.50 g/kg and 1.50~62.80, 12.00~352.00, 29.00~341.00 mg/kg, respectively, and all belonged to the medium variation. The exponential model was the most suitable model for all the studied four soil nutrients. The nugget effect was less than 25%, indicating that the nutrients were mainly affected by structural factors. All nutrient factors showed significant aggregation characteristics. More HH accumulation types were observed than those of Qiaotou, guanxi, guachao and other townships, more LL accumulation types than those of Mashi and Wanhe township. According to correlation analysis and regression analysis, it was known that the factors that had great influence on soil nutrients contents were mainly structural factors such as landform and parent material, and random factors, such as traffic and water conservancy, had a weak influence.

Abstract:Based on the soil data of 16 823 plow layer (0—20 cm) samples of cultivated land soil collected in Jiangxi Province, the spatial variation characteristics of soil nitrogen and the affecting factors at a province scale were studied by field survey, mathematical statistics analysis and geostatistics analysis methods. The results showed that the average contents of soil total nitrogen (TN) and available nitrogen (AN) were 1.57 g/kg and 164.13 mg/kg, respectively, which indicated that both the TN and AN in the study area were at a rich level. According to semi-variance function analysis, the values of the nugget to sill ratio were 62.03% and 78.97%, respectively, which suggested that the spatial variation of TN and AN in Jiangxi Province were determined by the co-effects of structural and random factors, but the random factors played a more important role. The contents of TN and AN were basically the same in the spatial distribution, which were much higher in the north area than those of south area by using ordinary kriging interpolation. The regression analysis results showed that soil parent materials, soil types, topography, soil erosion, straw returning pattern, farmland use types and nitrogen fertilization rates had very significant impacts on spatial variation of soil TN and AN (P<0.01). Soil TN and AN contents showed significant negative correlations with elevation and river dynamic index (P<0.05). The soil parent materials were able to independent explain 6.1% and 4.1% of soil TN and AN spatial variation, and the independent interpretation ability of soil types to TN and AN spatial variation was 4.2% to 4.7% and 3.1% to 4%, respectively, and topographic factors explained 4.2% of TN variation and 2.8% of AN spatial variation. Soil erosion explained 6.2% and 3.5% of soil TN and AN spatial variation. Straw returning pattern explained 4.2% and 3.3% of spatial variation of TN and AN, respectively. Farmland use types explained soil TN and AN spatial variation by 2.9% and 2.0%, respectively. The independent explanatory ability of nitrogen fertilizer application on spatial variation of TN and AN were 18.8% and 5.6%, respectively. Thus, the straw returning pattern and annual nitrogen fertilizer application rates were the main factors in controlling the spatial variation of soil nitrogen in Jiangxi Province.

Abstract:In this paper, taking a cadmium (Cd) contaminated brown soil as the test soil, the pot experiments were conducted to study the effects of cow manure and straw application on Cd species and Cd uptake by maize. The results showed that: (1) Compared with no cow manure and straw addition, the three treatments with cow manure and straw nitrogen ratios of 1:1, 3:1 and 5:1 reduced the exchangeable Cd content by 34.39%, 28.04% and 20.11%, respectively. The bound and residual Cd contents increased significantly. The organic-bound Cd and residual Cd extensively increased with the combined application of cow manure and straw. There was a significant negative correlation between the exchangeable Cd contents and soil pH values, and a highly significant positive correlation between residual Cd contents and soil pH. (2) Compared with no cow manure and straw addition, soil pH increased by 0.36, 0.17 and 0.16 units, respectively, for nitrogen ratio of cow manure to straw being 1:1, 3:1 and 5:1. (3) Compared with no cow manure and straw addition, the Cd uptake by different parts of maize decreased for the combined application of cow manure and straw. The unptaken Cd accumulated mainly in root, stem and leaf of maize, and Cd contents in grain reduced by 79.64%, 72.70% and 56.38% for the nitrogen ratio of cow manure to straw being 1:1, 3:1 and 5:1, respectively.

Abstract:Through the evaluation of the soil nutrient in a 7-year long-term fertilization experiment of wheat-maize rotation with different phosphorus application levels, the inorganic phosphorus fractions under the phosphorus depletion or accumulation in calcareous fluvo-aquic soils were studied. Path analysis and multiple regression analysis were performed to investigate the relationships among various soil available phosphorus determined by three methods, so did phosphorus fractions. The results showed that: (1) Compared with the initial soil, the total phosphorus under N0P0K0 and N2P0K2 were decreased by 15.2% and 29.7%, respectively, and the total inorganic phosphorus decreased by 13.5% and 11.8%. The total phosphorus under N2P2K2 and N2P3K2 were increased by 8.2% and 27.2% respectively, while the total inorganic phosphorus increased by 11.1% and 27.8%. The formations of inorganic phosphorus in the tested soil were mainly Ca₁₀-P and Ca₈-P. The application of phosphorus fertilizer could increase the relative proportions of Ca₂-P, Ca₈-P, Al-P and Fe-P. (2) In the depletion state of phosphorus, the inorganic phosphorus used by plants mainly came from slow-release phosphorus sources (Ca₈-P, Al-P, Fe-P; 75%), un-available phosphorus sources Ca₁₀-P (11.5%~14.0%), and available phosphorus sources Ca₂-P (7.5%~8.9%). At inorganic phosphorus surplus condition, excess inorganic phosphorus mainly converted to Ca₈-P (50%~70%), Al/Fe-P (10%~23%), O-P (8%), and Ca₂-P (0.2%~1.8%). (3) Ca₂-P and Al-P had positive effects on available phosphorus extracted by three methods with the greater contributions. Ca₂-P and Ca₈-P could be effectively extracted by the Olsen method. While, the Mehlich3 method mainly extracted Ca₂-P, Ca₈-P and Al-P, and the main extraction of AEM were soil Ca₂-P and Fe-P. (4) All the three methods were feasible for determining soil available phosphorus contents, and the Olsen method was the best.

Abstract:The method of potted swamp cabbage was adopted to research the remediation effects of soybean straw biochar on soil contaminated by lead-zinc tailings. In the contaminated soil, the concentration of Cu, Zn, Pb and Cd was 50, 400, 1 119 and 3.4 mg/kg, respectively. The results showed that whether the soil contaminated by lead-zinc tailings or not, adding 3% biochar could significantly improve soil pH and inhibit the soil pH value reduction leaded by lead-zinc tailings pollution. Soybean straw biochar had different effects on effective state of heavy metals in soil contaminated by tailings and uncontaminated soil; compared with the uncontaminated soil, the passivation of 3% biochar could not offset the increase of bioavailability of heavy metal caused by lead-zinc tailings pollution. The pollution of lead-zinc tailings inhibited the growth of water spinach, and the application of 3% biochar could eliminate the inhibitory effect. Biochar significantly reduced heavy metal content of swamp cabbage roots in pollution soil, but in the aboveground part of swamp cabbage, biochar had different effects on different heavy metals; adding 3% biochar could prevent the migration of Cu, Zn, Pb and Cd from lead-zinc tailings contaminated soil to shoot of swamp cabbage. The effect of soybean straw biochar on the absorption of heavy metals in swamp cabbage was different in lead-zinc tailings contaminated soil and uncontaminated soil, there were interaction between elements, and dilution effect caused by biomass increase of swamp cabbage after adding biochar. Under the experimental conditions, evaluating from the biomass and heavy metal content in the edible parts of swamp cabbage, applying 3% soybean straw biochar could remedy pollution soil leaded by lead-zinc tailings.

Abstract:To clarify the effects of different modifiers on the recovery of acidic tobacco-planting soil, the pot experiments were conducted to study the dynamic changes of soil pH, hydrolytic acidity, latent acid and soil exchange performance after applying Harvested Acidic soil amendment, Golden Leaf acidic soil amendment and lime. The results showed that soil amendments could increase soil pH by 3.01%~24.11%, reduce the soil hydrolytic acid by 16.08%~50.46%, decrease the exchangeable aluminum and exchangeable hydrogen by 51.80%~64.27% and 84.12%~93.56%, respectively, increase the total soil exchangeable base, the cation exchange capacity and salt saturation by 45.18%~46.16%, 0.33%~20.10% and 21.35%~49.78%, respectively. After applying the soil amendments, the soil pH increased first and then decreased, and it was stable after sixty days. The content of soil hydrolytic acid changed a little on the 30~90 day after transplanting of flue-cured tobacco, and increased slightly on the 120 days after transplanting. The exchangeable hydrogen and the exchangeable aluminum decreased in the soil with lime. But the exchangeable aluminum of the soil application with the Harvested Acidic soil amendment and Golden Leaf acidic soil amendment reduced until 120 days after transplanting the seeding of the flue-cured tobacco, and the exchangeable hydrogen increased during the 120 days after the seedling transplanting and then decreased drastically. After application the soil amendments, the exchangeable base, cation exchange capacity and salt saturation increased with small variation. Different soil amendments had different sources and components, and their recovery effects on acid soils were also different. The results of the study showed that recovery effect of lime was the best.

Abstract:Potted Miaoxiang 7 strawberry was selected and ¹⁵N isotope tracer technology was used to investigate the effects of urea combined with 0, 2, 4 and 8 mL nano-carbon sol (CK, T1, T2 and, T3), on soil physiochemical properties, plant nitrogen uptake and utilization, and plant growth. The results showed that the application of nano-carbon significantly increased the soil redox potential and soil urease activity, and with the increasing of nano-carbon amount used, soil electrical conductivity showed a downward trend at the early stage and showed an increase trend at the later stage. The application of nano-carbon promoted the absorption and utilization of nitrogen in strawberry plants, increased Ndff value of each organ of strawberry. Compared with the CK, the nitrogen utilization efficiency of strawberry plants in T1, T2 and T3 increased by 71.2%, 126.8% and 98.9%, and the soil nitrogen residue rate increased by 8.2%, 16.7% and 16.1%, respectively, reduced nitrogen loss significantly. The application of nano-carbon increased the net photosynthetic rate, transpiration rate, stomatal conductance and the chlorophyll SPAD values of plant leaves in different degrees. Compared with the CK, dry matter of leaves in T1, T2 and T3 increased by 17.5%, 45.8%, and 32.3%, respectively. The study showed that the application of urea with nano-carbon could improve soil physical and chemical properties, adsorb nitrogen in soil effectively, increase plant nitrogen utilization rate and soil nitrogen residual rate, reduce nitrogen loss, and promote the growth of strawberry plants.

Abstract:Coal mining often causes surface subsidence, resulting in poor soil nutrient and water deficiency, soil desertification and soil erosion, which limits the growth of vegetation in the mining area. However, the arbuscular mycorrhiza fungi (AM fungi) can promote the growth of vegetation. We took Xanthoceras sorbifolia as host plant and studied the effect of inoculated and non-inoculated AM fungi on plant growth and soil properties in the coal mining subsidence area by the method of in-situ field monitoring and lab analysis. The results showed that compared with the treatment of non-inoculated AM fungi, inoculation of AM fungi significantly increased the mycorrhizal infection rate and the hyphal density of outside the roots. The plant height, crown height, and ground diameter of X. sorbifolia inoculation with AM fungi in July increased by 31.89%, 23.07% and 9.89%, respectively. Compared with the treatment of non-inoculated AM fungi, the contents of total nitrogen, available nitrogen and soil organic carbon in rhizosphere soil treated with AM fungi in September increased by 0.29 g/kg, 13.0 mg/kg and 1.4 g/kg, respectively. Inoculation with AM fungi significantly increased the water content of the rhizosphere soil, total glomalin and easily extracted glomalin, while the content of available phosphorus and available potassium decreased significantly. Correlation analysis showed that there was a synergistic feedback effect between mycorrhizal infection rate, the hyphal density of outside roots and rhizosphere soil physical and chemical properties. Thus, the inoculation of AM fungi promoted the growth of X. sorbifolia and soil improvement in the coal mining subsidence area, which is of great significance to soil and water conservation, to maintain the stability and sustainability of the ecosystem in the mining area.

Abstract:Visible-near infrared (Vis-NIR) spectroscopy has been proved to be a rapid, timely and efficient tool for predicting content of soil organic carbon (SOC). In this study, FieldSpec4 was used to measure 104 soil samples collected from the Baodian mining area of Shandong province. Vis-NIR reflectance spectra and SOC content were measured under laboratory conditions. The spectral data were first denoised using the Savitzky-Golay (SG) convolution smoothing method, the multiple scattering correction (MSC) method, after which the spectral reflectance was subjected to reciprocal, reciprocal logarithm and differential transformations to improve spectral sensitivity. Finally, regression models for estimating the SOC content by the spectral data were constructed using partial least squares regression (PLSR). The results showed that: (1) Different spectral preprocessing methods had great influence on the modeling results, and the modeling results performed best when the spectral reflectance was preprocessed by Savitzky-Golay (SG) smoothing coupled with multiple scattering correction (MSC) and first-order differential transformation (modeling R²=0.86, RMSE=2.00 g/kg, verification R²=0.78, RMSE=1.81 g/kg, RPD=2.69). (2) The correlation curve between reciprocal and SOC content was similar to the correlation curve between the logarithm of the reciprocal and SOC content. They were inversely proportional to the reflectivity curve, and the modeling effect was far lower than the reflectivity; the first-order differential of spectral reflectance could significantly improve the correlation of the 500~600 nm band. (3) The spectral reflectance increased with the decreasing of SOC content. In addition, when the SOC content was low, the sensitivity of the spectrum especially that in the near-infrared band of the original reflectance to the change of SOC content decreased, and the direct modeling difficulty of the reflectance increased.