Abstract:The National Key R&D Program of " Eco-security technology for coal mining bases in the Northwestern arid desert regions in China " obeys the "CPC Central Committee and State Council on Accelerating the Construction of Ecological Civilization," (2015), "National Afforestation Plan (2011-2020 ) and the National "13th Five-Year Plan" – relevant policies on coal clean and efficient engineering to closely integrate the implementation of project , with innovation and development strategy, and also the " Belt and Road" strategy. The project is applied based on the basic theory research, the key technology research and so on. Also the content is aimed at clarifying the ecological degradation mechanism of the coal base in the arid desert area of Northwest China, developing the key technologies of water and soil conservation and utilization, dust control and vegetation restoration. The project will also establish demonstration area on ecological restoration. Above all, the project is aimed at providing technologies in coal mining base ecological restoration and security in the Northwestern arid desert regions in China .

Abstract:Supported by the Ministry of Science and Technology of China, National Key Research and Development Program of “Typical fragile ecological restoration and protection” has recently launched a project entitled “Soil conservation in the hilly red soil region of southern China” (2017YFC0505400)．This project will focus on the coordination between ecological functions and product functions, clarify the temporal and spatial variations of soil erosion in the hilly red soil region of southern China, and especially identify the relative contribution of natural factors and human activities. The project will carry out the following research on technologies and their application: controlling surface runoff, improving soil fertility, vegetation restoration and landscape pattern optimization. Base on trade-off analyses and synthetic integrated method of multiple ecosystem services, best management practices for soil erosion control will be established，which will also provide scientific and technological supports for the improvement of the regional ecological environment.

Abstract:Restricted heavily by the geology, soil erosion in karst regions of southwest China is obviously different from that in other regions. Due to the couple of chemical dissolution, gravitational erosion and water erosion, the erosion in the region had a mixture mechanism of soil surface loss and underground leakage. This paper summarized the characteristics of soil erosion briefly, including surface soil loss, underground soil leakage, soil erosion intensity and the grading standard, and the simulation of soil erosion process. Further, future research interests were discussed. From the point view of the research advance, the automation, located monitoring of soil and water loss was put forward, and the simulation model for dual soil and water loss should be developed further in karst regions of southwest China. This could give a reference for quantitative assessment of the effects of land use change on soil and water conservation, and then provide service for the control of rock desertification.

Abstract:Soil and Water Assessment Tool (SWAT) model is a useful tool for long term hydrological simulation in large scale and complicated watersheds. SWAT model has been widely used in research of hydrological cycle, soil erosion, pollution loads, and impact of climate and land use change. This model has achieved good simulation results, but the uncertainty is widespread. From the perspective of the model user, this paper discussed the main sources of uncertainty through the three important steps in using SWAT model, including input data preparation, sub-watershed delineation and data scale transformation, and model calibration. Input data with insufficient precision is one of the main uncertainty sources, owing to its inability to represent the spatial variability. Insufficient precision of sub-watershed delineation would cause over-lump of parameters during scale transformation, thus cause simulation errors. In calibration process, uncertainty is mainly induced by usage of inappropriate observation and evaluation index, and equifinality. A group of measures is suggested to reduce modeling uncertainties. Increasing resolution of input data and precision of watershed delineation to a certain threshold would reduce input uncertainty. Localization of key parameters and simulation functions based on local literature and expert knowledge can effectively reduce equifinality. And using multiple evaluation indices, automatic calibration combined with manual calibration, and calibration multi factors and multi stations can limit calibration uncertainty. Grasping the possible uncertainty sources of the main steps during the model applying, taking corresponding measures to reduce uncertainty according to the study area’s specific characteristics and research goals, is the necessary way to improve the credibility of the simulation results of SWAT model.

Abstract:As one of the important parameters, sediment transport capacity must be considered when developing physical models of soil erosion. It is necessary to research on the concentrate flow sediment transport capacity for a better understanding of rill erosion mechanism and for control purpose. An indoor concentrate scouring experiment was carried out to investigate the concentrate flow sediment transport capacity under different flow rates and slopes. Loessal soil, a kind of typical soil in the Loess Plateau, was prepared for this research. The relations between sediment transport capacity and inflow rate, slope were analyzed, the regression of sediment transport capacity with inflow rate and slope and with unit discharge per unit width and slope were established, and the relations between runoff hydrodynamic characteristics and sediment transport capacity were also analyzed. The results indicated sediment transport capacity increased with the increasing inflow rate and slope. Multivariate power function regression of sediment transport capacity with inflow rate and slope indicated slope was more influential on sediment transport capacity than that of inflow rate. However, unit discharge per unit width was more influential on sediment transport capacity than that of slope because of the flow convergence under steep slope. In general, all of runoff hydrodynamic characteristics can describe sediment transport capacity well, and the optimal factor in our research was stream power as it had the largest determination coefficient. The results provide valuable information for a better understanding of the sediment transport capacity in concentrate flow on loess hillslope.

Abstract:Clarifying the runoff and sediment in runoff plot under different soil and water loss control patterns plays an important role for large-scale soil and water loss. In this study, the runoff and sediment of red soil under three typical soil and water loss control patterns (S1 pattern: slope change ladder + Fruit trees, S2 pattern: contour trench and ridge + Crops, S3 pattern: flat wasteland slope + Herbs) were investigated through the field standard runoff areas under natural rainfall experiment in low hilly areas. The results showed that the average runoff volume under three control patterns was S3 (1.84?m3) > S1 (1.03?m3) > S2 pattern (0.78?m3), and the average sediment yield was S3 (1.191?t/hm2) > S1 (0.411?t/hm2) > S2 pattern (0.311?t/hm2). The cumulative runoff under the three control patterns was S3 (33.19, 15.25, 14.13?m3) > S1 (19.40, 9.06, 6.48?m3) > S2 pattern (16.60, 5.89, 4.15?m3) in the A, B, and C rainfall types (K-means clustering). The cumulative sediment also showed the similar trend that was S3 (14.474, 10.863, 15.153?t/hm2) > S1 (7.521, 2.695, 3.766?t/hm2) > S2 pattern (6.149, 1.685, 2.741?t/hm2). Different control patterns maintained a significant positive correlation between sediment yield had significant positive correlations with runoff volume under the tree control patterns (P<0.01, r > 0). The correlation coefficient (r) was 0.853, 0.920, and 0.677, respectively. Furthermore, the linear regression slope (k) of sediment yield and runoff volume was 0.356, 0.420 and 0.493, respectively under S1, S2, and S3 patterns, indicating the response degree of sediment to runoff in different control patterns was S3 > S2 > S1 pattern. Thus, three typical patterns have significantly different effects for controlling soil and water loss.

Abstract:Riparian vegetated filter strips (RVFS) are an efficient approach to reduce agricultural non-point source pollution transported in runoff before the water flows into watercourses. A field scale study was conducted in the upper reaches of Liaohe river for two years to determine the effect of vegetation types and the width on nitrogen and phosphorus retention in subsurface seepage. The experimental site consisted of three plots adjacent to agricultural edge (weeds-T1, sweet clover (Melilotus suaveolens L.)-T2 and sweet clover (Melilotus suaveolens L.)/China wingnut (Pterocarya stenoptera C. DC.)-T3). T2 and T3 were new established filter strips that were compared with weeds (T1). The results showed that all the RVFS did not significantly reduce the concentration of ground water nitrogen and phosphorus except for NH4+-N, The average interception efficiency was 18.03%~62.20%. The 13 m T3 had the best retention effect for NH4+-N which was 77.45%.T3 had the highest retention efficiency of TP and DP for 62.15% and 80.01% at the 13 m width. The overall T3 on the various forms of nitrogen and phosphorus retention effect is best, followed by melilotic belt. The plant vegetation filter on nitrogen and phosphorus accumulation capacity was Pterocarya stenoptera>Melilotus>weeds. Taking a harvest for sweet clover, the mount of nitrogen removed by the above-ground part varied in the range of 15.21~26.78 g/m2, and the phosphorus was in the range of 0.72~1.27 g/m2 .

Abstract:Five kinds of soil and water conservation measures in a typical red soil region in Changting County of Fujian Province were studied, the data of slope runoff, sediment yield and rare earth elements(REEs) migration were collected to reveal the benefits soil and water conservation measures on runoff and sediment reduction and rare earth migration resistance . The results showed that: (1) The average annual runoff reduction rates and the average annual sediment reduction rates of five kinds of soil and water conservation measures (the whole slope coverd by grass, closed forest, low-effect masson pine fertilization, mixture of trees with shrubs and herb, enrichment planting masson pine) were 65.41%, 69.29%, 63.42%, 86.19%, 72.59% and 91.87%, 84.21%, 81.54%, 94.13%, and 81.75%, respectively. (2) Under the rainfall, the REEs migration intensity of runoff and sediment were 85.13%, 94.86%, 66.89%, 95.46%, 93.10% and 89.92%, 80.38%, 70.18%, 93.38%, and 92.73% lower than those in control plot under five kinds of soil and water conservation measures, respectively, of which, the peak occurred in in moderate rain. (3) The LREE migration intensity of runoff were 55.68%, 40.38%, 85.76% and 85.94% lower than HREE migration intensity under five kinds of soil and water conservation measures except the whole slope covered by grass, and the HREE migration intensity of sediment were 82.29%, 81.25%, 78.38%, 75.35% and 77.05% lower than LREE migration intensity under 5 five kinds of soil and water conservation measures. In summary, five kinds of soil and water conservation measures have markedly benefits of runoff and sediment reduction and REE resistance, especially for of the mixture of trees with shrubs and herb. The results provide scientific basis and empirical support for making the best use the role of soil and water conservation measures applying in ecological restoration and rare earth migrations.

Abstract:To reveal the effects of soil surface roughness on sheet erosion, the changes of soil surface roughness on purple soils were studied during the whole growing stages of maize based on field artificial rainfall experiments, and the effects of soil surface roughness on runoff and sediment yield of sheet erosion process were analyzed. The results showed the soil surface roughness presented an increasing-first-and-then-decreasing trend with the advance of maize growing period under the rainfall intensity of 1.0 mm/min, and the maximum of increasing range appeared in maize seedling stage and the maximum of decreasing range appeared in mature stage. Under the rainfall intensity of 1.5 and 2.0 mm/min, the soil surface roughness presented a decreasing-first-and-then-increasing trend with the advance of maize growing period, and the changing range of soil surface roughness was the?greatest at the stage of maize seedling - jointing. Under the rainfall intensity of 1.0 mm/min, the changes of soil surface roughness presented a decreasing-first-and-then-increasing -and -decreasing trend, and these changeswere consistent with the changes of surface runoff under the rainfall intensity of 1.0 mm/min. At the stages of maize seedling-jointing and jointing-tasseling, the changes of soil surface roughness were consistent with the changes of surface runoff under the rainfall intensity of 1.5 and 2.0 mm/min, but inconsistent with the changes of surface runoff at the stage of maize tasseling- mature. At the stages of maize seedling and jointing, the changes of soil surface roughness showed the consistency with the changes of sediment yield intensity, however, they presented the opposite?changes in soil surface roughness and sediment yield intensity at the stages of maize tasseling and mature. In maize jointing stage, there was a very?significant negative relationship between the changing range of soil surface roughness and runoff amount, but a positive relationship between both in maize tasseling stage. In maize seedling, jointing and mature stage, there were the significant or very?significant positive relationships between the changed range of soil surface roughness and sediment yield amount, however, a very significant negative relationship in maize tasseling stage. These results would provide theory basis for posing the sheet erosion nature of soil surface roughness, and also serve for harnessing soil and water loss of the slope farmland.

Abstract:New reconstruction soil is in an unstable state, and just is the reconstruction of farming plots. In this paper, a field scouring experiment, designed as three scouring inflow rates (5, 15 and 30 L/min) and six different field widths (5,10,20,30,40,50 m), was conducted in farming reconstruction soil in hilly-mountainous region of Chongqing, in order to explore the characteristics of runoff and sediment and hydrodynamic parameters. The results showed: (1) During the scouring process, the trend of runoff rate was the fluctuated increasing period - stable development period. The trend of sediment yield rate was the fluctuated period – decrease - stable development period. (2) Hydrodynamic parameters, the mean rate values under the stable condition, and cumulative runoff and sediment yield increased with increasing scouring inflow rate. The effect of runoff and sediment yield and hydrodynamic parameters were different under different scouring inflow rates with different field width. The runoff and sediment yield fluctuated with the increase of field width. Under the scouring inflow rates of 30 and 15 L/min, the fluctuation was relatively large, and under the small scouring inflow rate (5 L/min), which was relatively slow. (3) The cumulative sediment yield increased with the increasing cumulative runoff yield, and there was a significant linear relationship between them (p<0.01). The sediment yield was affected by all hydrodynamic parameters, of which runoff power was the most important. The scouring inflow rate was positively related to the runoff and sediment yield and hydrodynamic parameters. The influence of field width was more complex, and the field width range of 20 and 30 m is the critical of new reconstructed soil erosion at slope 10°. In conclusion, the scouring inflow rate and slope width are both the driving forces of the new reconstructed soil erosion under farming plots reconstruction in hilly-mountainous region.

Abstract:The impacts of topsoil stripping on soil erosion and sediment yield and their characteristics were analyzed in karst slope by the simulated rainfall experiments. The “dualistic structure” of karst slope was simulated by a steel tank filled with soil and rock. An orthogonal test was conducted to study the characteristics of underground runoff yield and sediment yield in different underlying surface types (slope farmland, bare slope), different rainfall intensities (0.5, 0.8, 1.3 mm/min) and different degrees of underground hole (crack) (1%, 2%, 3%, 4%, 5%). The results showed that the changes of soil surface physical properties caused by topsoil stripping were the imperative affecting factors on the underground runoff and sediment yield variations. Underground runoff and sediment yield in slope farmland were mainly impacted by rainfall intensities, while the distribution ratios of runoff and sediment in the surface and underground were mainly influenced by different degrees of underground hole (crack). Topsoil stripping resulted in a significant increase in soil bulk density and fractal dimension, which made the soil water permeability, pore size and other soil physical properties change. When the rainfall intensity was 0.5mm/min, the underground runoff yield, runoff coefficient and sediment proportion in the bare slope were greater than those in the slope land, but when the rain intensity increased to 0.8 and 1.3 mm/min, the results were just reverse, the corresponding values in slope land were greater than the bare slope. The runoff and sediment yields in slope land with different rainfall intensities dwere 0.5 > 0.8 > 1.3 mm/min. However, the runoff yields in bare slope were 0.8 > 1.3 > 0.5 mm/min, and the sediment yields were 0.5 > 0.8 > 1.3 mm/min. The increased degree of underground pore fissure had a significantly (p<0.05) effect on increasing contribution of runoff and sediment yield of slope. Under the degree of underground hole (crack) of 1%~3%, there was a significantly difference (p<0.01) between the underground erosion proportions in two slopes, but the difference diminished?gradually with the degree of underground hole (crack) increasing to 4% and 5%. It was worth noting that, although the amount of underground sediment yield of the bare slope was less than that of the slope land, the proportion of underground sediment yield of the bar slope was greater. It should be paid more attention to control the underground leakage where farmland was employed to development and construction in karst area. The results could provide great assistance and reference for further research and controlling water and soil erosion in the Karst region.

Abstract:Tillage practices, which change the soil surface structure, lead to different soil erosion characteristics on the tilled surfaces compared to the smooth surface. The objective of this study was to analyze soil and water loss on the tilled surfaces in rainfall-erosion processes based on the simulated rainfall experiments. Experiment results would be used for evaluating the soil and water conservation benefit of the projects of return steep slope land to forestry. Tillage practices in this study included shallow hoeing (SH), deep hoeing (DH) and contour ploughing (CP). A smooth surface (SS) was served as control measure. Rainfall intensities were 60, 90 and 120 mm/h and rainfall duration was 80 min for three rainfall intensities. Results showed that: （1) On the tilled steep slope, three tillage practices delayed the beginning of surface runoff during the rainfall of 60 and 90 mm/h intensities, but no significant difference was found in surface runoff initiation time between SH and SS, and between DH and SS during the rainfall of 120 mm/h intensity; （2) The cumulative production flow of CP was lower than the SS under three rainfall intensities, but no obvious regularity in size of the cumulative production flow for SH and DH treatments compared with SS; （3) In rainfall of 120 mm/h intensity, the flow sediment concentration of slope with tillage practices was higher than SS, leading soil sediment from three tilled slopes was 2 ~ 5 times of SS. Therefore, on the tilled and bare steep slope, when the rainfall intensity is larger, the tillage practices not only fail to reduce soil erosion, instead will increase.

Abstract:The sediment characteristics of slope runoff are of great importance to study the slope surface erosion and sediment yield. In order to study the sediment characteristics and the dynamic processes of slope runoff, and to reveal the composite relations between sediment concentrations of slope runoff and the slope length and rainfall intensity, the artificial rainfall simulation were adopted based on the different combinations of slope length and rainfall intensity. The comprehensive analyses were used to analyze the monitoring data of 5 slope lengths (1, 2, 3, 4, 5 m) with 13 rainfall intensities under a designed slope (20°). The results showed that: (1) Under the different slope length, the correlations between sediment concentrations and the rainfall intensities were different. The increases of sediment concentrations were the most obvious with the increasing rainfall intensities in the slope length of 2, 3, 4 m, but the least in 5m. The linear correlation between sediment concentration of slope runoff and the rainfall intensity was better in the 1 m slope length, but its increasing slope was small. Thus, the slope length of 3m was the most suitable for studying the changes of sediment concentrations with different rainfall intensities. (2) The sediment concentrations of slope runoff decreased undulately with the duration of production flow. The fluctuating characteristic value of the sediment concentration was small and the fluctuating frequency was large in the slopes length of 2, 3 and 4 m, while with a large concentration and a small frequency in 1 m and 5 m slopes. The changing frequency of sediment concentrations of slope runoff was much higher than that in river flow. (3) There were significant correlations between the sediment concentrations of slope and the main hydrological elements and hydraulics characteristic parameters.The flow velocity, discharge and shear force were the important factors affecting the fluctuation of sediment concentrations. Because the starting velocity of sediment varies with different underlying surfaces, it is the key to measure the flow velocity and sediment concentrations timely, accurately and dynamically for the study of slope surface erosion and sediment yield processes.

Abstract:This study explored the effects of rainfall intensity and slope gradient on soil erosion and nutrient loss under two rainfall intensities (50 and 75 mm/h) and four slope gradients (5°,10°,15° and 20°) through simulated rainfall experiments. The results were as follows: (1) When the rainfall intensity increased from 50 mm/h to 75 mm/h on the same slope, the runoff yield time was advanced by 2.75 ~ 4.79 min. (2) On the same slope, with the increasing of rainfall intensity, the cumulative runoff and cumulative sediment yield increased by 12.53 ~ 15.80 mm/m2 and 0.47 ~ 3.61 kg/m2, respectively, and the increase ranges were 1.24 ~ 1.31 times and 0.77 ~ 2.90 times, respectively; there was a critical slope gradient in the process of slope erosion, and it was about 15°. (3) The loss of nitrogen in the runoff was dominant, and the amount of nitrogen loss in sediment was low, which accounted only for 1.4% ~ 9.7% of total nitrogen loss in runoff; when the slope gradient was low, the loss of phosphorus was mainly caused by runoff loss, while with the increasing of the slope gradient, it was mainly caused by sediment loss. (4) The concentration of total nitrogen loss in runoff had obvious linear positive correlation with runoff intensity, and there was a significant positive linear correlation between total nitrogen and total phosphorus loss and sediment yield rate.

Abstract:Eco-environmental vulnerability assessment for the ecological shelter zone was pivotal for protecting the water quality and maintaining the ecosystem of shelter zone in Three Gorges reservoir. By the aid of the fuzzy analytic hierarchy process and GIS & RS, this study performed an eco-environmental vulnerability assessment for the ecological shelter zone in Hubei province, and the main influencing factors were also analyzed. The main results were listed as follows: (1) The vulnerability of the ecological environment was mainly mild, moderate and potential vulnerability, accounting for 74.9% of the shelter zone area, which mainly located the middle part of Zigui and north part of Badong, and the 21.7% of the shelter zone was covered by the heavy vulnerability area which distributed in the southern part of Zigui and Yiling, middle and southern parts of Badong; (2) The heavy and very heavy ecological vulnerability areas mainly located in the area with the elevation lower than 800 m and the slope less than 25。, where the land was not well covered by vegetation but concentrated residence, and the anthropogenic activities was the main influencing factor on eco-environmental vulnerability; (3) Increasing the vegetation cover by constructing the agroforestry system, adopting afforestation and ecological restoration would be the effective treatments to decrease the eco-environmental vulnerability in this shelter zone.

Abstract:The ecological construction project is an important measure to control soil erosion and restore soil fertility in the Loess Plateau of China. It is of great importance to research the effects of ecological restoration measures (ie., returning farmland to forest and grassland?or terraces) on the soil organic carbon (SOC) and soil total nitrogen (TN), which helps to evaluate the carbon sequestration capacity and nitrogen fixation capacity and even the cycles of carbon and nitrogen accurately. In this study, soils were sampled in the typical small watershed with five different ecological construction types in Loess Hilly Region, to study the distribution of SOC and TN contents in different soil depths of 0—100 cm. Four land uses conversions included from sloping farmland into woodland, grassland, shrub land and terraces respectively. The results showed that both the land use changes and soil depth had significant effects on SOC and TN (P <0.01). The SOC and TN in woodland and shrub land were enriched in the 0—20 cm, whereas both of which were enriched in the 0—40 cm in grassland. In the terraced fields, the SOC were mostly enriched in the 0—20 cm, but no enrichment of TN was observed. Sloping farmland had no enrichment of SOC and TN. The SOC and TN contents and reserves would be increased after different ecological restoration measures. There were very significant correlations between SOC and TN in forest land and grassland, while the correlation was significant in shrub, and moderate in slope land and terraces. This study could provide a scientific basis for improving soil carbon and nitrogen prediction in the loess hilly region and promote a rational planning for regional ecological construction.

Abstract:In order to promote the quantitative study on mechanism of root-soil reinforcement, three kinds of common herbs including Paspalum notatum, Eremochloa ophiuroides and Bermudagrass were selected and artificially planted based on slope investigation and plants selection, and the direct shear test for remolded root-soil composite of these three herbs were designed and implemented on the basis of physical properties of undisturbed root-soil composite, such as dry density, moisture content and root content of quality in different depths. The results showed that: the shear strengths of three undisturbed root-soil composites rose gradually with the increasing of the root content under different vertical pressure; the cohesions and internal friction angles of three undisturbed root-soil composites decreased with the increasing of depth. Under the same condition, the effects of three plant roots on the cohesion were sorted as follows: Bermudagrass> P. notatum> E. ophiuroides，while the effects on the internal friction angle were sorted as follows: E. ophiuroides > P. notatum > Bermudagrass. The effects of plant roots system on shear strength were not only affected by plant species, but also related to the dry density and water content of soil, and the increase of dry density had a significant influences on the cohesion, but had little effect on the internal friction angle. The most suitable moisture content for the three kinds of disturbed root-soil composite was about 25%. It was difficult to explore the influences of the root content on the shear strength index in the direct shear test of remolded root-soil composite.

Abstract:In order to study the characteristics of slope runoff and sediment yield on the cone shaped engineering accumulation, a self-made platform was used to simulate the three-dimensional pyramidal engineering accumulation, and indoor artificially simulated rainfall experiments with different rainfall intensities (1.0, 1.5, 2.0 and 2.5 mm/min) were carried out. The heavy soil in Guanzhong area was used as test material, and different mass percentages of gravel (0, 10%, 20%, 30%, and 40%) were set. The results showed that: (1) The runoff rate and flow velocity increased rapidly first and then slowly increased to the stable with the time trend, the rainfall intensity and gravel content both had significance influence on runoff rate and flow velocity, and the rainfall intensity played a decisive role; (2) The mean runoff rate and flow velocity had very significant positive correlation with rainfall intensity and very significant negative correlation with gravel concentration; (3) When the rainfall intensity was 1.0 mm/min, the erosion rate first increased rapidly and then tended to be stable, when the rainfall intensity was greater than 1.5 mm/min the erosion rate showed a trend of continuous growth, while when the rainfall intensities were 2.0 and 2.5 mm/min, the erosion rate increased abruptly in the middle and late stages of rainfall; (4) The total amount of erosion showed an exponential increase trend with the increasing of rainfall intensity and a logarithm decrease trend with the increasing of gravel content.

Abstract:A series of simulated rainfall experiments were conducted to investigate the reducing effect of gravel cover on erosion of saline slope. The effects of gravel coverage on hydrodynamic characteristics of runoff and unit sediment load were analyzed under different slope gradients (15°and 30°) and rainfall intensities (92 and 119 mm/h). The cover rates of gravel were 0, 10%, 20%, 40%, 60% and 80%, respectively. The flow rate was measured by dyeing tracer method. Unit sediment load increased first and decreased then with the increasing of gravel coverage under different slopes and rain intensities. The changing tendency of Reynolds number and Froude number versus gravel coverage was determined by parabola curve. Manning roughness, Dracy-Weisbach resistance coefficient, the stream average shear force and the stream power had positive liner relationship with the gravel coverage. The stream power predicted sediment load rate well, and these two were logarithmic (R2=0.47).

Abstract:To determinate tillage erosion rate and hydraulic erosion rate of purple soil under different slope gradients, a series of simulated tillage experiments (5, 10, and 15 operation tillage) were conducted on 5°, 10°, and 20° slope farmlands, respectively. Then a series of scouring experiments with water discharge of 60 L/min were carried out on those slopes. Close-range photogrammetry technology was used to monitor the landform changes of purple slope farmland, and the high resolution digital elevation models (DEMs) were generated to calculate the net soil loss volume. Meanwhile, erosion pins were used to verify the accuracy of close-range photogrammetry technology by measuring the depth variation of soil layer, and the erosion rate and hydraulic erosion rate of purple slope farmland under different slope conditions were calculated. Results showed that the close-range photogrammetry technology was reliable and efficient to monitor landform changes and calculate the soil erosion rates. The calculated results of DEMs were similar to those of erosion pins. The average tillage erosion rates were 69.85, 131.45 and 155.34 t/(hm2·tillage pass) on 5°, 10° and 20° purple slope farmland, respectively, and tillage erosion rate showed an increase trend with the increasing of slope gradient, while it decreased with the increasing of tillage intensity. The average hydraulic erosion rates were 1 892.52, 2 961.76 and 4 405.93 t/(hm2·h) on 5°, 10° and 20° purple slope farmland, respectively. Hydraulic erosion rate was positively related to the slope gradient. Meanwhile, hydraulic erosion rate showed an increase trend with the increasing of tillage intensity, indicating that tillage erosion would accelerate the hydraulic erosion. These results could provide technical support and data foundation to the studies about soil erosion in purple slope farmland under tillage erosion and hydraulic erosion.

Abstract:To study the mechanical effect of shrub plants on slope protection and to investigate the friction characteristics of root-soil interface, the roots of Indigofera amblyantha were sliced and the root surface roughness of this kind of plant were calculated. In order to evaluate the influence of different root diameters, soil moisture content and soil particle size on friction characteristics of root-soil interface, pull-out friction tests and shear friction tests were conducted on the root - soil composites with the particle size of 0 ~ 0.5,0.5 ~ 1.0,1.0 ~ 1.5 and1.5 ~ 2.0 mm which prepared by sieving and remolding. The results showed that there was no significant difference in root surface roughness of I. amblyantha with the gradual increasing of root diameter, the pull-out shear stress of root system was concentrated in 17.36 ~ 32.76 kPa, and the friction coefficient of root-soil interface varied between 0.10 and 0.20. The pull-out shear stress of roots and the friction coefficient of root-soil interface in soil-root composites presented a downward trend with the increase of soil moisture content and soil particle size. When soil particle size and soil moisture content were small, the effects of root morphology on the pull-out shear stress of I. amblyantha roots and the friction coefficient of root-soil interface were more significant. These results were great guiding significance to analyze the influence factors of root-soil interface friction characteristics, and use shrub plants to improve the stability of slope soil structure and prevent soil erosion and other geological disasters.

Abstract:In this study, we used the direct shear apparatus to study the direct shear friction characteristics of root- soil interface under different soil moisture content in the Midwest of Inner Mongolia. Five kinds of typical local plant, including Caragana Korshinskii, Hippophae rhamnoides, Hedysarum fruticosum, Medicago sativa and Astragalus adsurgens, were selected as experiment plants. The results showed that friction coefficients of root-soil interface for the five plants were all higher than those of soil - soil interface when soil moisture content varied between 4.5% and 24.5%. And friction coefficients of root-soil interface and soil-soil interface both decreased with the increasing of soil moisture content. The friction coefficient of root-soil interface and cohesion of Hippophae rhamnoides were both greater than those of other four plants, and this indicated that the effect of Hippophae rhamnoides roots on soil erosion resistance was greater than the other four plants according to the interaction between root system and soil. The cohesions of root-soil interface and soil-soil interface all increased first and then decreased with the increasing of soil moisture content. For different plant species, the soil moisture content was different when the cohesion peak appeared.

Abstract:A series of tests on undistured dry soil and remoulded Malan loess were conducted by using improved ZC-2015 air permeameter. Gas permeability experiments analyzed the effects of soil volume, permeability diameter, dry density and sampling depth on air permeability (ka), and loess permeability was explained by the pore structure parameters, which were obtained by electron microscopy in SEM tests. The results showed that ka was not only a quantitative index of the gas seepage, but also was an important parameter that describing the pore and structure characteristics of unsaturated Malan loess. Due to the size effect in different soil volumes of loess, and their permeability increased with the increasing of volume of soil samples. In addition, ka decreased with the increasing of dry density and permeability diameter. Comparing the test results and the SEM photographs of three different types of Malan loess, and combined with the statistics of the pore structure parameters, we can conclude that ka has a certain regularity in area and depth. Regionally, the content of clay particles in the soil particles increased, while the total pore and macropore area decreased, and the effective seepage porosity decreased, and ka of remolded soil with the increase of soil depth has a little decrease.

Abstract:In order to seek the optimum tied-ridging tillage system with good controlling on soil erosion, and high utilization of precipitation in semi-arid area, a field experiment with a randomized complete block design was conducted on two slopes (5° and 10°) during alfalfa growing season. The experiment was designed to investigate the effects of different tillage systems (ridging without ties and tied-ridging) on soil water storage, plot runoff efficiency, runoff, sediment loss, alfalfa fodder yield and water use efficiency (WUE), and traditional planting (TP) was taken as control. On the 5°slope, compared with TP, average soil water storage, alfalfa fodder yields and the WUE for ridging without ties increased by 9.3 mm, 20.4% and 4.78 kg/(hm2·mm), respectively. The corresponding parameters for tied-ridging increased 15.0 mm, 8.9 % and 4.58 kg/(hm2·mm), respectively. Runoff and sediment loss on the same slope for ridging without ties decreased by 21.9% and 80.8%, respectively, while these two parameters of tied-ridging decreased by 41.2% and 83.3%. On the 10° slope, compared with TP, average soil water storages, alfalfa fodder yields and the WUE for ridging without ties and tied-ridging increased by 11.2 and 16.2 mm, 22.4% and 9.0%, 4.89 and 4.06 kg/(hm2·mm), respectively, while the runoffs and sediment losses of these two tillage systems ridging decreased by 24.8% and 36.4%, 74.5% and 82.0%, respectively. Average plot runoff efficiencies of TP, ridging without ties and tied-ridging were 11.6%~14.1%, 9.2%~10.0% and 6.7%~7.8%, respectively. Soil water storage in 5° slope increased by 4.3 mm compared with slope of 10°. The differences of net fodder yield, actual fodder yield and WUE between 5° and 10° slopes were not distinct. The runoff, sediment loss and plot runoff efficiency of 10° slope were 1.2 times greater than those of 5° slope. Ridge-furrow rainwater harvesting was good on water and soil conservation, and fodder yield increasing. Tied-ridging was particularly effective for water and soil conservation, while ridging without ties was particularly effective for increasing of fodder yield.

Abstract:Through indoor infiltration of clean water film hole irrigation and four different silt contend and four clay and sand grade of infiltration of muddy water film hole irrigation tests under the same condition, the influence of infiltration characteristics of muddy water film hole irrigation under different silt contend and clay and sand grades was studied. In the study eight different kind of muddy water were configured, four of them were different in clay and sand grades, but had the same silt content of 5%, and others were different in silt content that respectively by 2%, 5%, 7% and 9%. Soil dry density was 1.40 g/cm3. The effects of silt content and clay and sand grade on freedom infiltration characteristics of muddy water film hole irrigation were examined. Considering the combination of silt content and clay and sand grades, the concept of relative clay content was proved. Based on the concept above, the model involved film hole cumulative infiltration volume, horizontal wetting front movement and vertical wetting front movement was established, and we also found that the model had high precision. Further, the mathematical model of irrigation uniformity analysis under the free infiltration of muddy water film hole irrigation was put forward. The findings provide a theoretical foundation for further study of muddy water film hole irrigation, and technical support for the practical production and application of muddy water film hole irrigation.

Abstract:Aiming at the problems such as poor effect of water and nutrient retention, instability and leakage in barren gravel land at the northern foot of Qinling Mountain, raw soil in Shaanxi Province was chosen as the tested soil to study the characteristics of water and nutrient leakage in topsoil with different structure. By filling the soil column hierarchically with different bulk density, five kinds of topsoil structure were set to analyze the leakage characteristics of water and nutrient in the artificial plough layer. The results showed that: (1) The initial leakage ability and the attenuation degree showed a negative correlation relationship with the underlying soil bulk density, and the infiltration process could be simulated by the modified Kostiakov infiltration empirical formula; (2) The underlying soil bulk density greatly affected the cumulative amount of leakage, water leakage rate and nutrient loss amount, and they showed negative correlation relationships; (3) From the perspective of the total nutrients leakage amount, there was an optimal structure of topsoil, which had the best effect of retaining fertilizer. By analyzing the leakage of water and nutrient comprehensively, the optimal structure of topsoil was that the bulk densities of the soil layers from the bottom to up were 1.5, 1.3 and 1.2 g/cm3, respectively.

Abstract:In order to explore the relationships between soil splash erosion and water repellency, three types of soils (yellow cinnamon soil, brown-red soil, latosolic red soil) under different land uses (cultivated land, forest land, waste land) were selected to investigate the variations of soil water repellency (SWR) and its effect on soil splash erosion. Main results are shown as follows: (1) The SWR was the lowest for the arable soil among the studied three land uses, and it was higher in the surface soil layers than in the subsurface. Among all test soils, the SWR was largest for the cinnamon soil (13.15 sec). The SWR was significantly affected by soil mechanical composition and free iron aluminum oxides (R2 < -0.40, p < 0.01). (2) Soil splash erosion rate generally increased initially, and then decreased. The relationship between the cumulative splash amount and rainfall duration could be well fitted by the logarithmic function model. (3) The SWR had a significant positive effect on splash erosion under a certain range of rain intensity, also showing a logarithmic function (R2 ≥ 0.90, p < 0.01). These findings could provide theoretical reference basis for rainfall erosion mechanism research and erosion process model.

Abstract:The study about the temporal and spatial variation characteristics of rainfall and rainfall erosivity and theirs causes was significant to monitor, evaluate, forecast and govern local soil erosion. The Wei River basin, a typical arid and semi-arid area in China, was selected as a case study. The change trends of rainfall and rainfall erosivity were analyzed by Mann-Kendall test. The heuristic segmentation algorithm was employed to detect the mutation points of the rainfall and rainfall erosivity in the Wei River basin. The cross-wave analysis method was used to explore the relationship between ENSO (El Ni?o-Southern Oscillation), Arctic Oscillation, Sunspot and rainfall as well as rainfall erosivity. Results indicated that:(1) Rainfall and rainfall erosivity both showed downward trends; (2) There were change points in the rainfall series at Huashan and Xiji stations, and change points in the rainfall erosivity series at Huashan and Lintao stations, and these change points implied that the consistency of rainfall amound and intensity at some stations in the Weihe River Basin was destroyed; (3) All of ENSO, Arctic Oscillation and Sunspot variations showed strong impacts on the rainfall and rainfall erosivity variations, and the impacts followed the order of Sunspot > ENSO > Arctic Oscillation. The results would be helpful to guide the agricultural production, the construction of soil and water conservation and ecological restoration of the Weihe River basin.

Abstract:The effects of continuous straw returning and no-tillage on soil aggregate stability and contents of soil organic carbon (SOC) in topsoil (0 - 20 cm) and sub-surface soil (20 - 40 cm) were studied in paddy fields of subtropical China. Soil samples were collected from 8-year experimental field located in Wuxue city, Hubei province. Four treatments including conventional tillage (CT), straw returning with conventional tillage (CTS), no-tillage (NT) and straw returning with no-tillage (NTS), were designed. The results showed that CTS, NT and NTS treatments significantly increased the contents of water-stable aggregates greater than 5 mm and the mean weight diameters (MWD) of water-stable aggregates in the 0 - 20 cm soil layer, and straw returning significantly increased MWD of water-stable aggregates in the 20 - 40 cm layer. Compared with CT, the treatments of CTS, NT and NTS significantly increased the contents of SOC by 20.83%, 21.98% and 32.76%, respectively. In addition, CTS and NTS significantly increased the SOC contents in aggregates those > 5, 5 ~ 2 and <0.25 mm in diameter, and NT treatment significantly increased the SOC contents in the aggregates with diameter of >5 and 5 ~ 2 mm in the 0 - 20 cm soil layer. Meanwhile, the CTS treatment significantly increased the SOC contents of the aggregates greater than 0.25 mm in the 20 - 40 cm soil layers. Straw returning increased contents of carbon (C), hydrogen (H), nitrogen (N) and oxygen (O) in topsoil. In topsoil, no-tillage reduced the content of H, increased the contents of other three elements, but this treatment increased H content in sub-surface soil. Compared with the treatments of CT and CTS, the H/C ratios were reduced under NT and NTS treatments, indicating that the aliphatic components of soil were increasing. The contents of alcohol, phenol, aromatic, aliphatic compounds and carbohydrates in soil increased under straw returning treatment, while the no-tillage mainly increased the contents of aliphatic compounds. The increase of these organic components contributed to enhancement of aggregate stability.

Abstract:In order to study the spatial and temporal distribution of soil organic carbon in wetland under different disturbance levels, we selected four study areas disturbed with different levels (Huanghekou station, Yiqianer station, Dongying port and Wuhaozhang) in the Yellow River Delta to investigate the organic carbon content, organic carbon density and organic carbon storage of different vegetation communities. The results showed that organic carbon content, organic carbon density and organic carbon storage in Yiqianer station, Dongying port, Wuhaozhuang and Huanghekou station were 3.504, 3.433, 3.698 and 3.815 g/kg, 4.84, 4.58, 5.02 and 5.56 kg/m2, and 4237.00, 3807.42, 4272.77 and 4917.63 t/km2, respectively, in May, while the parameters for the four study areas in August were 3.90, 3.63, 3.45 and 3.62 g/kg, 5.32, 4.83, 4.46 and 5.25 kg/m2, and 4588.02, 4010.10, 3614.95 and 4623.12 t/km2. The organic carbon content, organic carbon density and organic carbon storage per unit area were smaller in Dongying port and Wuhaozhuang with strong disturbance. The organic carbon contents of bare flats were lower than those of wetlands with vegetation. The organic carbon content and organic carbon density of Spartina alterniflora wetlands were higher than those of other wetlands in May, while in August the organic carbon storage per unit area of Phragmites australis wetland in Huanghekou station and Yiqianer station were higher than those of S. alterniflora wetlands. Human activities had great influence on organic carbon content, organic carbon density and organic carbon storage of costal wetland, and protecting integrity of wetland played an important role in reducing carbon emission and maintaining the carbon sink function of coastal wetlands.

Abstract:The macro-aggregates content (R0.25), mean weight diameter (MWD), geometric mean diameter (GMD), the percentage of aggregate destruction (PAD) and contribution rates of aggregates to organic carbon (F), which were selected to analyze the effects of different age of alpine desertification land planted branchy tamarisk on soil aggregates stability and organic carbon distribution in northwestern Sichuan. The results showed that soil mechanical stability aggregates and water-stable aggregates were mainly composed of micro-aggregates (<0.25 mm) in different restoration years of branchy tamarisk restoration pattern. With the increase of recovery period, soil surface (0—20 cm) >2, 0.5~2 mm aggregates increased significantly, and the ranking of R0.25, MWD and GMD from low to high was:0 year <5 years <10 years <15 years, while PAD presented opposite trends. The planting of branchy tamarisk caused a significant increase in soil organic carbon content in the surface layer (0—20 cm). With the increase of recovery period, organic carbon content of >2, 0.5~2 mm aggregates increased significantly, and the contribution rates of >0.5 mm aggregates to soil organic carbon was 34%~60%. The effect of planting of branchy tamarisk to soil aggregates and organic carbon on sub-surface layer (20—40 cm) was not significant. The results indicated that soil aggregates stability and organic carbon can be used as the adaptable index of soil ecological restoration in northwestern Sichuan, and the planting of branchy tamarisk has an important effect on improvement of desertification soil.

Abstract:In order to study the effects of soil freezing and thawing process on carbon and nitrogen turnover in spring, the contents of microbial biomass carbon (MC), microbial biomass nitrogen (MN), soluble organic carbon (DOC) and nitrogen (DON) in two kinds of forest soil in Changbai Mountain area during spring thawing were measured and analyzed through continuous sampling in situ culture. The results showed that: during the soil thawing process, the temporal variations of MC and MN were different in the two types of soil, moreover the MC and MN showed obvious vertical spatial heterogeneity, and MN content in 0 - 10 cm soil layer was significantly higher than that in 10 - 20 cm soil layer. Except for individual periods, MC content in 0 - 10 cm soil layer was also significantly higher than that in 10 - 20 cm soil layer. During thawing process, the DOC content dynamics in 0 - 10 cm soil layers were basically the same in two types of soil, but the maximum DOC release in 10 - 20 cm soil layer presented earlier in Korean pine broad-leaved forest than that in Secondary birch forest. The DOC releases of the two forest types were both concentrated in the middle and late stages of thawing. During the thawing period, the temporal dynamic changes of DON in two forest types were consistent, and the maximum DON release occurred in the late stage of thawing. There were obvious vertical spatial distribution characteristics for DON content in two forest types during thawing period, and the content of DON in 0 - 10 cm soil layer was significantly higher than that in 10 - 20 cm layer.

Abstract:To evaluate the water conservation function of ecological system in Mount Tumor Nature Reserve, we selected the upstream of the Tailan River as the study area to quantitatively analyze the water conservation capacities of typical Picea schrenkiana forest, shrub woodland and grassland by using the combined method of field observation and laboratory experiments. The water conservation capacities in three layers including the forest canopy, litter layer and the soil layer, as well as the comprehensive capacity were analyzed. The result showed that the canopy interception capacity of Picea schrenkiana forest was greater than that of the shrub woodland in the study area, and the average throughfall and canopy interception were both greater than those of the shrub woodland. The average thickness of undecomposed layer was higher than that of semi decomposed layer in all kinds of vegetation, and the thickness and volume of litter layer in Picea schrenkiana forest were significantly greater than those in the shrub woodland. In all three types of vegetation, the natural and maximum water holding capacities of the semi decomposed layers were all higher than those of the undecomposed layers, and the natural and maximum water holding capacities of litter layer in Picea schrenkiana forest were both higher than those in the shrub woodland. The modified interception amounts of undecomposed layer were higher than those of semi decomposed layer in Picea schrenkiana forest and the shrub woodland. The average soil bulk density of different vegetation types followed the order of grassland > shrub woodland > Picea schrenkiana forest, while the order of soil porosity mean value was opposite; the natural moisture content, saturated water content and non-capillary water holding capacity of different vegetation types followed the order of Picea schrenkiana forest > shrub woodland > grassland, but the water storage capacity of soil layer deeper than 30 cm varied among different vegetation types. The water conservation capacities of different vegetation types were 181.06 ~ 237.63 mm, and the comprehensive and effective water conservation capacities both listed in the order of Picea schrenkiana forest > shrub > grassland. The soil layer contributed greatest in water conservation, and the total effective storage capacity was far less than the total water. In summary, Picea schrenkiana forest and shrub woodland in the study area had better water conservation ability. Grazing intensity and human disturbance were the important factors that affected the water conservation function of different vegetation types in the study area, especially for vulnerable grassland.

Abstract:In order to further research the application of γ-PGA in agriculture, different contents of γ-PGA (0, 0.1%, 0.2%, 0.5% and 1%) were applied in sandy loam and silty loam without granular structure to study the effects of γ-PGA on soil physical structure and water retention characteristics. Results showed that: with the increasing of γ-PGA content, water retention capacity of soil increased under the same absorption force. Values of α in the VG model were all larger than those in the control group, and n value decreased progressively. When the content of γ-PGA increased to 1%, the bulk density of sandy loam decreased by 0.087 g/cm3, and the porosity increased by 3.28%; corresponding parameters of silty loam were 0.108 g/cm3 and 4.08%, respectively. The addition of γ-PGA reduced the proportion of capillary pore, and increased the proportion of invalid pore, indicating that effect of γ-PGA on the physical characteristic of silty loam were greater than those of sandy loam. Power function positive correlation existed between the saturation moisture content and the γ-PGA content, while negative correlation existed between the saturation diffusion rate and the γ-PGA content. The relative error between the saturation diffusion rates calculated by parameters of VG model and horizontal infiltration method was smaller than 10% in silty loam. Except for the wilting coefficient, γ-PGA had significant effects on other soil water constants, wherein the constants increased with the increasing of γ-PGA content. In the soil, proportions of film water and capillary water increased, whereas the proportion of gravitational water decreased significantly. When the γ-PGA content was 1%, the proportion of available water was 64.83% in silty loam, whereas the value was only 56.14% in sandy loam. Adding γ-PGA was beneficial to improve pore distribution in soil and water retention capacity, and prevent deep seepage of soil moisture.

Abstract:To investigate the characteristics of soil phosphorus forms in Phyllostachys praecox stands, samples of upper (0-20 cm) and lower (20-40 cm) soil layers were collected from fractions which were intensively managed for 3, 9 and 15 years, respectively. The soil physo-chemical properties such as pH, soil organic carbon (SOC), total phosphorus (TP), Olsen P, and Mehlich-3 P were determined. Additionally, the concentrations of different phosphorus fractions were measured with modified Hedley’s sequential extraction procedures. The results showed that the pH of top soil significantly decreased in the 9- and 15-year intensive management plots where acidifications of subsurface soil were observed. The SOC mainly accumulated in the top soil layer, and the highest SOC content was observed in the 15-year intensive management stands, which increased by 183% compared to the 3-year intensive management plots. Moreover, the contents of TP, Olsen P, Mehlich-3 P, labile P (H2O-P+NaHCO3-Pi+NaHCO3-Po) and moderately labile P (NaOH-Pi+NaOH-Po) in both soil layers all increased with the prolonging of plantation time. Compared with the 3-year intensive management plots, the proportion of labile P and moderately labile P in the 15-year intensive management stands increased by 63% and 83% for topsoil layer, and 88% and 128% for the lower soil layer, respectively, however, the proportions of sparingly labile P (HCl-P+Res-P) decreased from 58% to 26% for topsoil layer and from 66% to 29% for lower soil layer, respectively, whereas the contents of sparingly labile P had no significant difference between these two treatments. Thus, applied phosphorus fertilizer was mainly built up in the labile P and moderately labile P fractions under the P. praecox stands. According to the Mehlich-3 P-H2O-P linear equation, we could speculate that phosphorus loss may have occurred in both soil layers. Therefore, fertilization should be properly managed in P. praecox stands to avoid excessive phosphorus loss.

Abstract:Apple replant disease (ARD) is a major factor that restricted the sustainable development of apple industry. In this study, the apple plant seedling biomass, root repiration rates, soil enzyme activities and soil environments under different phosphorus levels in continues cropping soil were determined to reveal the effect of biochar combined with phosphorus fertilizer on the control of ARD and select suitable amount of phosphate fertilizer, so as to provide theoretical basis for the renewal of old orchard and the prevention and control of ARD. Pot experiments including six treatments, which were the control (CK), methyl bromide sterilization (F), 2% biochar (B ), 2% biochar + 0.5‰ phosphate fertilizer (BP0.5), 2% biochar + 1‰ phosphate fertilizer (BP1) and 2% biochar + 2‰ phosphate fertilizer (BP2), were carried out. The biomass and root respiration rate of Malus hupehensis Rehd. seedlings, soil nutrient and soil enzyme activity were measured by conventional methods. The results showed that methyl bromide sterilization treatment increased heights, ground diameters as well as fresh and dry weights of seedlings, which were 1.6, 1.5, 2.9 and 2.5 times of the seedlings in the control, respectively. The root respiratory rates and activities of protective enzymes in the F treatment were all higher than those in the control or other treatments. The treatments of B and BP0.5 both significantly enhanced heights, ground diameters, fresh and dry weights of seedlings, which were 1.2, 1.1, 1.6, 1.4 and 1.4, 1.2, 2.2 and 1.9 times of the seedlings in the control, respectively. The root respiration rates increased significantly in the treatments of B and BP 0.5. Biochar combined with 0.5‰ phosphate fertilizer improved the activities of SOD, POD and CAT, and decreased the content of MDA in the seedling roots. Compared with the control, biochar combined with 0.5‰ phosphate fertilizer significantly improved the content of organic matter in soil, increased the contents of nitrate nitrogen and available phosphorus, and promoted the activities of urease, sucrase and phosphatase in soil. In conclusion, compared to the single application of biochar, application biochar combined with phosphate fertilizer could improve the development of M. hupehensis seedlings under continues cropping, increase soil organic matter content, enhance soil enzyme activity. Therefore, the integrated measures of biochar and phosphate fertilizer can better prevent and control ARD.

Abstract:To find optimum application rate of nitrogen under drip irrigation in the semi-arid region of Jilin province, two years (2015 - 2016) field experiments were conducted in spring maize fields mulched with plastic film to study the effects of different nitrogen application rates (0, 70, 140, 210, 280 and 350 kg/hm2) on yield, nitrogen absorption and utilization, inorganic nitrogen accumulation in soil profile (0 - 200 cm) and nitrogen balance under drip irrigation. The results indicated that maize yield increased with the increase of nitrogen application rate when the nitrogen application rate was in the range of 70 ~ 210 kg/hm2, and no significant difference was found among treatments when the nitrogen application rate was over 210kg/hm2. Based on the fitting model between maize yield and nitrogen application rate, the optimal parameter was 195.1 and 201.0 kg/hm2, respectively. Nitrogen application significantly increased nitrogen accumulation at different growth stages of maize, and the highest nitrogen accumulation showed in the treatment supplied with 210 kg/hm2 of nitrogen at the grain filling stage and the mature stage. Recovery efficiency, agronomic efficiency and partial factor productivity of nitrogen all decreased with the increasing of it application rate. At the mature stage of maize, NO3--N and NH4+-N contents both gradually reduced with the increasing depth of soil profiles (0 - 200 cm). Compared with the control, NO3--N and NH4+-N contents of 0 - 200 cm soil layers were both increased in treatments applied with nitrogen, and NO3--N contents of 40 - 200 cm soil layers in treatments supplied with 280 and 350 kg/hm2 of nitrogen were significant higher than those in other treatments. Nitrogen absorption of maize , soil inorganic nitrogen accumulation and nitrogen apparent loss were positively correlated with the nitrogen application rate, and they accounted for 21.6% ~ 23.3%, 33.0% ~ 37.4% and 41.0% ~ 43.7% of the nitrogen input. Under the experimental conditions, according to the comprehensive yield, nitrogen absorption and utilization, soil inorganic nitrogen content and nitrogen balance and other factors, the appropriate amount of nitrogen fertilizer for spring maize should be controlled at 195 ~ 210 kg/hm2 under drip irrigation with plastic mulching in the semi-arid region of Jilin province.

Abstract:In order to provide the basis for the application and popularization of control-release urea (CRU) in fresh edible maize, field experiments were conducted to study the effects of CRU applied in different depth (0, 5, 10 and 15 cm) on yield, dry matter accumulation, nitrogen utilization efficiency of fresh edible maize and inorganic nitrogen content in soil. The results showed that different application depth of CRU mainly affected the dry matter accumulation during the periods of tasseling to harvesting, moreover fertilizing CRU in 10 cm and 15 cm depth produced significant greater dry weight than fertilizing in 0 cm and 5 cm depth. Fresh ear yield, total nitrogen uptake of plants during milk ripening period, partial factor productivity (PFP), agronomic efficiency (AE) and apparent recovery efficiency (RE) of nitrogenous fertilizer all increased with the increasing of CRU application depth. Compared with fertilizing in 0 cm, fertilizing CRU in 5 cm depth had no effect on fresh ear yield, total nitrogen uptake, PFP, AE and RE of nitrogenous fertilizer. Fertilizing CRU in 10 cm depth significantly increased total nitrogen uptake and RE. However, fertilizing CRU in 15 cm depth significantly increased fresh ear yield and total nitrogen uptake by 13.3% and 53.0%, respectively, and increased PFP from 70.9 kg/kg to 80.4 kg/kg, increased AE from 6.8 kg/kg to 16.3 kg/kg, and increased PE from 3.3% to 33.7%. The results of leaf photosynthetic characteristics determination during tasseling stage indicated that application of CRU could increase the leaf area per plant, leaf area index and the photosynthetic rate of ear leaf. Moreover, compared with the 0 cm fertilization, fertilizing CRU in 15 cm depth increased the leaf area per plant, leaf area index, photosynthetic rate, transpiration rate and intercellular CO2 concentration of ear leaf. The results of soil inorganic nitrogen test at key growth stages indicated that the increasing of CRU application depth significantly increased inorganic nitrogen content in 0 - 20 cm soil layer of fertilizer band at jointing, tasseling and harvest stages, and increased it in 20 - 40 cm soil layer of fertilizer band at tasseling and harvest stages, and increased it in 0 - 20 cm soil layer of non-fertilizer band at harvest stage. These results indicated that deep application of CRU could significantly improve the soil nitrogen supplying ability and leaf photosynthetic characteristics after tasseling stage, and promote dry matter accumulation and nitrogen absorption, and thus improve yield and nitrogen utilization efficiency of fresh edible maize. Under the conditions of this study, the optimal application depth of CRU was 15 cm for fresh edible maize.

Abstract:Fine root decomposition is the main source of soil organic matter and soil nutrients in grasslands. Fine root decomposition dynamics under the background of global nitrogen deposition plays an important role in carbon and nutrient cycling of terrestrial ecosystem. In this study, buried bag experiment was used to investigate fine root decomposition rate and nutrient release characteristics of three dominant grass species on the Loess Plateau, and their response to nitrogen deposition (10 g N /m2/a). The results showed that the decomposition process of fine roots could be divided into rapid (0~60 d) and slow (60~719 d) decomposition stages. The root mass residual rates of Stipa grandis, Stipa przewalskyi and Artemisia sacrorum were 86.3%, 86.2% and 90.7% on the 60th day, respectively, and they were 58.1%, 64.7% and 70.5% on the 719th day, respectively, indicating that the fine roots decomposition of S. grandis was the fastest and it of A. sacrorum was the lowest. Correlation analyses showed that the decomposition constant of fine roots was positively related with nitrogen content and N/P ratio, and negatively correlated with the carbon content and C /N ratio. During the fine root decomposition, the carbon transfer models of the three species were all direct releasing, and the nitrogen transfer models were enriching, and phosphorus exhibited enriching-releasing model, and all of them tended to decrease generally. Simulated nitrogen deposition suppressed the fine root decomposition rates of S. grandis, S. przewalskyi and A. sacrorum, with the decomposition constants decreased by 21.3%, 26.8% and 47.4%, respectively. While, it increased the carbon remaining rates of S. grandis, S. przewalskyi and A. sacrorum by 26.8%, 20.7% and 16.6%, respectively, and increased nitrogen remaining rates by 18.2%, 17.0% and 13.4% at the end of our study period. However, phosphorus remaining rates of fine roots in all three species were not significantly influenced by simulated nitrogen deposition. Nitrogen deposition in the future will inhibit the fine roots decomposition rates of the three dominant species in fenced grassland on the Loess Plateau, and slow down the process of inputting carbon and nitrogen from plant into soil.

Abstract:In order to find out the difference in absorbability of different aquatic plants on nitrogen (N) and phosphorus (P) existing in surface water, and even to explore its mechanism, the simulated ditch experiment and pot experiment were conducted using 8 different aquatic plants. And the plants with great difference on absorbing N and P were selected to make further exploration on root physiological characteristics and microbiological changes of sediment. The results showed that the concentrations of N and P in ditch water decreased significantly after planting aquatic plants, among 8 aquatic plants, the greater biomass was observed in Pontederia cordata, watermifoil, Sorbaria sorbifolia, Zizania and thalia dealbata, which could absorb more nutrients, resulting in consequently, the decreased nutrients in ditch water. Compared with the treatment of no aquatic plants, nutrient residual in ditch water decreased significantly, total N decreased by 22.4%~44.0%, ammonium nitrate decreased by 24.5%~36.8%, nitrate decreased by 13.6%~51.6%, total P decreased by 15.6%~34.6% and water-soluble P decreased by 26.3%~41.3%, respectively. Aquatic plants could absorb more nutrients was due to their stronger root activity, more xylem sap or higher SAP nutrient concentration. But these advantages could not exist in one specific aquatic plant, for example, Zizania had the stronger root activity, while the N and P concentrations in xylem sap were higher in watermifoil, Pontederia cordata and Sorbaria sorbifolia. In the ditch water planted aquatic plants, where the decreased proportions of N and P were larger, the total number of microorganisms, nitrobacteria and denitrifying bacteria, even the microbial biomass C, N and P were also higher, and vice versa.

Abstract:In order to fully evaluate nutrient availability of greenhouse soils under different irrigation treatments, field experiments were conducted to investigate the effects of drip irrigation, subsurface irrigation and furrow irrigation on the contents of organic matter, CEC, the composition and ratios of soil exchangeable bases in greenhouse. The results showed that the soil organic matter, CEC and exchangeable base ions were all higher in the surface soil layer under three irrigation treatments. The contents of soil organic matter and CEC of soils followed the order of subsurface irrigation > furrow irrigation > drip irrigation, the contents of exchangeable base ions were the highest under subsurface irrigation. Base ions saturations in 0-60 cm soil layer under three irrigation treatments all followed the order of Ca2+ > Mg2+ > K+ > Na+, saturations of Ca2+ and Mg2+ both increased with the increasing of soil depth. While the saturations of K+ and Na+ decreased first and then increased with the increasing of soil depth. Saturations of Ca2+ and Mg2+ in the 0 – 30 cm soil layer were higher under drip irrigation, while they in the 30 – 60 cm soil layer were higher under subsurface irrigation. Saturation of K+ was the highest under subsurface irrigation and the lowest under drip irrigation. The ratios of Ca/K and Mg/K were the highest under drip irrigation and the lowest under subsurface irrigation. According to the influence of different irrigation treatments on the composition and proportion of exchangeable bases in greenhouse soil, drip irrigation could not only save water and effectively provide nutrients, but also benefited to maintain a balance between nutrients, which was a more appropriate irrigation method in this study.

Abstract:Muddy water irrigation is the main feature of irrigation in the Yellow River irrigation area of the Yellow River Basin. The sediment content in muddy water has important impact on soil water infiltration. The muddy water and clean water film hole irrigation experiments were conducted to reveal the infiltration reduction characteristics of bilateral interference under muddy water film hole irrigation. The relationship between infiltration reduction rate of free infiltration under muddy water film hole irrigation compared to clean water and infiltration time, and the relationship between the infiltration reduction rate of bilateral interference under muddy water film hole irrigation compared to free infiltration and infiltration time had been established in this study. Then we proposed a model to reconstruct the infiltration volume of bilateral interference infiltration under film hole irrigation with muddy water by the infiltration volume of free infiltration under clean water film hole irrigation. The results showed that the infiltration reduction volume of free infiltration under muddy water irrigation compared with clean water increased with the increasing of infiltration time, but the increasing degree reduced gradually. The infiltration reduction volume increased linearly at the later stage of infiltration, and the infiltration reduction rate increased rapidly and then decreased slowly with the increasing of infiltration time. It maintained stable at the later stage of infiltration. The infiltration capacity reduced obviously when the intersection infiltration occurred. The infiltration reduction rates of bilateral interference infiltration and one-way intersection infiltration compared with free infiltration were both increased with the increasing of infiltration time. Compared with one-way intersection infiltration, the bilateral interference infiltration also had the effect of reducing infiltration. The change rates of three infiltration curves were decreased with the increasing of time.

Abstract:Based on the coupling characteristics of farmland water utilization and land resource development, this study sought to define the precision irrigation management zones in farmland according agent-based model for optimal land allocation (AgentLA) in Naoli River Basin, and then determined the farmland utilization area with key irrigation control. All the above analysis used the Landsat Satellite images for OLI sensor, the DEM data and the long-term sequenced meteorological data as fundamental data resources. Remote sensing and GIS technology were used to study quantitatively the water profit and loss of farmland, and finally AgentLA model was utilized to delineate the key farmland irrigation area. The results showed that by comparing with the conventional density division method, AgentLA model not only considered the water profit and loss of farmland, but also took into account the spatial morphological properties, and the key irrigation zones defined by this mode covered the target area suffered high water deficit, had high compactness as well, meanwhile avoided the key irrigation area and its spatial pattern too messy and broken to carry out daily irrigation management. The model running results showed that when the irrigation area of the farmlands was 20% in Naoli River Basin, 83.40% of farmlands with moderate water deficit, 99.86% of farmlands with severe water deficit, 0.71% of normal farmlands and all farmlands with serious water deficit needed to be controlled by irrigation in the future. This study results could be used as references and consultancies for precision irrigation management in the Naoli River Basin, and provide the basis for related scholars.

Abstract:To examine the physiological responses of Z. schneideriana seedlings to drought stress and to screen out the physiological indexes of drought resistance, a pot water control test was conducted. The drought resistance was also evaluated based on the membership function values. Two materials (Z.schneiderana ‘Hentiangao’and common Z.schneideriana grafted seedlings) were studied under three water conditions: light drought (LD), moderate drought (MD) and severe drought (SD). The results showed that with the increase of drought stress, the contents of the relative electric conductivity (Rec), malondialdehyde (MDA), water saturation deficit (WSD) and free proline (Pro) of the two testing materials were increased. And their peroxidase (POD) activity, superoxide dismutase (SOD) activity and chlorophyll (Chl) contents also increased with the changed drought stress, as a 'parabola' trend. The SS contents increased with the increase of drought stress for Z. schneideriana ‘Hentiangao’, but increased first and then decreased for Z. schneiderian. Principal component analysis based on 8 drought stress indexes hinted that Rec, MDA, WSD, Pro and POD had the close relationships with the drought resistance of Z.schneideriana, and could be used to evaluate its drought resistance. The calculated membership function values of the 8 physiological indexes and the comprehensive index from the principal component analysis indicted that the drought resistance of ‘Hentiangao’ (0.58) is stronger than the common Z. schneideriana’s (0.56). Considering the drought resistance of ‘Hentiangao’ is match with oriental arborvitae, it can meet the application requirements of urban landscape and highway greening from the point of drought resistance.

Abstract:The different cadmium (Cd) contaminated (1.0 and 10.0 mg/L) soils were simulated in laboratory. And the effects of fixed addition of biochar and zeolite (1:1) on soil pH and the changes of Cd morphology were studied. The addition amounts of the mixture were low (0.4%), medium (2%) and high (10%), respectively. Results showed that the values of pH were higher in the contaminated soil than the control, and increased with the increasing addition amount of mixture. With the increasing?incubation?time, the value of pH was gradually decreased in the lowly contaminated soil, whereas increased earlier, then decreased, and finally stable in the highly contaminated soil. In the late stages of incubation, the decreased percentages of effective Cd with the mixture addition of 2% and 10% were highest for the lowly contaminated and highly contaminated soil respectively, i.e. 56.78% and 27.33%. The exchangeable Cd percentage was gradually increased with the addition of biochar and zeolite mixture in soil. The percentages of exchangeable Cd were reduced by 8.35%, 13.81% and 20.65%, respectively, compared with the control soil in the lowly contaminated soil, and by 10.02%, 22.34% and 33.01%, respectively in the highly contaminated soil. The contents of exchangeable Cd could be reduced in soil with the passivation agent, through increasing the Cd contents of Carbonate bound, Fe-Mn oxide-bound, organic-bound and residual Cd. The Cd content of organic-bound Cd was higher in the lowly contaminated soil than the highly contaminated soil. Thus, the fixed addition of biochar and zeolite could reduce the bioavailability of heavy metals in soil, providing a theoretical foundation for farmland soil remediation.

Abstract:The pot and plot experiments were conducted to study the effects of intercropping on the remediation efficiency of Trifolium?repens plant under lead (Pd) contamination. Salvia splendens, Callistephus Chinensis and Iris germanica L. were intercropped with Trifolium?repens respectively to study the influences of different intercropping combinations on the growth of Trifolium?repens and Pd accumulation. The results showed that intercropping with Iris germanica L. improved the shoot biomass and the whole plant biomass of Trifolium?repens, but intercropping with Salvia splendens and Callistephus Chinensis reduced the shoot biomass and whole plant biomass compared with monoculture of repens. In the intercropping system, the total biomass of plants always fell in between the monoculture of two species. By intercropping with Salvia splendens, Callistephus Chinensis and Iris germanica L., all the Pd contents in shoots of Trifolium?repens increased, by 11.39%, 17.88% and 42.18% respectively compared with Trifolium?repens monoculture in pot experiment, and by 2.64%, 13.22% and 23.94% respectively in plot experiment. The total Pd accumulation in shoot of Trifolium?repens and Iris germanica L. intercropping system was higher than the monoculture of the two species respectively, and the other intercropping treatments were between the monoculture of the two species. In plot experiment the total Pd accumulation in shoots per unit area in Trifolium?repens and Iris germanica L. intercropping system was highest of all intercropping?patterns, which reached up to 242.777 mg/m2, improved by 371.83% and 8.38% respectively compared with the monoculture. The?removal?rates?of Pb in soil of Trifolium?repens and Iris germanica L. intercropping system were the highest of all intercropping?patterns, which reached up to 15.11%, improved by 326.84% and 10.70% respectively compared with the monoculture. Therefore, in terms of the whole restoration efficiency, the Trifolium?repens intercropping with Iris germanica L. performed the best，which could be used to enhance the remediation effect of Pd contaminated soil.

Abstract:The study object was the typical tree species of photinia leaves in Huainan, samples were collected from six different functional areas to analyze the distribution characteristics and sources of Cr, Ni, Cu, Pb and Zn in photinia leaves and their directive role in air pollution. The results showed that the average concentrations of Pb and Zn in leaves of commercial traffic area were significantly higher than those of park green land (P < 0.05), and even were 2.95 and 1.78 times of the park green space, respectively. The average concentration of Cu in leaves of coal transportation area was significantly higher than that of the residential area (P < 0.05) and park green (P < 0.05), and was 2.30 and 2.81 times of the residential and park areas, respectively. However, the differences of Ni and Cr in the different functional areas were not statistically significant. The Pb and Zn in photinia leaves mainly came from traffic emissions, Cu mainly came from coal mining, coal-fired power generation and transportation, Ni and Cr primarily from natural sources. There were significant correlations between the concentrations of Cu, Pb and Zn in leaves and the total contents of Cu, Pb and Zn in leaf dust, indicating that the concentrations of Cu, Pb and Zn in photinia leaves were significantly affected by their contents in leaf dust. The Cu, Pb and Zn in the photinia leaves were mainly absorbed from the atmosphere, while Ni and Cr from the soil. Thus, the monitoring of Cu, Pb and Zn in the atmosphere by photinia leaves could achieve good results for air pollution.

Abstract:Through the determination of soil physical and chemical properties and the major elements in soil water and rocks, the principal component multiple regression model was built to investigate the main influencing factors of major elements migration, and their contribution rates were calculated. The results showed that the Mg and Ca content at each soil monitoring points ranged 1 393.98 ~ 5 497.42 mg/kg, 880.47 ~ 3 133.43 mg/kg respectively, which were higher than K and Na, i.e., 498.58 ~ 3 315.42, 32.98 ~ 186.75 mg/kg, respectively. Soil CO2 concentration and soil temperature had the significant seasonal characteristics, which gave the higher values in summer and autumn than in winter and spring. Soil porosity decreased with the increasing depth, and the contents of HCO3- and Ca2+ in soil water were higher than other ions. The migration ability of main elements was Na > Ca > Mg > K, and the migration coefficients in summer of all elements were the highest. The factors with high contribution rate to major elements migration included precipitation, soil CO2 concentration, soil temperature and the content of anion in soil water, and their cumulative contribution rate reached up to 52.84% ~ 79.06%. The cumulative contribution rate of soil bulk density and the major elements content in soil and soil water was 22.98%, significantly lower than the aforementioned factors. The contribution rate of total soil porosity and aeration porosity were even lower, just 2.19% ~ 8.76%.

Abstract:To determine the appropriate drip irrigation mode for southern desert aged red jujube when changing flood irrigation into drip irrigation, the effect of different irrigation quotas (900, 1 050, 1 200 mm) and irrigation times (10, 14, 18) on soil salt distribution of 0-200 cm in the whole red jujube growth period and yield after using drip irrigation are examined using the two factor combination test design. The results showed that every process in the horizontal direction performed as follows: the soil salt content became higher with the increasing distance to the tree trunk, and the increased irrigation quota could increase the soil salt content remarkably in the 0-20 cm soil layer at 60 cm distance to the trunk; the increased irrigation frequency could reduce the soil salt content significantly in the 0-80 cm soil layer at 60 cm distance to the trunk. The soil salinity appeared as an“S”shaped distribution in the vertical direction, and an obvious accumulation phenomenon in the surface soil. Different irrigation quotas showed a low salinity zone (<2 g/kg) in the vertical direction, and the depth of the low salinity zone would increase with the increasing irrigation quota. Compared with the drip irrigation, the soil salinity of the flood irrigation was not changed much in the horizontal direction, and there was no obvious salt accumulation phenomenon. During the whole growth period, the soil salinity peak appeared in June of the new shoot period or July of the flowering stage. As for the 0-200 cm soil layer, the salt leaching effects of the irrigation treatment with 10 times and 1 200 mm and the treatment with 14 times and 900 mm were similar to the flood irrigation. The flood irrigation treatment was only obviously better than the drip irrigation in the 0-100 cm soil layer. The effect of irrigation times on soil salt content of 0-200 cm was weaker than the irrigation quotas. After changing into drip irrigation, neither the too low nor the too high irrigation quota was conducive to improve the yield of red jujube. Eighteen times and 1 050 mm irrigation showed a not only reasonably salt distribution but also the highest yield (7 549 kg/hm2) and water use efficiency, increased by 12.87% in yield and 30% in water saving compared with the other treatments. Thus, it can be used as the local drip irrigation regime of red jujube for the water-saving, high yield and high efficiency purpose.

Abstract:This study investigated the effects of different organic materials on soil fertility and crop nutrient absorption and utilization, so as to achieve farmland fertilization and improve crop nutrient use efficiency. A field fertilization experiment was conducted in Jiangxi Institute of Red Soil in 2015 to compare the effects of full scale chemical fertilizer and 40% of chemical fertilizer combined with different organic materials on soil fertility and crop nutrient use efficiency. Nine fertilization treatments were set in this experiment, including no fertilizer (CK), chemical fertilizer (CF), reduction of chemical fertilizer (RF), chemical fertilizer combined with straw (CFR), reduction of chemical fertilizer combined with straw (RFR), chemical fertilizer combined with biochar (CFB), reduction of chemical fertilizer combined with biochar (RFB), reduction of chemical fertilizer combined with pig manure (RFP), reduction of chemical fertilizer combined with vermicompost (RFV). The results showed that compared with the treatments of CF that added chemical fertilizer only, the application of organic materials increased the yields of rapeseed and sweet potato, and the yields in RFP and RFV treatments increased significantly, with an increase of 76.69% and 75.01%, 84.73% and 69.72%, respectively. The application of organic materials enhanced the content of organic matter, total nitrogen, total phosphorus, available phosphorus and potassium, and the soil nutrient level was also further improved under continuous fertilization. In sweet potato and rape seasons, compared with the CF treatment, the application of organic materials could promote the apparent recovery efficiencies and partial factor productivities of nitrogen and potassium fertilizers, and the effect of RFP treatment was best in sweet potato season, the corresponding parameters increased to 43.22%, 48.55% and 22.00 and 21.45 kg/kg respectively, however, the apparent recovery efficiency (1.91%) and partial factor productivity (3.25 kg/kg) of phosphorus in this treatment were low. In rape season, fertilizer contribution rate in the RFV treatment was the highest (80.41%), but the agronomic efficiency was low, which was just 0.67 kg/kg. Therefore, the application of organic materials can improve soil fertility, increase crop yield and the utilization of fertilizer nutrients, which is significance for agricultural production.

Abstract:Pot experiments with selenium-enriched soil were conducted to investigate the effects of moisture condition on selenium forms in soil and selenium accumulation in rice. The treatments included alternation of wetting and moderate drying (AWMD), alternation of wetting and severe drying (AWSD), conventional (C) and flooding (F) water management. The results showed that the rice grain yield was the highest in the AWMD treatment, 22.17% higher than that of the F treatment, and the difference between these two treatments was significant. The selenium contents in different parts of rice were in the order of root (0.411 ~ 0.695 mg/kg) > stem (0.214 ~ 0.378 mg/kg) > leaf (0.187 ~ 0.327 mg/kg) > shell (0.156 ~ 0.235 mg/kg) > grain (0.132 ~ 0.185 mg/kg) in all treatments. The selenium contents of grain and available selenium contents in soil both were the highest in the AWSD treatment, and the lowest in the F treatment，and the selenium contents of grain was significantly different between the two treatments. Significant or extremely significant positive correlations were found between the available selenium contents in soil and selenium contents in roots, stem, shell and grain of rice. The correlation coefficients were 0.939**, 0.896**, 0.793** and 0.723*, respectively. The selenium absorption coefficient in rice root was the highest in the AWSD treatment (0.438), and the lowest in F treatment (0.259), indicating that the dry and wet alternation enhanced selenium absorption capacity of rice. In summary, wetting and drying alternated irrigation could not only improve rice yield, but also increase selenium absorption of rice, and this kind of irrigation saved water than normal management. The overall performance of the AWMD treatment was the best.

Abstract:In order to solve the problems of low precipitation, inconsistency of rain season and water demand period for winter wheat, low and unstable yield in the dry highland of Loess Plateau, a 4-years field experiment was conducted to optimize the cultivation pattern of highyield and high efficiency in winter wheat production. In this study, the effects of residual plastic film mulching on rainfall reserving and soil moisture conservation in summer fallow period, and the effects of annual film mulching on yield and precipitation use efficiency of winter wheat were studied under three planting patterns, including uncovered and sowing in line (USL), ridge filming and sowing in furrow (RFSF) and whole field filming and hole sowing (WFFHS). The results showed that residual plastic film mulching in summer fallow period enhanced the capacity of rainfall reserving and soil moisture conservation. The water?storage?content in 2m depth of soil during fallow period were 12% ~ 22%（P<0.05）and 14% ~ 30%（P <0.05）greater in RFSF and WFFHS treatments than that in USL treatment, respectively, and the fallow efficiencies in these two treatments ranged from 29% to 42%, which were significant greater than that in USL treatment, meanwhile, the difference increased with the increasing of precipitation in summer fallow period. Compared with the USL treatment, the average yield in WFFHS treatment increased by 40%. Plastic film mulching improved the thousand-kernel weight and spike?number per?hectare of winter wheat, and there existed a?significant positive?correlation between grain yield and spike?number?per?hectare (r=0.830**), so plastic film mulching and reasonable population constructing were considered as the important measures to increase the yield of winter wheat in dry highland of Loess Plateau. The water production efficiency, precipitation production efficiency in fallow period and annual precipitation production efficiency of WFFHS treatment were the highest among all the treatments, which were 19.3, 9.3 and 11.7 kg/（hm2·mm）, respectively. The water consumption depth was more than 2 m during growth period of winter wheat, the water consumption under film mulching condition was greater than that of USL treatment, and furthermore, film mulching promoted the water consumption in soil layer deeper than?1 m. In a comprehensive consideration of grain yield and precipitation use efficiency, the whole field filming and hole sowing pattern combined with annual film mulching was the recommendable cultivation mode for winter wheat in the dry highland of Loess Plateau.

Abstract:A pot experiment was conducted for water control test of spring maize. Three water control levels (normal water supply, moderate drought, severe drought) and two periods (droughting, rewatering) were set up to research the effects of different degrees of drought stress and rewatering during seedling stage on light response curve, CO2 response curve, curve fitting parameters and antioxidant enzymes activities of spring maize. The results showed that the light radiation utilization capacity of spring maize leaves was decreased under drought stress. [1]Along with the increasing drought stress, maximum leaf net-photosynthetic rate (Pnmax), apparent quantum efficiency (AQY), light saturation point(LSP), the maximum electric transportation rate (Jmax), and even the maximum carboxylation rate (VCmax) of spring maize leaves were all decreased significantly, however, light compensation point (LCP), the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in leaves were apparently increased. After rewatering, the Pnmax, AQY, LSP, Jmax and VCmax under moderate drought stress in early stage were generally higher than those of normal water supply and moderate drought. However, the above parameters (except Jmax, VCmax ) under the severe drought did not reach the level of normal water supply, but higher than the severe drought. The SOD, POD and CAT activities had decreased, which still were higher than the normal water supply and drought level, and had a less decrement after severe drought stress. These results implied that a moderate drought hardening at the seedling stage could bring the higher antioxidant enzymes activities and remove the reactive oxygen species. Consequently, the reduced degree of membrane lipid peroxidation would make the membrane easier to be repaired after rewatering. These facts made the photosynthetic efficiency of the leaves produce a super-compensation effect. But after severe drought, the membrane repair was delayed, and the photosynthetic efficiency was just partially compensated. Hence, drought hardening should be limited in the level of medium drought for spring maize production in arid area northwest China, avoiding severe drought.

Abstract:Using peanut variety 606 as experimental material, five treatments including CK(no fertilizer application), JCF(applying common compound fertilizer at jointing stage), JCRF(applying controlled-release compound fertilizer at jointing stage), FCF(applying common compound fertilizer at flagging stage), FCRF(applying controlled-release compound fertilizer at flagging stage) were set under the same application rates of N-P2O5-K2O, to test the effects of different fertilizers and different application methods on chlorophyll content, chlorophyll fluorescence parameters of leaves, root system vigor, the nitrate reductase activity and antioxidant activity at different growth stages of peanut. The results showed that there was no significantly difference in Fv/Fm, Fv/Fo and ФPSⅡ between applying controlled-release compound fertilizer and applying common compound fertilizer before pod-setting stage, but the three parameters of applying controlled-release compound fertilizer were significantly higher than those of applying common compound fertilizer at pod-filling and mature stages. Trends of root vigor and nitrate reductase activity were similar with those of Fv/Fm, Fv/Fo and ФPSⅡ. There was no obvious difference in the contents of SOD, POD and APX between applying common compound fertilizer and applying controlled-release compound fertilizer at seedling stage, but these parameters of applying controlled-release compound fertilizer significantly increased at middle and later stage, while MDA content decreased, and topdressing fertilizer at flagging stage was better than that at jointing stage. Controlled-release compound fertilizer had no significant effect on wheat yield, but significantly increased the yield of peanut. The pod yield and kernel yield in the JCRF treatment were increased by 5.1% and 7.6%, respectively, compared with the JCF treatment, and the yields in the FCRF treatment were increased by 5.9% and 8.0%, respectively, compared with the FCF treatment. Under the conditions of same application rates of N-P2O5-K2O and equal nutrient, controlled-release compound fertilizer could meet the nutrient requirement of peanut at the later growth stage, improve the photosynthetic ability of mesophyll cell, enhance root vigor and nitrate reductase activity, and promote nutrient absorption capacity of root system. Meanwhile, controlled-release compound fertilizer could increase the ability of scavenging active oxygen at the late stage, help to delay leaf senescence, thereby improving yield of peanut. Two types of fertilizer both could increase yields of wheat and peanut, and topdressing fertilizer at flagging stage was the best , and the effect of topdressing fertilizer at jointing stage followed.

Abstract:In order to elucidate the advantage of bio-organic fertilizer to vegetable production, a pot experiment was carried out. The effects of two kinds bio-organic fertilizers on rape physiological metabolism, yield, and soil biological characteristics and nutrient content were studied through replacement of 10% to 30% chemical fertilizer with the same amount of the bio-organic fertilizers. Results showed that the bio-organic fertilizer, which was equivalent with the reduced chemical fertilizer, could promote rape growth, chlorophyll content and root activity. Meanwhile, the enhanced activities of antioxidant enzymes (SOD, POD, CAT) and reduced content of reactive oxygen species (MDA, O2? ?) indicated the increased photosynthetic performance and oxidation resistance. Compared with the conventional fertilization (100% chemical fertilizer), the rape yield increased by 4.60% to 24.55% in bio-organic fertilization. The population of soil bacteria and actinomycetes was significantly increased by 111.26% to 210.76% and 12.49% to 34.09%, respectively, but the number of fungi was decreased by 20.37% to 39.68%. With the partial absence of chemical fertilizer, the soil phosphatase, invertase and catalase activities were increased, but soil urease and dehydrogenase activities were decreased, resulting in the increased soil available nutrient and organic matter. The above results suggest that, application of bio-organic fertilizer with the partial absence chemical fertilizer can change soil enzyme activities and available nutrients by improving the number and structure of soil microbial community, and consequently, optimize the rhizosphere environment and increase the root activity and plant stress resistance and photosynthetic ability, finally, enrich soil and increase crop production.