Abstract:Nitrite-dependent anaerobic methane oxidation (N-DAMO) refers to a process of microbial physiology that allows methane to be oxidised to carbon dioxide with nitrite as electron acceptor. Although current researches on N-DAMO focus mainly on its importance to artificial environments, more and more evidence becomes available indicating that N-DAMO bacteria distribute extensively in a variety of natural ecosystems, such as rivers, lakes, wetlands and marine ecosystems, and confirming that N-DAMO process occurs in several natural ecosystems, which demonstrates that the N-DAMO process as a previously overlooked methane sink may play an important role in reducing global methane emissions. This review presents an introduction to classification of N-DAMO bacteria and mechanisms of their biochemical reactions, a summary of distribution characteristics and effect intensity of N-DAMO bacteria in various natural ecosystems, and analyses of major environmental factors that may affect distribution and role of N-DAMO bacteria in various natural ecosystems. In addition, the review also explores potential importance of the N-DAMO process as an overlooked methane sink in controlling emission of greenhouse gases.

Abstract:In order to make soil N management more scientific, N fertilizer application more reasonable and soil N utilization rate of crops higher in Jiangxi Province, spatio-temporal variation of total N in farmland soil of Jiangxi Province from 1985 to 2012 was analyzed by means of the Inverse Distance Weighted interpolation(IDW) method, overlay analysis method and Fisher statistical method in GIS technology based on the large volumes of soil samples collected during the second national soil survey and the project of soil-test-based formulated fertilization. According to the standard of the second national soil survey, total N contents in the farmland soils of Jiangxi have 6 grades, i.e., Grade 1 (>2.0 g kg^-1), Grade 2 (1.51 to 2 g kg-^-1), Grade 3 (1 to 1.5 g kg^-1), Grade 4 (0.76 to 1.0 g kg^-1), Grade 5 (0.51 to 0.75 g kg^-1) and Grade 6 (<0.5 g kg^-1). Soils in Grade1 and Grade 2 are regarded to be high, in Grade 3 and Grade 4, moderate and in Grade 5 and Grade 6, low in total N. Results show that total N contents in farmland soils varied sharply between soils in 11 cities and between soils of different types temporally and spatially in both 1985 and in 2012; and on average the farmland soils of the whole province were all 1 grade higher in 2012 than in 1985. The soils of the high total N level in Jiangxi were mainly distributed in the southern part of Poyang Lake Plain, basins along the Zhe-Gan Railway and Jitai basin in 1985, and more extensively in the whole Poyang Lake plain, basins along the Zhe-Gan Railway, Jitai basin and Ganzhou basin in 2012. In 1985 the soils in Pingxiang were the highest in total N content, in Jiujiang the lowest and in Ganzhou the highest in spatial variability of soil total N content, while in 2012. the soils in Xinyu were the highest in total N content, in Jiujiang the lowest, and in Jiujiang, the highest in spatial variability. Compared with 1985, 2012 was 7.24% higher in total N content in paddy soil and the growth was particularly obvious in soils of the high N level while the areas of the moderate and low levels decreased. The paddy soils the highest in total N content were in Pingxiang in both 1985 and 2012 and the paddy soils the lowest, in Ji'an, Ganzhou and Jiujiang, in 1985 and in Yingtan, Ganzhou and Jiujiang in 2012. Total N content in upland soils increased rapidly in 2012 or on average by 43.88% over that in 1985 and the area percentage of upland soils high in total N increased from 7.38% in 1985 to 88.16% in 2012.

Abstract:The probability of heavy metal potential risk is gradually increased with the development of industry, agriculture and urbanization. Early warning of heavy metal potential risk becomes one of the hot topics of the land environmental risk management. The methods and strategies for risk countermeasures of heavy metal pollution was developed in Beijing study area, and the prediction of variation trend and environmental quality risk was calculated for the next 30 years. In Beijing study area, input-output flux model and heavy metals accumulation rate model were established at town-wise units by taking into account the datasets acquired from the literatures, statistical yearbooks and field survey. Fluxes and accumulation of Cr, Ni, Zn, Hg, Cu, As, Cd and Pb were calculated following the material balance principle in 2006. 2006 results as a reference base, the trend and environmental quality risk of each heavy metal was estimated based on criteria of the early warning system for the next 30 years. The spatial pattern of the trend and early warning for each heavy metal was interpolated by the probability model of Kriging. Results show in the next 30 years, (1) the risk of Pb, Cr, and Ni were relative lower, and their concentrations will linger below Grade II criteria of the national standard for soil environmental quality, and the other metals will be over Grade II criteria of the national standard with different degrees of environmental risk. (2)Compared with Ni and Cr, the high risk values of Pb are mainly distributed in the urban area, where primary atmospheric deposition. Cr and Ni content are higher in the northeast of Beijing, where the corresponding control measures should be taken. (3) Cu, As and Zn will maybe reach medium level, while Hg and Cd may be up to alarm level three and level four. As and Zn have low potential risk with the similar tendency of heavy metal potential risk early warning, indicating their homology sources from soil parent materials. The risk of Hg and Cd will vary spatially in warning levels and probability. Among the 8 heavy metals, Cd will be highest in environmental risk with the large areas, and some of the risk will mainly spread in the far-reaching suburban related to agricultural activities. The high Hg risk areas will expand with the urban sprawl largely by human influence. Firstly, eight heavy metals show different environmental risk levels, relevant departments should make difference control measures for different regions according to specific environment risk levels and types of soil heavy metal pollution. Secondly, the geostatistics technology coupled with the regional flux model could provide an excellent technical tool for macro-scaled early-warning of regional soil heavy metals pollution.

Abstract:Deep application of straw (DAS) refers to a technique of incorporating crushed corn stalk into the subsoil layer (20~40 cm). It may effectively improve straw utilization rate, reduce straw burning rate, extend the extent of soil building from previously topsoil down to subsoil, contribute to accumulation of organic matter in the subsoil layer, help solve problems like thinning of the plow layer, shallowing, thickening and hardening of the plow pen, and lacking organic matter, and achieve the ends of higher soil fertility, higher water holding capacity, and higher crop yield. There used to be quite a number of researches focused on effect of DAS on soil physical properties, and few on soil chemical properties, let alone its effect on humus composition in soil aggregates. This paper mainly studies changes in structure of humic acid (HA) in soil aggregates in the topsoil and subsoil layers caused by DAS, so as to provide some theoretical basis for solutions to how to improve soil fertility and build up a proper plow layer. Soil samples were collected from an experimental mono-cropping corn field which had two plots, DAS and non DAS, in the Jilin Agricultural University. Four factions of soil aggregates, >2 mm, 2～0.25 mm, 0.25～0.053 mm and<0.053 mm were screened out of the samples separately, with the wet sieve method and HA extracted for analysis of element composition with infrared spectroscopy and differential thermal analysis. Comparison was performed to determine effects of DAS on HA composition. Results show that the black soil tested was dominated with the fraction of 2~0.25 mm soil aggregates; however, the content of the dominant fraction and the content of organic carbon in the topsoil was lower than their respective ones in the subsoil; DAS was conducive to formulation of soil aggregates of the dominant fraction and increased the organic carbon content in the soil aggregates. Compared with that in the subsoil, the HA in soil aggregates, regardless of fractions, in the topsoil was lower in condensation degree and oxidation degree and thermal stability, and higher in aliphatic-C/carboxylic-C (2 920/1 720) and aliphatic-C/aromatic-C (2 920/1 620) ratios. DAS was found to reduce condensation degree, oxidation degree and thermal stability of HA in all soil aggregates in the topsoil and subsoil layers, especially HA condensation degree in the topsoil. On the other hand, oxidation degree and thermal stability of the subsoil layer also decreased obviously. The HA in the topsoil was simpler in structure and younger than that in the subsoil layer. So, DAS may also promote accumulation of organic carbon in the soil and make HA simpler and younger in structure.

Abstract:Excessive application of nitrogen fertilizer is a widespread problem in vegetable field in Taihu Lake basin, which would not only cause severe non-point source pollution, but also induce soil acidification, and hinder vegetable growth, too. A number of studies have demonstrated that having a strong N adsorption capacity, biochar is able to affect nitrogen recycling in the soil and regulate soil pH in various ecosystems, but little is known about effects on vegetable soils and vegetable production. In this study, impacts of biochar application on vegetable growth, N absorption N utilization, N transformation, soil readily available N and soil pH are explored. A pot experiment was carried out using acidified garden soil collected from Taihu Lake region and biochar prepared out of wheat straw under 450oC. The experiment was designed to have four treatments: biochar and urea (BC+U), only urea (U), only biochar (BC), and no N fertilizer treatment (N0, control) and 6 replicates for each treatment. Five continuous croppings of pakchoi (Brassica chinensis L.) were planted. For the first 3 crops, urea (N 100 kg hm^-2) was applied into related treatments, i.e. Treatments BC+U and U; and for the following two crops, no N was applied soil N as designed as N depletion period. Biomass of and N accumulation, nitrate and amino acid contents in pakchoi and dynamics of soil readily available N was measured during the harvest season. Soil pH was determined at the end of the experiment. Results show that application of biochar significantly promoted vegetable growth, and yield of and N accumulation in the vegetable of the 2rd and 3rd cropping was increased by over 70% and 60%, respectively, in Treatment BC+U as compared with that in Treatment U. In the last two croppings without N fertilization, the yield of and the N accumulation in the vegetable in Treatment BC+U still remained quite high, almost twice as high as that in Treatment U, thanks to the presence of biochar in the soil. N application increased nitrate and amino acid contents in the vegetable, while addition of biochar could effectively decrease nitrate content and significantly increase amino acid content in the vegetable. The apparent N recovery rate of chemical N fertilizer is quite low, ranging from 0.01% to 22%. The application of biochar obviously improved N utilization efficiency. The comprehensive average N utilization rate of the 5 croppings in Treatment BC+U reached 34%, 6.4 times as high as that in Treatment U. Treatment BC+C remarkably lowered the content of soil readily available N left in the soil and the proportion of nitrate-N after the crop was harvested. However, during the N depletion period (the last 2 croppings), Treatment BC+U still maintained a quite high content of readily available N in the soil, which was much higher than that in Treatment U. Continuous application of N fertilizer put soil pH on a declining trend, while addition of biochar dulled the declining trend effectively. Soil pH in Treatment BC+U was 0.5 higher than that in Treatment U. The findings of the experiment indicate that addition of biochar can optimize nitrogen supply of the soil by regulating nitrogen adsorption and release, stimulate N uptake and transformation by the crop, and uphold high yield of the crop. However, as for long-term impacts of biochar application on soil N recycling and crop growth, more in-depth work needs to be done in future.

Abstract:Camellia oleifera Abel is the unique woody oil plants in south China, it has high development and utilization value. Water and fertilizer are two important factors that affect the yield of C. oleifera Abel. Combined with nutrients and moisture to discuss the effects of water and fertilizer on the yield of C. oleifera Abel can provide the scientific basis for sustainable management of C. oleifera Abel forests. The experiment was set in Xinzi county Jiujiang City in Jiangxi Province, and 7-year old Gan-wu high yield clones of C. oleifera Abel were used as materials. Adopting quadratic general rotary unitized design, 5 different levels of application volumes of nitrogen (N), phosphorus (P), potassium (K) and irrigation water (H₂O) were designed to explore the effects of water and fertilizer on fruit yield of C. oleiferaAbel. The results of single factor effect analysis indicated that the N, P, K and H₂O has significant effects on fruit yield of C. oleifera Abel. When the amount levels of each factor was -2 C. oleifera Abel showed parabolic trend with the increment of N, P, K and H₂O. With the conditions of setting other factors for middle level, no matter fertilizer or water, the more were not the better, but each has its optimum amount. In order to get the maximum of fruit yield of C. oleifera Abel, the optimum amount of nitrogen fertilizer was N 168.0 g plant^-1, P₂O₅ 48.9 g plant^-1, K₂O 156.6 g plant^-1, and the optimum amount of irrigation was 26.9 kg plant^-1. The results of interaction analysis of N, P, K and H₂O four factor showed that there had significant interactions effect between nutrient element N and K, K and H₂O on fruit yield of C. oleifera Abel. Within a certain range, N and K has obviously positive synergistic effect, the increment of N or K will promote the fruit yield of C. oleifera Abel. But the excessive amount of fertilizer could cause the inhibition, and either N or K fertilizer applied into a small quantity, the fruit production of C. oleifera Abel would be affected and could not obtained high yield. When two species fertilizer increased suitable measure, fruit production reached maximum value 3 174 g plant^-1, it’s obviously higher than the maximum value in N or K single factor effect analysis. The interaction effect between K and H₂O interaction showed a similar pattern, when K fertilizer and irrigation also increased to a certain value, the maximum fruit yield of C. oleifera Abel reached to 3 173 g plant^-1, any lower levels of these factors would lead to lower maximum fruit yield of C. oleifera Abel. What’s more, the excessive irrigation or potassium are not conducive to fruit yield of C. oleifera Abel. Therefore, in the management of C. oleifera Abel forest, we should not only take into account the reasonable ratio of nutrients, but also pay attention to the balance between nutrients and water. Fertilization and irrigation are critical factors that determine fruit yield of C. oleiferaAbel, and the interactions between these factors significantly affect the fruit yield of C. oleifera Abel, when the yield reached maximum, the coding value of the four factors, N, P, K and H₂O, was 1.03, 0.62, 1.19 and 0.92, respectively. That is to say, if each plant receives available nutrients 181.8 g N, 48.6 g P₂O₅and 287.1 g K₂O and 29.2 kg water annually, or the C. oleiferaAbel field is applied with 795 kg N, 80 kg P₂O₅and 474 kg K₂O, and irrigated with 48 m³ water per hectare, fresh fruit yield of C. oleiferaAbel can reach as high as 5 131 kg hm^-2.

Abstract:During the past 40 years, more than 400 000 hm² of the tide flat in the Yangtze River delta of China have been reclaimed for agriculture. The polders must be washed to have the salt in the soil leached away before they can be used to grow rice. However, strong evapotranspiration brings salt back from deep soil layers, and the salt accumulates in the root-zone (0~1 m). So accurate three-dimensional soil salt maps can serve as decision-making basis for rice farmers of the polders to work out rational cultivation programs. So far little has been reported on three-dimensional space variability of soil salts and most of the researches in this field at home and abroad are using two-dimensional space variation maps to express three-dimensional space variability. How to express three-dimensional space variability of soil properties is a challenge to the traditional soil profile sampling, space variation analysis and three-dimensional visualized expression. In this project, the paddy field in the polder of Zhejiang Province was cited as a case of study. First, apparent electrical conductivity (ECa) of the paddy field was measured using an EM38 from different heights above the ground and then a linear model coupled with the Tikhonov regularization method was used to inverse electrical conductivities at 10 different soil depths of a profile of 0~110 cm. The data gathered from the 56 soil profiles in the field were used as basis in the study on three-dimensional space variability of soil salinity. Then, the soil ECa was interpolated three-dimensionally on a field scale using the Three-dimensional Inverse Distance Weighting (3D-IDW) method. In the end, the sphere, section and plume models of the Virtual Reality Modeling Language (VRML) were used separately to build soil electrical conductivity virtual reality visualized models for scattered electrical conductivity points on profiles, sections of two dimensional space variation at the horizontal and vertical directions and three-dimensional soil solum model, and eventually to realize distribution of VRML models on the internet (http://agri.zju.edu.cn/3d/). The descriptive statistics of profile soil salinity shows that the minimum, median and maximum values of EC all increased with soil depth. On the field scale, 3D-IDW is a fairly good method for prediction and interpolation of three-dimensional space distribution of soil EC, and VRML is a good one, too, for visualized modeling to exhibit and analyze three-dimensional space distribution laws of soil EC. Horizontally, soil salinity increased gradually form the northwest to the southeast of the filed, and vertically, it did with soil depth. Soil salinity was the highest in the southeast corner of the field. The spatial distribution of soil salinity is true, The drainage ditches around of the field helped drain soil water from the field, lowering the soil humidity. Besides, the field declined from northwest to southeast in topography. River water was led into the field in the west to wash soil salt and drained through the trunk into the Hangzhou Gulf. As the northwest corner was higher in topography, it got free of the impact of sea water earlier and soil salt therein was easily leached off, while salt-containing groundwater flew continuously toward the lower southeast corner. Users can access the website for VRML models, and do some basic operations, such as pan, zoom in, zoom out and rotation, to the VRML models. With the aid of EM38, 3D-IDW and VRML it is feasible to plot visualized three-dimensional soil properties space variability maps, which can be shared via network.

Abstract:Soil organic matter (SOM) is an important soil component playing a critical role in various chemical and physical processes in soil, and meanwhile, may serve as a crucial index in assessing soil carbon stock, soil fertility and soil quality of an agro-eco-system. Therefore, to reveal the law of SOM spatio-temporal variability is a precondition for realizing sustainable utilization of soil resources. Then how to collect soil samples is the first issue that has to be dealt with in quantitative expression of spatial distribution of SOM content. And moreover, characterization of SOM spatial variability is closely related to size, density and distribution of soil sampling. Changes in the number and distribution of sampling sites may directly influence accuracy of the deduction and prediction of SOM spatial variability. On the other hand, generally speaking, usually the bigger, the number of samples to be collected, the more, the human resources, material and time to be consumed in sampling and lab analysis, but if the number of sampling sites is too small, it is very likely that some important spatial information of soil properties would be missed. Consequently, it is very meaningful to find out how the number of sampling sites affects characterization of SOM spatial variability and it is of some important practical significance to have a scientific designing of soil sample collection in an attempt to save soil sampling cost. On the basis of the 351 SOM valid data, a field experiment was laid out in Luhe County of Nanjing, Jiangsu Province to have 5 series of sampling designs, different in number of sampling sites, that is, 300, 250, 200, 140 and 100, set in line with the completely random sampling (CRS) and minimum sampling distance sampling (MSDS) methods. Based on deviations in variability deduction and spatial prediction of the 100 repeated samplings at each sampling series, effect of number of sampling sites on characterization of SOM spatial variability was explored. Results show that the nugget-to-sill ratios (C₀/Sill) of SOM derived from soil samples collected using two different sampling methods decreased with decreasing number of soil sampling sites, and it is more obvious with MSDS than with CRS, indicating that properly reducing the number of sampling sites may minimize the effect of sampling sites mismatching to SOM variation scale on variability deduction and hence improve reliability of characterization of SOM spatial variability. Comparison of SOM predictions using OK in deviation shows that using either sampling methods, RMSEs of spatial prediction, though fluctuating with decreasing number of sampling sites, were lower than that derived from all the sampling sites as a whole. The minimum RMSE was achieved when the number of sampling sites was reduced to 250 and the MSDS method was used, and about 6% lower than that of the prediction based on all the sampling sites as a whole. All the above findings imply that rationalizing the layout of sampling sites in number and density to match density of sampling sites to SOM variability scale is more important than simply increasing the number of sampling sites.

Abstract:Soil moisture, affected jointly by rainfall and groundwater, plays an important role in terrestrial water recycling. Hydrogen and oxygen isotopes can be used as tracers to study water movement and migration in the soil. Stable isotope compositions of soil water can be used to reveal information about a number of hydrological processes in soil, including infiltration, evaporation, transpiration and percolation, which is difficult to obtain by other techniques. The Loess Plateau in northern Shaanxi with loessal soil as its dominant type of soil, is arid in climate and scarce in water resource. Anumber of studies documenting tracer movement in the soil column except for using loessal soil to study soil water movement under differential recharge based on hydrogen and oxygen isotopes. Researches on soil water movement and migration in loessal soil may help understand characteristics of soil water movement, guide local agricultural production and improve water utilization efficiency in the Loess Plateau. A simulation experiment using soil columns was carried out in the State Key Laboratory of Northwest Arid Area Experimental Ecology and Hydraulic Engineering, Xi'an University of Technology. With the aid of isotope technology, exploration was done of temporal variation of soil water movement in loessal soil, temporal variation of distribution of isotope in soil water in the soil profile and relationship between oxygen and hydrogen isotopes in the soil water as affected by rainfall or groundwater, in an attempt to elaborate characteristcs of soil water movement in loessal soil relative to source of the recharge. During the experiment distributions of soil water content and hydrogen isotope in the soil profile were monitored 1, 3, 5, 10, 15, 20 and 30 days after the end of the recharge and relationship between oxygen and hydrogen isotopes in the soil water was fitted with a linear model. Results show that （1）being recharged with water from either source, rainfall or groundwater, the soil water increased in volumetric content as the time going on and leveled off in the end and that movement of the soil water obviously lagged behind. （2）Hydrogen isotope in the soil water was affected by source of recharge water, exchanging and mixing of the waters and evaporation of the water in the soil, and with the time going on, the effect of source of the recharge water gradually weakened, while the effects of exchanging and mixing of the waters and evaporation of the water in the soil gradually stood out. Eventually the soil water reached its dynamic balance. （3）When being recharged by rainwater or groundwater, soil water moved in a piston-driven way. With rainfall infiltrating into the soil, δD in the soil water first decreased, and then increased with increasing soil depth and eventually leveled off. The soil water in the surface 0~5cm soil layer was enriched in heavy isotope as a result of evaporation and the soil water in the 5~20cm soil layer stayed for the longest time, indicating that the soil layer is the highest in water retaining capacity. When being recharged by groundwater, the soil water decreased in δD with soil depth. The water in the upper soil layer was enriched in heavy isotope as a result of evaporation, and the water in the deep layer impoverished in isotope by recharge from groundwater. （4）Under either recharge modes, δD and δ¹⁸O in the soil water displayed a nice linear relationship. Isotope fractionation effect of soil water evaporation was greater when soil water was recharged by rainfall than by groundwater. Soil water recharged by groundwater tended to stay longer in the soil. Obviously, rainfall, groundwater and soil water evaporation all have some impacts on soil moisture. The variation of soil water isotopes with a certain regularity. So adoption of underground irrigation in the Loess Plateau region is conducive to preservation of soil water for agricultural production.

Abstract:Application of fertilizers, unreasonable in rate and formula, has been the main factor limiting maize production. A large number of on-farm fertilization experiments have been conducted on maize across the main agro-ecological regions of China, and large volumes of first-hand data were collected for analysis in this study to explore region-specific optimal NPK recommendation (including rate and formula) in anticipation that the study may provide some technical support to improving the maize production in China and a theoretical basis for designing region-specific and crop-specific fertilizer. Based on the county’s GIS-based agricultural statistical database and relevant literature, the maize production areas in China were divided into 4 major regions by geographic location and production layout and further into 12 fertilization sub-regions in light of climatic, crop cultivation, topographic and soil conditions. Meanwhile a total of 1 752, 7 081 and 6 328 groups of on-farm N, P and K fertilization experiments were conducted all over the maize production areas during 2005-2010, and results and data of the experiments were collected, sorted and collated by fertilization sub-region. Then, sub-region-specific recommendation of N rate for maize was worked out using the N fertilizer total amount control technique and proper ratios of basal/sidedressing were determined in the light of the features and production practices of a region and nutrient demand of the crop; sub-region-specific recommendation of P rate for maize was, using P building-up and maintenance technique and sub-region-specific recommendation of K rate for maize, too, using the technique of yield response to K application. Based on the technical approach of ‘regional fertilizer formula plus site specific adjustment’, sub-region-specific fertilizer formula and application technique was designed for all the maize growing areas. Northeast China (RegionⅠ) and Northwest China (Region Ⅲ) was quite high in maize yield, reaching 9.0~10.5 t hm^-2, while North China Plain (RegionⅡ) and Southwest China (Region Ⅳ) was quite low, being 7.5~8.3 t hm^-2. For the 12 sub-regions, the recommended N rates were averaged to be N 181 kg hm^-2, ranging from N 150 kg hm^-2 for the cold sub-region in Northeast China (RegionⅠ-1) to N 219 kg hm^-2 for the irrigated oasis sub-region in the Northwest China (RegionⅢ-3); the recommended P rates, P₂O₅ 75 kg hm^-2 on average, ranged from P₂O₅ 46 kg hm-2 for the north-central sub-region in the North China Plain (RegionⅡ-1) to P₂O₅ 123 kg hm^-2 in the irrigated oasis sub-region in the Northwest China (RegionⅢ-3); and the recommended K rates, K₂O 54 kg hm^-2 on average, ranged from K₂O 30 kg hm^-2 for the irrigated oasis sub-region in the Northwest China (RegionⅢ-3) to K₂O 64 kg hm^-2 for the south sub-region in the North China Plain (RegionⅡ-2). For the 12 sub-regions, a total of 16 region-specific fertilizer formulas were worked out, including 12 formulae with basal plus top-dressing fertilization approach and 4 formulae with only basal fertilization application. The regionalization of maize fertilization can well reflect the layout of maize production in China and region-specific climatic, topographic, soil and relevant crop cultivation conditions. The significant differences between the agro-ecological regions in maize grain yield and recommended fertilizer rates reflected the specificity of each region in soil fertility, yield response to nutrient application and crop nutrient demand. The region-specific fertilizer formulas designed on the basis of the region-specific fertilizer recommendation and characteristics of the regions well match the maize productions in the regions and optimize regional fertilizer application techniques. These region-specific fertilizer formulas will play an important role in guiding optimization of compound fertilizer products and provide a theoretical reference for designing regional fertilizer formulas for relevant crops in future.

Abstract:Soil organic carbon (SOC) content has long been recognized as an important indicator of soil quality. Soil aggregates are considered as the basic structure of soil. Soil aggregation and SOC accumulation are interrelated: SOC or its fractions are basic to aggregation process, whereas SOC sequestered within aggregates is protected against decomposition. This relationship between aggregates and SOC is considered as an important mechanism of physical protection of SOC. A number of studies have been conducted by scientists at home and abroad, focusing on distribution of SOC in aggregates in paddy soils, black soils, and degraded soils. However, few have reported about effect of fertilization on SOC distribution in aggregates in coastal saline soil. In this paper, an experiment was carried out in a field of coastal saline soil in North Jiangsu, to study effects of fertilization on soil organic carbon and SOC distribution in aggregates various in size. The experiment was designed to have four treatments: no fertilizer (CK), farm yard manure (FYM), commercial organic fertilizer (COF) and inorganic fertilizer (IF), and three replicates for each treatment. Soil samples were collected from the 0~10, 10~20, 20~30, 30~40, 40~60, 60~80, 80~100 cm soil layers, and then air-dried, and ground to pass a 0.15 mm sieve for determination of soil organic carbon with the oxidation method using potassium dichromate in 0.4 mol L-1 K2CrO7-H2SO4 solution. Distribution of water-stable aggregates was measured according to Haynes (1993). Analysis of variance producers were conducted using the SPSS statistical procedures. Results show that all the treatments were obviously higher than CK in content and density of soil organic carbon in the 0~30 cm soil layer, with Treatment FYM, in particular, which increased the content and density by 0.66 g kg^-2and 0.07kg m^-2, respectively. The water-stable aggregates in the studied field were dominated by those >5 mm and 0.25~0.5 mm, in particle size, which accounted for 37%~57% and 13%~20%, respectively. The fraction of >5 mm decreased in content, while the fraction of 0.25~0.5 mm increased along with soil depth in all the treatments. Treatment FYM significantly increased the content of the fraction of >5 mm, but decreased that of the fraction of 0.25~5 mm significantly. Distribution of SOC in aggregates was found to be that in aggregates varying from 0.5~1 mm to >5 mm in particle size, the smaller the aggregates, the higher the SOC content therein. The fraction of 0.5~1 mm size was the highest (6.83 g kg^-1) in SOC content. Compared with all the other treatments, Treatment FYM increased SOC content in all the fractions of aggregates. In the experiment field, SOC content in the soil was a positively related to that in the fraction of >5 mm (p <0.01), and negatively to that in the fraction of 0.25~5 mm (p <0.01 or p >0.05).

Abstract:Soil samples collected from a 17-year old long-term fertilizarion field experiment in Zhejiang Province, China, were analyzed to evaluate effects of the use of chemical fertilizers and amendment of organic manure on distribution of aggregates and aggregate-associated organic carbon in paddy soil. The experiment was designed to have six treatments, including CK (control, no fertilizer applied), NPKRS (NPK fertilizers and rice straw), NPKOM (NPK fertilizers and organic manure), NPK (NPK fertilizers), RS (rice straw alone), and OM (organic manure alone). The wet-sieving method was used for evaluation of physical stability of soil aggregates and their particle-size composition. Fourier transform infrared spectroscopy (FTIR) was employed to characterize inherent chemical composition of soil organic carbon (SOC) at the molecular level in the 2 ~ 0.25 mm and < 0.053 mm aggregates. In comparison with CK, Treatments NPKOM, OM, NPKRS and RS significantly (p < 0.05) increased the proportion of > 2 mm and 2 ~ 0.25 mm water stable aggregates, and mean weight diameter of soil aggregates, thus enhancing the effect of macroaggregates physically protecting SOC. The SOC content of the bulk soil and all aggregate fractions, as well as the contribution of macroaggregate-associated (i.e., > 2 mm and 2 ~ 0.25 mm) SOC to total soil organic C in Treatments NPKOM and NPKRS were significantly higher than that, respectively, in CK. However, no significant difference was observed in accumulation of SOC between CK and Treatments NPK or RS. The 2 ~ 0.25 mm fraction of aggregates contained SOC, accounting for 34.16% ~ 48.6% of the total SOC in the soils in all the treatments, suggesting that 2 ~ 0.25 mm aggregates were the main carriers of SOC in the paddy soil. The FTIR spectra of the 2 ~ 0.25 mm and < 0.053 mm aggregates show that the ratios of aromatic-C to total SOC in Treatments NPKOM, OM, NPKRS and RS were 29.9% ~ 45.2% higher than that in CK, and 22.3% ~ 36.6% higher than that in Treatment NPK. The highest ratio was observed in Treatment NPKOM. The FTIR spectra also indicate that in Treatments NPKOM, OM, NPKRS and RS aliphatic-C groups increased slowly but steadily. The increases in aromatic-C and aliphatic-C were attributed mainly to the inputs of recalcitrant compounds derived from organic amendments, and/or to the reduction of H-bonded O-H hydroxyl groups of phenols induced by biochemical processes in soils treated with organic amendments. The findings of the research indicate that both enhanced physical protection of SOC by macroaggregates and increased proportion of chemically recalcitrant organic compounds contribute to carbon accumulation in the paddy soil treated with organic amendments, with the most prominent effect being observed in Treatment NPKOM. Long-term combined application of organic manure and chemical fertilizers appears to be a sustainable environment-friendly strategy to achieve both high agricultural production and soil carbon accumulation.

Abstract:A field experiment was carried out in a paddy field under rice-wheat rotation, to study effects of biochar amended at the rice or wheat season on paddy CH₄ and N₂O emissions throughout the cycle of rotation, their consequential global warming potential (GWP) and greenhouse gas intensity (GHGI), with a view to providing some scientific basis for extrapolation of the use biochar in mitigating global warming potentials and in agricultural production as well. The field experiment was designed to last an entire cycle of crop rotation, that is, two cropping seasons, rice season and wheat season, and to have eight treatments in triplicate, i.e. Treatment RB₀-N₀ or CK (zero N fertilizer applied & zero biochar amended in the rice season), Treatment RB₀-N₁ (250 kg hm^-2 N fertilizer applied & zero biochar amended in the rice season), Treatment RB₁-N₁ (250 kg hm^-2 N fertilizer applied & 20 t hm^-2 biochar amended in the rice season), Treatment RB2-N1 (250 kg hm^-2 N fertilizer applied & 40 t hm-2 biochar amendment at rice season), Treatment WB₀-N₀ (zero N fertilizer applied & zero biochar amended in the wheat season), Treatment WB₀-N₁ (250 kg hm^-2 N fertilizer applied & biochar amended in the wheat season), Treatment WB₁-N₁ (250 kg hm^-2N fertilizer applied & 20 t hm^-2 biochar amended in the wheat season), and Treatment WB₂-N₁ (250 kg hm^-2 N fertilizer applied & 40 t hm^-2 biochar amended in the wheat season). Biochar was amended before rice transplanting on June 10, 2012 and wheat seeding on November 10, 2012. CH₄ and N₂O gas emission fluxes were monitored with the static chamber and gas chromatography method. Results show that Relative to Treatment RB₀-N₁ Treatment RB₁-N₁ did not have much significant effect on N₂O and CH₄ emissions, GWP and GHGI, while Treatment RB₂-N₁ significantly improved crop yield by 17.2%, and significantly reduced total CH₄ emissions and GWP by 8.6% and 9.3%, respectively. Treatment WB₁-N₁ did not have much effect on GHGI and GWP, but did increase wheat yield by 21.6%, which in turn significantly reduced GHGI by 21.7%. Treatment WB₂-N₁ significantly reduced N₂O and CH₄emissions by 20.9% and 11.3%, respectively and GWP and GHGI by 15.7% and 23.5%, respectively. In terms of total GWP on a 100-year horizon, the treatments followed an order of RB₀-N₁ > RB₁-N₁ > WB₀-N₁ > WB₁-N₁ > RB₂-N₁ > WB₂-N₁ > RB₀-N₀ > RB₀-N₀, while in terms of GWPs per unit crop grain yield, they followed another, i.e. RB₀-N₁ > WB₀-N₁ > RB₁-N₁ > RB₂-N₁ > RB₀-N₀ > WB₁-N₁ > WB₀-N₀ > WB₂-N₁. Obviously biochar application is more effective in the wheat season than in the rice season, in reducing N₂O and CH₄ emissions, lowering the GWP and GHGI and increasing crop yield of the rotation system. Although Treatment WB₂N₁ was lower than Treatment WB₁N₁ in N₂O and CH₄ emission, and also in wheat yield which to use depends on balance between GHG mitigation and grain yield. However, consequential effects and underlying mechanisms of the use of biochar in the field on scale need further field study Results incorporation at rice season had no significant difference on N₂O and CH₄emissions, GWP and GHGI. Relative to the RB₀-N₁ treatment, the RB₂-N₁treatment significantly improved crop yield by 17.2%, significantly reduced the total CH₄ emissions and GWP by 8.6% and 9.3%, respectively. The crop yield of biochar incorporation at wheat season with 20 t h^-2 significantly improved by 21.6%, and significantly reduced 21.7% GHGI compare with WB₀-N₁. Biochar incorporation at wheat season with 40 t h^-2 significantly reduced N₂O and CH₄ CH₄missions by 20.9% and 11.3%, respectively, significantly reduced GWP and GHGI by 15.7% and 23.5%, respectively. Biochar application at wheat season was better than rice season. iochar incorporation at wheat season on improved crop production, reduced N₂O and CH₄ emissions, while simultaneously lower the GWP and GHGI were superior to the biochar incorporation at rice season in the rice-wheat rotation system.

Abstract:Annually about 0.6~0.7 billion tons of crop straw is produced in China, however nearly half failed reasonable use, causing a series of problems such as resource waste and environmental pollution. Biochar, a pyrolyzed biomass high in carbon concentration and stable C, can improve soil carbon pool rapidly when applied to soil. The application of crop-straw derived biochar does not only increase carbon sequestration, reduce emission of greenhouse gases and improve soil quality, but also serve as an effective way to realize diversified comprehensive utilization of straw resource. Nevertheless, owing to its unique physico-chemical properties, biochar, once applied as a soil conditioner, would certainly alter soil property and then influence crop growth. In order to assess the potential of biochar in application to farmland of cambosols (pH 8.30) in North China Plain, a two-year field experiment (4 croppings or two cycles of wheat and maize crop rotation beginning in fall of 2011), was conducted in the Fengqiu Agro-ecological Experiment Station, Chinese Academy of Sciences, Fengqiu, Henan Province. The experiment was designed to have four treatments in biochar application rate, i.e. Treatment BC0 (0 t hm^-2; as control or CK), Treatment BC2.25 (2.25 t hm^-2; low level), Treatment BC6.75 (6.75 t hm^-2; medium level) and Treatment BC11.3 (11.3 t hm^-2; high level). The total biochar application rate of the 4 croppings was 0, 9, 27 and 45.2 t hm^-2, respectively. Each treatment had three replicates and the plots of the treatments were laid out in randomized complete block design (RCBD), 16 m² each in area. For wheat N 240 kg hm^-2 (urea), P₂O₅150 kg hm^-2 (triple superphosphate) and K₂O 90 kg hm^-2 (potassium sulfate) was applied, while for maize N 200 kg hm² and the same rate of P and K as for wheat were. P and K fertilizers were applied all at once as basal dressing, while N fertilizer was applied in split dosing, i.e. 60% as basal and the remaining 40% as side dressing at the jointing stage. The fertilizers were broadcast into the wheat fields, and applied in pits in the maize. The crops were irrigated after fertilizer application, and their subsequent water demand was met by rainfall. Crop yield, grain quality, N uptake, mineral N (NO₃^--N and NH₄⁺-N) in soil, pH, soil bulk density, water content and water holding capacity were monitored for all the plots. Results show that for the first three crops (wheat-maize-wheat) no statistically significant difference (p>0.05) in yield was found between CK and the other three treatments. When it came to the fourth cropping, the crop of maize increased its yield by 8.43% in Treatment BC6.75. The yield of the four crops were also increased by 4.92% and 4.54% in Treatments BC6.75 and BC11.3, respectively. Biochar application had no negative effects on protein content in wheat and maize grains or bulk density of and wet gluten content in wheat grain, however Treatment BC11.3 was found to have increased bulk density of and protein content in wheat grain. Although no significant effect of biochar addition was observed on nitrogen uptake and accumulation by shoots of the crops and soil mineral nitrogen and soil pH, nitrogen uptake and accumulation of the grains of the 4 crops increased by 6.55%~7.98%, soil water content in the plough layer by 10.3%~20.2%, and soil water holding capacity by 14.5%~15.0%, yet, soil bulk density decreased by 2.99%~10.4% in Treatments BC6.75 and BC11.3. All the findings suggest that successive application of crop straw derived biochar does have some positive effects on crop yield and no negative influence on grain quality, and that biochar has no significant effects on mineral nitrogen content in the topsoil or N uptake and utilization by crops. The beneficial effects of biochar of improving soil physical properties, like in bulk density, soil water content, and water holding capacity may be the major cause to yield increase after the application of biochar in cambosols. It is necessary to do some further in-depth studies on effect of long-term biochar application on soil water and nutrient dynamic and some other physico-chemical properties of cambosols and nutrient translocation in plant in the hope that the study may provide some scientific data to support extrapolation of the application of crop straw derived biochar in upland of North China.

Abstract:When a colloidal particle carrying surface charge is dispersed in an aqueous solution, it adsorbs a large volume of ions, reverse in charge at its solid/liquid interface, thus forming an electric double layer (EDL), which plays a vital role in ion sorption and desorption at the solid/liquid interface of charged colloidal particles and in stability of the colloidal particle suspension and stability of protein system According to the theory of the EDL model, a shear layer exists between the shear plane where Zeta potential (ζ) exists in the electric double layer and the particle surface, and thickness of the shear layer is the distance between the shear plane and the particle surface. Thickness of the shear layer is not only an important physical parameter in the research on colloid and interface chemistry, but also closely related with some electro-chemical properties, such as electrodialysis, electrophoresis, streaming potential and sedimentation potential. Nowadays, researchers commonly use the colloidal particle double electro layer model and DLVO theory in their studies on thickness of the shear layer and hold that the shear layer is very close to the Stern layer or the outer Helmholtz layer; and as thick as the diameter of about 2 ~ 3 water molecules, about 0.5 nm, because they deem zeta potential approximate to the surface charge of colloidal particles. Meanwhile some researchers have figured out that the shear layer is 0.03 μm, 0.1 μm, < 0.25 μm or no more than 2 μm and believe that particle surface charge is infinite. And also some researchers have concluded through theoretical analysis that the shear layer is very closed to the Gouy plane in the electric double layer, however, its actual position is hard to determine. In light of the above described analyses, it is quite clear that the results the researchers obtained as to thickness of the shear layer vary sharply, mainly because it is very hard to measure accurately colloidal particle surface charge. In the colloid diffuse electro double layer theory, although it is still not clear where the particle shear layer actually is, it is certain that it lies in-between the outer Helmholts layer and the Gouy layer. Therefore, it is feasible to use the Gouy-Chapman potential distribution equation to describe the relationship between potential φ(x) of any point in the double electro layer and its corresponding point x. In this paper, from the Gouy-Chapman theory an equation was derived to calculate thickness of the shear layer (xS) in the single electrolyte system. Based on the soil colloid surface potential and zeta potential measured by zetaPlus, thickness of the shear layer (xS) was calculated. (1) Surface potentials and zeta potentials of colloidal particles in acidic, neutral and calcareous purplish soil samples are much higher in the 1:1 type electrolyte system than in the 2:1 type electrolyte system, and in the two single electrolyte systems, the variation of surface potential with concentration of the electrolyte is much sharper than that of zeta potential. (2) In the two single electrolyte systems, all the three purplish soils show the colloidal shear layer is quite far away from the Stern layer, but quite close to the Gouy layer in the diffuse double layer (DDL), and the shear layer is much thinner in the 2:1 type electrolyte system than in the in 1:1 type electrolyte system. (3) The shear layer gets thinner with rising concentration of the electrolyte in all the three soils. On different soil colloidal particles with surface charge, the shear layers differed significantly in thickness when concentration of the electrolyte is low (p<0.05), and not so significantly when concentration of the electrolyte is high (p>0.05). This study has not only brought forth a new theory and method for calculating thickness of the shear layer of soil colloidal particles in the single electrolyte system, but also provided some bases for enriching the theories of colloid diffuse double layer structure.

Abstract:Chromium and its salts are widely used in alloys, electroplating, leather, dyes, printing and dyeing, catalysis, medicine and other industries as an important industrial raw material. Therefore, there is a serious chromium contamination problem in many legacy chemical plants , making it difficult to re-use. Chromium contaminated site remediation problem of the industrial wastelands is imminent. Currently, the repair of chromium contaminated sites are mainly chemical leaching repair technology, electrochemical remediation, bioremediation, chemical fixation, and chemical reduction methods. The surface soil was selected from a deserted chemical plant in Jinan as the experiment samples, including the following five samples, the titanium white workshop sample, chromic salt workshop sample, the ten thousand ton chromic salt workshop, the east chromium slag dump site sample and the north section of the plant sample. Chemical oscillation leaching experiments was used to repair the contaminated soil samples. The vast majority of Cr (Ⅵ) was removed from the soil samples by using the eluent. The majority of the use of chemical eluent Cr (Ⅵ) is removed from the soil. While the Cr (Ⅲ) was stable in soil, part of Cr (Ⅲ) was displaced, the chromium contaminated soil at the site get repaired in some degree to provide the basis for the chemical plants chromium chemical remediation of contaminated soil. Laboratory simulation tests were conducted to examine effects of different leaching reagents(water, 0.1 mol L^-1 EDTA, 0.1 mol L^-1 CTA, 0.1 mol L^-1 HCl，0.1 mol L^-1 CaCl₂，0.1 mol L^-1 NaOH and 0.1 mol L^-1H₃PO₄) extracting Cr from the soils sampled from the plant with a view to screening out one that is the most effective in remedying Cr contaminated soil. By measuring total chromium and Cr (Ⅵ) of the filtrate, the best eluent was selected from the eluents we have chose by leaching experiment. According to the selected best eluent, we explored the conditions of eluent concentration, soil liquid mass ratio, oscillation time, the eluent pH on leaching effect. Setting the eluent concentration gradient, 0.005, 0.01, 0.02, 0.05, 0.1, 0.15 mol L^-1, different soil liquid mass ratio, 1: 2, 1:5, 1: 10, 1: 15, 1: 20，different oscillation time, 0.5, 1, 2, 4, 8 h, the eluent pH ,4.5, 5, 6, 7, 8, 9, 10, we found the leaching removal different under the different conditions. We proposed “I”, the chromium contaminated soil activity index, to indicate the proportion of Cr (Ⅵ) in total chromium of the soil sample. The results showed that all the soil samples exceeded the national standard for soil environment in Cr contamination; the soil samples from the Titanium white production workshop were the lowest in pollution degree, while those from the north section of the plant were the highest, reaching as high as 7 149 mg kg ^-1; in terms of soil activity index “I”，the soil samples from the ten thousand ton chromic salt workshop were the highest, reaching up to 0.291 8, whereas those from the ordinary chromic salt workshop the lowest; the reagents, Water, HCl, CTA,CaCl₂, NaOH and H₃PO₄, were all quite low in total chromium removal rate; EDTA was the most effective one, when it was 0.1 mol L-1 in concentration, 1:10 in soil liquid mass ratio and 5 in pH for 1 h of leaching oscillation. On the whole, the removal of Cr (Ⅵ) was low, the removal of Cr (Ⅵ) was ideal. In treating the soil samples from the north section of the plant, its total Cr removal rate reached as high as 22% and Cr⁶⁺ removal rate 98.5%. With the continuous optimization of elution conditions, oscillation leaching removal is constantly improved . But the chromium content is still more than the national standard after soil leaching process, we need further processing of contaminated soil. we can consider adding an oxidant to activate the chromium ions, promoting the activity of migration ,then improve the leaching removal.

Abstract:A field survey was performed of some deserted ionic rare earth mine tailing dumpling sites different in age in the Dingnan County, Ganzhou, Jiangxi, to investigate vegetation composition, soil physico-chemical properties, soil microbial and enzymeactivities, in an attempt to explore factors limiting restoration of the dumping sites. Results show that vegetation coverage of the dumping sites increased with the age, reaching 72% at the sites 10 years after the desertion, but plant composition of the vegetation at the sites remained still quitesimple (only three species recorded). In comparison with the surrounding areas with normal vegetation, the sites were much lower insoil organic matter content (0.5~1.5 g kg^-1), andclay content (6.00%~9.66%), but significantly higher in bulk density (1.26~1.43 g cm^-3). The one-year old deserted dumpling sites were much higher insoil electrical conductivity (EC) than those 3~10 years old and the surrounding areas, and moreover, reached as high as 400 mg kg^-1 and 500mg kg^-1 inammonium nitrogen and available nitrogen, while those 3~10 years old tended to be as low as trace, and the sites, 3 and 6 years old, were also extremely low in ammonium nitrogen in the 0~100cm soil layer, indicating that soil ammonium nitrogen in the sites were almost depleted completely to below 10mg kg sup>-1 within three years. So severe soil erosion and the resultant soil N deficiency are among the main factors limiting restoration of vegetation at the sites. Besides, the soils at the sites were significantly lower than the surrounding areas insoil microbial carbon content (< 26.7 mg kg^-1), soil urease activity (<29.9 NH₃-N mg kg^-1 h^-1) and soil acid phosphatase activity (<7.10 phenol mg kg^-1 h^-1), indicating that soil nitrogen and phosphorus recycling in the soils of the sites was inhibited.The findings of the present study suggest that the soils at the sites did not have much improvement in the years from the 3.^rd to the 10.^th physical, chemical and microbial properties. So vegetationrestorationat the sites is facing an issue of reconstructing, their soils, which requires some appropriate artificial interventions, like soil amelioration, before vegetation can be restored.

Abstract:Organochlorine pesticides are likely to travel over a long distance in the atmospheric environment, bringing about adverse effects on human health and ecological environment. Owing to the excessive use of pesticides in the past, the detection rate of OCPs residue in soil is still quite high, though the residue in soil has so far been greatly reduced. During the period of 2005—2008, from 15 cities or counties in the Liaodong and Shandong Peninsulas collected were a total of 265 surface (0~20 cm) soil samples, of which 151 soil samples were from the Liaodong Peninsula, involving 5 types of land use (vegetable garden, grassland, orchard, paddy field and corn field) and 114 soil samples from the Shandong Peninsula, also involving five types of land-uses (vegetable garden, wheat field, cotton field, orchard, and corn field). Before the soil samples were analyzed for α- and β-endosulfan, endosulfan sulfate, α-, β-, γ- and δ-HCH, p,p’ -DDT, p,p’-DDE and p,p’-DDD with GC-ECD, they were subjected to ultrasonic extraction using acetone/petroleum ether(1/3,V/V), purification with a glass chromatography column, and leaching with hexane/dichloromethane(1/1,V/V) for constant volume. On such a basis, annual variation and spatial distribution of endosulfan, HCHs and DDTs residues in the soils of the studied regions and volumes of OCP residues in the soils relative to type of land use were analyzed and characterized. Results show that the residue of endosulfan and HCHs in the soils of the Shandong Peninsula was 6.30 μg kg^-1 and 4.82 μg kg^-1, respectively, about 9 and 1.3 times as high as that in the soils of the Liaodong Peninsula, while the residue of DDTs in the soils of the Liaodong Peninsula was 45.70 μg kg^-1, about 2.5 times as high as that in the soils of the Shandong Peninsula. The detection rates of α-HCH, p,p’-DDE and p,p’-DDT in the soils of the Shandong Peninsula were all higher than 80%, while the detection rates of β-HCH and p,p’-DDE in the soils of the Liaodong Peninsula were above 80%, too. HCHs and DDTs residues were quite common in the soils of the studied regions. It was found that the highest content of endosulfan residue was in Xingcheng, being 1.294 μg kg^-1, whereas the lowest was in Laizhou, being 0.062μg kg^-1; the highest content of HCHs residue was in Gaizhou, being 10.46μg kg^-1, whereas the lowest was in Dawa, being 0.618μg kg^-1; and the highest content of DDTs residue was in Xingcheng, being 110.9μg kg^-1, whereas the lowest was in Dawa, being 0.867μg kg^-1. In terms of residue content in the soil, the fractions of OCPs displayed an order of DDTs > HCHs > endosulfan in the Liaodong Peninsula and an order of DDTs > endosulfan > HCHs in the Shandong Peninsula, while in terms of content of OCPs residues in soil, the five types of land use followed an order of orchard (59.92μg kg^-1) > corn field (56.14μg kg^-1) > vegetable field (39.35μg kg^-1) > grassland (12.71μg kg^-1) > paddy field (10.29μg kg^-1) in the Liaodong Peninsula and an order of orchard (38.16μg kg^-1) > vegetable field (29.04μg kg^-1) > corn field (26.72μg kg^-1) > wheat field (25.73μg kg^-1) > cotton field (18.63μg kg^-1) in the Shandong Peninsula. The mean content of endosulfan residues in the sampling regions was 3.09 μg kg^-1, lower than that in other areas in China. And the mean content of HCHs and DDTs residues was 4.69 and 26.83 μg kg^-1, respectively, both below Grade I criteria of the National Standard for Soil Environment Quality (GB15618-2008), though content of the residues in some individual samples were found to be higher than the criteria. Samples with HCHs and DDTs residues higher than the criteria accounted for 4.53% and 9.05%, respectively, of the total number of samples. Among them, only 2 samples exceeded Grade II criteria of the national standard in content of HCHs residues and 5 did in content of DDTs residue. To sum up, in the soils of the two peninsulas the contents of endosulfan, HCHs and DDTs residues were fairly low.

Abstract:In South China, application of winter green manure crops into the double rice cropping system has been proved to be a high effective rotation pattern in improving soil environments, soil fertility and rice yields，and is very beneficial to the sustainable agriculture. The effects of long-term application of green manure crops on soil microbial biomass carbon, soil microbial biomass nitrogen and the seasonal fluctuation of soil microbial biomass properties in red paddy soil were still not clear enough. Based on a 31-year long-term field experiment on cultivation of double cropping rice and winter green manure in red paddy soil in South China, soil microbial biomass properties were investigated at different stages, aimed to provide a theoretical basis for deliborating mechanism and effects of winter green manure on transformation of soil carbon and nitrogen in the paddy ecosystem. The long-term field experiment includes 4 treatments, i.e., rice-rice-milk vetch (RRV), rice-rice-winter rape (RRP), rice-rice-ryegrass (RRG) and rice-rice-winter fallow (RRF). Soil samples were collected at 4 different typical stages, i.e., flowering stage of winter green manure crop (S1), after the incorporation of green manure (S2), mature stage of early rice (S3), and after the harvest of late rice (S4), for analysis of soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), soil microbial quotient and soil microbial biomass carbon to nitrogen ratio (SMBC/SMBN). The results showed that the cultivation of green manure crops increased the contents of SMBC, SMBN and soil microbial quotient. Especially at the S4 stage, when soil properties were relatively stable, all the green manure treatments were significantly higher than those in the RRF treatment, and similar trends were observed for the annual mean values. The SMBC and SMBN were most influenced by the leguminous green manure milk vetch. Compared with the RRF treatment，they were increased by 21.12% and 98.45%, respectively, at the S4 stage, and by 15.92% and 3.49% for the annual mean values, respectively. The annual average values of soil microbial quotient in RRV, RRP, RRG were 3.61%, 3.66% and 3.61%, respectively, significantly higher than that in RRF treatment (3.13%). Although the SMBC, SMBN and soil microbial quotient were affected by sampling time profoundly, they all showed similar trends at all the 4 sampling stages, i.e., no significant differences between the stage of S1 and S2, down to the lowest level at the S3 stage, and up again at the S4 stage. The SMBC to SMBN ratio did not vary much among different treatments but fluctuated obviously with the sampling stages, i.e., highest at the S3 stage (when soil being flooded) and lowest at the S4 stage (when soil being non-flooded). It could be concluded that soil microbial properties were improved obviously after the long term cultivation of winter green manure crops in red paddy soil in South China, furtherly supporting that the cultivation of winter green manure crops is an effective way for soil fertilizing in red paddy fields.

Abstract:To study effects of intercropping tomato with leguminous crops on growth of tomato, a field experiment was carried out in the suburbs of Shanghai, East China. The experiment was designed to have four treatments: (I) monocropping tomato, as control; (II) intercropping tomato and kidney bean (Phaseolus vulgaris L.); (III) intercropping tomato and Phaseolus vulgaris L. var. humilis Alef. (IV) intercropping tomato and amaranth (Amaranthus mangostanus L.). Rape cake manure was applied to each plot as base fertilizer at a rate of 1.0 kg m ^-2. No sidedressing of fertilizers, pesticides or herbicides were applied during the whole experiment to exclude their disturbances to tomato growth, soil nutrients and enzyme activities.It was found that intercropping tomato with legume could significantly increase plant height of tomato. Compared with control (Treatment I), Treatments II and III increased plant height of the tomato by 10.0% and 10.1%, respectively; and Treatment II increased tomato yield by 15.7%. The two treatments also significantly increased soil nutrients. Compared with control, Treatment II increases total N in the soil by 16.9%; alkali-hydrolyzable N by 14.0%; available P by 26.6% and available K by 23.4%. Likewise, Treatment III increased alkali-hydrolyzable N and available P by 8.0% and 22.9%, respectively. Besides, the treatments significantly increased soil enzyme activities. Compared with control, Treatment II increased the activities of urease, sucrase and phosphatase by 64.6%, 26.8% and 25.5%, respectively. Likewise, Treatment III increased the activities of sucrase and phosphatase by 17.2% and 15.1%, respectively. In contrast, intercropping with non-leguminous crop, Treatment IV, had no obvious effects on plant height, reduced yield of the tomato by 11.1%. It did not have any positive effects on soil nutrients, except for soil available K. However, it improved the activities of sucrase and phosphatase by 17.4% and 7.5%, respectively. In Treatments II and III, nitrogen fixation by leguminous crops and dense root system of the intercropping system that decomposes soil minerals improved soil fertility significantly, which is the main reason for the increase in tomato yield. In Treatment IV, the non-leguminous crop, amaranth, does not have any capability of fixing nitrogen. So Treatment IV reduced yield of the yield as a result of their competition for N and P nutrients. In Treatment II and III the activity of soil urease was significantly enhanced as the treatments increased soil N. The activities of sucrase and phosphatase were significantly enhanced in all the intercropping treatments possibly because intercropping had denser roots.Urease activity was significantly correlated with the contents of total N, alkali-hydrolyzable N, available P and available K in all the plot soils (p<0.05). Especially, the correlation coefficient between the urease activity and alkali-hydrolyzable N reached 0.928 (p<0.01). The activity of sucrase was significantly correlated with the contents of total N, alkali-hydrolyzable N, organic matter, total P, available P and available K（p<0.05）in the soils; and that of phosphatase significantly with total N, alkali-hydrolyzable N, available P and available K（p<0.01）. This fully suggests that there is a close relationship between enzyme activities and nutrient contents in the soils. Intercropping tomato with leguminous crops can not only raise soil fertility, but also increase tomato yield, thus making it feasible to reduce the use of fertilizer. Especially, intercropping of tomato with kidney bean can not only increase yield of the crop, but also make full use of space and raise land use efficiency, as the stems of kidney bean grow upward and wind around tomato plants. This, therefore, is a promising cultivation mode for tomato.

Abstract:With a field plot experiment, differences in fusarium wilt disease index between three faba bean cultivars different in resistance to the disease were studied, and with a nutrient solution culture experiment, contents of free amino acids in root exudates of the plants were determined and their relationships with incidence of fusarium wilt were analyzed. Results show that the resistance to fusarium wilt of all the three cultivars of faba bean cultivars increased with increasing total content of free amino acids in the root exudates Of the fifteen kinds of amino acids detected in the root exudates of faba beans histidine was specific to resistant faba bean cultivars while proline was to susceptible cultivars. Arginine was not found in the root exudates of all the three faba bean cultivars. Disease index was negatively related to the contents of serine, methionine and lysine, with serine being the most significant, but fusarium wilt disease index was positively related to the contents of the other thirteen amino acids. High contents of serine, methionine and lysine and high Ser/Gly and Ser/Ala ratios were found inhibiting occurrence and development of faba bean fusarium wilt, while high contents of Aspartic, threonine, glycine, alanine, valine, tyrosine and phenylalanine were inducing occurrence of faba bean fusarium wilt. Faba beans different in variety vary in content and composition of free amino acids in their root exudates, which is one of the main reasons why the beans are different in resistance to fusarium wilt.

Abstract:A field experiment was conducted to investigate effects of wheat and faba bean intercropping on diversity of metabolic functions of rhizosphere fungal community using the Biolog micro-plate technique for analysis. Results show that compared with that in CK (single cropping) rhizosphere fungi in the intercropping treatment was obviously higher in average well color development (AWCD), and the effect was more significance with Faba bean, rather than wheat. Biolog FF plateanalysis indicates that intercropiping enhanced thecapacity of the rhizosphericfungiunder intercropped wheat and faba bean of utilizing carbonsin polymers, carbohydrates, carboxylic acids, amino acids and amines, increased their substrate richness by 29.2% and 30.3% respectively, total carbon utilization intensity 63.30% and 52.02%,respectively. Among the six categories of carbon sources, carbohydrates, carboxylic acids and amino acids, was much higher than the others in carbon utilization intensity, reaching36.66%~45.99%, 25.65%~27.70% and 16.37%~20.67%, respectively. Shannon index (H) and richnes index(S) were also found to be higher in the intercropping system than in the monocropping one. Principal component analysis demonstrates that intercropping significantly altered the rhizosphere fungal communityunder thewheat and faba bean.Therefore, it can be concluded that intercropping apparently increases metabolism intensity of the carbon sources by the rhizosphere fungi under the wheat and faba bean and significantlytheir diversity and richness, thus altering their community structure. Hence, intercropping of wheat and faba bean is an effective approach to improving micro-ecological environment of the rhizosphere of monocroppedfaba bean．

Abstract:Soil nitrogen-fixing bacterial communities play a key role in nitrogen recycling in phyllostachys edulis plantations forest soils. However, so far little has been reported on changes in structure and abundance of the nitrogen-fixing bacterial community in Phyllostachys edulis plantations with age of cultivation. In this study, soil samples were collected from the topsoil (0~20 cm) layers of four Phyllostachys edulis plantations different in cultivation history (5 a, 9 a, 15 a and 18 a, respectively) and a Pinus massoniana plantation similar in ecological background (as control, CK). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time fluorescent quantitative PCR (qPCR) were employed to characterize changes in structure and abundance of the soil nitrogen-fixing bacterial communities in the soils, separately. Factors affecting structure of the nitrogen-fixing bacterial communities in soils were analysed using the redundancy analysis method. Results show that soil pH and contents of readily available potassium, available phosphorus, organic matter and ammonium nitrogen in the soil increased greatly 5 years after the transformation of Pinus massoniana stand into Phyllostachys edulis stand, but then decreased gradually and leveled off with the plantation going on. Shannon and richness indices and nifHgene copies of the soil nitrogen-fixing bacterial communities show similar trends. Sequencing of DGGE bands reveals that in the soils under Phyllostachys edulis plantations, the N₂-fixing bacteria are all unculturable azotobacteria that are quite similar to Bradyrhizobium sp. Redundancy analysis (RDA) shows that age of cultivation clearly affected structure of the soil nitrogen-fixing bacterial communities in Phyllostachys edulis plantations and the community structures in the soils after 5 a and 9 a of cultivation differed sharply from that in control. However, differences between the plots of 15 a and 18 a and control were not so significant. Besides, soil readily available potassium, available phosphorus, organic matter and pH were the main factors affecting nitrogen-fixing bacterial community in soils under Phyllostachys edulis plantations. Therefore, changes in soil fertility induced by long-term Phyllostachys edulis plantations can potentially influence diversity of the soil nitrogen-fixing bacteria and alter their community structure.

Abstract:To explore effects of different N fertilizer application types on quality and quantity of soil organic matter, soil samples were collected from plots under a long-term (32 a) fertilization field experiment in Huaibei City, Anhui Province, China, for analysis of soil organic carbon storage. Results show that compared CK (no fertilization) and Treatment NPK (chemical fertilizer), Treatment OM (organic manure only) significantly decreased soil bulk density. Although, Treatment NPK and Treatment OM both had obvious positive effects on contents of soil organic matter and active soil organic matter, Treatment HMNPK (high rate of organic manure plus NPK) was the most significant in the effect. The treatment also showed significant positive effect on soil carbon pool management index (CPMI), while Treatment NPK lowered CPMI, indicating that soil fertility decreased under the effect of Treatment NPK.In terms of soil organic carbon storage in the 0～20 cm soil layer, Treatment HMNPK was the highest and followed Treatment OM, Treatment NPK and CK, sequently. Therefore, it can be concluded that long-term application of organic manure helps build up soil quality, especially, when in combination with application of chemical fertilizer, both at a rate higher than N 262.5 kg hm^-1 a^-2.

Abstract:A field experiment was carried out of interplanting forage grasses (Trifolium repens Linn., Vulpia myuros C. and Lolium perenne L. ) in a two-year old ‘Fuji’ apple (M. domestica Borkh. cv. Red Fuji/ Malus hupehensis Rehd. ) orchard to explore effects of grass interplantation on growth of the apple trees, and utilization, loss and residue of nitrogen in the 0~60 cm soil layer of the orchard, using the ¹⁵N-labeled tracer method. Results show that compared with the apple trees in the plot without grasses interplanted, the trees in the plot with grasses interplanted were found to have an increasing trend in total fresh weight of a plant, thickness and length of new shoots and root-shoot ratio; The effect on root length, roots length density and roots surface area of apple trees was the most significant in the plot interplanted with Trifolium repens Linn., which was followed by the plot with Vulpia myuros C. and the plot with only apple the last; Nitrogen utilization rate also varied sharply between plots, being the highest in the plot with Trifolium repens Linn, which was followed by the plot with Vulpia myuros C. and the plot with only apple in the end; In the plots interplanted with herbage ¹⁵N residue was found mainly in the 0~20 cm soil layer, and higher in content than that in the 0~20 cm soil layer in the plot of apple only. However, the amount soil of residual ¹⁵N in the 20~40 cm and 40~60 cm soil layers was the highest in the plot with apple only, which was followed by the plot with Lolium perenne L., and the plot with Trifolium repens Linn. in the end. In terms of nitrogen loss rate, the four plots displayed an order of apple only > Lolium perenne L. > Vulpia myuros C. > Trifolium repens Linn.. In short, all the findings indicate that planting Trifolium repens Linn., Vulpia myuros C. and Lolium perenne L. in apple orchards improves nitrogen utilization rate and consequently reduces nitrogen loss rate by a certain degree.