Abstract:The ¹⁴C tracing technology and isothermally sealed incubation method were used to study effect of inorganic N on mineralization of straw ¹⁴C in a combined fertilization system of mineral N and plant residue for one year.Results indicated that in non calcareous soil,application of inorganic N accelerated mineralization of straw C,but relatively strengthened the immobilization process of indigenous soil C.It might be likely that the increase in the amount of straw C mineralized compensated for the increase in the amount of indigenous C immobilized,hence,inorganic N might have only little ef ect on mineralization of total organic C in soil.The annual mineralization rate of straw ¹⁴C was greater in submerged soil than in upland soils,and the increase in the annual mineralization rate of straw ¹⁴C by inorganic N was similar either in submerged soil or in upland soils.In calcareous soil,inorganic N retarded mineralization of both straw ¹⁴C and soil native C.Promotion of organic C decomposition by inorganic N was not found in this study.This paper put forward some new views about the effect of N fertilizer on transformation of organic C,and about the role of N fertilizer in the internal cycling of soil organic C in the combined fertilization system of mineral N and plant residue.

Abstract:Effects of iron and two nitrogen forms(nitrate and ammonium nitrogen) on remobilization of iron from diferent iron pools in maize plants were studied in a split-root system in nutrient solution under controlled conditions.The results showed that,Fe nutrition status in young leaves of maize was affected not only by Fe pools strength in maize plants,but also by diferent nitrogen forms under Fe deficiency stress.When there was no Fe pool in root system,NH₄-N supply led to 32% of Fe in the primary leaves to be remobilized to young leaves of maize plants,and 40% of Fe in roots with Fe pool to be remobilized.Regardless of root Fe pool,active Fe in new leaves and Fe concentration in xylem sap were increased by NH₄-N application.

Abstract:Variation of phenolic acids during decomposition of some organic materials was studied by means of moist and aerobic cultivation.The results show that rice straw,pig feces and sawdust contain some kinds of phenolic acids such as p-hydroxybenzoic acid,p-coumaric acid and frulic acid.The contents of p-coumaric acid in rice straw and pig feces are the highest,and followed by that of frulic acid.The content of p-hydroxybenzoic acid in sawdust is the highest,followed by that of p-coumaric acid.During decomposition,the main kinds of phenolic acid in rice straw and pig faces are p-coumaric and frulic acids while in sawdust p-hydroxybenzoic and p-coumaric acids.The total phenolic acid contents are in a decreasing order,rice straw,pig feces,and sawdust.The total phenolic acid contained in the three organic materials reached the maximum after 20~30 days of decomposition,and reached a stable and minimum state after 40~50 days.

Abstract:In central Jilin a ¹⁵N micro-plot experiment was conducted in a piece of farmland of black soil to study ef ect of the depth and frequency of N application on utilization rate of N fertilizer.Results show that the treatment of sidedressing twice at a depth of 10~15cm increased the rate from 24.5% in the CK,the traditional once for all shallow sidedressing on the ridge,to 39.0%,clearly indicating that deep and split application of N fert ilizer improves utilization rate.The total fertilizer N loss was 16%~27%;N residual in the soil 34%~54%;about half of the ¹⁵N labeled fertilizer was taken up by maize during the grain-forming period after Aug.1;70%~90% of the loss occurred within the 35 days after the N fertilizer was sidedressed;and crop response to the application was not significant.

Abstract:Time domain reflectometry(TDR) is widely used in determining water content for general agricultural soils.But for soils with high bulk electrical conductivity,such as saline soils or heavy clay soils,the TDR measurement was not ideal because of dielectric losses.Based on experiments,this work intended to explain the phenomenon of TDR measured value deviating from actual water content.The result showed:when the water content was low(sand,<0.15cm³cm^-3;sandy loam,<0.18 cm³cm^-3),increasing electrical conductivity was not linely to induce a higher measured value.While the water content was high and the electrical conductivity up to 8 dS m^-1(sandy loam) and 11 dS m^-1(sand),TDR measured value was apparently higher than the actual water content.In the case of higher electrical conduct ivity(<16 dS m^-1),K a was still in linear correlationship with the actual water content,while the slope and int ercept were influenced by dielectric loss.In this study,a calibration equation was set up,considering the influence of electrical conductivity was set up.The increase in soil clay particle content also induced TDR measurement deviation.When the soil water content was low,the measured value was lower,and when the soil water content was high,the measured value was higher.If the clay content was<50%,the measured error would be<0.02cm³cm^-3.

Abstract:The change of water use efficiency over the years was calculated from the long-term data of crop yields,precipitation,the amount of irrigation water diverted from the Yellow River or pumped wells and replenishing water from ground water in Fengqiu county.Results showed that water use ef iciency in this county has enhanced steadily from 2.25 to more than 9.00 kg hm^-2mm^-1 due to technological development.The increase of water use efficiency was mainly caused by the establishment of water conservancy facilities,soil improvement,extension of new crop variet ies and continuously increasing application rates of N,P fertilizers.According to our studies,fertilizers had a great potential for the further increase of the efficiency of water use in Fengqiu county,especially for crops with growth period in autumn.With economic development,advanced technologies,such as plastic cover and trickle irrigation shall be steadily made popular.

Abstract:The paper addresses hygroscopic coefficient and wilting point(with barley,H ordeum sativum Jess,as an indicator) and their relations to soil particle<0.01mm content and salt content of saltaf ected soils in Jingdian irrigation zone,Gansu.The results il ustrated that salt content significantly af ected hygroscopic coefficient.In soils with total salts of 7.58~17.39g kg-1 it could reach 17.39%~38.30%(gravimetrically).With decrease in salt content,effect of particle<0.01mm content on hygroscopic coefficient increased.The influence of salt component on hygroscopic coefficient varied in the order of Cl^->Na⁺>Mg²⁺\Ca²⁺>SO₄^2-.It seems that there was no great difference between the effects of particle<0.01mm content and salt content on wilting point,which,however,both reached a significant level.Comparat ively,wilting point was less sensitive to salts content than hygroscopic coef icient was.The effect of salt components on wilting point was similar to that on hygroscopic coefficient.On the correlation of wilting point with hygroscopic coefficient,particle<0.01mm content,salt content and electrical conductivity,three models were presented to predict the wilting point of salt-affected soils in the zone.

Abstract:China is a country with a vast territory and a huge variety of soil types.The soils of China contain not only organic matter and humus but also plenty of disperse carbonate,calcareous concretions,or shell and coral etc.,which are good objects suitable for radiocarbon dating.Quite a number of types soils have been dated,belonging to 12 orders:Histosols,Anthrosols,Spodsols,Vertisols,Aridsols,Halosols,Gleysols,Isohumisols,Ferrisols,as well as Luvisols,Cambisols and Ent isols.Authors place emphasis on radiocarbon dates of organic matter and humus composition in chestnut soils(Isohumisols order),calcareous concretions and disperse carbonate in shajiang black soils and swelling clay soils(Vertisols order),and shell-coral in the soils in South China Sea Islands(belonging in Isohumisols,Halosols and Entisols respectively).Organic and inorganic ¹⁴C dates show that most soils in China are products of Holocene,with those of the late-and mid-Holocene in dominance.The soil ages of Stagnic and Orthic Anthrosols are closely related to the long agricultural history of China of more than 6000 years.Comparatively,only a few soils formed at the end of the late Pleistocene.And some soils have several formation and development phases.Therefore,their ages,spanning different geological periods,have polygenetic features.

Abstract:Based on the data gathered of the growth of E.grandis×E.urophylla stands and of the soil under the stands and with the aid of a new method-artificial neural network,study was conducted on leading soil factors inf luencing growth and yield of E.grandis×E.urophylla in South Fujian hilly area.The BP model was established simulating the relationship between the leading soil factors and the growth of E.grandis×E.urophylla.The results demonstrate that the leading soil factors,i.e.,the soil capillary moisture-holding capacity,humus layer thickness,soil layer thickness and available phosphorus,are in a nonlinear mapping relationship with the growth of E.grandis×E.urophylla.The accuracy of BP model in simulating the fast growth and high yield of E.grandis×E.urophylla in South Fujian hil y area is 96.39%,fairly higher than the traditional linear regression model.Therefore,this study not only provides a basis for improving E.grandis×E.urophylla,but also opens up a new train of thought in the application of artificial neural network to the research of selecting forest-suitable sites.

Abstract:In this paper,efforts are made to illustrate the significance of statistics of the reserve and density of organic carbon in soil,to introduce the latest development of the research in this field both at home and abroad,and to explore an accurate method for calculating densities of carbon in soils with an example,and hence to provide a potential approach to a general meticulous statistics of the organic carbon reserve in the soils of China.

Abstract:The paper is intended to provide a structured,logical pathway for determining whether or not a carefully designed form of land management is likely to prove sustainable in a particular situation over a set period of time in a regional scale.Based on the five aims of the FESLM:An international framework for evaluating sustainable land development by FAO,i.e.productivity,security,protection,viability,and acceptability,the authors put forward a basic framework for evaluating indicator system consisting of 46 evaluating factors and establish weights,target values of the indictors in regional sustainable land management.Comprehensive evaluation is made on sustainable land management of Wuxi City in 1997,with a resultant value of 65.42%.The result shows that the land management at present in Wuxi City is st ill at a developing stage.The authors put forward a new method to diagnose the obstacles in sustainable land development.All indicators individual into 4 obstacle layers with 0.5% of gross aim in sustainable land management.The chiefreasons accounting for low level of sustainable land management exist in land use in Wuxi City at present as follows:Firstly,though the agricultural output value and products have been growing,the land and labor productivity remains at a still low level.Secondly,there are frequent flood disasters and serious environmental pollution.Thirdly,the median and low productive land is in the ascendant and the basic establishments draggle.Fourthly,R & D are so low that the product ivity is limited.Lastly,it is dificult to form scale economy and gain scale benefits because of small-scale land management,which leads to low income.According to the above said problems,the authors put forward some measures as follows:Firstly,increase the funds for R&D,alternate the way of growth and improve the productivity.Secondly,restructure basic establishments of farmland,use fertilizer reasonably and protect arable land.Thirdly,improve the ability of resisting disasters and optimize the environment.Fourthly,expedite agricultural industrialization,accelerate scale land management,and increase farmers.income.Lastly,prefect mechanism of land management and establish perfect rules and regulations on sustainable land management.

Abstract:In this paper presented are results of a study on N pollution in water bodies in Suzhou region,which is located in the center of the Taihu Valley.The present situation of N pollution in the major rivers and lakes as well as in the shallow groundwater in rural areas are evaluated.For diferent water bodies,concentrations of PO₄^3- and different forms of inorganic N,N source in the rivers,lakes and well waters are investigated.Seasonal variation of N polution in the rivers and lakes are compared and countermeasures are brought forward for mitigating N polution in water bodies in this region.

Abstract:Laboratory study on dynamics and forms of ¹⁴C-metsulfuron-methyl residual was investigated in 15 soils.It was found that there was a steady loss of ¹⁴C-metsulfuron-methyl with time in soils,which could be described by the firs-torder equation.Soil pH was positively related to the half-life,total ¹⁴C-residues and extractable ¹⁴C-residues,but negatively to the bound ¹⁴C-residues.The degradation rates and ¹⁴C-residues binding rate varied with the soil microbial biomass.The humic substances and clay could also influence the degradation rates and residual forms of ¹⁴C-metsulfuronmethyl in soils.Soil pH,microbial biomass and fulvic acid were the most significant factors controlling the degradation rates and forms of ¹⁴C-metsulfuron-methyl residual in soils.The regression equations between metsulfuron-methyl residues and soil propert ies were established after the stepwise regression analysis.

Abstract:Biodegradation is an effective way to degrade organic chemicals in a soil-wate-rmicrobes system.In order to account for the recalcitrance of residual chemicals in soil,a new theory-organic chemical sequestration inside soil particles has been applied in this paper.A mathematical model,which is developed based on this theory,can predict the time and extent of PAHs biodegradation.The model simulation results match successfully with the field data of a bioremediation process in LTU site on Alcoa's Massena,New York.By using mathematical model,3,4,5 and 6-ring-PAHs biodegradation processes and regularities in remediation sites have been predicted in this paper.

Abstract:The variety and contents of organic and amino acids produced by strain NBT under culture of feldspar were deterimented.The results showed that strain NBT was able to produce Oxalic,tartaric,citric and malic acides,whose concentrations ranged between 5.16~217.30mg L^-1,3.44~291.94mg L^-1,4.08~113.31mg L^-1 and 3.15~108.89mg L^-1 respectively.Several kinds of amino acids were also produced.In media with nitrogen,the strain NBT could produce IAA,GA3,ZR and IPA.Their concentrations ranged between 0.54~3.77nmol mL^-1、0.19~2.97nmol mL^-1、0.91~2.62nmol mL^-1 and 5.49~31.15nmol mL^-1 respectively.The flask shake experiment showed that the strain NBT was capable of not only releasing potassium from soil minerals but also absorbing most of the potassium released.The K adsorbed by the cells accounted for 88.86%~95.05%of the Kreleased by the strain NBT.

Abstract:长江中游平原湖区地势低洼、洪涝频繁,历史上洪水带来的大量泥沙是该区土壤母质的主要来源.由于人类活动的影响、特别是长江干堤的兴建加固和围垸垦殖,使堤内新沉积极少,只有堤外的老洪泛区即洲滩常有洪水沉积,堤防内外土壤发育环境因而发生了深刻的变化.堤内沿着耕作土壤的方向发育,多为灰潮土或淹育型水稻土;而堤外则形成了自然或半自然状态的草甸土.1998年长江大洪水过后推行了“平垸行洪,退田还湖”治洪措施,使受洪水沉积影响的范围明显增加.据统计,洞庭湖计划退田还湖和长江干流平垸行洪的民垸总面积有1846km².

Abstract:影响土壤降水入渗的主要因素是土壤自身的性质如土壤质地、容重、含水率、地表结皮、水稳性团粒含量、利用方式等.土壤质地不同^[1],土地利用方式不同^[1,2],土壤入渗速率均存在较大差异.周国逸等人的研究认为,地表结皮的形成能很快降低土壤入渗速率,使裸地土壤入渗速率减小到未形成结皮前的4.84%^[3];蒋定生等研究黄土高原土壤入渗速率时发现,土壤瞬时入渗速率与土壤容重、含水量、水稳性团粒含量间存在显著相关性^[4].由于受野外降雨入渗试验装置的限制,上述研究均停留在双环法试验或室内外人工模拟降雨定点小区实(试)验水平上,而有关整个流域土壤入渗空间变异性问题却研究较少.

Abstract:以天然或合成的聚合物作为土壤结构改良剂在近年来引起了人们的关注^[1～3],聚合物土壤结构改良剂通过其带功能基团的分子和分散土壤颗粒之间以缠绕、包裹、贯穿、吸附乃至形成化学键等方式创建和稳定水稳性团粒结构,在提高土壤物理肥力,改善土壤保肥性、保水性、改良盐碱土以及特别在抑制水土流失方面具有重要作用^[4].本文选取代表南亚热带地区土壤的赤红壤为实验土样,该土壤酸度大,养分含量低,表层砂化普遍,有机质含量一般较低,质地较轻,结构性能较差,团粒结构水稳性差,极易分解,因此,土壤的保水和保肥能力差,水土流失严重^[5].