Abstract:Based on observed data of textural layers from a lot of soil profiles in a 15km² area in a fluviogenic plain (North China Plain),this paper deals with spatial variations of some indexes of clay layers and probability distribution characteristics of different types of textural layers in the area by geostatistical method and general probability statistics.The results show that the maximum relative distances of the thickness and emerging depth of first clay layers,and the total thickness of clay layers in lm depth and 2m depth are all in the range of 1500-2000m,and that the thickness of each type of textural layers is distributed lognormally.

Abstract:The Korla area,Xinjiang Autonomous Region was selected as the case study of the wind eroded area in western China.The Caesium-137 technology was employed first time to elucidate the relationship between the land use types and land degradation. Sampling sites can be divided into three groups,including barren land,arable land and grass land.The average soil loss rates in the past 31 years for barren land,arable land and grass land are 5987.21,3537.29 and 3171.31t/km²·year respectively.It is significant to apply the new tracing technology to do some quantitative research on land degradation in the wind eroded area in China.

Abstract:The method and process of the grading of agricultural lands were studied using ARC/INFO software.Based on ARC/INFO platform,the second development about the software was conducted to realize the automation of inquiry and check.The soil series combined with land use was regarded as the assessment unit,and the land quality situation was illustrated by quantitative analysis in the research area.

Abstract:This paper deals with the distribution and transformation of cadmium species in rhizosphere and nonrhizosphere of wheat and rice in red soil and yellow brown soil using a rhizobox or rhizobag and a sequential extraction procedure for the speciation of Cd.Results showed that predominant species of Cd in two soils are not same. EXC-Cd(exchangeable-Cd) is the most important form in red soil while in yellow brown soil Carb-Cd (bound to carbonates) is the most important.In red soil,the contnet of FMO-Cd (bound to iron and manganese oxides) and OM-Cd (bound to organic matter) in rhizosphere of rice are higher than those in nonrhizosphere,which may he due to the activity of rice root and the action of microorganisms on the root surface.The interaction between Pb and Cd showed that the content of EXC-Cd is higher in the presence of Pb in both rhizosphere and nonrhizosphere.the content of OM-Cd,however,is much lower in the presence of Pb.

Abstract:Calcium-bound organo-mineral complexes in soil belong to a kind of outer sphere complexes.SO₄^2- in sodium sulphate,as a coordination agent,can destroy Ca-bound organomineral complexes by coordinating Ca²⁺ and extract Ca-bound humus.This work examined the ability of sodium sulphate to destroy Ca-bound organo-mineral complexes and to extract humus from soils and synthetic organo-mineralcomplexes.It was proved that sodium sulphate was a suitable agent to differentiate Ca-bound complexes from Fe/Al-bound complexes in soils.A detailed method for separating Ca-bound complexes by sodium sulphate is described.Finally,a follow-up extractant to sequentially extract Fe/ Al-bound complexes from soils is also proposed.

Abstract:The adsorption and desorption of the herbicide imazethapyr,(RS)-5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) nicotinic acid,on various soils were studied.Adsorption isotherms conformed to Freundlich equation.The K_f values increased with increasing organic carbon content of the soils.On the other hand,the behavior of imazethapyr in the soil is strongly affected by pH and clay content.As pH decreased,imazethapyr was more strongly absorbed,reducing its mobility and plant availability.Desoiption isotherms also conformed to Freundlich equation,but K_des values were higher than those of adsorption and increased with increase in the concentration of initially adsorbed imazethapyr.Through preparing the homoionic Na⁺-, Ca²⁺-,Cu²⁺-,and Al³⁺-saturated clay self-carrier membrane and using FT-IR,we studied the interaction mechanism of imazethapyr with the clay mineral.The results of X-ray diffraction also revealed that imazethapyr can enter the inner layer of bentonites and fornl complexes with the interlayer canons.

Abstract:¹⁴C-labelled goat manure,elephant grass and its root were incubated with alfisol at 30℃ for 365 days,under 70% WHC (upland) and submerged conditions.Another set of incubation experiments using ¹⁴C-labelled rice straw and maize straw with ultisol and vertisol were conducted at 30℃ for 112 days under the same water regimes.The rate of decomposition of ¹⁴C-labelled goat manure and all the related plant materials or residues obviously revealed faster in submerged soils than those in 70% WHC soils irrespective of soil types,consequently the amount of residual ¹⁴C remained in soils showed the opposite trend.The half life of added organic substrates was 1.4 to 2.0-fold greater in 70% WHC condition than that in submerged condition.Contrary to the traditional concepts of decomposition rates of organic matter in upland soil and submerged soil,it is considered that either the rate or the amount of organic carbon decomposition in submerged soil is substantially greater than that in upland soil if both soil conditions are adequate to microbial metabolism.

Abstract:A flow technique was applied to investigate the effect of organic acids with low-molecular-weight on phosphorus release from 3 soils:2 calcareous soils and 1 acidic soil (red earth).It was indicated that the release of soil phosphorus was significantly stimulated by organic acids for all of 3 soils tested.For calcareous soils, the ability of mobilizing soil phosphorus of organic acids followed the order:oxalic ≥ citric> malic>tartaric acid.As for red earth,the release of soil phosphorus was highly correlated with soil aluminum and iron extracted,and the mobilizing ability of organic acids for phosphorus followed the order:citric>oxalic>malic>tartaric acid.Regression analysis revealed,that parabolic diffusion equation was applicable to describe the release kinetics of soil phosphorus,as affected by organic acids (r>0.94). Both citric and oxalic acids increased the P diffusion coefficients significantly in all of 3 soils.However,remarkable increase of P diffusion coefficients by tartaric acid only occurred in acidic soil.

Abstract:According to the studies on dynamics of nutrients in the agroecosystem of red soil for 5 years,the laws of nutrient cycling and balance in red soil agroecosystem are discussed,the evaluation of nutrient balance is illustrated with examples,and some measures for regulating nutrient cycling and balance are put foward.

Abstract:Based on a pot experiment conducted with seven upland soils collected from Huhei and Hunan Provinces,a research was made on the dynamics of hot-water soluble boron(HWSB),Mannitol-B and NH₂OH·HCl-B during rape growing periods.The results showed that from before rape transplanting to flower-bud appearing,then to fully blooming,the content of HWSB in the treatment without boron had a tendency of constant increase,but that in the treatment with boron went up slightly after it had decreased obviously.And the content of Mannitol-B tended to keep increasing in both the treatments.At the same time,the content of NH₂OH·HCl-B tended to be stable.The relationships among the three kinds of soil boron were that Mannitol-B and HWSB could transform with each other under the effect of environmental factors;NH₂OH·HCl-B and HWSB were fundamentally the same boron fraction,which was due to that the soils were acidified and the Mn oxyhydroxides were reduced strongly after the several planting experiments.For the same reason,relationship between Mannitol-B and NH₂OH·HCl-B in the experimental soils weakened compared to that in the primary soils.

Abstract:The classical one-domain model with convection-dispersion equation was used in this study for describing a nonreactive solute transport in soil.By the experimental studies on the effect of soil aggregate size and pore water velocity on the transport of nonreactive solute in soil column,it was found that:tritium breakthrough curves could be well predicted by convection-dispersion equation;with the increase of aggregate size,early breakthrough,tailing and small peak were more pronounced by tritium breakthrough curves in soil column,best fitted D value increased as well;and D was proportional to pore water velocity in this study,and dispersion increased with the increase of pore water velocity,which is of great importance for studying the transport of reactive solute in soils and for predicting the fate of agricultural chemicals in field conditions.

Abstract:The characteristics of temporal and spatial distribution and fractions of thallium in floodplain sediments (soils) of Liaoning Province were dealt with in this paper based on the basic thought of "chemical time bombs (CTB)".Seventeen samples of floodplain sediments (soils) which covered all the area of Liaoning Province were obtained through wide-spaced sampling,and four fractions,i.e.,silicates-bound (SILB), sulfides-bound (SLJLB),organically bound (ORGB) and Water-soluble (WS) fractions, were found through fractionation.The results indicated that:1.From pre-industrialization (1943) to now (1993),the content of thallium in soils of Liaoning Province increased obviously with the rapid development of industry and agriculture,and some parts such as the Daling River Basin and Taizi River Basin have been slightly polluted by thallium,therefore,it could be predicted that the area polluted by thallium would increase fifty years later (i.e.,the year 2043).2.Thallium mainly existed in SILIB and WS fractions,secondarily in SLTLB and ORGB fractions.3.The accumulation of thallium in the soils and sediments was mainly caused by human activities,and the rate of accumulation was closely related to the fractions of thallium.4.The fractions of thallium in the soils and sediments were related to the physical and chemical properties of soils and sediments themselves such as soil types,pH and organic matter to a certain extent.

Abstract:This paper deals with the reasonable (protective) application of nitrogen fertilizer for soybean.It was by means of the ‘nitrogen-factor effect' of wheatstraw with a high ratio of C/N to regulate the immobilization mineralization process of soil or fertilizer nitrogen.The biological effect of protectively applied nitrogen on modulation N-fixing activity,nitrogen forms in Xyloid liquid,and amount of assimilated nitrogen in soybean were studied.Results indicated that protectively applied nitrogen could decrease even eliminate the inhibiting effect of nitrogen fertilizer on nodulation and N-fixiing activity of soybean,condinate the supply of nitrogen from nodule and soil and increase the relative content of ureide-N and the content of organic nitrogen in its xylon.The normal development and function of symbiotic nitrogen fixation system would be protected.It is beneficial for the synthesis of soybean protein. Therefore,as 20kg/hm² and 40kg/hm² of nitrogen fertilizer were applied,N in the straw of soybean increased by 5.1% and 23.0% and N in the seed increased by 23.0% and 32.6% respectively with protectively application of nitrogen.

Abstract:A luminescence measurement of the luxAB-genes-marked strain (Pseudomonas fluoreseens X16L2) was carried out in liquid culture and soil microcosms.The curves of luminescence kinetics of X16L2 in the liquid culture and soils were similar.The time reaching stable luminescence was about 7 nun after the luciferase substrate (n-decanal) was added.The results also showed that the bioluminescence could reflect the biomass of X16L2 in liquid culture,and the light output of X16L2 was closely related to not only the number.of viable cells but also the cell physiological activity.Soil conditions and native microorganisms had great effects on the survival of the introduced strain,including the number of viable cells and light output as well as the potential luminescence of X16L2.This study also demonstrated that luminometry could not only in situ detect the physiological activity of lux-genes-marked strain in the samples,but also measure its population indirectly.This method was a rapid and economical technique with high stability and sensitivity,and strong selectivity for tracking and recovering target microorganisms released to the environments.

Abstract:The soil moisture (SM),organic matter (OM) and total nitrogen (TN) contents in loess in China have been first evaluated and analysed with near infrared (NIR) spectroscopic method in this paper.The results show that the values measured by NiR are closely correlated with that measured by chemical analysis method and its errors are smaller than the latter.The tested results of 52 samples indicate that the multicorrelation coefficients of soil moisture,organic matter and the total nitrogen are 0.974,0.938 and 0.942 respectively,and their standard deviations are 1.08,023 and 0.042 respectively;The tested results of 74 samples show that the correlation coefficients for three tested items (R) are 0.969,0.921 and 0.928;and the estimated standard deviations are 1.14,0.28 and 0.046 respectively.All the results of the three tested items close to the results obtained by the chemical analytical method in laboratories.

Abstract:A new,simple method has been adopted of measuring the soil thermal inertia in field conditions combined with determining the thermal capacity of the soil in laboratory,by which the relation between the actual value of soil thermal inertia and the content of soil moisture can be calculated.This method is introduced in the present paper and has been applied to different types of soil in North China Plain. The reproducibility,stability and accuracy of the method were examined when the thermal inertia values for different soil (including 4 types of soils and 4 kinds of soil texture) were given.The results showed that the proposed method was applicable.