Abstract:By testing and analysing saturated hydraulic conductivity in soil, water characteristic curve, water diffusion rate and water constant of loamy soils, with different levels of organic matter (O. M.), the relationship between hydrodynamic parameters and soil O. M. contents was explored in this work.

Abstract:Spatial variability and fractal dimension of soil water and bulk density were studied in a soil grown with winter wheat. The area of each plot was 7.5m×7.5m. The measured grid unit was 0.5m×0.5m. Two methods, soil sampling and time domain reflectometry, were employed to determine the gravimetric (θ_g) and volumetric (θ_v) water contents. Soil bulk density (ρ) was calculated from θ_v/θ_g.The data were analyzed with both traditional and geographical statistical methods. Some difficulties were met with the traditional statistical technique. Combined with fractal theory, the fractal dimensions of θ_v,θ_g and ρ were determined, being 1.58-1.75, 1.67-1.75, 1.77-1.83 respectively. Our results suggested that the soil was not a medium with theoretical fractal phenomenon, and the fractal features only existed in the range of specific space.

Abstract:This paper deals with the study on the dynamic changes of water content in upland red soil derived from Quaternary red clay in Jiangxi Province from 1990-1993.Results showed that the physical properties of upper layer of the upland red soil had apparent changes compared with those of the uncultivated red soil. For example, the soil bulk density and soil resistance were decreased, but the soil porosity was increased. The physical properties of that soil in the lower layer were still similar to those of uncultivated soil, but the water-releasing ability and specific water capacity were declined remarkably. Results also indicated that the water storage of upland red soil in different periods of a year was higher than that of uncultivated red soil. As a result, the delay of wilting point in surface layer appeared and the draught depth in soil was shallower in upland red soil in comparison with those in the uncultivated red soil. This behavior shoved that the increase in the acceptance of rainfall and soil water content were beneficial to upland red soil after leveling reclamation of uncultivated red soil. According to the comparison of the water storage measured in field condition with the calculated data of water-storage volumetric capacity, the 0-300cm layer of upland red soil was basically filled with water during the first six months of a year. pore space in water-storage volumetric capacity of 0-100cm layer of upland red soil could increase the acceptance of rainfall during the second half of a year, but in that time richer water storage was still maintained beneth 100cm depth of that soil.Consequently, how to use the water storage in the deep soil layer would be of important significance for alleviation of the draught harm of hilly region in summer and autumn.

Abstract:A new forecast method of the field soil moisture in dry season is built based on the artificial neural networks of the backlpropagation model. The results showed that the forecast accuracy is high enough as compared with the measured values. In general, this method is suitable for routine forecast of the soil moisture in computator condition of IBM PC/386. This new method can be used to study the rational utilization of the soil moisture resources and to decrease the waste of agrometerogic resources of the light and heat for the dry farming regions and dry season in China. It is likely to be a new approach to use valuable observational data of soil moisture.

Abstract:In this study, soils with 2-year continuous no-tillage treatment were sampled from 5 experimental sites representing 5 agricultural districts in Jiangsu Province. The shrinking property and crushing strength of these soils were measured. Soil structure and drainage state could be improved by no-tillage. There existed close relationship between soil volume change rate and the content of clay with diameters of both 0.01mm and 0.001mm. The difference of soil crushing strength between conventional tillage and notillage was also related to clay content. Therefore, in these agricultural districts or soils with a high clay content, it was more important to pay attention to soil filth and to choose a suitable tillage method.

Abstract:Extractable noncrystalline aluminum in red soils could be fractionated into exchangeable Al (ExAl), adsorbed inorganic hydroxy-Al (HyAl), organic complexed Al(OrAl), Fe oxide bound Al (DCBAl), interlayered Al (InAl) and noncrystalline aluminosilicate (NcAl), by the 1 mol/L KCl, 0.2mol/L HCl, 0.1 mol/L Na₄P₂O₇ (pH8.5), DCB solution, sodium citrate (0.33 mol/L, pH7.3) and 0.5 mol/L NaOH sequential extraction. All Al forms were characterized by the intrinsic feature in their composition and properties and closely related to the corresponding properties and ecological characteristics of red soils. In the same soil sample the amounts of various Al forms were of the order NcAl>InAl>DCBAl>OrAl>HyAl>ExAl. With the exception of ExAl content the contents of other five forms of aluminum in the red soils derived from basalt were higher than those from granite. In soils most of the aluminum existed in layer aluminosilicate minerals. Individual extraction of the Al forms in soils was compared with the sequential extraction method.

Abstract:The kinetics of changes in active N (0.05mol/L CaCl₂-extractable Ni) in six different soils was studied in laboratory. Two-constant rate equation,y=ky₀t^1/m,could well describe the changing process of active Ni over time. The parameter k could represent the change rate. The higher the k value, the slower the active Ni changed. The parameter k was negatively correlated with soil pH and CEC, but positively with the transfer coefficient (Tc) of Ni from soil to plant. In addition, the practical application of this equation are discussed as well.

Abstract:The effect of phosphorus application rate and its interaction with soil moisture or/and temperature on the self-diffusion coefficient (Da) of phosphate in four textural unsaturated soils was studied. Although a linear increase in the Da value with increasing phosphorus application rate from 0 to 400 mg per kilogram soil was observed in all the soils, the increase extent was greater in the lighter textural soil or the lower buffer capacity soil at the same phosphate rate applied. The Da values influenced by the interactions of factors such as soil moisture, temperature and phosphorus fertilizer rate applied in different soils were different. In order to express the difference in quantity, according to the nonlinear multiple regression equations between Da value and the factors, the "water coefficient", "temperature coefficient" and "fertilizer coefficient" of phosphate diffusion rate were proposed in this paper using the partial differentials of the equations. It was found under the same conditions, these coefficients in the four soils decreased in order as loessal soil>black lu soil> lou soil>yellow cinnamon soil, which.indicated that the effects of the interactions between the factors on the Da value were closely related to soil texture.

Abstract:The release of phosphorus from secondary phosphate rock is influenced by the Ca-P-adsorbing layer on surface of the rock. Washing with NaCl, KCl or NH₄Cl to remove adsorbed Ca on the surface of phosphate rock resulted in a large increase in P extracted subsequently with water. It was suggested that the removal of adsorbed Ca could accelerate the dissolution of apatite by creating a sink for Ca at the solid surface.

Abstract:Adsorption and desorption of boron in the main upland soils of Hubei Province and the boron uptake of rape shoot were studied. The experimental results were fitted to the Freundlich and Langmuir isotherm equations. It was found that there was a significant hysteretic desorption of boron in some tested soils. In this case, the shape of adsorption curve was different from that of desorption curve, and K_e' or n' of desorption equation was larger than that of adsorption equation. Hence, the difference due to hysteretic desorption could be described by the hysteretic coefficient (△K+△n) qualitatively. When △K+△n>0.25, the hysteretic desorption was more significant. The reasons for the hysteretic desorption of boron in soil were very complicated. The contents of amorphous Al and Mn oxyhydroxides were positively correlated with the hysteretic coefficient in the experiment (n=11, r=0.790^** and 0.744^**,respectively).The boron content of plant had a better relationship with adsorption-desorption property of soils. The value of △K+△n was significantly correlated with the content of boron taken up by the plant shoot(r=-0.761^**, n=11). In the case of boron application, the effect of hysteretic desorption on boron uptake by plant could be decreased partly, and plant could absorb more boron in the soil.

Abstract:The hydrodynamic dispersion coefficient is an important parameter for simulating solute transport through soils. KH₂PO₄ solution infiltrated into horizontal columns of five types of soils was tested, and their hydrodynamic dispersion coefficients D_sh(θ) were calculated. results showed that the D_sh(θ) of P was the natural exponential function versus the soil water content θ. The increase of D_sh(θ) with θ was faster when the reaction of P with soil was stronger.

Abstract:Some environmental behavious of cetane were studied using the tracing technique of ¹⁴C-cetane, rice pot culture and sequential solvent extraction method. Results showed that cetane entered easily into rice plant and accumulated in rice grain, thus giving harmful effects on human health. Existing forms and metabolic process of ¹⁴C-cetane in soil and rice were also studied. ¹⁴C originated from cetane maily existed as solvent-extracted form (about 39% of all ¹⁴C), and second one in undecomposed remains of plants (about 25%) and fulvic acid (about 23%) in soil. ¹⁴C existing as carbonat was about 10%. ¹⁴C entering in humic acid (include humin) was less (about 3%). Cetane mainly existed as bound residue in rice, with amount being 98% of all ¹⁴C in plant. The organic solvents-extracted (petroleumether, ether and ethanol) amount was 2%. The shorter the time passed after cetane addition in rice system, and the less the form of bound residues,the more the petroleum etherextracted part.Polar metabolites with a bigger R_f-value accounted for 21% solvent extracted part.

Abstract:Three wheat (Triticum aestivum) varieties,‘Dexij86-33-25' ‘Ke 26' and ‘Lumai No.10’,were exposed to different concentrations of NaCl-Na₂SO₄ (0-50-150mmol/L) in a controlled pot culture system for 40 days.Fresh weights of roots, dry weights and the sodium and potassium contents of stems,leaves and roots were measured to determine growth rates of wheat plants, K/Na ratios, Na uptake rates, Na transport rates and K-Na selectivity ratios (S_K,Na).

Abstract:Using simulated rainfall experiment, interill erosion and rill erosion on slope farmland of loess area were researched through putting nylon net cover on runoff plots to eliminate raindrop kinetic energy, increasing raindrop falling height to increase raindrop kinetic energy and turning up the soil as the contrast tests. The results showed that erosion and sediment can be divided into 4 stages, that is, raindrop splash, interrill erosion, rill erosion and runoff erosion after raining. After eliminating 99.6% of raindrop kinetic energy, interrill erosion and rill erosion were obviously reduced, interrill erosion was decreased by 35-61% and rill erosion was reduced by 35-64%. In addition, affecting mechanism of raindrop kinetic energy on interrill erosion and rill erosion was analyzed.

Abstract:In this paper, the authors summarized briefly the retention of phosphorus by soil constituents. Roles of soil.microorganisms, plant roots, mycorrhizae and earthworms in the enhancement of plant availability of soil phosphorus are reviewed. The mobilization of soil phosphorus by soil biota involved mainly solubilization of insoluble inorganic phosphorus by excretion of protons and organic acids, and hydrolysis of organic phosphorus by phosphatases. The processes of phosphorus mobilization were regulated by the equilibrium between soil phosphorus supply and plant P demand. In the last part, possibilities of alternatives of P fertilizers are discussed. It was suggested that by increasing soil biota population and activity soil phosphorus supply could be in sychronization with plant phosphorus demand.

Abstract:The paper deals mainly with the features of phosphatase and the distribution regularities of several enzymes (invertase, alkaline phosphatase, urease and protease) in afforested soils of silting coastal areas of northern Jiangsu. In the fluvo-aquic soil of coastal afforested area, alkaline phosphatase made up 62.6% of the total phosphatase. Suppose the activities of total and alkaline phosphatase are y and x₁ respectively (unit: phenol mg/g), their relation may be discribed by y=-0.04765+1.67426x, r=0.9731. Soil enzyme activities became lower from top to bottom, and they had significant differences in the soil profile. The depth of 60cm for soil sampling could completely meet the need of precision (α=0.05) for the afforested lands and the number of soil samples was 3~4. When the depth was 40cm, the number of soil sample should be at least 4. According to variance analysis, soil enzyme activities had a significant difference in horizontal direction, being far higher in the afforested and farm lands than in the beach land. In the afforested land, the greater the forest age was, the more active the soil enzymes were. Soil enzyme activities in the farm land were similar to those under young forests with intercrops. The same results were also obtained by other statistical methods.

Abstract:The dominant genera of heterotrophic bacteria and filamentious fungi in soils under different types of forest on Wuyi Mountain were studied in this paper. The results showed that the soils had dominant specific genera and relative density of heterotrophic bacteria and filamentous fungi under different types of forest. It was also true even in the different layers of the same soil profile. Generally speaking, in the fertile soils, the dominant genera were large in the amount, with a higher relative density.

Abstract:The experiment results showed that pH of the red earth in hilly orangery was decreased with increasing amount of N applied (r=-0.905) on the basis of the application of organic manure, P and K fertilizers. The mandarin yields varied greatly with the amounts of N applied (y=33.02+12.94x+5.07x²-6.04x³).After application of N the mandarin yield had a significant or correlation with the contents of available N, P and K in the soil and leaves. The invert sugar, reducing sugar and V. C contents were linearly correlated with the amount of N applied but the total acidity was negatively correlated with the of N applied (r=-0.918).So N application could raise the quality of mandarin.

Abstract:The studied area is located at the southeastern edge of the steppe Uap-Ustic lsohumisols, being a transitional zone between fanning and animal husbandry, with seriously desertified lands. Although fanning was developed there on a large scale in the past decades, extensive cultivation and overuse of soil resources has made Uap-Ustic lsohumisols become seriously degraded. The soil degradation was mainly reflected in the changes of soil nutrients, soil texture and water retention. The nutrient distribution with soil depth changed towards that of Aridisol. The contents of gravel and sand increased obviously in the plough horizon. Mechanical composition of that flat farmland developed towards that of aeolian sand sediment. With the increase of farming years the degradation of nutrients, texture and bulk density weakened the soil abilities of water and fertility retention. The mitigation and control of Uap-Ustic lsohumisol degradation need to popularize protective farming techniques, remodel traditional agriculture and increase farming investment.

Abstract:本研究以中国科学院千烟洲试验站为例,为小区域水平上土壤时空变化的定量化评价提供了一种方法,并用于千烟洲试验站开垦利用11年后土壤性质和质量变化的评价。通过土壤信息系统和土壤变化数据库的建立,方便而有效地进行了不同土壤类型和不同土地利用方式下土壤变化的定量化评价、监测和制图。研究了该区不同土壤开垦利用为水田、旱地、桔园、马尾松、湿地松、杉树、天然林、枫香、牧草、荒草地等二+多种土地利用类型后土壤性质和土壤质量的变化特征。通过建立数学模型,模拟和预测了研究区内C、N等养分含量以及降雨、林冠透雨、树干流、径流和淋溶引起的元素输入和输出。提出了相对土壤质量指数(RSQI)的概念,并且依据土壤RSQI的变化值△RSQI较好地研究和评价了研究区内土壤质量变化。

Abstract:松茸[Tricholoma matsutahe(S.Ito ct Imal)Sing.]又称松口蘑、松曹,是名贵的食用菌。近些年,在长白山区鲜松茸的收购价格为600-1000元/kg,并且在当天用飞机将鲜松茸出日到日本。松茸之所以价格昂贵,是由于该食用菌为赤松(Pinus densdlora Sieb.etzucc.)的营养共生型的外生菌根菌。其生态习性十分特殊,菌种分离和扩繁困难,迄今为止还不能实现人工栽培^[1]。长白山区是我国松茸的主要产区之一,它是我国东北地区的第一高山,横跨辽、吉、黑三省。其总的走向是东北一西南。中段山势最高的白头山天池一带,海拔高度超过2000m。其它山岭较低,呈丘陵状态。