Abstract:Information of soil hydraulic properties is required to predict water flow in unsaturated soils. Soil hydraul properties include, soil water characteristic curve and hydraulic conductivity. In this paper an integral method is used to solve the problem of water absorption into an one-dimensional and horizontal soil column. According to solved results, a simple infiltration is established to estimate the parameters, zα and n,in the van Genuchten model of a soil water characteristic curve. The two parameters,α and n, in the characteristic curve model are estimated by the characteristic length of wetted zone.sorptivity, and saturated hydraulic conductivity.Unsaturated soil hydraulic conductivity is then estimated from the parameters'determined in the soil water characteristic curve. This new method uses both Richards’ equation and the closed form equations of soil hydraulic properties. The simple infiltration method provides a transient water flow approach to estimate the soil water characteristic curve instead of the usual equilibrium method. This is a new and simple means to determine soil hydraulic properties.

Abstract:In recent years, some process-based soil erosion prediction models are proposed in order to promote soil loss prediction on slope. In such prediction models,estimation of hydrodynamic parameters in soil erosion processes is the key to predict soil loss on slope exactly. Based on the runoff experiments in laboratory, themechanism of rill erosion and sediment transport in rill are studied and the method to estimate the妙draulics of flow in rill, such as critical shear stress for rill initiation,mean velocity of flow in the rill, Manning roughness coefficient, soil erodibility for grill erosion, as well as rill section characteristic are discussed in this paper.

Abstract:In this paper, a mathematical model of water exchange for hillslope, with which hysteresis was incorporated, was presented. The solution conditions of various boundary conditions were analyzed in this model. At the same time, the model was proved systematically by using the natural rainfall-infiltration-runoff data of hillslope of Wangdong gully small watershed, Changwu in Shaanxi. The simulated results showed that the model was of high precision, especially when the hysteresis was considered, the predicted results were approximated to measured results. Hysteresis results in decreasing in water content in the wetting front measured at the end of infiltration, slows down the redistribution. During the process of rainfall-infiltration-runoff,hysteresis has a great effect on water content, infiltration rate, flow process and flow volume.

Abstract:Based on the field infiltration experiments of natural freezing and thawing'soils within the freezing and thawing periods, in this paper the freezing and thawing features of cultivated soils are analysed, the basic characteristics of reduction infiltration of freezing and thawing soils are discussed, and the reduction infiltration mechanism of freezing and thawing soils is inquired into. The results indicated that at different freezing and thawing stages, the formation, thickness, number and position of frozen layers in soils are different and the frozen layers have different control and effect on infiltrating flow, that the characteristics of reduction infiltration varies with the freezing and thawing stages, and that under freezing and thawing conditions, reduction of soil water conductivity is the basic reason for reduction of soil infiltration ability and the phase change of liquid water in soil is the origin of the reduction of soil water conductivity. The results are of theoritical value to further study on the infiltration law of field freezing and thawing soils in the districts with seasonal freezing and thawing soils and are of practical value to determine technical parameters for saving-water irrigation within the winter and spring irrigation in these districts.

Abstract:Modified jackknife test was applied to examine the robustness of a topology-polarity correction model for estimating the sorption coefficient(K_oc) of organic compounds. The test was performed by four methods:1) random deletion of a single chemical from the data set (100 times);2) deletion of a chemical with abnormal value (difference between predicted and measured values is larger than 0.9 log-units,27 outliers);3) deletion of 50 chemicals randomly selected from the data set (30 times);and 4) deletion of a set of chemicals belonging to the same class (17 classes).The results indicated that similar trends were observed with various jackknife tests.The coefficient of determination (R²) of the multivariate regression model showed relatively high robustness compared to other regression coefficients. The sixth-order chain molecular connectivity index (⁶X_ch) was the least robust parameter in the model.Among the 17 polarity factors, the robustness of SO₂, O, F, NH₂ and SO were lower than the others.

Abstract:This paper reported severe degradation of soil organic matter and nutrient pool under CF (artificial Chinese fir forest). Remarkable drop of litter matter and its nutrients under CF were observed compared with those under BF (natural broadleaped forest) and MF (artificial mixed forest of Chinese fir and broad-leaved forest).And similar drop trends of soil OM content and total N and hydrolyzed N in soil profile distribution were also found. The degradations of litter layer and nutrient pool under CF were abruptly as the conventional reforestation was implemented. In addition,an unitary composition of standing forest with less litter and nutrients returned to soil is another factor inducing the degradation of organic nutrient pool. It is suggested that the degradation of soil organic matter and nutrient pool could be control by improving forest regeneration technique and forest component.

Abstract:The effect of applying lime and gypsum on element leaching in red soil derived from Quaternary red clay was studied with soil columns repacked in laboratory.Results showed that lime application decreased the leaching from the short columns (0-10cm layer) of canons exclude Ca²⁺,but increased the leaching of SO₄^2- and HCO₃^-.Supplying gypsum increased the leaching, from topsoil column of all cations,especially of Al³⁺,but has no effect on the leaching of HCO₃.Ca²⁺ leached mainly in the form of free ion, and the percentage of SO bound Ca²⁺ rose when adding gypsum. For the leaching of A1³⁺ from the long column(0-30 cm layer), it was mainly in the form of free ion.For the leaching of Al>³⁺ from the topsoil column, it was mainly in the form of OH^- bound Al>³⁺ in lime treated soil;however,the main form was SO₄^2- bound Al in the early stage and free ion in the later stage in gypsum treated soil. Besides that the percentage of OH^- bound Al>³⁺ enhanced in the topsoil solution in all lime-addition soils, that of SO₄^2- bound Al>³⁺ increased in all subsoil solution and in topsoil solution in gypsum treated soils.

Abstract:In this work,effects of anion adsorption and pH on the electrokinetic properties of constant charge soils and variable charge soils were studied. Yellow Brown soil and Phaeozem were used as representatives of constant charge soils, and Latosol was used as representative of variable charge soils.The results showed that the zeta potential of Latosol particles which had adsorbed different anions changed to negative from positive in sign with the increase in pH and an isoelectric point (IEP) occurred on all the zeta potential-pH curves. In the pH range of 3.5-8.0, the absolute value of change in zeta potential of Latosol particles adsorbed different anions was of the order HPO₄^2->F^->SO₄^2->Cl^->NO₃^-.The zeta potentials of yellow brown soil and Phaeozem particles referred as constant charge soil were always negative in sign and no IEP occurred on zeta potential-pH curves.The shape of zeta potential-pH curves varied with the soil type, the anion kind and the pH. In the pH range of 5.5-9, the absolute value of change in zeta potential of yellow brown soil and Phaeozem which had adsorbed different anions was of the order SO₄^2->HPO₄^2->F^->Cl^->NO₃^-.

Abstract:A pot experiment in greenhouse was carried out to study the effect of soil drying on CH₄ flux from rice paddy soil.The soil drying practice was performed two times from 43 and 102 days respectively after rice transplanting, and the soil drying periods were 28 and 113 hours respectively. The results showed that a large amount of methane emitted to the atmosphere during 16 and 42 hours after the soils fell dry,and an emission peak occurred quickly after the soils fell dry when the soils was dry and soft. As soil dying continued, the soils began to crack and CH₄ emissions decreased to nil. Soil drying accelerated the release of soil-entrapped methane. CH₄ emissions during soil drying accounted for 5.960%-10.05% of the total seasonal emissions.Although soil drying increased CH₄ exmssions by 9.68%-145.94% during soil drying,CH₄ emissions from the soils once imposed by soil drying decreased by 21.59%-54.45% during the period flooded after soil drying,compared with that from the soils flooded continuously.Considering overall CH₄ emissions during soil drying and the period flooded again,soil drying reduced CH₄ emissions by 17.7-43.91 percent.

Abstract:The mean rate of methane production from soils of Avicennia marina mangrove forest at Dongzhai Harbor in Hainan Province and at Western Harbor in Xiamen were 3.59 and 11.59 ng/gd, respectively. It was higher than that of a coastal barren shoal (1.62ng/gd) and lower than that of a mangrove forest slash (48.96ng/gd). The mangrove vegetation may enhance methane production from costal wetland due to decay of its roots.There were similar seasonal patterns of methane production rates (warmer season's>colder season's) in the two mangrove forest.By multi-factor linear regression analysis, we concluded that soil water content,organic matter, Ca²⁺,Mg²⁺ and SO₄^2- had great effects on methane production rates of the mangrove forest in Hainan, while soil water content,total N and Cl^-/SO₄^2- ratio had great effects on mangrove forest in Xiamen.

Abstract:Seven soils with a large range of soil organic carbon and nitrogen were fractionated according to particle size by ultrasonic dispersion and sedimentation, then the distribution of soil C, N, P and K in the clay, silt and sand fractions was determined. At the same time, the availability of N in each fraction was also studied.The results showed that the C and N contents and their percentages in the soil organic C and N decreased with the increase of particle size, but the C/N ratio increased with the increase of particle size. The availability of N in <2μm fraction was highest and decreased with increase of the particle size.Soil P was mainly distributed in the fine fractions on the acidic soils, however on the calcareous soils in the coarser fractions.The exchangeable and non-exchangeable K was concentrated on the <50μm fractions, indicating these fractions were the important K source to plant in the soil.

Abstract:The adsorption of acetochlor and metolachlor on 6 kinds of soils was measured using batch equilibration technique. It was found that adsorption isotherms couldfit Freundlich equation well. According to the analysis of the correlation between K_af(1 /n) and the physical and chemical properties of the soils, organic matter content of soils was the dependent factor in the adsorption.Theresults showed that the adsorption of metolachlor on soils was weaker than that of acetochlor. Hydrogen bonding was found to be the common mechansm in the adsorption of acetochlor and metolachlor.Charge-transfer was the additive mechanism of acetochlor.

Abstract:The parper deals with the influence of changes of cropping system from upland farming to rotation of rice and upland farming on the total content, form and availability of zinc in Shajiang black soils studied by using the sequential-extraction method in combining with the mathematical analysis methods of principal component analysis and linear regression. The residual, crystalline iron oxide-bound, amorphousiron oxide-bound, organically bound and exchangeable Zn of soils accounted for 75.60%-78.13%, 16.47%-20.00%, 2.19%-3.27%, 0.82%-2.86% and 0.56%-0.97% of the total Zn, respectively. These forms could be divided into three groups.The first group was exchangeable Zn, which the available Zn mainly came from,being the intensity factor of available Zn in soils. Organically bound Zn, amorphousiron oxide-bound Zn and crystalline iron oxide-bound Zn belonged to the second group which was the capacity factor of available Zn, in soils.The third group was the residual Zn, which was unavailable to plants but could be activated under artificial cultivation.Under the rotation of rice and upland crops, the ratios of exchangeable Zn and crystalline iron oxide-bound Zn to total Zn decreased, but those of organically bound Zn and amorphous iron oxide-bound Zn to total Zn increased, which enabled Zn in soils to be activated and be more movable, and thus reduced the contents of total Zn and available Zn in cultivated layer of soils.

Abstract:The content and distribution characteristics of rare earth elements of 204 soil samples in 68 typical soil profiles of six main soils in Guizhou Province were studied.Results showed that the rare earth element conent (264.44μg/g) in the typical soils of Guizhou Province are higher than their average content (195.7μg/g) in soils of some other areas of China. Also such is the case of light rare earth elements contents (199.1μg/g). It may be considered that these soils belong to a typical soil type containing more light rare earth elements. The rare earth element in all of these typical soils in Guizhou Province obeyed the rule of Oddo-Harkins. Element Ce enriched in these typical soils. The contents of the rare earth elements are the highest in the calcareous soil. In additon, the main factors which affected the content of rare earth elements are also studied.

Abstract:Soil fauna Communities were investigated in three artificial forests and one secondary forest in three seasons, from 1991 to 1992. The composition of groups,distribution of the number of individuals, diversity index of soil fauna were analysed.Results showed that Acarina and Collembola were the dominant community in the four forests in the year round. The seasonal fluctuation of individuals and communities of soil fauna was:April>August>January, and the individuals of soil dominant fauna increased obviously in April. Individuals and their communities on the surface soils were more than those in deep soils. Soil fauna diversity index in different seasons were compared. H'index in secondary forest was higher than that in artificial forests.

Abstract:Available model of reclaimed soil productivity is of inevitably short for evaluating reclaimed soil productivity. After developing a model to explain the mechanism of reclaimed soil, modified index model of reclaimed soil productivity (MPI) is conducted.Interactions of factors, which affect reclaimed soil productivity and their variability,are considered in MPI. An example for verifying the advantage of MPI is given in this paper.

Abstract:砂姜黑土是黄淮海平原主要中低产土壤之一,以往的研究认为它缺N、少P而富K^[1],因此施肥一般皆为N、P肥。随着近10多年来耕作施肥活动的加强,土壤养分肥力已发生较大变化^[2]。本研究是通过连续施肥的定位试验,探讨其N、P、K养分的持续供给能力。

Abstract:城市和典型农业区之间的过渡区域,即城市郊区,是一类比较特殊的自然地域。它虽然是从乡村演变而来,但其在结构与功能方面已不同于一般的乡村。城市郊区具有很强的开放性,其主要功能是向城市提供鲜活的禽、蛋、鱼、肉、蔬菜、水果以及部分粮油作物等农副产品。现在,由于市区的工业污染物质和生活废弃物的大量输入,城市郊区环境质量受到严重影响;同时,城市郊区环境质量的优劣,尤其是区域土壤环境质量的好坏,反过来又直接影响到向城市供应的各种农副产品的质量^[1]。因此,研究城市郊区区域土壤环境质量,具有特别重要的意义。

Abstract:把水稻土分为“爽水、滞水、侧渗、漏水与囊水型”,即水稻土的“五水”分类,提出于1979年^[1]《中国太湖地区水稻土》一书(下文简称《太》书)的出版^[2],使人们进一步了解到“五水”分类的全貌。朱莲青从水稻上指示性层段的观念对“五水”分类提出了有相当根据的不同看法,指出了其中“主要的错误和混淆”^[3]。本文仅就水稻土分类研究中尚可商榷的某些数据和观念予以讨论。