Abstract:Effects of soil texture,soil temperature and soil Eh at 5 cm on CH₄ emissions from rice paddy fields were investigated in the Fengqiu Ecological Experimental Station, Chinese Academy of Sciences, under field conditions in 1993 and 1994. The results showed that CH₄ emissions from the studied fields were low, ranging from 0.16-1.86mg CH₄/m²h in the mean fluxes throughout the period of rice growth under intermittent irrigation. Soil temperature and soil Eh might not be dominant factors influencing the patterns of seasonal variation of CHa flux from the rice paddy fields, but they affected the diurnal variations significantly. The CH₄ emissions from clayey rice paddy fields were significantly lower than those From the sandy and loamy paddy fields in 1993 and 1994. The highest CHCH₄ emission was observed in the loamy field in 1993 but in the sandy field in 1994.

Abstract:Potassium release rate characteristics of twenty low-hilly red soils under electric field strength of 44.4 V/cm and 88.8 V/cm were described with a second-order kinetic equation. The rate equations of K release and the initial K release rates (v₀) were calculated from the second-order equations. The values of vo ranged from 1.17 to 21.23 and from 1.93 to 61.58, with an average of 5.36 and 9.54 mg(kg·min)^-1 at the electric field strength of 44.4 and 88.8 V/cm, respectively. The relative grain yield, relative total dry matter yield and K uptake in NP plots of 20 corn experiments and the available K, NHO₃-soluble K and slowly available K of soils were used as reference standards to assess the practical applicability of v₀.The correlation analysis showed that v₀ was very significantly correlated(P=0.01) with the above six reference standards, with the correlation coefficients of 0.6275^**, 0.5645^**, 0.6624^**, 0.7277^**,0.7843^** and 0.6299^**,respectively, at electric field strength of 44.4V/cm. v₀ was significantly correlated with relative total dry matter yield(P=0.05, r=0.5445^**) and very significantly correlated with the other five reference standards, with the correlation coefficients of 0.6064^**, 0.7216^**, 0.7523^**, 0.8202^** and 0.6686^**, respectively, at the field strength of 88.8V/cm. It was suggested that v₀ could be used to estimate the supplying power of soil K and to characterize K status in soils.

Abstract:The influence of pH on the dissolution of aluminum in acid soils and the distribution of aluminum ion species in soil solution were studied. The results indicated that the dissolved aluminum increased with the decrease in pH The effcet of pH on the dissolution of aluminum varied with the soil type. The extent of pH influence on the dissolution of aluminum in three acid soils was in the order red soil>lateritic red soil>latosol. It suggested that the sensitivity of aluminum dissolution to external acid was different among the three soils. The distribution of aluminum ion species in soil solution varied with pH The proportion of Al³⁺ to total monomeric inorganic aluminum increased with the decrease in pH but that of Al-F complexes increased with the increase in pH Within the range of studied pH the proportion of Al-0H species was not higher than 5 percent. Temperature affected the aluminum dissolution and the distribution of aluminumion species in soil solution. Both the dissolved aluminum and the proportion of Al³⁺ species increased with the drop in temperature, but the proportion of Al-F complexes varied with temperature in an opposite trend. A decrease in pH resulted in a decrease in the proportion of polymeric aluminum ion species in soil solution. Therefore its rtion was very small in acid to strongly acid soils (pH<4.5). The results obtained from the red soil and latosol indicated that the solubility of aluminum in soil solution was controlled by aluminum oxides in soils.

Abstract:Reports of groundwater contamination by several pesticides have increased in recent years. In this work, one model in terms of pesticides' potential to leach through the crop root zone and to intrude into grounderwater was established to evaluate the potential of pesticide groundwater contamination with soil characteristics, regional climate and pesticide properties as its running parameters. The results showed that paclobutrazol was more likely to contaminate groundwater than dimehypo, but trifluralin was very unlikely. Groundwater in red soil region was very likely contaminated by pesticides. In case of rice planting, the potential threat of pesticide groundwater contamination increased.

Abstract:Transport characteristics of cadmium in 4 soil-water systems were studied. The results showed that the diffusion coefficients of cadmium ranged from 5.6×10^-8 to 9.3×10^-7cm²/sec. Comparison between the parameters from the single and two-surface Langmuir equations demonstrated that the maximum adsorption capacity (b₂)of low-energy sites was much greater than the maximum adsorption capacity (b₁)of high-energy sites, resulting in high transportability of cadmium in the soil-water system. The variation of adsorption capacity of cadmium with pH had three distinct stages, i. e., low adsorption stage at pH6.0. The adsorption capacity of cadmium was positively correlated with pH at the stable adsorption stage. The bioavailability of adsorbed cadmium increased with increasing pH when pH<6 but decreased with increasing pH when pH<6.

Abstract:A contrast experiment in field and a rhizosphere experiment in greenhouse were conducted to study ion transport in soil-crop rhizosphere system under different conditions. Salts of irrigation water were accumulated in the surface layer of soil under fallow conditions, but in the root zone of soil under cropping conditions. Cl^-、SO₄^2-、Na⁺、Ca²⁺,Mg²⁺,were accumlated in the rhizosphere of wheat in the process of irrigtion with mineralized water, but K⁺ was depleted in the rhizosphere. The differences of ion concentrations of soil solution between rhizosphere and nonrhizosphere became larger with the growth of wheat. The accumulation and depleted of ions in rhizosphere related to the uptake amount and rate of ions by crop. Cl^-、SO₄^2-、Na⁺、Ca²⁺ and Mg²⁺ concentrations of soil solution in rhizosphere and nonrhizosphere decreased with the increase of leaching water volume. The descending rates of ion concentrations in soil solution of rhizosphere were obviously lower than those of nonrhizosphere. More Cl^- than SO₄^2--was leached out both in rhizosphere and in nonrhizosphere.

Abstract:In this study, effects of humic acid(HA) on the dispersion of soil (red soil and yellow-brown soil) and clay minerals (kaolinite and montmorillonite) were investigated. The results showed that HA played an importmant role in dispersion of soil and clay minerals. The removal of soil organic matter with H₂O₂ obviously decreased the clay dispersion, whereas the addition of HA led to a great increase in the clay dispersion. The dispersion of Na-kaolinite clay was very week, but that of Na-montmorillonite clay was very strong, which were related to the resources and amounts of the charges. On the other hand, with the addition of HA, the dispersion of Na-kaolinite clay was improved abruptly, but that of Na monttnorillonite clay changed little. The results Further indicated that HA effect on clay dispersion was affected by the mineral types.

Abstract:The diffusion amounts of phosphate in soils at varying time were determined by half-cell technique using ³²P. Fve kinetic equation were used to fit the dynamic process of phosphate diffusion in the soils. It was found that parabolic found that parabolic. equations was the best model to describe the process diffusion. The temperature quotient (Q₁₀) of phosphate diffusion in the soils at 20% water content was 1.2 or so, which was in agreement w ith that diffusion is a physical process. The activation energy E_a^D of phosphate diffusion in soils, calculated by Arrhenius equation, decreased with increasing soil moisture and varied from 12 to 34 kJ/mol with an average value of 25kJ/mol under low water tension range(<10⁵ Pa), which was close to the activation energy of nutrient ion diffusion in solution. Therefore, it was suggested that the phosphate diffusion in soils at low water tension condition occurred mainly in the liquid phase. Moreover, the absolute reaction-rate theory was transplanted and used to investigate the diffusion process in soils. The parameters, net activation energy, activation entropy, activation enthalpy and activation free energy of phosphate diffusion in soils, were derived from the theory. The results showed that these parameters in the four soils at the same water content changed in the similar to E_a^D,which indicated that the parameters could be used to describe the energy characteristics of phosphate diffusion in soils.

Abstract:This paper deals with a study on the water characteristics and water regime of red soil derived from Quaternary red clay mixed with the weathering material of Tertiary sand stone in an orange orchard of Jiangxi Province. Results showed that the available water content of the soil was higher due to lower clay content in the soil layer as compared with that of the surrounding typical clayey red soil. The water regime of red soil in orange orchard reflected that water content of 0-100cm layer of the soil was usually lower than the range of available water content even in the first half of a year. It might be related with large consumption of soil water by the growth of orange trees and the high bulk density of subsoil of the soil. However, the water storage beneath 100cm soil layer was still richer either in the first half of a year or in the second half one. Results also showed that the value of W_f.c in 0-100cm layer of the red soil in orange orchard was lower than 1 throughout a year, which meant that a higher amount of empty waterstoring capacity layer where can accept continuously the rainfall could be found. Moreover the W_f.c beneath 100cm of that soil was more than 1,reflecting a richer water storage at the soil layer of beneath 100cm in the second half of a year with severe shortage of rainfall. Consequently, to increase the acceptance of rainfall in the first half of a year and to use the richer water storage in deep soil layers in the second half of a year are of important significance for alleviating the draught in summer and autumn and raising the use efficiency of water resource in red soils.

Abstract:Based on the non-equilibrium themodynamic theory, the thermal driving forces and the fluxes in heat and mass transfer process for unsaturated soil were analyzed. The. mechanics of heat and mass transfer in unsaturated soil were discussed and the phenomenological equations to describe the transport process in unsaturated soil were established. By means of the diffusion law and the equation of state for ideal gas, the expressions of the coefficients in the phenomenological equations were deduced. The effects of temperature, water content and partial vapor pressure on the phenomenological coefficients were also discussed.

Abstract:Experiments were carried out to study the changes of soil microbial biomass C, N and P and the transformation of N after application of organic and inorganic fertilizers by using isotope of ¹⁵N. The results showed that the soil microbial biomass C, N and P increased greatly after application of organic manures at the beginning of the experiment, and thereafter the biomass C decreased, but the biomass N and P remained constant. The immobilization of ¹⁵N rose to the highest about 10 days after application of ¹⁵N-labelled (NH)₂SO₄ and one month latter about 17% of the ¹⁵N was still in the soil microbes; when combined with organic manures the immobilization of ¹⁵N from (NH;), SOS increased. About 19-25% of ¹⁵N from the ¹⁵N-labelled organic manures was also immobilized in the microbes at the 30th day after application. In case (NH)₂SO₄ was applied alone the loss of N was about 18%, however, when combined with organic manure the loss decreased.

Abstract:The genotypic differences in P utilization efficiency, photosynthetic rate, water utilization efficiency and resistance to aging were studied in hydroponics and a field trial. The results showed that chlorophyll content and CO₂ fixation rate of the P-efficient genotypes were 32.0% and 26.0% higher than those of the P-inefficient ones. However, the latter's transpiration rate was 130.0% higher than that of the former's. Subsequently, the water content in rhizospheric soils of the P-efficient ones was 56.5% higher than that of the P-inefficient ones. Malondialdehyde (MDA) content in the leaves of the former was 75.0% lower than that of the latter. This indicated that the P-efficient ones were more resistant to aging than the P-inefficient ones under low P stress. All the genotypes' P utilization efficiencies were raised significantly under the stress condition. The values were increased from 171.5 (full P strength) to 1136.4 for the P-efficient genotypes and from 200.0 to 331.1 kg DM/kg P for the genotypes from the other type. These suggested that light and water utilization efficiencies and resistance to aging related closely to the efficiency of phosphorus utilization by wheat genotypes.

Abstract:The source area of the Urumqi River in the central part of Tianshan Mountains underwent several glacier environmental changes. Tills extended outwards 12 km from the end part of the No. 1 glacier. Soil development kept pace with the biological evolution. On the bare surface of moraines, microbial and algae communities appeared firstly, then lichen and moss grew, finally they evolved into alpine meadow. With the same pace of vegetation development, the alpine soils first were (A)-C profile firstly, then developed to A-C profile and finally became A-(B)-C profile. Alpine soils have negative temperature and icy soil body, undergoing a freezing-thawing-freezing process with state changes of ice-water-ice. Frost heaving and stone polygons appear on the soil surface with squamose structure, and soils have weak humification and decomposition of minerals. Alpine soils have different degrees of profile formation. No profiles in primitive soils, obvious humic horizons in Cryic-orthic Entisols, and perfect A and B horizons in Mattic-crvic Cambisols can be found.

Abstract:A multi-layer hierarchical time series model was used for the prediction of soil salinity. The method was simple and the prediction precision was improved by forecasting and tracking the parameters of the model. The comparison between the predicted and measured results in a large irrigation area showed the good reliability of the method.

Abstract:A systematic study concerning the effects of persistent fertilization and plastic sheet-covered culture on forms of Zn, Cu and Mn in a brown soil of Shenyang was conducted. The results showned that the consumptions of various forms of Zn, Cu and Mn increased after plastic sheet-covered culture. The forms of these three elements varied greatly in different fertilization treatments. The major forms absorbed by corn from soil were ogranic Zn and Cu, oxide bound Cu, exchangeable Mn and carbonate bound Mn.

Abstract:Beryllium-7, a cosmogenic nuclide, has stable sources in origin and half-life of 53.3 days, which provide essential conditions as a geochemical tracer for seasonal particle transport in the environment. A major portion of ⁷Be (about 95%) in the soils is bound to organic, Fe-Mn oxides and residual fractions. It can be removed with soil particle transport and be used to trace suil erosion. The characteristics of ⁷Be vertical distribution in the soil profiles provide sufficient evidence for trace of seasonal particle transport. ⁷Be inventory, apparent activity and maximum penetrative depth in soil cores as well as relative erosion or accumulation rate can be taken as trace parameters for sail ernsion.

Abstract:The severely eroded granitic red soil were improved on four different patterns in Changting County, Fujian, and the soil chemistry, soil microbes, soil enzymes and soil respiration over different patterns were studied in 1992. The results showed that the amounts of soil bacteria, fungi, actinomyces and total microbes were increased obviously, the soil hydrolytic and oxidation-rcduction cnzymcs and soil rcspiration were enhanced evidently, the storage of soil nutrients and supplying intensities of various available nutrients were promoted pronouncedly, demonstrating that the fertility of the soil improved on all the patterns was restored to varying degrees. Therefore, proper biological measures and essential supplementary engmeenng measures are effective in improving the fertility of severely degraded red soil.

Abstract:土壤肥力状况对作物产量、品质及营养状况影响的研究迄今已有不少^[1-4],但对作物光合特性影响的研究则不多,对其相互联系方面的探讨则几乎没有^[5]。本文研究了三种肥力紫色土对莴笋产量的效应、光合特性以及莴笋营养状况等的影响,以期通过研究,探明其相互间的关系和联系,同时也为作物高产、优质、高效施肥等提供更为有效的依据。