Abstract:Chemical fertilizer Industry of China has already made great progress since 1949. By 1993, the total fertilizer production capacity that has been built was 27.8 Mt, including 20.9 Mt of N, 6.73 Mt of P₂O₅, and 200 thousand t of K₂O. The accumulated ammount of fertilizer nutrients applied into soil during 1949-1993 was 380.6 Mt of which 90 Mt was imported accounting for 23.6% of the total. It is estimated that by the end of the century 42 Mt of fertilizer would be needed to meet the requirement of agricutural production in China. It's supply should mainly rely on China's own Industry. The average nutrients content of fertilizer of China is 26.5% now which is still much lower than the world average (about 40%).So China should pay even greater attention to the production of higher grade fertilizers. A few low grade fertilizers like single superphosphate and NH₄HCO₃ will still be important sources in Ghina in the near future. Improvement of technigue of fertilizer production in order to lower the energy comsumption and better equipment for the industry are also the main proints needed to. solve.

Abstract:The contents of ten trace elements in soils from northern China were determined. The effects of parent material and soil types on the element abundances were investigated statistically by the methods of ANOVA and multiple classification. The adjusted independent variances, calculated based on the factor score, were computed to describe the influence of soil formation processes on the contents and distribution of the trace elements in the soils.The significant differences in element abundances among various types of soil and among soils derived from various types of parent materials, especially the latter, were observed. The soil formation processes related to element content might be categorized as a) the leaching process, and b) formation of clay, biological absorption, and humification. The influence directions of the two kinds of processes are different, but the strengths of them sll decreased from east to west at the same time. The leaching tendencies of trace elements from east to west, therefore, decreased first and then increased, due to the co-effects of the two kinds of the processes. The majority of elements including copper, nickel and chromium was characterized by leaching during the formation of soil, while significant influences of the second kind; of processes were noticed for manganese and zinc.

Abstract:Mehlich 3 (M3) reagent is applicable to a wide range of soils for the determioration of both available macro- and micro-nutrients, perhaps to serve as an universal.soil extractant. However correlation between M3 value of soil nutrient and plant response to nutrient in field or pot experiment of calcareous soils was scarcely studied. Using the micronutrient uptake of tomato and sugar beet seedlings cultured in a mico-pot experiment and the relevant conventional soil test values as reference terms, the correlations between M3-ICP values of the calcareeous soils in Beijing and Hebei and the reference terms were studied in the present work. The results indicated that there were significant correlations between the values of M3-B、-C、-Fe、-K、-Mn、-P and -Zn and the values of corresponding conventional methods. Significant correlations were also found between the values of M3-B、-Cu、-Mn, -M o、-Zn、-A1、-Mg and-Na and the corresponding nutrients uptake of the seedlings for both the two plants; and between the values of M3-Ba,-Ca,-Cd,-Co,-Cr and -Ni and the corresponding uptake of the seeding for one plant; but no statistically significant correlation was obtained for values of M3-Fe,-Pb and -Ti. Furthermore, M3-ICP method had many other advan tages when it served as an universal soil extractant. Mechanisms and the several relevant problems are also discussed. The concept of acidic extractant being not used as a good soil extractant on calcareous soil should be questioned, and M3 reagent possibly could be used as an universal extractant of acid, neutral and alkaline (calcareous) soils in China.

Abstract:Kinetics characteristics of phosphate adsorption-desorption by Loessial soils were studied under the conditions of continuous liquid current. Phosphate was adsorbed and desorbed at different rates. According to the rate, the reaction of adsorbing-desorbing could be divided into three types: fast, middle and slow reactions. Elovich equation was the best model to decribe the adsorption and desorption of phosphate, while the first-order and parabolic diffusion equations were the worst; but the worst models were "sensitive" to the changes of reaction rate and could be used to classify reaction type and to study the reaction meachanism. The rates of adsorption and desorption were closely related to the soil clay and CEC. The influences of free Fe₂O₃ on adsorbing rate and CaCO₃ on adsorbing rate under lower temperature and desorbing rate under higher temperature were siginficant. The rapiddly available phosphorus was an important factor to control the desorption rate. The rate of phosphate adsorption was significantly influenced by temperature, but the effect of temperature on the desorption rate was not significant. The adsorption and desorption rates, capacit, of phosphate and reaction time varied with soil types and horizons.

Abstract:HA and FA composition and binding characteristics of soil combined humus differentiated by the modified Hseung's method were studied. The results obtained are summarized as follows: 1.It was observed that with the rise of soil pH, there was a tendency to increase the loosely combined humus(H₁) extracted with 0.1mol/L NaOH from soil and to decrease the stably combined humus(H₂) extracted sequentially by a 0.1mol/L NaOH-0.1mol/L Na₄P₂O₇ mixture from the residues. Statistical analysis showed that H₁ was very significantly positively correlated to free Fe and Al but negatively to exchangable Ca, and that H₂ was significantly positively correlated to exchangable Ca but negatively to free Fe and Al. No significant correlation was found between tightly combined humus(H₃) and pH or various binding materials of soil. 2. The ratio of humic acid to fulvic acid (HA/FA) was lower in H₁ than in Hz. The former was positively correlated with free A1 and the latter positively with pH and exchangable Ca of soil.3. Elemental analysis results of the extracting solution indicated that H, was actually Al/Fe-combined humus with less Ca-combined humus, and H₂ was mainly Ca-combined humus.

Abstract:The contents of amporphous Fe and Al oxides and complexed Fe/Al oxides inereased to varying degrees in the soil and its organomineral complex under application of organic manures for 9 years, and there existed an antagonism between tomplexed Fe oxide and complexed Al oxide (r=0.7998 n=7). The increase in the contents of soil organic matter was principally due to the increase in the contents of organic matter in light fraction, and degree of organo-mineral complexing in soil was decreased. The rate of loosely combined arid tightly combined humus in heavy fraction was comparatively increased. The sequence of organic matter in complexes was 0.25-0.01lmm> <0.002mm>1-0.25mm>0.01-0.002mm, and the degree of organo-mineral complexing and the rate of loosely combined and tightiy combined humus declined with the particle size and their average degrees of complexing were significantly lower than those in the soil. The content of Fe₂O₃ and the rate of Fe/C in soil loosely combined humus were higher, but the content of Al₂O₃ and the rate of Al/C were lower, and the contents of Fe₂O₃, and Al₂O₃, in humic acid were lower than those in fulvic acid. The sequence of contents of Fe₂O₃ and Al₂O₃ in loosely combined humus in complexes was consistent with that of the content of organic carbon.

Abstract:An experiment on the characteristics of Co, Cu, Pb and Zn adsorption by seven highly weathered acid soils derived from different parent materials in different areas of southern China was conducted to study affinity characteristics and factors affecting affinity as well as the mechanism of adsorption reaction by using shapes of adsorption curve, pH values and competitive adsorption equations and distribution coeffieients. Clay fractions(< 11tm) separated from red soils with different properties were allowed to react with solutions of Co, Cu, Pb and Zn in 25 ml 0.05 mol/L Ca(NO₃)₂ as supporting electrolyte containing the desired amount of adsorbate ion, respectively. The pH values of suspention were adjusted by adding appropriate amounts of 0.1 mol/L N0₃ or saturated Ca(OH)₂ solution prior to metal addition to obtain a series of suspentions with various pH values.

Abstract:Oxidative degradation of 10 phenolic compounds by manganese oxides in latosol and red soil and the kinetics of redox reaction between manganese oxides in soils and phenolic compounds were studied. The reactivity of phenolic compounds with manganese oxides in soils depended on their nature and structure and increased with decreasing pH. Both reductive dissolution of manganese oxides in soils by phenolic compounds and oxidation of hydroquinone by manganese oxides in soils followed the kinetic equation of the first order reaction. The order of the reaction of reductive dissolution of manganese oxides in soils with respect to [H⁺] was 0.16. Besides oxidation by manganese oxides in soils, hydroquinone was possibly adsorbed by soils and so on, and total reaction rate of hydroquinone was composed of and so on, and total reaction rate of hydroquinone was composed of two terms, i.e.the oxidative rate and other reaction rate.

Abstract:Many factors can affect the regional differentiation of soil selenium. Among them, soil type, soil texture, land use type and vegetation type are four main factors by pricipal component calculation. 41 Soil types. were regionalized in China according to the study, and the safety threshold of soil selenium contents in different regions was determined. The results would provide scientific basis for formulating the environmental quality standard of soil selenium in China.

Abstract:Based on considerable data a preliminary assessment of Cd,Cr,Pb,As,Hg and 3.48(a) P contents in soils and grains when calcareous clay and slightly acid soil were ameliorated with coal ash(≤600 000kg/ha) was made by the methods of pollution initial values and pollution indexes. The results show that coal ash could not cause soil and grain pollution. Through triple-cropping every two years in the simulated ash dispoal area and k_m determination, Cd,Cr,Pb,As and Hg contents were found stable in general. Though there existed week leaching or enrichment of specific element in surface or subsoil stratum, there were no great changes among layers and years.

Abstract:Crop water stress index (CWSI) for wheat and soil water stress ind index (SWSI) for bare soil were determined based on the data observed for canopy temperature of wheat, surface temperature of bare soil, main meteorological factors and soil water content during 1990 and 1991 in Handan district, Hebei Province. The main cause influencing the values of CWSI and SWSI out of 0-1 range was that the soil water content was out of the range which could be reflected by SWSI and CWSI and thus causing the Tc-Ta and Ts-Ta too high or too low. The correlations among CWSI, SWSI and relative soil water content were analyzed and drought grades indices of the soil water with various thickness layers were suggested. CWSI and SWSI could be applied in various regions for drought monitoring, but the timely obtaining of the information of drought would be influenced because more data and parameters should be obtained.

Abstract:The new method of observing annual soil loss and its parameters is made upeof eight observing items and means. It is audio-visal, economical, simple and convnient. The results observed in experimental areas of southern and northern China show that the new method has better adaptability, more practicality and the same accuracy as conventional method. So, the new method can obtain a. lot of observing data which can be used in creating models of monitoring annual soil loss or revising formulation of USLE erosion factors to realize monitoring annual soil loss over province or county area by using remote sensing and GIS. Meantime, the results obser-Ped by using the new method show that changes of annual soil loss are seriously subjected to the cover degree of vegetation or crop, particularly in red soil regions.

Abstract:A study was made on 12 soil biochemical activities in three degenerated grasslands (Dasiphora fruticosa shrub, Kobresia Pygmaea meadow and Festuca sinensis grassland) of the northwestern Sichuan in China. Results show that the soil biochemical activities and the correlations among them were influenced significantly by the degree of grassland degeneration. Soil biochemical activities, especially cellulose de-composition, nitrogen fixation and protease activities, in the grasslands decreased with the degree of grassland, though the differences carer not statistically significant. But the correlations among biochemical activities of the soils were significantly correlated with the degree of grassland degeneration. The worse degrnerative grassland, Festuca sinensis grassland showed no such significant correlations among the 12 soil biochemical activities. Based on the research results considered that the measures for the improvement and amelioration of degenerated grasslands should be adopted according to the soil ecological changes and the correlations among soil biochemical activities.

Abstract:The distribution map of the saline-alkali soils complied based on the 1 to 100000 and 1 to 250000 scale TM pictures reflects the real situation of the salinealkali soils during the middle and late 80's in Heilong-gang region. By calculation there are 393400ha of salt-affected soils of which over half is slight saline-alkali soils. Under the natural and anthropogenic effects, the area of the saline-alkali soils is obviously decreasing and its harm is lightenning, especially in the upper part of plain. This same trend is found in the coastal area, although the salinization is still very serious. By comprehensive analysis, the lightenning of the salinity improves the development of agriculture, forestry and animal husbandry in this region, but the descending of the underground water level and the shortage of water resources will bring out unfavorable effects on the environment quality. So it is necessary to combine agriculture, forestry and animal husbandry in this area to make the resources be fully and rationally utilized.

Abstract:在土壤水分能量研究方面,热力学函数表达形式愈来愈引人注意^[1,9,10]。大家普遍接受的能量概念“水势”,因数值随温度变化而改变,使得它的应用受到一定程度的限制。张一平、高俊风等通过对SPAC水分热力学的研究,提出了水势温度效应概念¹⁾,确定了SPAC水分热力学函数的测定方法和计算公式^[2-5]。魏朝富等也进行了紫色土的水势温度效应及水分热力学函数的研究^[6]。这些研究,尽管是在室内模拟条件下进行的,但所得出的一些有价值的结论,为进一步的深人研究奠定了理论及实践基础。本文拟在此基础上,首先讨论在田间自然条件下温度对土壤水势的影响,企望将室内土壤水分热力学研究引向田间土壤。