Abstract:Experiments of minimum and no tillage an clayey and sand loamy paddy soils were conducted in the farms north of the Yangtze River in Jiandsu from 1981 to 1984. Resalts of the experiments showed that the rice on the two soils under conditions of minimum and no tillage tended to be increased in yield, as compared with the soils under condition of conventional tillage; the loosenes of the soils could not be loept so long efter tillage, while appropriate compactness of the soils was conducive to migration and diffusion of nutrients and their absorption by crop roots in soil;minimum and no tillage was favorable for maintenance of stable structures in soil, resistance of the crops against the harmful condition and coordinatibn of the factors affecting the soil fertility.

Abstract:Ammonia volatilization of SN-labelled nitrogen fertilizer incorporated with soil as basal fertilizer for rice was investigated in a special designed closed enclosure. Results showed that (1) the rate of ammonia volatilization and its influence on the total loss of fertilizer N was enhanced with the increase of the flushing frequency of air passing over the standing water on the soil surface, and approached the maximum at the flushing frequency of 15-20 times/min.(2) in acidic soil, denitrification was the major pathway of ammonium sulfate and ura in cooler season, however,ammonia volatilization became important for the loss of urea in warmer season, and both denitrification and ammonia volatilization were the important pathways of N loss of ammionium bicarbonate;(3) while in calcareous soil, ammonia volatilization and denitrification both were the important pathways of N Ibss of ammonium sulfate and urea, and N loss of ammonium bicarbonate mainly resulted from ammonia volatilization.

Abstract:Results of experiment showed that, for the hybrid rcie with a high yield of more than 1000 jin per mu, the N requirement of early hybrid rice was more than that of general cultivar, while that of late hybrid rice was less than that of general cultivar. The amount of N absorbed by hybrid rice in the middle growing stage was over half of the total amount absorbed in its whole growing period;however, the N supply by soil was less in the middle growing stage of rice. To meet the N requirement of hybrid rice, a method of applying larger part of N fertilizer in middle growing stage nn the basis of maintaining steady supply of N in early growing stage was adopted, which gave a yield increase of early rice ranging from 2.97-8.99% and that of late rice rangins from 7.54-14.06%. It also found that due to the adoption of this method, the number of ears per mu and that of grains per ear were increased, all these indicate that the application method is suitable for hybrid rice characterized by vigorous growth of root system and tillers in early growing stage, and growing predomince of ears and grains in middle growing stage, and it may also prevent the rice from premature senility. Therefore, it is favorable for promotion the yield potential of the hybrid rice.

Abstract:Study on the soils of the Zhujiang River Delta showed that the average total K content was 1.68±0.33%, slowly available K 225±139 ppm and exchangeable K 118±52ppm. The potassium content of the soils in the region belongs to the medium level as compared with that of the soils in other reeions of Guandong Province. The slowly available K constituted 1.34% of the total K and the exchangeable K was only equal to 520% of the slowly available K. The content of exchangeable K was decreased from the fringe to the top of the delta.The slowly available K being absorbed earlier in growing stage indicates the less K supply ability of the soils, The curves of the accumulated content of K in various growing stages of rice shows that the content of K in rice plant in the middle growing stage is higher than that by the early and late growing stages. More K absorbed by rice in middle growing stage inticates the better K supply ability of the soil.

Abstract:The characteristics of moisture retention of fluvo-aquic soils with different textures in the flood plain of the Huanghe River were studied by pressure menbmane method.Results showed that the modsture retention, distribution of pore space and specific water capacity of the soil were generally closely reated to soil texture. The moisture retention was increasing with the soil texture getting clayey. As to the relationship between the pore space distribution and soil texture, it was found that the gravitationa water pore space was decreasing with soil texture getting clayey;and the slowly availalble water pore spare cad nnavailable water pore space were increasing with soil texture getting clayey;however, available water pore space in clayey soils tended to be de creasing with soil texture getting clayey. The specific water capacity of gravitiona water was increasing with soil texture gettinn clayey;and the specific water capicity of regidly available water of loamy soil was higher than that of the soils with sandy and clayey textures;while the specific water of slowly available water of light-clayey soil wus higher than that of the soils with orther textures.

Abstract:The extraction of the enzyme-humus complexes with protease activity from soil using a series buffered eatractants was studied. It was shown that the extraction of 0.1 M pyrophosphate (pH 7.0) was most efficient. Some characteristics of the extraeted enzyme were different from those of the enzyme measured in soil. The reasults also showed than the K_m value (0.97-1.0mg casein/ml) and optimum temperature (50°-60℃) for the extracted enzyme were lower than those of the enzyme in soil and the V_max value (74.91-75.35 mg tyrosine/g · 24hr.) optimum pH (9) and temperature coefficient (1.93) were higher than those of the enzyme in soil. The effectiveness of the estractants was in order of distilled water<0.1 M phosphate (pH 7.0)-0.3 M KCl-0.01 M EDTA 3 <0.05 M phosphate-citrate (pH 7.0) <0.1 M Na-Pyrosphate (pH 7.0).

Abstract:According to the causes吐formation and properties of Quaternary red clay and their influences on red earths developed on it in the hilly regions of central subtropical China, the soils are distinguished into four families, i.e. siferryc residual red earths, siferric red earths, siferric plinthie red earths and siferric gravel red earth. The principles for distingushing the red earths in the category of soil species suggested by the eauthor are as follows:(1)in a given family with same pattern of solum stracture, the soil species are distinguished according to the fertility level of surface soil;(2) the soils with different patterns of solum structure are distinguished in different soil apecies in spite of soil fertility;(3) for cultivated soils, the soil species are distinguish according to the development deb}ree of surface and subsurface mil horizons resulting from fertilization and management of the soil. The association patterns of red earths being generally found in hilly regions of central China a} as follows:(1) weakly Proded pattern with all horizons overlaped, (2) weakly eroded,pattarn with residual catena, (3) strongly eroded cumulative pattern with apposite distributive order on the slope,(4) patch-like pattern with stronge hgdratian of iron oxides on gentle slopes, (5) strongly eroded gully-like pattern, (6) lithological symmetrical distributive pattern with hombgenous parent material, (7) lithological symmetrical distributive pattern with heterogemeous parent materials, (8) litholoaical belt-like covering pattern with heterogeneous parent materials, (9) eroded-annular distributive pattern.

Abstract:Volcanic ash soil in Tengchong is derived from eruptive pyroclastic materials of Quaternary volcano. Generally, the soil is acid in reaction, and has pumice and other kinds of blocky ejects in its solum. The A horizon is characterized by a very dark colour, a very high content of organic matter, a very large water holding capacity, and a particularly low bulk density. There are considerable quantity of allophane in the clay minerals. A large amount. of fine hmnus particles and vitric debris are present in soil matrix. The soil is fairly fertile and productive. The formation process of the soil is dominated by accumulation of organic matter which belongs to lithomorphic meadow type, and ferrallitization accompanied by the biological silicatization in A horizon. Many of the genetic characteristics of these soils are similar to those in other regions of the world.

Abstract:环境中的铬主要以三价和六价态存在,六价铬的毒性比三价铬大.天然水中的三价铬和六价铬可以相互转化,土壤中的铬通常以三价态的Cr⁺³阳离子及CrO^-₂的阴离子和六价态的Cr₂O₇^2-及Cr₂O₄^2-存在^[3].

Abstract:自然界广泛存在的粘土和腐殖酸经常结合在一起,它们直接影响和决定着土壤结构和水/土界面的其它性质^[4-6].关于土壤胶体动电性质的研究五十年代比较活跃,但在以后却被大大地忽视了^[1].本工作研究了钠蒙脱土以及蒙脱土结合腐殖酸以后的粒子在水中的界面动电性质，考察了动电性质随pH的变化.这种纯粘土及其和腐殖酸结合体系的研究对于土壤胶体性质的认识是必要的.