Abstract:In comparison with the late-rice in double cropping system, the amount of soil nitrogen mincralized during the growth of early rice in triple cropping system was considcrably lower owing to its shorter growing period togcther with a colder climate in its early stage of growth (from the middle of May to early June). The percentage contribution of soil nitrogen to the nitrogen absorbed by the single cropping late-rice (75.9%)was significantly higher than that by early rice(57.8%),and therefore heavy application of chcmical nitrogen fertilizer, apecially at its carly stage of growth, is indispcnsable for high yield of the early rice.

Abstract:Tai-lake basin locates at the lower YanQtse delta under a northern monsoon climate. It covers an area of about 30 thousand square kilometers. Paddy fields occupy about 90% of the total cultivated area.Historically, most of the land are used for rice-wheat rotation annually. At present, when conditions are favorable, large areas have been adapted for three crops a year i.e. rice-rice-upland crops (barley, rape or wheat). It is one of the high productive areas in this country with annual yield averaging 9-10.5 tons of grain per hectare. Since paddy soils are developped under long time of submersion with periodical wet and dry cultivation, the main pedogenic process of paddy soil is alternative of reduction and oxidation accompanied with the formation of ferro-humic coating and streaks and formation of Paitu. In consequence, the morphological feamrc of paddy soils as well as their physical, chemical and biological properties are diverged Erom the original upland soils. The presence of a plowed layer, plowpan, perco-submugic layu or illuvial gley sported layer usually charactcrizes the specific features of a paddy soil profile.

Abstract:Ammonium bicarbonate is a low grade nitrogen fertilizer. It is easily volatile and of poor physical properties. However, at present, a large number of small nitrogen factories are still operating to produce this fertilizer for local usage in China. Recently, deep drill of NH₄HC0₃ pills bellow soil surface has been found much more effective to crop growth than top dress of NH₄HC0₃ powder. The pills weigh about lgm, are pressed out by a double-roll prilling machine. Present investigation deals with the coating technique of NH₄HC0₃ pills for preparing a slow-release fertilizer and the factors affecting the release rate of N from coated pills. The efficiency of this controlled nitrogen ferrilizer has also been studied.

Abstract:In recent years some Chinese fir (Cunninghamia lanceolatas) stands in the southern China have been found "yellowing", i.e., the trey become stunted with yellowish to needles and root rot, and even dry up at last. The preliminary investigation revealed that it isn't infectious disease but physiological hindrance caused by inhibiting factors of soil. Owing to the complexity of the inhibiting factors in soil, we have failed to find out any critical value of soil characters by simple comparison of them. Therefore, a discriminant analysis of soil characters was conducted for two sets of surveyed data.

Abstract:The present article deals with the study on the evaluation method of soil resources based on the soil map of Guizhou province on the scale of 1:500,000 and supplementary soil surveys.The main poirns obtained in this study are sumarized as follows. 1. Firstly, the principles of soil resources evaluation should be decided according to the natural and economic characteristics of the district. Reasonable evaluation method which invol adoptation of suitable system, factors, criteria and procedure of evaluation should be consistent with the principle of evaluation.

Abstract:The applicability of thermometric titration method for the determination of sulfate in soil was studied.A thermistor was used to indicate the temperature change of the tat solution. A constant flow device was used to deliver the barium chloride solution as titrant. The titration curves were recorded automatically by a strip-chart recorder. It is found that the reproducibility of recovery of added sulfate was only about ±10% when thermometric titration method was directly applied to the determination in soil extracts. But in 50% alcohol solutions a reproducibility of about ±4% was obtained. The accuracy as compared with gravimetric method was about ±4%.The minimum content of sulfate which can be measurcd with:reasoaabl a accuracy is 1 meq/100g soil when proportion of soil to water is 1:5.It is concluded that the method has the advantage of rapidness with an accuracy comparable to indirect titration method by EDTA.

Abstract:众所周知,一切生物的生命活动都直接依赖于它们所能获取的能源。由于土壤中的绝大多数微生物属有机营养类型,它们只能在通过分解有机物的过程中摄取能量作为合成细胞有机体及维持其生命活动的能源。因此,土壤中微生物的生命活动及其强度,必然受土壤中提供有机物质的数量及其可给程度的影响。

Abstract:近十年来,扫描电镜已在土壤微形态和矿物风化超微特征方面广泛应用,丰富了微土壤学的研究内容^[3,4]。本文应用JEM-100B电子显微镜二次电子扫描附属装置对东北地区几种土壤(表1)的特征层进行了观察,试图通过对土体中粘粒和其它细土物质部分的表面形态、空间排列和它们在形成微孔隙中的结构特征观察,进一步认识土壤中粘粒和某些细土物质的性状和作用。

Abstract:据在安徽省城西湖农场和江苏省常熟县等地调查,各地地下排水的暗洞寿命长短相差很大,从一、二年到十多年不等。国外文献也有类似的记载,但都感到对这一问题研究不足。过去我们曾经认为,暗洞失效是由于泥沙随水注入暗洞淤积而堵塞了通道^[1]。其后通过实地调查发现,暗洞洞壁倒塌,尤其洞顶塌方,才是暗洞失效的根本原因。就是说,暗洞寿命的长知决宁干暗洞洞壁的稳固程度。