Abstract:The application of chemical fertilizer combined with farm manure is popularly practised in Chinese farming.In order to clarify the characteristics of nitrogen supply in such a fertilization system,pot experiments were conducted using ¹⁵N labelled crotalaria and ammonium sulphate as organic and inorganic nitrogen sources respecLively.Some preliminary results are summarized as follows:1.Rice plant utilized much more soil nitrogen than fertilizer nitrogen.treatments only about one third of the nitrogen assimilated by the rice plant came from the fertilizers.The ratio of soil nitrogen to fertilizer nitrogen taken up by rice palnt was closely related to the kinds of soil.In general,the more fertile the more soil nitrogen was assimilated by rice plant.

Abstract:Following the development of water irrigation project,and the extending of double cropping rice under the condition without proper measures of soil management,the area of gleyed paddy soil is expanding.This has been found in Guangdong,Guangxi.Hunan,Hubei,Jiangsu and Shanghai.According to imperfect statistical data,the area of gleyed paddy soil has increased by 20% in some regions in past 10 years or so.The process by which a normal paddy soil profile turned into a gleyed one is generally denourinated as secondary gleization.In some places,the term secondary gleization is called "waterlogged injury".Due to the low soil temprature in spring,inadequate supply of available nutrients,especially phosphorus and potassium and the accumulation of reducing matter,the growth of rice seedlings is retarded,the maturity of rice plant is dclayed,and the proportion of empty gain is increased,all these may result a decrease of 750-1500 kg/hect.of grain in each rice yield.

Abstract:According to the data from the field investigations with soil physical and chemical analysis,micro-morphological and electron-microscopical identification in the laboratory,the influence of plateau uplift on soil-forming environment in Qinghai-Xizang region is discussed on the view point of soil genesis.It shows that since Pliocene,the most noticeaLle changes of soil-forming environment in this area were the raising of the altitude of land surface,the increasing of the complexity of geomorphology,the reconstruction of atmospheric circulation by which specific climatic characteristics of plateau were formed,the gradual decreasing of the forest coverage replaced by the vegetation of alpine meadow,alpine steppe and alpine desert,and the soil-forming weathered crusts with diversity and complexity.Under these conditions,a particular soil region was formed on the plateau.

Abstract:Most of the lakes in Ali area of Xizang belong to the tectonic,faulted ones.At the end of the middle Pleistocene the violent tectonic movement caused faulted zone accompanied with rift and hydrothermal activity.The spring water abounding with boron and lithium continuously flowed into the lakes.With uplifting of the plateau,the climate within the plateau became drier,and leaded the withdrawal and lowering of the water level of the lakes.Up to the early Holocene,the climate became more anal more dry.The concentration of the lacustrine water brought about the enrichment of soluble salts.The solonchaks in this area are developed from the deposits of the lake terraces Ⅰ and Ⅱ formed in Holocene.

Abstract:In this paper,the activities of enzymes (catalase,polyphenol oaidase,invertase,crease,alkaline and neutral phosphatases) in black soils with different fertility and the correlations between enzymatic activities on the one hand and soil humic substances and other elements of fertility on the other hand are discussed.It has been shown that:1.Among six kinds of enzymes tested,most of the enzymes have significant correlation with soil organic matter or its components.Their activities can be used as an index to characterize the contents and status of organic matter.Polyphenol oxidase has negative significant correlation with C/N and humic acid/fulvic acid.Its activity characterizes the humification degree of humic substances.The activities of various kinds of enzymes characterize specifically or compositely the soil carbon,nitrogen and phosphorous status,cation exchange capacity and aeration status.In addition,there are some definite correlations among various kinds of soil enzymes.

Abstract:Soil structure is one of the important factors of soil fertility.This paper deals with the effect of the application of organic fertilizer,deep ploughing and the utilization of soil transported from other place on the formations of soil structure.These measures not only increased waterstable granular aggregates,but also incteased the microaggregates and temporary aggregates.The solum structure of soil layer of 0-50 cm was changed due to the variation of soil structure properties,three layers of different structure were formed.Therefore the changes in soil structure induced the change of the regime of water and air in soil,the total pores approximated to 60% of which big pores were about 15%,soil aeration were improved significantly below the soil layer of 20 cm,the soil waterholding capacity was increased in 3-5%.The improvement of soil structure may play an important part in providing a better soil nutrient condition and stimulating the activity of soil microbes of the subsoil.

Abstract:Based on the spectral data obtained from laboratory and field experiments in Tengthong spectral test area,the automatic identification and classification of soil types and hand use patterns had been carried out by the use of the principal component analysis.Two principal component equations based on the laboratory data can be used to identify soil types developed from different parent materials and of different land use patterns:Another two principal component equations based on field data can be used to distinguish different land use patterns such as fallow,bare land,wheat field and water etc.

Abstract:六十年代以来,硫在农业上的重要意义日益受到人们重视.缺硫面积日益扩大.这一情况的造成,据认为有以下几种原因:一方面随着作物产量的增加,由土壤带走的硫增加了,另一方面含硫化学肥料(如硫铵和过磷酸钙等)的施用量却大大减少了.

Abstract:晚近的研究表明,土壤养分供应大致通过三个途径:即质流、扩散和根系截获.并认为NO₃^-、Ca⁺⁺、Mg⁺⁺等营养离子主要通过质流,而磷、钾、铵则主要通过扩散.因此,土壤中磷的扩散是判别土壤磷素供应和提高磷肥效率的重要指标.然而,由于影响磷扩散的土壤因素很多,所以在鉴别某一土壤的磷素供应,或研究如何进一步发挥磷肥肥效时,必须首先了解影响土壤中磷素扩散的一些因素.本文即为此目的对三种不同类型水稻土中的磷素扩散及其影响因素进行了初步研究.

Abstract:太湖地区由麦稻二熟制大面积改为麦稻稻、肥稻稻双三制以来,由于土壤全年渍水时间的增加和不合理耕作等方面原因,一些地区出现了土壤结构性变差的现象.田间大土块增加,土团变硬(抗压碎强度增加)、变僵(粗孔隙减少、细孔隙增加)^[1].