Abstract:In the northern,northwestern,northeastern and the coastal regions of China,salt-affected soils are found in large areas.The distribution of such soils is so extensive and the natural conditions under which they exist are so complex that the soil types are numerous and their salinity and properties are varied.In order to promote our agricultural production and bring into effect the moderne nation in agriculture at a greater speed,it is necessary to delimit all the salt-affected soils of our country for reclamation and utilization,in addition to making an overall planning and a comprehensive management.

Abstract:The double-cropping rice is known as the principal type of cultivated rice in the suburbs of Shanghai.In comparison with them late-maturing single-cropping rice,the former is fundamentally characterized by its short growing period.as well as its appearance of panicle primordial differentiation in tillering stage,thereby giving rise to an outstanding peek of nutrient up take within 2 or 3 weeks after transplantation.During this period,there is an drastic increase in both the concentration of the nutrient content and the quantity of daily absorption of the plant above the ground.ht is estimated that during a period of three weeks after transplantation,the nitrogen ahsorption amounts up to 60-70% of its grand total throughout the whole growth period.In the peak uptake stage,the nitrogen percentage of the plant is significantly correlated with the number of ripening grains,available ears and grain production.

Abstract:1.Because the growing period of rice under "rice-rice-wheat" rotation,as compared with that under "rice-wheat" rotation,is greatly shortened,the amount of nitrogen mineralized in soil absorbed by rice plant is diminished to such a considerable extent that the need on fertilizer nitrogen has to be increased significantly.At the sane time,the dower rate of mineralization of soil nitrogen under low temperature in the early stage of early rice can not meet the need of higher nitrogen absorption rate of early rice at that time,and it is indispensible to increase nitrogen fertilizer applied in the early stage of early rice.

Abstract:Studies were made during the past years on the total content of the trace elements such as B,Mo,Mn,Zn,Cu in the main soil types of Chinas,and their available part for plants.The aanount of trace elements in the soil is largely determined by the soil types and,to some extent,by its content in the underlying parent rock,the mature of which has a direct effect on the eontent of trace elements in soils.

Abstract:The formation and distribution of the coastal salt-affected soils in Northern Kiangsu is influenced by various soil-forming conditions,among which the age of sediments,the distance from the sea and the history of cultivation and utilization are the most important factors.Under the influence of these factors,the belts of soil-ground water parallel to the coast line come into being.All the soils of each belt are derived from the salt-affected mud-sediments.

Abstract:This paper deals with the mellow soil of Tachai Brigade in Shansi Province develbped from loessal deposits by long term fertilization arid intensive cultivation within a period of more than score years:The micromorphological characteristics of this soil was investigated.It was found that there were a great number of compound aggregates,considerable voids with various size.and shape,and abundant organic matters decomposed in different levels in the soil.

Abstract:It was found that u,xLder waterlogged condition the concentrahion of water-soluble ferrous iron in paddy soils,depending on soil conditions,varied within the range of 14-360 ppm,among which about 10-30 per cent was in the compleged farm associated with organic matter.All of the compleged ferrous iron can be chelated by a-a' dipyridyl within 48 hours,implying that there would be no tightly-bound iron compleg in the water extract.The compleged iron with positive or negative charge accounts far 10-15 per cent or less than 10 per cent of the total ferrous iron respectively.

Abstract:Electrochemical methods with micro-electrodes were used for studying the release and subsequent diffusion of granulated fertilizer in paddy soils.The measurements included electrical conductance,concentration of ammonium ions and pH of the soil.The sensitive part of the constructed micro-electrodes was of the order of 1mm in diameter.Ammonium bicarbonate,a low grade and easily volatilizable nitrogen fertilizer,granulated to a diameter of about 5 mm was used for the study.

Abstract:Effect of the drainage on the melioration of soil moisture condition of paddy field for winter crops was studied in field plots.The soil investigated was a slightly acid,silty clay loam,derived from lacustrine deposit in Tongting Brigade,Wusi,Kiangsu.The land was used under a rotation of three crops in one year rice-rice-winter crops (mainly wheat),with a total yield of about 15 tons per hectare.A wet surface soil in rainy spring usually restrained the good growth of wheat plants.The ground water often rised up to the soil surface after a daily rainfall above 50 mm.

Abstract:Cheng-si-hu Farm At Huochiou County in Anhwei Province is located in a lowland with soils clayey,heavy and moist in nature.The crops (mainly wheat,barley or naked barley) in this area are injured seriomly by waterlogging due to the illdrainage of the soil in rainy season.This condition has been greatly improved by means of the wide application of the mole channel drainage.The experiment in a disastrous rainfall of approximately 100 mm per day showed that the drainage of mole channel laid in an interval of 10m,60-70cm in depth and combined with surface drainage of shallow ditches in an interval of 50-100 m could resist the concentrated rainfall of moderate intensity.