Abstract:The present paper deals with the principles and methods of regionalization of soils in China. The soil resources of the whole country may be delimitated into three high level categories i.e. Ⅰ. Great soil region;2. Soil zone;3. Soil region. Firstly, the whole territory of China is divided into four great soil regions based on the main variation of soil features and natural environments, namely, Ⅰ. Allitic great soil region (or ferrallitic great soil region);Ⅱ. Siallitic great soil region;Ⅲ. Arid great soil region;Ⅳ. Alpine great soil region. Under these four great soil regions, different soil zones (or soil belt) are divided mainly according to the zonal soil types and their related bioclimatic conditions. The soil zone is further subdivided into soil regions. Each region represents different soil sequence and related landscapes. The utilization, management and ameliorative measures in a soil region are generally similar.

Abstract:Tai-lake region lyinn on the Yangtze and Qiantang delta at the juncture of north and central subtropics is an independent agro-ecological region. Through thousands years of human activities of agricultural practice, this region started from its ecological stage of soil swamping, through the stages of polder farming, cropping of rice and wheat, to a stage of coexisted multiple systems of agriculture, forestry, fishery and sericulture. A well efficient and functional agro-ecological system with stable stricture, high resistibility to natural calamities has been formed, which leads to the region being developed to be,one of the most notable integrated agricultural bases in China.In recent years, triple cropping system. has been adopted extensively regardless of the local conditions, which results in deterioration of soil environment and its fertility. In order to improve this situatiop, it is necessary to study agno-ecological regionalization of this region.

Abstract:In both calcareous and noncalcareous paddy soils, the fate of urea ammonium sulfate and ammonium bicarbonate were investigated in microplot experiments laid out in the rice fields using ¹⁵N tracer technique. The results obtained showed that when the N-fertilizers were surface-broadcasted as basal dressing, the recovery of ammonium bicarbonate was the lowest, while the N-loss was the greatest. The balance sheets of urea-N in the strongly calcareous, slightly acid and strongly acid paddy soils showed that the recoveries in rice plant were 22.3%, 27.5% and 39.8%, the N retained in soils were 30.4%, 18.6% and 16.4%, and the N deficits were 47.3%, 53.9% and 43.8%, respectively. In the two noncalcareous paddy soils, the recovery of ammonium sulfate amounted to 50.1% and 58.7%, but in a calcareous paddy soil, it decreased to 22.5%. Obviously, the nitrogen loss through ammonia volatilization in the calcareous paddy soil may play an important role in addition to denitrification. The deep-dressing of granulated urea and ammonium bicarbonate was the most effective method for the application of N-fertilizers. Besides, experiments also revealed that N-fertilizer top-dressed at the middle stage of rice growth gave a high recovery about 60% by the rice plant. Experiments also showed that the loss of fertilizer nitrogen were not significantly affected either by temporary drainage at the vigorous tillering stage or by the application of nitrification inhibitor (CP).

Abstract:This article deals with silicon supplying capacity of paddy soils in south China. 1. The content of SiO₂ in the surface soil extracted by HAc-NaAc (pH 4) for the soils with 5% increase of rice yield due to application of Si-fertilizer was generally less than 9.5 mg per 100 g soil. For the soils with more than 5% increase in rice yield due to application of Sifertilizer, the critical percentage of SiO₂ in straw was usually less than 10% (at ripe stage). 2. The Si-supplying capacity of paddy soils in south China is divided into 3 types: The first type is the soils with low level of Si-supplying capacity, the average available SiO₂ in soil of this type is less than 8 mg, and the SiO₂ in rice straw is about 8.5%. Application of Si-fertilizer to rice plants on the soils of this type may give more than 5% increase of yield. This type includes paddy soils derived from granite, red sand stone and the quaternary red clay occurring on the second terrace of the rolling hills. The second type is the soils with medium level of Si-supplying capacity, the available SiO₂ amounts to 12 mg, while the SiO₂ in plant straw is about 11%. The paddy soils derived from the quaternary red clay occurring on lower slope and valleys of hilly land belong to this type. When they are heavily dressed with nitrogen fertilizer, Sifertiliser might give yield increase. The third type is paddy soils with high level of Si-supplying capacity. This type includes the paddy soils developed on lateritic soils of basalt origin, and those derived from lacustrine deposits and alluvial deposits of the delta regions, generally rice plant gives no response in yield to Si-fertilizer on soils of this type.

Abstract:The present paper deals with a matrix equation for one,dimensional flow through unsaturated soil derived from the finite element method and a BASIC Program which has been applied to solve the problem of lateral seepage in soil in a DJ-130 computer.Better agreement is observed between the results obtained from the equation and the data from exPeriment as well as Philip's analytieal and quasi-analytieal solution,and the program is Proved applieable.With the aid of this progrem,the rate of lateral seepage,the relationship between wetting front and time,the vertieal infiltration upward from ground-water table and that downward from wetted soil surfaoe are computed and discussed preliminarily.

Abstract:This paper deals with the problem of secondary salinization of soils caused by irrigation with bitter water in the arid and semiarid regions of southern Ningxia. Sierozem is widely distributed in this region. For development of agricultural production, it is necessary to irrigate with bitter water due to lack of the fresh water in this region. After irrigation with bitter water containing a large amount of soluble salts, the soil secondary salinization occured immediately by which the crop yield was affected. Some conclusions obtained from the study on the dynamic regime of water and salt in soils irrigated by bitter water are summarized as follows: 1. It was observed that the lower limit of soil moisture for the water movement in light loamy soil was about 10% (by dry weight).If the soil water content was above 10%, it could dissolve the salts and carry the salts to move up and down in the soil profile. If the soil water content was below 10%, it could not dissolve the salts. 2. From the view point of long term irrigation with bitter water, the light loamy soil with good filtration and high permeability is suitable to be used for irrigation with this water, although it has low retention capacity of water and nutrients. Under the condition of the ground water level more than 20-30 m in this region, the irrigation can leach the harmful salts downward from the upper soil, which will be beneficial to improve the saline soils. On clay soil, irrigation with bitter water is more successful in the initial stage due to economy of irrigation water. however, owing to the poor permeability of the clay soil,,long term irrigation with bitter water inevitably firings about accumulation of salts in soil and hence servere secondary salinization of the soil. Therefore, the area of clay soil is not suitable to be used for irrigation with bitter water. 3. It was proved that the secondary salinization of the soils irrigated with bitter water in the initial stage was mainly caused by the salts brought up by the capillary water from the subsoil containing a large amount of salts, while the salt carried by irrigation water was insignificant on the secondary salinization of the soil. 4. The movement of water-salt in the soil mainly depends upon the seasonal variation of climatic factors such as temperature, rainfall, evaporation, etc. According to the annual variation of salinization and desalinization in soil, it is divided into four periods in a year:(1) period of violent salinization, (2) period of desalinization caused by irrigation, (3) period of the natural desalinization and (4) period of slow accumulation of salt.

Abstract:Data of observation indicated that the genesis and evolution of the seasonal frozen soil was the main factor to restrain the movement of water and salt in winter and spring which constituted the peculiar pattern of water and salt movement in soil. During the soil freezing period, soil salt was accumulated in the frozen soil layer with the freezing of the soil. While in spring with the thawing of frozen soil layer, a part of thawing water and salt infiltrated into the ground water, another part of the water was evaporated and salt was accumulated in the surface soil. Therefore the accumulation of salt in the surface soil in spring is actually the result of redistribution of salts in frozen soil layer accumulated in winter. According to the results of the study on relationship between the accumulation of salt in frozen soil layer and the ground water table at the begining of frozen period and experiments, it is proved that if the ground water table is controlled bellow 1.5-2.0 m before frozen period, the accumulation of salt is decreased significantly in the process of soil freezing, the accumulation of salt in the surface soil in spring then can be prevented.

Abstract:Shanghai is an alluvial plain in the Yangtze delta. The main soil types are mostly swampy soil, meadow soil and coastal saline soil derived from alluvium of the Yangtze river. Variation of trace elements content in soils is mainly depended upon the different parent material. The range and mean value of the total content (in parenthesis) of trace elements in soils of Shanghai are as follows: Zn 20-102 ppm (65.5±11.0 ppm),B 20-76 ppm (52.6±11.8 ppm),Mo 0.3-2.0 ppm (0.75±0.34 ppm), Cu 11-38 ppm (23.0±4.6 ppm), Co 11-27 ppm (19.4±3.7 ppm), Mn 280-1076 ppm (540.7±127.7 ppm). The content of available trace elements varied greatly. The content of available copper of the soils in Shanghai (extracted by DTPA) was rather high with a mean value of 5.2±2.2 ppm. However the content of available molybdenum was very low with an average of 0.14±0.05 ppm (extracted by Tamm sol.).At the same time, there are a larger area of soils with lower or deficient in B, Co, Mn and Zn.Among the soil types mentioned above, coastal saline soil was higher in available B (0.82±0.30 ppm, extracted by hot water) and Mo (0.16±0.06 ppm), but lower in available Zn (0.82±0.42 ppm, estraeted by DTPA) and Co (0.34±0.18 ppm, extracted by 0.1 N HCl);the swampy soil was lower in available B (0.57±0.23 ppm),Mo (0.13±0.05 ppm) and Mn (122±49 ppm, extracted by 1 N neutral NH₄Ac+0.2% Hydroquinone),but was higher in available Co (1.09±0.38 ppm). The available content of B, Mo, Co, Zn in some meadow soils were lower. In recent years, more than 50 field experiments of trace element fertilizers in the suburbs of Shanghai revealed that B, Zn, Mn, Mo were effective to rape, wheat and vegetables in some soils.

Abstract:This paper deals with the preliminary experiment of the automatical classification and mapping of soils by means of remote sensing method which was part of the research work of the author in Mexico. Experimental results showed that the automatical classifieation method not only raised the working efficiency by nearly twofolds, but also increased the cartographical precision up to the level required by a soil map on the scale of 1:250,000. But different soil types vary in mapping pattern error. According to the errors occurred from minimum to maximum, the soils are arranged as follows: (a) pellic vertisol. deep phase, (b) orthic phaeozem, deep phase and cnomire luvisol, deeply lithic phase, (c) pellic vertisol, deeply lithic phase and lithic phase, (d) orthic phaeozem, deeply lithic and lithic phase;natric vertisol, deep phase;natric phaeozem, deep phase. Of course, some mapping patterns of the soils with great errors are below the level of cartographical precision required.

Abstract:A cryoscopic method has been used for the determination of number-average molecular weight of humic substances. Samples were dissolved in dilute alkali solution and then the pH of the sample solution was adjusted to that of the equivalent point of neutralization with the aid of canon exchange resin. Apparent molecular weight was corrected by determining the concentration of Na⁺ in the sample solution by means of the sodium ion electrode. The accuracy of this method is about 1-3%. For water soluble humic substance, it gave identical value as that obtained by Hansen and Schnitzers method. The Mn of humic substances from different origins examined by this method ranged from 600 to 3600.

Abstract:稻田泥炭土主要分布于东北三省寒温带河谷平原及山谷洼地^[2],是开垦草炭土或腐泥土,种植水稻而形成的一种低产土壤。 据调查,吉林省泥炭土有232万亩^[4]。其中稻田约有22万亩,水稻亩产一般为300斤,不到矿质稻田的三分之二。