Abstract:1. Negative correlation was found between the total N absorbed by rice and F/T (The ratio of fertilizer N absorbed by rice to total N absorbed by rice) in four paddy soils of Jiangsu Province. It means that the more the N uptake by rice, the less the proportion of fertilizer N in the total N uptake. 2. Regular distribution of three levels of rice yield was found in the figure on which the. total N uptake by rice was plott ed against F/T. It was shbwed that the high yield of rice was mainly dependent on soil nitrogen. 3. Isotopic study showed that contrary to the inorganic fertilizer N, the recovery of organic fertilizer N in grain was higher than that in straw. 4. It was found that the duration of nitrogen supply from inorganic fertilizer could be lasted when it was mixed with organic matter. In present experiment, the N supply status of inorganic fertilizer nitrogen seemed to be similar to that of organic fertilizer nitrogen. 5. The fate of inorganic and organic fertilizer nitrogen applied in rice-soil system has been determined respectively after harvest.

Abstract:Milk vetch is a popular and tranditional green manure for paddy soils in South China. In order to study the decomposition and transformation of the nitrogen of milk vetch in soil, plot, microplot and pot experiments were carried out in 1980 on paddy soils derived from red earth in Jinhua County of Zhejiang Province. The milk vetch and urea labelled by ¹⁵N were used in microplot and pot experiments.Results obtained from the. experiments are summarized as follows: (1) The decomposition rate of milk vetch, i.e. the percentage of the loss o.f dry matter ranged from 64-70% during the growing season of the early rice (85 days), and 30% of C was remained in soil after harvest. (2) The recovery rate of N in milk vetch by the early rice estimated by difference method between plots ranged from 24-42%. The effect of 22.5 t./ha of milk vetch (fresh matter) on the yield increase and recovery rate of N was greater than that of 11.25 or 33.75 t./ha of milk vetch. The results obtained by difference method in field experiment were approximately equal to those obtained by ¹⁵N-labelled method in pot experiment. (3) The effect of milk vetch applied on early rice in red earth was significant, but the recovery of residual N in soil by late rice was only 7-8%. (4) The uptake peak of N from milk vetch and urea by early rice. appeared at the tillering and jointing stages. Although N recovered from milk vetch and urea amounts to 3000, the fates of the milk veth-N and urea-N in soil are different. About 50% of milk vetch-N was still remained in soil, while 50% of urea-N was lost. This indicates that the milk vetch can promote not only the accumulation, but also the decomposition of the N in soil, and it may also accelerate the regeneration and circulation of the organic N in soil.(5) Although the ezperi.ment has shown that about 50-80% of the total N in plant was come from the mineralized soil-N, and only 10-25% took up from the N of milk vetch and urea, it is of great significance for the yield increase of early rice to apply milk vetch and urea so as to meet the need of N in its peak growing stage.

Abstract:The present paper deals with forms of organic C, N and P and their distribution, as well as their supplying capacities of the nutrients in three black soils with different fertilities (virgin, fertile and infertile black soils).The contents of organic matter and major nutrient elements in virgin black soil are more than those in cultivated soils including both fertile and infertile black soils. The content of total C, N, P and organic P dicreases in the following sequence:virgin soil>fertile soil>infertile soil.Under reasonable cultivation, fertile soil applied with organic manure is characterized by:(1) higher content of organic C and thick cultivated layer;(2) more humic acid A and fulvic acid in subsoil than those in surface soil;(3) more humic acid B and humin N in subsoil of fertile soil than those in subsoil of virgin and infertile soils;and (4) decrease of highly stable organic P and increase of moderately active organic P. These characters mentioned above indicate the greater potential and supplying capacity of major nutrients of fertile black soil.

Abstract:Longgang Natural Reseave Area is one of the typical karst area under evergreen monsoon forest nearby the north margin of the tropics in China. Studies on chemical composition of soils, rocks, plants and ground water have showed that the main soul type is brown rendzina in this area. During the process of soil formation, the loss rate of elements by leaching is more than 70%. The trauslocation sequence of the elements by leaching is as follows: Ca>Mg>IC>P>Al>Mn>Fe>Si The calcium content of the soils derived from the rocks rich in Ca up to 50% (CaO) may decrease to 1-5% in the process of soil formation. However, calcium is still the most important element in biogeochemical environment of limestone soils. A great deal o,f calcicolous plants have grown in this area, which then brings about the accumulation of calcium to some extent in soils. The sequence of elements absorbed by plant is as follows: Ca>K>Na>P>Mg>Si>AL>Fe, while the sequence of element recovery is as below: N>Ca>Na>K>Mg>P>Si>Fe>Al. According to the data calculated from corrosion rate of limestone, specific gravity of calcite, amount of elements eluviated and illuviate.d and soil b ulk density, it is estimated that to form a solum with a thickness of 1 cm needs about 13,000-32,000 years. Because the li-mestone soils are usually characterized by the higher fertility and thin and erodible aolum, vigorous biological cycling of materials and rich biological resources. The eco-system in the region of this soil is fragile, once the system is destroyed, it is difficult to recover. It is suggested that in utilization of the soils, account should be taken into the conservation of the natures resources, which includes plantation of special economic forests.

Abstract:Yanqi basin is an important region of food production in Bazhou of Xingjian. Owing to the soil salinization the food crop yield is still not very high. The characteristics of salt accumulation in the soils are basically similar to those in the ground water, in which Na, Mg chlorides or sulphates are dominant. In addition, the accumutation of soda and magnesium carbonate in soil is commonly found in this region. (Far planning and developing agricultural production and comprehensive improvewent and reasonable utilization of the soils in this basin it is necessary to carry out soil regionalization.) On the basis of characteristics of topographical, hydrological and hydrogeological conditions and characters of soil salinization of the region, this basin is delimited into five regions of soil meliosation and utilization: 1. The region of diluvial fan of piedmant; 2. The region of diluvial-alluvial plain; 3. The region of Kaidn rives delta; 4. The region of southern and extern shores of Bohu lake; 5. The region of fishery and reed beds of Bohu lake.In order to prevent salinization of water in Bohu lake., some measures should be adopted such as (1) accelareting circulation of the lake water;(2) increasing the input of fresh water to the lake;and (3) controlling the salt content of the water input to the lake.

Abstract:The paddy soil is an anthropie soil. Under long term rotation of rice and upland crops, a compact solum with abundent capillary pores and marked vertical joints is formed. In submerging season the water percolates downward unevenly, the larger pores are filbed with water, whereas the closed pores are still occupied by air. Part of iron and manganese come from the plowed horizon are oaized and illuviated irn solum, and some illuviated iron and manganese in solum may be reduced again by the soluble organic matter, and greyish coating and gleyed spots are formed on the surface of larger pores or cracks. Together with the rusty streaks, the gleyed spots and Fe-Mn mottlings form the unique mined mottled or spotted solum of the soils.In order to study the characteristics of the mottled solum, soil samples with gleyed spots and rusty mottlings were callected from different types of paddy soil and various. genetic horizons of the soils respectively. Analytical data of various forms of iron and manganese showed that there was a remarkable difference in content of iron and manganese not only among different types of paddy soil, but also among different genetic horizons of a paddy soil. From the distribution of different contents of free and total Fe-Mn in soil, it can be found that where there is high content of Fe and Mn is just the place of ilhuviation of Fe and Mn, while the site of low content of Fe and bin is the locality of the eluviation of Fe and Mn. The illuviation and eluviation of iron and manganese in paddy soils are very complex, which, are closely related to water regime of the soil. Generally speaking, under the influence of percolating water, eluviation and illuviation are alternatively and frequently occurred in the plowpan, percolating horison and aide bleaching horizon, which results in a well developed spotted layer with gleyed spots and Fe-Mn mo ttlings, while in stagnating horizon such layer is weakly developed.

Abstract:In soil forming process, it is assumed that the velocity of soil chemical reactions is increased by three times with the temperature rising every 100C;the mean air temperature in ten-days, t, is changed linearly during a year;and when t<0℃, the soil forming velocity equals zero. Under these conditions, the temperature effect of soil forming process, T, may be expressed by the equation:

where t₁ and t₂ are the mean air temperature in the coldest and the hottest ten-days respectively.

Abstract:A direct-current four-electrode method for the measurement of electrical conductivity of soils in situ was devised. Red copper electrodes and a high voltage (90 V) were used. Measurements were made several minutes after the insertion of electrodes into the soil, and readings were taken 10-20 seconds after the passing of current through the circuit. It was found that electrical conductivity values measured by the proposed method were nearly equal to those measured by alternating-current four-electrode method, with a mean proportional factor of 1.006 for 31 measurements, and had a close relationship with those. measured also in situ by conventional two-electrode method. It is shown by the application of this method that, in addition to salinity aml the distribution of soluble salts in the profile for salinized soils, electrical conductivity may be used as a comprehensive. indez of soil fertility of the cultivated layer of acid and even neutral soils as well as base status of the profile, and also reflects the effect of fertilization the on content, of soluble ions of soils.

Abstract:Three hundred and fifty paddy soil samples collected from representative districts of China were studied. The analytical results showed that the content of BHC remained in the plowed layer (1-15 cm) ranged from 0.021 to 1.96 ppm with an average of 0.307 ppm. In 83.1% of samples, the residue of BHC in sail was less than 0.5 ppm. The sequence of the residues of four isomeric BHC were in the order of β>α>δ>γ. Experimental results showed that under the submerged conditions these isomers were degradated rapidly and almost disappeared within two months.The analytical results of 25 samples of brown rice showed that correlation between the content of BHC in brown rice and its residue in soil after harvest was not significant (r=0.379). However, the content of BHC in brown rice was increased with the increase. of the amount of applied BHC in growing season of the rice. Its correlation coefficient r=0.68 and the significance amounts to 99%.

Abstract:This article deals with some biological factors affecting the competition of nndulation between different strains of Rh. leguminosarum on vetch. The results are summarized as follows: 1. Nodulation competition of Rhizobium is mainly affected by the host plant. It is shown that host plants are quite susceptible to definite strains of Rhizobium, either in the case of a definite strain infecting different species o.f plant or in the case of various strains infPeting the same species of host plant. And, the susceptibilities of the Rhizobium to different species of host plant are more sensitive than that to the varieties of host plant.2. Rate of nodulation of the inoculant is decreased with the increase of the amount of native strains in soil. 3. Rate of nodulation is increased with the increase of the amount of inoculant applied in soil where native strains are populated. But, it is not true by seed inoculalion under the same soil condition.

Abstract:棉花的生长发育与其它作物一样,需要一个适宜的热量环境。这个环境状况影响或决定了棉株生理机能的活动和棉花的产量以及品质。对于热量的研究,以往多注意地上的空气温度,而较少重视土壤热量变化对作物产生的影响。实践证明作物根系的生命活动、生理生化过程、摄取水分和养分的速率^[6]都与土壤温度有关。早在1905年,Hedrick就提供了有关土壤温度与作物生长关系的可靠知识^[3]。

Abstract:土壤溶液是由各种阴离子和阳离子所组成的复杂盐溶液,通过土壤溶液中盐分的分析,可以确定盐分的类型和含量,了解盐渍土的性质,研究盐渍土的利用和改良对策。土壤盐分的常规分析方法是用水浸提液来测定可溶性盐分的阴阳离子组成,这种方法不能指出盐分在土中的实际化学特征,因此,常应用化学中的溶度积法来探求盐分的类 型,如Duff和Doneen^[5]应用溶度积的概念来预测含有石膏的土壤溶液中的盐分组成;Nakayama^[6]利用溶度积常数解决土壤中碳酸钙、硫酸钙的溶解性问题,研究了混合盐溶液中的盐分组成。