Abstract:The geographical distribution of soils deficient in trace elements including boron, molybdenum, manganese, zinc and copper in China has been studied. Five nationwide maps of the content of these elements are compiled based on the soil map of China on the scale of 1:10,000,000. These maps show that in the country there are not only the soils which result in trace elements deficiency of plants, but also the soils which result in the imbalance of trace elements of plants, all these soils will affect the crop yield.There are large areas of boron-deficient soils in the eastern and southern China. The content of laoron in soils varies with the soils types and parent materials. Laterite, lateritic soil and red earth derived from granite and other igneous rocks, gneiss and sandstone are lower in total and available boron. Symptoms of boron-deficiency of crops may be observed on these soils: In the cases of severe boron-deficiency, even complete failure of rape yield was found. Many molybdenum-deficient soils are distributed in China including two main Mo-deficient soil regions. One of these is the region of loessial soils and lightcolored meadow soils derived from alluvium of the Yellow River, in which the contends of total and available molybdenum are low. The other one is the region of laterite,lateritic soils, red earth and yellow earth, in which the content of total molybdenum is high and content of available molybdenum is low. Good response of leguminoues crops to molybdenum fertilizers has been found on these soils.

Abstract:The physical properties of the major red earths widely distributed in the tropical and subtropical China were studied. The results showed that the clayey red earth containing about 60% clay particles formed under certain tropical bioclimatic condition not only had the particular chemical properties, but also possessed special physical behaviours. Their characteristics such as water retention and movement, soil rupture modulus, Broil adhesion and Atterberg's constants were quite different from the soils with clayey texture, but similar to the soils with sandy texture. One of the important reasons resulting in the physical behaviours mentioned above is attributed to the abundance of the water stable microaggregates in these soils.The unique physical properties of clayey red earths is of great significance to its rational exploitation, utilization and management.

Abstract:The composition and properties of humus in the cultivated red earth is influenced to a great extent by farming measures. Especially, under the conditions of organic manuring and rice planting, the composition of humus may go beyond the influence of geographical zonality and degree of humification can be increased significantly, the valne of ΔlogK can be decreased gradually and the ratio of humic acid to fulvic acid may be more than 1. The ratio of H.A./F.A. in paddy soil derived from the red earth with higher fertility is 1.4, that in paddy soil with medium fertility is about 0.5 and that in paddy soil newly reclaimed is 0.2-0.3 which is similar to that in virgin red earth;and the ratio in dry farming red earth with higher fertility is about 0.9. All these mentioned above showed the characteristics of soil humus under cultivation and manuring of high yield rice, and the ratio of H.A./F.A. might be considered as the.main index of fertility of red earth. This study also showed that the variation of contents and properties of humus of red earth was restricted in the surface soil, and with the duration of cultivation it was gradually influenced in the other horizons of the profile.Because of excess of water and lack of oxygen, the composition of humic acid in paddy soils derived from red earth with lower and medium fertility is simpler than that in upland soils, though the humus in these soils is accumulated faster. After a long period of rice planting, the rotation of rice and upland crops can regenerate the soil organic matter and improve its quality, being conducive to the improvement.

Abstract:The present paper deals mainly with the characteristics of isotherm of ammonium adsorbed by several typical soils and clay minerals and cation-exchange resin from binary solution of NH₄⁺-Ca⁺⁺ chloride and incidentally with the selectivity of the soils for ammonium ion. Some information of soil samples are given in Table 1. Binary solution were prepared with NH₄Cl at 8 concentrations ranged from 0.002 N to 0.02N and various amounts of CaCl₂ were added in order to keep the total ionic concentrations of binary solution at 0.02N as are showed in Table 2.The ratio for soil or kaolinite to binary solution in the experiment was 1:20, and that of bentonite or resin to the solution was 1:100. Each sample was put in a definite volume of binary solution and shaken for half an hour, and then filtrated. In filtrate, the ammonium ion was determined by semi-micr,odistilled method and calcium ion was sometimes determined by EDTA volumetric method. The difference between initial and final concentrations of NH₄⁺ and Ca⁺⁺ in solution is the amount of NH₄⁺ and Ca⁺⁺ adsorbed.The adsorbed ammonium by soil was positively correlated with the NH₄⁺ concentration in solution. The equation (1) or (2) derived from Ratio Law gave the beat results as are showed in Fig.1 and Table 3-5.The increment of adsorbed ammonium of soil samples removed the organic matter and samples after submerging were not related to the ammonium ion concentration of binary solution, while the increment of adsorbed ammonium of soil samples removed free iron oxides was positively correlated with the ammonium ion concentration of binary solution. The correlation coefficient (r) was 0.950^*** for yellow brown earth 0.993^*** for red earth and 0.950^*** for laterite respectively. The authors suggest that the ezchange sites released from soil samples after removed organic matter and treatwent under submerged condition have a strong affinity for ammonium ion. Therefore there were no difference between the increments of ammonium adsorbed in binary solution with lower concentration and higher concentration of ammonium. however, the exchange sites released by removed free iron oxides were oppsite to those released by removed organic matter and treatment of submergence. In addition, in accordence with the results of Table 8 and with the released amount of adsorbed ammonium the relative affinity of soil samples for ammonium ion may be as follows:Yellow brown earth ≥ Red earth ≥ Laterite.

Abstract:The loss of fertilizer-N in submerged paddy soil was investigated with ¹⁵N-labelled ammonium sulfate in special designed pots. The gaseous composition of the atmosphere in the upper-space above the water in the sealed pot controlled by transmitting or N₂ gas during the experiment period (4-6 weeks after transplanting).The N through nitrification-denitrification was estimated by deducting the ¹⁵NH3 volatilized from the deficit in the balance sheet of ¹⁵N-labelled fertilizer-N The results obtained are discribed as follows: 1. In the neutral paddy soil investigated, nitrification-denitrification was the most important pathway of the losses of fertilizer-N. 2. The loss of fertilizer-N in the treatment of transmitting N₂ gas through the upper-space in the sealed pots approximated to that of transmitting air, implying that. nitrification-denitrification taken place in the oxidized layer on the soil surface and the reduced layer under it may not be the sole mechanism of nitrification-denitrification losses of fertilizer-N applied as basal dressing in soil. 3. The losses of fertilizer-N in the pots with rice were markedly lower than that without rice. The competition of the absorption of ammonium by rice plant with nitrification may be the reason of the decrease of N losses. 4. In the treatment of transmitting N₂ gas through the upper-space in the pots without rice, there was still a significant loss of fertilizer-N expelling the soil ari by transmitting N₂ gas through the solum before flooding had little effect on the reduction of N losses. Therefore, it is necessary to further investigate whether any other oxides might be able to act as an electron acceptor in the oxidation of ammonium in submerged paddy soil, resulting in a subsequent denitrification loss.

Abstract:The precept paper deals with the effect of salinity of saline soil on distribution and antagonistic properties of streptomyces. The results obtained are summarized as follows: 1. The number of actinomycetes is closely correlated with the salinity of saline soils in northern Jiangsu Province. It decreases with the increase of soil salinity while it is less than 0.2%. The curve of actinomycetes tends to be flat, when soil salinity is over 0.2%. 2.456 antagonistic actinomycetes out of 632 isolated from 6 saline soils with different salinity. The number of actinimycetes in cultivated land with low salinity is higher than that in virgin land with rather high salt content. However, the percentage of antagonists in total a,ctinomycetes in virgin saline soils is higher than that in cultivated land. 3. Numbers of the groups of streptomyces in cultivated soils are larger than that in virgin saline soils, and the kinds of group are different greatly between the two soil types. Aureus group is predominant in the desalinized soils cultivated for 20 years, while in virgin saline soils with high salinity Roseospours is predominant, and Cinereus comes to the neat. 4. Streptomyces with wide antimicrobial spectrum commonly occur in cultivated soils, among which Aureus and Griseofuscus are more effective in antagonism against both bacteria and pathogenic fungi. The antagonistic intensity of those groups range from 40-70%. In virgin saline soils, most of the isolates with antagonistic action belong to Roseosporus, Cinereus, Glaucus and Flavus groups and their antagonism are usually confined to Staphylococcus aureus, Bacillus subtilis or Monilia albicans.

Abstract:The clay mineral composition in soil varies regularly with the vertical distribution of soils on the north slope of Mt. Taibai. From the altitude of 1330 m on which the mountain cinnamon soil developed on residual deposits of marble contains dominantly hydromicas with some montmorillonit.e and kaolinite. To the altitude of 1570 m on which the mountain brown earth developed on the residual deposits of gneiss under mixed forest of coniferous and broad-leaved trees is predominated by hydromicas and vermiculite with a small quantity of montmorillonite and chlorite;while on the altitude above 2790 m, the mountain podzolic soil derived from the same parent material under fir forest contains large quantity of vermiculite and montmorillonite and accumulates more iron oxides in the lower layer of the profile. With the transition from forest to alpine meadow on the altitude of 3744 m, the mountain meadow soil there contains also mainly hydromicas with more vermiculite and montmorillonite.

Abstract:The analytic method of synthetic numerical value is a mathematical method in which the principal composition analysis and the discriminatory analysis are integrated into a single combination. In experiment of classification of soil spectra, with this anethod, not only the soil samples can be divided into different types by calculation, but also the delimitation index of various soil properties (reflectivity,of wave band ρΔλ)can be calculated. Therefore, it may be regarded as the method with a bright prospect in the practice and research of soil classification. In the application to the subdivision of alkaline soil, this method exhibits its simplicity and reliability to a larger extent. The results obtained in the experiment of subdivision of alkaline soil by this method may be useful for the classifying the alkaline soils of Huang-Huai-Hai plain into 1 over categories. The basic concept of analytic method of synthetic numerical value, in addition to its application in soil classification, may also provide a way for processing the data involved in spectrum reflective characteristics of soils and may be possibly used in the soil classification and identification of remote-sensing image as well.

Abstract:There have been several mathematical models for the transportion of nutrient ions in soil towards single root or root system of a single plant. But wheather these models can match the root systems of the rice plants grown in a clump remaines to be verified. In order to test the models, rice plants were grown in a box consisting of two compartments separated by a sheet of nylon sieve to form a plane of rice roots. A comparison was made between the values of relative concentration of potassium ion in soil near the root surface predicted from Nye's model and those measured with a miniature potassium selective electrode. The results obtained showed that the measured values of relative concentration of potassium ion in the soil of rice rhizosphere were approximate to the theoretically calculated values, and their agreement was even better when water flue increased. It is possible to predict ion concentration near root surface using mathematical modelds even under more complex situations. In this experiment it was also observed that there were a deficit zone of potassium and a neutral or weakly alkaline pH environment in micro-areas of rhizosphere of rice plant.

Abstract:This paper deals with the relationship among the methods of available phosphorus. determination, phosphorus forms and response of crops to superphosphate on three main soils in Sichuan Province. Results obtained from the experiment showed that Olsen and Al-Abbas methods were suitable for fluvisol and purple soil. Fe-P and Al-P could be extracted proportionally by these methods from soils and both of them were the phosphorus resources in the soils for the crops investigated. Bray Ⅱ method was suitable for yellow soil. Ca-P and Al-P were extracted proportionally by this method, and Ca-P was the phosphorus resource in the soil for the crops investigated.

Abstract:荒漠碱化土壤的主要化学特性是碱度和pH值较高。这是由于碱化土壤含有一定量的交换性钠(镁),以及有时出现Na₂CO₃或MgCO₃等碱性盐之故。因此,在实践中,用酚酞反应方法在田间鉴别土壤是否含有苏打,测定时往往受空气(包括土壤空气)中CO₂分压的影响使pH值降低。

Abstract:为了实现农业现代化,加快粮食生产,农业科学工作者正在从各个角度研究提高单位面积产量的规律。水稻占我国粮食总产量百分之七十以上;故研究影响于水稻产量的各种客观因子更具有现实意义。根据土壤科学与植物营养的原理,在品种性能与气候条件既定的前提之下,我们认为决定水稻产量的关键因子乃是土壤的养料肥力以及对水稻的养料供应状况。