Abstract:The present paper deals with the requirements of paddy soils for tillage and through study on the relattonship oetween the pnysicai properties of soil and the growth of crops. Experiment results revealed the great effect of the soil mechanical disturbance on water potential, which indicated that it is a major factor resulting in soil puddling; moisture content and the capacity of effective moisture were higher in topsoil than in subsoil, which shower that soil puddling increases water retention. The linear negative correlation between moisture content and bulk density was statistically significant (n=62,r=-0.909^**). Thus long-term zero-tittage soils can suvolv insufficient water for crop erowth. The most favorable codition for wheat. growth on paddy soil was the soil moisture suction ranging from 0.02 to 0.5 bar. Because field capacity is higher than plastic limit, plowing and pulverizing the soil following rice inevitably leads to soil puddling. The best growth of rice appeared at the bulk densities ranging from 1 to 1.3 g/cm², which was similar to those after the flooding of the soil of zero-tillage following wheat. Therefore, zero-tillage is suitable for paddy soil under cropping system of rice and wheat. The grain yields of rice and wheat under zero-tillage were increased by 142.5 kg/ha and 367.51kg/ha, respectively as compared with traditional tillage, according to the results obtained from 52 experiments of rice and 23 experiments of wheat. The physical properties were not deteriorated in permeable paddy soils under zero-tillage for three years and in waterlogged paddy soil for two years.

Abstract:Study on affecting factors of rill formation and development was conducted by using simulated rainfall and field investigation. The results have been shown that rainfall and runoff energy (especially runoff energy), soil erosion durability, slope degrees length, shape and land management are principal factors affecting rill erosion. For this reason, the authors consider that the key measues to control rill erosion is to reduce rainfall and runoff energy and to improve soil erosion durability.

Abstract:Nitrogen fertilizer status in the rhizosphere varied with different N forms and the soil moisture condition. It was revealed that there existed a depletion zone of NH₄⁺-N in rice rhizosphere under submerged condition. The exponential correlation was found between the depiction rate and the distance from the root surface for both (NH₄)₂SO₄ and (NH₂)₂CO. The depletion of NHS-N was also observed in the area of 1-3 mm from root plane of upland crops, such as maize, barley, and ryegrass. Being different from that of rice, the maximum of depletion value was not near the root surface. In other words, NH₄⁺-N was relatively accumulated in the rhizosphere soil within the rhizosphere area .of 1-3 mm from the root plane. The furthm results showed that a considerable amount of labelled nitrogen was detected in the rhizosphere of upland crops, indicating part of NH₄⁺-N relatively accumulated near the root surface is contributed by the nitrogen exuded from the plant root. The amount of exuded N or the rate of relatively accumulation of N was related to the crop species and soil water condition. On the contrary, in the case of NO₃^--N, significant accumulation of labelled NO₃^--N was found in the zone of 0-5 mm from root plane of both rice and maize under either submerged or dryland condition. It can be considered that NO₃^--N is mainly transferred to the root by mass flow, which is different from ammonium nitrogen by diffusion, and accordingly it is not depleted but accumulated in the plant rhizosphere soil.

Abstract:The effect of ammonium fixation on the transformation of N labelled fertilizer N in three soils was studied in a pot experiment. Little fertilizer N was fixed by clay minerals in a paddy soil derived from red earth, while 56-77% of fertilizer N applied was fixed in bleacked paddy soil and calcareous permeable paddy soil. Availability of these "newly" fixed ammonium N was so high that over 90% of it was recovered by rice plant or microorganisms within 30-50 day after the transplantation of rice seedlings. The availability of the biologically immobilized N to the current crop was much less than that of the "newly" fixed ammonium N. In a field microplot experimant conducted on bleached paddy soil, it was found that 20-86% of the residual fertilizer N taken up by the succesive crops (2nd and 3rd crops) was derived from fixed ammonium nitrogen. The authors consider that far soils with fairly strong NH₄⁺-N-fixing capability, only the NH₄⁺-N-fixation by clay minerals and its release are known, can the N immobilization, remineralization be evaluated.

Abstract:The fixation of phosphate by pure CaCO₃ was studied. The results indicated that at lower initial phosphorus concentrations, the phosphorus was mainly adsobed on CaCO₃ concentrations, precipitations occurred, and a large amount of phosphorus could be fixed by CaCO₃. The fixation of phosphorus by calcareous soils was then studied. The results indicated that at lower range of phosphorus concentrations (0-200 μgP/ml), clay played a major role in fixing phosphorus, while at higher concentrations(>200 μgP/ml), CaCO₃ became important. Thus it is showed that calcareous soils have high fixation power of phosphorus.

Abstract:This paper deals with the chelate dissolution-differential photometric method for determination of phosporus in calcium superphosphate and rock phosphate samples. A mixed chelate solvent consisting of 15% of citric acid -9% of aluminium nitrate which can control the interference of citric acid and fluorine ion is proposed. The pH value of this mixture solution system is 1.33±0.02. The results obtained has showed that relative error of the chelate dissolution}ifferential photometric methods, as compared with acid dissolution-gravimetric method, is lower by ±1% But for calcium superphosphate with lower phosphorus content, a relative error about ±1.5% is obtained. It is found that the recovery of P₂O₅ added is about 99.0-100.4%.

Abstract:Response of paddy rice to copper fertilizer in permanently waterlogging and long-termed waterlogging paddy soils in hilly region of southern part of Anhwei Province is discussed in this paper. 67% of the field experiments showed response to copper fertilizer, with ideld in prease of 5.2-41.4% (45 kg/mu on average); while 89% of the field experiments conducted in permanantly waterlogging paddy soils was responsive to copper fertilizer. The available copper of permanently waterlogging paddy soils extracted with the same solution was 317 ppm on average. In these soils the organic matter content averaged 3.99% and Eh 71 mV. It indicates that the available copper and Eh are lower, while available iron and organic matter are higher than those in long-termed waterlogging paddy soils and ameliorated paddy soil.

Abstract:On the basis of elucidation of genetic properties of the soils, organic matter, humie acids and humin in chestnut soils on basalt platforms were dated by ¹⁴C method. Results of radiocarbon dating showed that the chestnut soils of China and the mollisols in other countries of the world were the product of the same period, formed about 6000 years apo. The age of organic matter fractions from the chestnut soils was in the following. homic acids > humia > total soil organic matter.

Abstract:The comparative study of purple lithomorphic soils, their parent materials and rocks showed that the indicator characters of genesis of purple lithomorphic soils were high physical weathering rate, enrichment or weak loss of elements, lower free iron content and clayization coefficient, higher silt clay ratio and the similarity of silica-alumina ratios between soils, parent materials and bed rocks. Great group of purple lithomorphic soils can be divided by comparison of free iron content, silsca-alumina ratio(<1μ) between soil and bed rock or parent material; subgroup by weathering degree; family by the combined type of partical composition, chemical composition and mineral composition; and sepcies by the soil depth, gravel content, soil erosion degree and soil water condition.

Abstract:TCA residue in soil, wheat and corn plants in different periods was studied by field and pot experiment. Result obtained showed that TCA could be kept in the soil under field condition for seven months; the highest TCA content was detected in seedling (trifoliate) stage of the plant, TCA content decreased ripadly with the plant growing, and a very small amount of TCA was detected in seed. Discussion is made on the factors affecting absorption of TCA by crops and the relationship between TCA residue in soil and TCA content in plant.

Abstract:Investigation tinder field, microplot and pot experiments for the effect of phosphorus fertilization on VA mycorrhizal response were conducted under unsterilized soil conditions. It was indicated that 8 jin P₂O₅/mu (60 kg/hectare) in form of superphosphate was the most favorable P level for VA mycorrhizal infection in 4 types of fluvo-aquic soil in Huang-Huai-Hai Plain of North China. Under such P level both growth and P uptake of plants were promoted by myeorrhizal inoculation while the lag phase of root infection was greatly shortened.

Abstract:The soil samples were collected from Haibei alpine meadow ecosystem research station. The types of vegetation are Kobresia humilis meadow, Dasiphora fsuticosashrub, Elymnsrrs nutans meadow, and Fosbs meadow. Depth of sampling soil were 0-10 cm, 10-20 cm, 20-40 cm, and 40-60 cm. Data of respiratory intensity showed in table 1. Experimental results showed that intensity of soil respiration varied with the types of vegetation and presented a noticeable diurnal and nocturnal fluctuation, the diurnal respiration was stronger than nocturnal one. Data also showed that the intensity of soil respirations varied with the depth of soil. The highest respiration intensity occurred in the surface layer and gradually diminished with the increased of the soil depth. Soil respiration in four types of vegetation was correlated with the number and activity of microorganisms, enzymic activities, and soil temperature respectively. Significant correlation could be found between the soil respirations and the total N, pH. cation-exchange capacity, organic matter, available K, hydrolyzable N respectively.

Abstract:在干旱、半干旱地区,地下水位和矿化程度过高,是土壤盐渍化的根本原因.地下水的盐分组成与含量,以及分散在水中的一定量的有机物质,对毛管水的上升无疑会产生影响.但是影响的程度如何?作用机制是什么?都是值得研究的问题.

Abstract:本区位于我国北部,属高纬度寒温带大陆性季风气候,气候寒冷,年平均气温为-2℃-1.0℃,活动积温(≥10℃)1600-2400℃,无霜期为80-125天,作物属一年一熟制,年平均降雨量450-650毫米,年日照时数为2400-2800小时,一般春季干燥,夏季温润.不利的气候因素有低温、干旱、内涝、霜冻、冰雹和大风等灾害.