Abstract:The availability of mineral nutrients for plants is determined by the chemical, physical and biological characteristics of soils, especially by root-induced changes in the rhizosphere. Mineral nutrient supply to the root surface is mediated mainly by mass flow or diffusion. Accordingly, root surface area is important for the acquisition of nutrients. Acquisition of most nutrients is particularly dependent upon root-induced changes in rhizosphere pH, redox potential and the release of low molecular weight organic solutes. Depending on their chemical nature, these solutes can mobilise mineral nutrients directly, in the case of organic acids and phytosiderophores, or indirectly, by enhancing the activity of microorgpnisms in the rhizosphere. Rhizosphere microorganisms may, however, also decrease nutrient availability or affect nutrient acquisiton via changes in root morphology caused by hormones or by the infection of plant roots with mycorehiza. Root-induced changes in the rhizosphere vary between genotypes, and are affected by the nutritional status of the plant (e.g. phosphorus or iron deficiency). The extent of root-induced changes in the rhizosphere is important for adaptation of higher plants to soils with extreme themical and physical properties.

Abstract:More than 2000-year history of agriculture in China has demonstrated that the grain yield could be sustained and the soil productivity could be maintained and gradually improved through recycling the nutrient elements and raising the efficiency of organic manure. The input of non-agricultural material and energy is a most effective way to increase the crop yield and is oae of important characteristics of modern agriculture. But there is a tendency in some regions that the farraers prefer only chemical fertilizer. The long-term application of sole chemical fertilizers will cause many soil problems and exert a bad influence on crop quality and human health. Particular attention could be given to the development, production and application of the organic inanures, so as to solve the problem of organic manures, to improve soil properties and to develop sustainable agriculture.

Abstract:In the light of the data on soil salt regime in 60 points in the northern part of Quzhou Couaty (247.4 km²), Huang-Huai-Hai plain, observed in spring and summer, 1987, and the study results of some predecessors. all kinds of factors influencing the salt regime in sails, such as the texture of soil profile (mainly the thickness of clay layer), the depth and saly content of groundwater, precipitation, irrigation and the initial saly content in soils are used as independent variables in the statistical models for prediuing soil salt content in spring and summer developed with the method of stepwise regression. The dependent variables are contents of total dissolved saly in 0-100 and 0-40 cm deep soils at next time interval. The factors seriously affecting the salt regime are all selected into the predicting equations. The independent variables thst,ase selected into the equations are different with the season and soil depth. There is a good agreement between the predicted results and observed data. Preliminary test demonstrates that the models can at least be used for the prediction of soil salinity in agriculture production. The prediuing models can only be used in such situations that the year type of predicting ime it the same as 1987 and the natural conditions are similar to Quzhou County's.

Abstract:Underground metal pipelines are severely corroded in weakly leached soils such as coasal solonchak, salinized fluvo-aquic soil and yellow fluvo-aquic soil. Within 10 years they cast be perforated at a number of points, with a maximum rate of hole corrosion of 1.5 mm/yr. The number of perforated holes is associated with such factors as the resistivity, salt content, and chloride cgntent of soil, of which the chloride content is the most important. In moderately leached soils such as Shajiang soil, brown earth, dark loessial soil, cinnamon soil and castanozam,the pipelines are corroded less severely, and commonly no perforation will take place wirhin 10 yssrs; while in strongly leached soils such as paddy soils with Fe-humic coatings, paddy soils developed on red earth and lateritic red earth, as well as lateritic red earths, thry are corroded most slightly, with a maximum rate of hole corrosion of 0.01 mm/yr. Yet, in areas of boggy paddy soil under anaerobic conditions in South China, the maaimum rate of hole corrosioa may be up to 0.5 mm/yr, due to a corrosion by microbes.

Abstract:This paper discusses the result os research on the efficiency and technique of potassium fertilization in paddy soils with different water conditions and show that the potassium efficiency on these soils was in the order of gleyed paddy soil (GLP)>periodically waterlogged paddy soil (PWLP)>submergic paddy soil(SMP). The role of potassium fertilization in increasing soil redox potential percentage, decreasing soil reducing substance content, increasing the percentage of soil aerobic bacteria and decreasing the percentage of soil denitrifying bauerium and the ratio of potassium uptaken by rice from fertilizer to the total potassium uptaken were GLP>PWLP>SMP as well. Otherwise, the soil and wader temperature in rice growing season, soil potassium supplying ability and the amount of porassiun uptaken by rice from soil was SMP>PWLP>GLP.The present paper also show that the soil available K critical values of efficient application of potassium were 54, 82 and 141 mg kg^-1,respectively, SMP, PWLP, and GLP. The research also indicated the potassium fertilization rates for maximuth rice yield and optimal economic rice yield and the optimum timing of potassium fertilization on rice soils with different water conditions and different available K levels. It provided the scientific basis for rational fertilizstion of potassium.

Abstract:Pot and solution culture experiments were conducted to study the mechanism of phosphorus-zinc interaction in brewer's barley grown on calcareous soils. The results showed that the effect of Zn supply on the yield depended on the available Zn concentration and P/Zn ratio in soil; high rate of phosphorus did not affect the available Zn concentration in soil and the Zn application did not affect the available P concentration in soil, either; Zn-efieency increased P concentration in shoots but decreased P concentration in roots; and Zn-deficiency inereaaed membrane permeability, which enhanced P uptake and translocation from roots to shoots.

Abstract:Broadbean, as a widely planted legume in the southern part of China, contains abundant provein and is often grown as a forage crop or a green manure crop, but, the yield of broadbean is very low on the purplish soils of Sichuan Province, especially on grey-brown purplish soil. In the recent years the effects of VA mycorrhiza on trace element absorption by plants have been emphasized. But so far there has been few report on the effect of VA mycorrhiza on Mo and P absorption of broadbean grown on purplish soils. The biological effect on nutrient absorption of VA mycorrhiza was studied to find the way of using VA mycorrhiza in purplish soils. Research results showed that VA mycorrhiza could promote Mo and P absorption of broadbean plant. Ground phasphate rock was difficult to be directly uptaken by plants, but it could be utilized when plant was inoculated with VA mycorrhiza. VA mycorrhiza also could promote the grouth of host plants. The roots of the plants inoculated with VA mycrrhiza developed better, especially when Mo, P and VA mycorrhiza were used together. Result show that the nodules on plant treated with Mo+P+VA mycorrhiza were bigger in size and the greatest in quantity and those treated with Mo+VA mycorrhiza carne the second. Meanwhile, the resistance of broadbean plants treated with Mo+P+VA myeorrhiza or Mo+VA myeorrhiza to Botrytis fabae sardina and senility was enhanced.

Abstract:The present paper deals with the effect of hydrous oxides on zero point of charge (ZPC) of red soils, kaolinites and synthetic amorphous aluminosilicates, and the distinction of hydrous oxide-type surfaces in soils. The results show that hydrous oxide-type surfaces could be divided into two subgroups which have completely different characteristics. In the samples of the soils and clays studied, the iron oxide (Fe-OH) and aluminium oxide (Al-OH) surfaces with s high ZPC were pH-dependent positive charge sub-surface, which tended to increase the ZPC of the samples, and silica (Si-OH) surface with a low ZPC was pH-dependent negative charge sub-surface, which tended to decrease the ZPC of the samples. The ZPC of synthetic amorphous sluminosilicates were significantly positively correlated to the Al₂O₃/SiO₂ molar ratio of the satnpies.

Abstract:Based on the studies on the profile characteristicts of root density, root weight and soil anti-scouribility, the sidement reduction effect of herb roots and the range of soil anti-scouribility increased by herb roots distributed in different soil layers are first quantitatively analyzed. The results obtained show that the intensified value of soil anti-scouribility by the roots was more closely correlated with the root density than with the root weight. Within top 20 cm soil layer, the effeu of sidement reduction was not influenced by slope and rainfall intensity. This effect, however, was evidently weakened with the increase in profile depth. According to the comprehensive analyses of the effect curves of herb roots to increase soil antiscourbility and sediment reduction effects under conditions of different slopes(150,200 and 300) and rainfall intensities (0.5, 2.0 and 4.0 mm/min), the density range and lower depth limit of herb rotxs to obviously increase soil ati-scouribility are proposed.

Abstract:In this paper, the relationship between the microwave backscattering coefficient and soil moisture of bare and vegetation (sweet potato, soybean and peanut)-covered fields is discussed, and the comparision between the results of X- and C-bands is made. The study results indicate that for microwave remote sensing of the soil moisture of bare fields, when incidence angle θ=6°, the sensitivity S_v is the maximum; when θ=45°, S_v=0; and while θ>45°, the backscattering coefficient is getting lower with the increase of soil moisture.At small incidence, X- and C-bands are quite similar in the accuracy. For microwave remote sensing vegetation-covered fields, the sensitivity and accuracy of X-band are lower than those of C-band, but X-band still has a certain sensitivity and accuracy as long as proper working parameters are selected. The prediction error of soil moisture which has been estimated by a simple model proposed in this paper is about ±25% at X-band.

Abstract:This paper deals with the characteristics and classification of major soils in the mountaiainous area of the southern Anhui Province. The soils in the area are strongly weathered and leached, with obvious enrichment of alumina. The characteristics of soils varied with the altitude. In B horizons of the soils distributed below 600-700m above sea level, the soil colour is reddish brown or bright reddish brown (5YR5/6-5/8), the ratio of silt/clay smaller than 1.00, the coefficient of weathering and eluviation lower than 0.35, the base saturation lower than 35% and the silica-alumina ratio of clay smaller than 2.4. Kaolinite is dominant in clay minerals. Both the degree of activation and the degree of complex of iron oxide are low. HA/FA in surface soils is smaller than 0.35. The soils belong to yellow-red soil (a subgroup of red aoil).

Abstract:杂交水稻具有较强的吸钾能力和吸钾强度。由于种植杂交水稻较之常规水稻能获得更高的产量。因此,当前在杂交水稻高产栽培中重施钾肥已带有普遍性。据调查,生产水平较高的水稻产区,每公顷施钾量(K₂O)多在150-225公斤。鉴于我国当前钾肥资源贫乏,不少研究者,从杂交水稻对钾素的吸收、利用角度进行研究,以探讨钾肥的合理施用^[2-5]但从杂交水稻各生育时期吸钾特点出发进行施钾技术的研究则见诸甚少。本试脸系根据杂交水稻各生育时期的吸钾特点以及该时期的土城供钾特点为础,以研究其施钾技术,为合理施用钾肥提供科学依据。

Abstract:十九世纪末叶,J. Kjedahl, J. lawrence Smith等相继提出了土壤全量N. P. K的分析方法。百余年来其分析,检测技术虽然发展较快,但上述三元素试样的熔融和消煮等所需的时间与最后检测所需时间之比,仍为5:1至20:1,耗时甚多。况且尚无三元素一次性联合消解方法和仪器,严重影响了分析速度^[1,4-6]。经多年实验研究,我们提出了在80-260℃条件下土壤全量N. P. K试样一次性联合消解的原理、方法和仪器,均取得了满意的结果。