Abstract:Effects of potassium, calcium and magnesium fertilizers applied to soils on rice growth, nutrient migration and nutrient uptake by rice plants in soils with low base content in southern regions of China were investigated. Results showed that on the basis of NP fertilizers with the increase of K, the rice growth was retarded and its biomass decreased, Applying Mg on the basis of NPK fertilizers increased the rice biomass. Applying Ca, Mg on the basis of NPK fertilizers resulted in the synergistic effect to make the biomass remarkable increase. It is suggested that the triangular interactions of K-Ca-Mg are positive interactions. Simulation experiments using ion-exchange resin showed the positive interactions between K-Mg, K-Ca and Mg-Ca in the process of nutrient migration to roots. Pot culture experiment showed an antagonistic effect between K-Mg and Mg-Ca in the process of nutrient uptake by rice plant. However, combinative use of K-Ca-Mg increased the total uptake of nutrient, showing a synergistic effect It is mainly due to the promotion of rice root growth. In addition, the possibility of decreasing the requirement of K by the triangular interaction of K-Ca-Mg was also discussed.

Abstract:The effects of combined application of organic manure and fertilizers on senescences of root and flag leaf in winter wheat (Triticum aestivum L.) were studied through experiment with soil column culture. The results showed that the combined application of organic manure and fertilizers resulted in a decrease of lipid peroxidation and an increase of superoxide dismutase (SOD) activity in root and flag leaf after anthesis, increased the root vigour and dry root weight especially in 40-100cm soil layer, reduced the decline rate of photosynthetic rate of flag leaf, delayed the senescences of root and flag leaf, increased the grain weight, biomass, economic index and grain yield.

Abstract:Fate of urea, ammonium bicarbonate and potassium nitrate applied to a black soil growing spring wheat was investigated by the ¹⁵N tracer technique and microplot in the field. The experiment was conducted in suburbs of Hailun city, Heilongjiang Province. Nitrogen fertilizer at a rate of N 75 kg/hm² was deeply placed in 10 cm soil layer. Results showed that deep placement is an effective measure to decrease nitrogen loss and. increase the efficiency of fertilizers N utilization in spring wheat black soil system. The plant recoveries of potassium nitrate (58.4%) and urea (55.9%) were comparable, and significantly higher than that of ammonium bicarbonate (42.6%). The residual N in soil from applied potassium nitrate (28.7%) was significantly lower than urea (38.2%) and ammonium bicarbonate (38.8%). The total nitrogen losses for the three sources of N fertilizers were in the range of 5.8%-18.6% with the lowest from urea and the highest from ammonium bicarbonate. The priming effect of N fertilizers applied to the black soil was rather low. Results also showed that about 1/3 of the N taken up by wheat was derived from the applied N fertilizers and 2/3 from soil.

Abstract:Pot sand culture of summer corn with Hoagland solution and soil culture of winter wheat with application of routine dosage of 0.15g N,0.05 g P and 0.10 g K per kg of soil were carried out in greenhouse of Nanjing Agricultural University. Leaves of corn and wheat were wiped or dipped with ¹⁵N-labelled 10 g/L urea, 10 g/L KH₂PO₄, 5.4 g/L KCl and their combinations from jointing stage of both crops to the silking of corn or heading stage of wheat. The root activities of both crops were rapidly declined after jointing stage, but this decline apparently delayed as foliar application of urea especially foliar feeding with N, P and K cooperated. Foliar feeding with macro-element fertilizers enhanced physiological activity of function leaves. Among the three elements for raising physiological indexes of function leaves urea-N was most efficient except small variation of total activity of RUBPase. Foliar application of N, P and K cooperated would be the measure for prolonging the life of leaves to the most limit. Statistical results showed that compared to foliar spray of water, urea+KCl and urea+KH₂PO₄ increased the yield of wheat significantly, while for corn only urea+KH₂PO₄ increased its ear and grain yields. Foliar application not only increased N, P and K content of plants, but also changed their distribution in organs and stimulated translocation of N to grain. Absolute protein contents of wheat and corn grains increased by 22 g/kg and 4.9 g/kg, respectively, due to foliar feeding during the middle and latter growing periods.

Abstract:Solution culture is conducted to investigate the effects of iron oxides and root exudates on cadmium uptake by rice. The results showed that iron oxides may absorb cadmium from nutrient solution. The amount of Cd accumulated on rice root surface increased with the increase in amount of deposited iron oxides. Therefore, iron plaque can influence the Cd uptake. When Fe nutritional status of rice are different, the effect of iron oxides on Cd uptake by the rice roots is also different. Generally, with the increase of Cd concentration in medium, the amount of Cd deposited on root surface and Cd content in rice shoot increased. Rice root exudates (PS) may mobilize Cd accumulated by iron oxides on the surface of rice root and significantly enhance Cd uptake in the rhizosphere. When Cd concentration in nutrient solution was different, the effect of PS on Cd uptake was also different.

Abstract:The reaction of synthesized Ca-bound, Fe-bound, and Al-bound organo-mineral complexes with Ca²⁺,Fe³⁺,and Al³⁺ ions in solution, respectively, was studied. The results showed that the Ca²⁺ or Al³⁺ in solution could not exchange the bound-Fe in complex, the Ca²⁺ or Fe³⁺in solution could exchange little bound-Al in complex, and Fe³⁺ or Al³⁺ in solution could exchange more bound-Ca in complex. However, the exchangeable capacity was related to pH in solution and type of clay minerals. Although the bound ions in complexes were hardly exchanged, the Ca²⁺,Fe³⁺,or Al³⁺ in solution could complex with organo-mineral complexes.

Abstract:Experimental results indicated that fulvic acid can significantly promote the volatilization of MnO₂-Hg,Fe₂O₃-Hg and kaolinite-Hg, but suppress that of bentonite-Hg and CaCO₃-Hg. Generally brown humic acid can enhance the volatilization of all the mineral-bound Hg except for Fe₂O₃-Hg. The effect of grey humic acid is the weakest. The influence of humus fractions on the activity of mineral-bound Hg is dependent on the complex capacity and complex stability of humus fractions with Hg, adsorption capacity and adsorption strength of the mineral with Hg as well as the interaction characteristics between humus fractions and minerals.

Abstract:The results from a laboratory experiment showed that the composition and total amount of CO₂, CH₄ and N₂O emitted from a clayey soil were affected significantly by water regime and amendment of wheat straw. Under the flooded conditions, the emission was small for N₂O, but large for CH₄,and CO₂; in contrast, under the aerobic conditions, the emission was not detectable for CH₄,but large for N₂O; the drainage of flooded water acceleseted N₂O emission, but depressed CH₄ emission. And the emissions of CO₂, CH₄ and N₂O under the flooded/drained alternate conditions were the middles between those under flooded conditions and under aerobic conditions. The overall potential for greenhouse effect (OPGE) caused by the emitted greenhouse gases, calculated according to their potential in absorbing thermal radiation, was the highest under the flooded conditions and the lowest under the flooded/drained alternate conditions. It clearly demonstrated that the change in water regime would not only alter the composition of greenhouse gases emitted from soil but OPGE as well.

Abstract:The content, distribution and speciation of rare earth elements (REE) of soils in a typical geochemical landscape (REE mine area) in southern Jiangxi Province were studied. Soil samples were collected from three elementary landscapes (eluvial landscape, accumulative leaching landscape and superaqual landscape). Results show that the content and distribution of the REE were different in soils of three elementary landscapes. There occurs Ce positive anomaly in soils of eluvial landscape and accumulative leaching landscape, but Ce occurs negative anomaly in superaqual landscape. Speciation of the REE in soils of different elementary landscape is various. In short, exchangeable and bound to organic matter REE are the main forms of the REE in soils, and the REE of soils is very active in the studied area.

Abstract:This paper deals with the soil structure degradation characteristics and its possible mechanism in Udic ferralisols. Results showed that compared with the soil under zonal natural vegetation it suffered more structure degradation under secondary or man-made vegetation. It was found that the structure degradation in Udic ferralisols was characterized by sandification of surface soil, lowering of aggregates stability, decrease in bigger aggregates, deterioration of soil porosity, increase of bulk density and lowering of bigger pore content. For natural Udic ferralisols, the increase of bulk density and decrease in bigger pore aggregate content were more obvious, however, for cultivated lands, the lowering of aggregates stability and sandification of surface soil were more serious. Mathematical analytic results indicated that the nutrients improvement, especially the organic matter deficient, might be the main interior factor causing structure degradation of Udic ferralisols.

Abstract:The basic farmland information system (BETS) supported by geographic information system (GIS) was established, which could manage the data systematically and dynamically. With the BETS, a method in both quantitative and qualitative natures was developed to grade the farmland productive capacity. Evaluation factors were chosen, a hierarchic structure was constructed, single-factor evaluation models were built and the weight for each factor was calculated through correlation analysis, factor analysis, fuzzy evaluation, and hierarchic analysis respectively. The evaluation results indicated that the land productivity grade could be completely evaluated饰the natural factors of farmland today with the quick development of computer technique. The results, tested on the farmland of Gaoyou city, was shown to be more objective and more accurate, avoiding the defects of subjectivity just by the empirical methods and the blindness of pure mathematical methods.

Abstract:This paper introduced the contents of soil information system of Yujiang County, Jiangxi Province. The techniques for building up the system, especially the technique used for coding soil attributes, the technique in digitizing lines and polygons of concerned maps, and soil data treatments and analyses, and some proposals for establishment of the system were dealt with.

Abstract:The measures of afforesting soil and water conservation forest of Acacia auricalaformis and cultivating fruit trees of Iitchi chinensis, Euphoria longana,Myrica rubra were took to control soil erosion on the lateritic red soils of serious deterioration area. Antierodibility under different treatments and controls were studied, the results showed that the order of the soil antierodibility followed: Myrica rubra of 27 year-old(T₂₃);Acacia auricalaformis of 6 years-old (T₁₂), Iitchi chinensis and Euphoria longana of 28 year-old (T₂₁,T₂₂); Litchi chinensis of 6 year-old (T₁₁). Index of erodibility (F_VA), organic matter;>1mm water-stable aggregate composition, rate of structure deterioration, and erosion raito could be used to indicate the lateritic red soil antierodibility in this area. To introduce legume into orchard for increasing coverage is one of the effective measures to enable the combined effect of harness and development in seriously deteriorated lateritic red soil.

Abstract:With a simulated rainfall equipment the pattern of soil nutrient loss from a loessial soil under different rainfall intensities was preliminarily studied by plot test on a sloping surface. Results showed that soil nutrients mainly migrated with sediment in unsoluable forms while the amounts of soluble nutrients removed with runoff were very little. The different forms of nutrients were enriched in sediment. The amounts of nutrient loss were in direct proportion to rainfall intensity. There was significant positive correlation between the amounts of soil loss and nutrient loss.

Abstract:The mechanism of magnetic susceptibility (χ) of soil derived from basalt in Zhejiang and Yunnan Provinces was studied by applying mineral magnetic measurement technique and X-ray powder diffraction. Results showed that χ of soil derived from basalt in Zhejiang Province ranged from 100×10^-8-500×10^-8m³/kg. χ of soils derived from basalt in Yunnan Province ranged from 500×10^-8-2000×10^-8 m³/kg. χ of synthesized goethite and hematite were 31.9×10^-8m³/kg and 84.5×10^-8m³ /kg, respectively. χ of synthesized iron oxides increased as aluminum-substituted amount of iron oxide increased. The magnetic parameter and X-ray powder diffraction pattern of soils indicated that χ of soil derived from basalt in Yunnan Province mainly contributed to the superparamagnetic maghemite and magnetite, which is pedogenic origin. χ of soils derived basalt in Zhejiang Province came from the contributions of both primary magnetic grains and secondary magnetic minerals, and hematite.

Abstract:This paper describes the structure and function of plant sterile culture laboratory in details. Some key steps in plant sterile culture such as sterilization of nutrient solution and culture of aseptic seedlings were tested successfully. Results from sterile experiment for rice organic N nutrition showed that amino acid could be directly taken up by plants. The effectiveness of N sources at equal N concentration (N 10mg/L) for rice followed the order: glycine-N (sterile culture)>glutamic acid-N (sterile culture)>ammonium sulphate-N (sterile culture)>ammonium sulphate-N (conventional culture) under frequent renewal of nutrient solution in the experiment. This indicated clearly the differences among the effciency of various organic and inorganic N compounds, and sterile and conventional growth conditions on rice N nutrition.

Abstract:土地荒漠化是一全球性的严重环境恶化现象,引起了众多学者的关注和研究。但什么样的退化土地才是荒漠化土地,土地荒漠化的发生发展以及程度和区划等问题的定量确定,至今未见有关报道^[1,2]。金沙江干热河谷区自然资源丰富^[3],但土地荒漠化严重,这一现象的定量认识更为重要。本研究围绕该区土壤的基本理化性质(包括土壤普查所能测定的指标)与其植被盖度(荒漠化程度的直观指标),以阐明该区土地荒漠化程度和预测的有关有效指标。

Abstract:土壤无机硫主要是水溶和吸附态SO₄^2-,它能被作物直接吸收。有机硫是作物利用硫的主要来源,分为HI还原有机硫(硫酸酯)、碳键硫(C-S)和惰性硫。有机硫只有转化为SO₄^2-后才能为作物吸收^[1]。土壤硫形态转化规律室内培养和盆栽研究较多^[1,2],田间试验研究较少,国外探讨了油菜一休闲制中土壤硫形态转化规律^[3]。水一早轮作制是中国主要轮作制之一,该轮作制中土壤处于干一湿交替之中,土壤硫转化规律可能有其特异性。本研究选择油一稻轮作制为研究对象,研究土壤硫形态消长和分配规律。其结果将为评价土壤供硫能力和了解土壤硫肥力维持机制提供依据。