Nitrogen Economy in Tropical Soils

Forms and nature of organic N in soil. Seasonal fluctuations of native available N and soil management implications. Effect of cultivation on the nitrogen fertility of selected agro-ecosystems in south Africa. Assessment of biological nitrogen fixation. High productivity analysis of 15N and 13C in soil/plant research. Adapting the potencially mineralizable N concept for the prediction of fertilizer N requirements. Field application of the 15N isotope dilution technique for the reliable quantification of plant-associated biological nitrogen fixation. Rational nitrogen fertilization in intensive cropping systems. Nitrogen assimilation by legumes-processes and ecological limitations. Fate of CO(NH2)2 -15N applied to taro (colocasia esculenta var. esculenta) in an acid vertisol of trinidad. Brown leaf spot disease and fertilizer interaction in irrigated rice growing of different soil types. Use of 15N for fertilizer N recovery and N mineralization studies in semi-arid kenya. Significance of timing and method of N fertilizer application for the N-use efficiency in flooded tropical rice. A conceptual assessment of the importance of denitrification as sorce of soil nitrogen loss in tropical agro-ecosystems. Soil, plant and atmospheric conditions as they relate to ammonia volatilization. Nitrous oxide (N2O) emissions from soils in warm climates. The role of Azolla in curbing ammonia volatilization from flooded rice systems. Downward movement of nitrate and ammonium nitrogen in a flatland ultisol. 15N isotope dilution techniques to study soil nitrogen transformations and plant uptake. Nitrogen transformations in wetland rice ecosystems. Urea-N uptake by dasheen (colocasia esculenta L. schott) in relation to the fertilizer placement method. Nitrogen fixation by trees in relation to soil nitrogen economy. Extension of symbiotic biological nitrogen fixation technology in developing countries. Nitrogen fixation associated with grasses and cereals: recent progress and perspectives for the future. Recent developments on the use of urease inhibitors in the tropics. Biological N2-fixation and its management in wetland rice cultivation. Managing nitrogen for sustainable crop production. Searching for criteria for the selection of efficient tree species for fallow improvement, with special reference to carbon and nitrogen. Nitrogen balance and root behavior in four pigeonpea-based intercropping systems. Recent research on problems in the use of urea as a nitrogen fertilizer. Nitrate contamination of groundwater: measurement and prediction. Alternatives for nitrogen nutrition of crops in tropical agriculture. Behaviour of urea and ammonium sulfate fertilizers and their N uptake relationships in calcareous soils. Simple field testing sites to determine the extent of nitrogen leaching from agricultural areas. Comparison of legumes and fertilizer nitrogen for wheat production in subtropical Australia. Long-term N-fertilization calibration experiments - environmental aspects. Nitrification inhibitors, with emphasis on natural products, and the persistence of fertilizer nitrogen in the soil. Land use related nitrogen and global change. Response of sugarcane to nitrogen fertilization practices on some sugarcane soils in trinidad. FAO/IAEA international networking in soil/plant nitrogen research. Nitrogen losses by leaching and runoff: methods and conclusions. Optimizing non-symbiotic nitrogen fixation in an acid vertisol.