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The objectives of this study were 1) to describe the yield of continuous grain sorghum in the Texas Blackland Prairie as a function of applied nitrogen (N) and degree of water deficit under field conditions and 2) to use this information to obtain a more accurate N fertilizer recommendation in the Texas Blackland Prairie based on a knowledge of available soil water at the time of fertilizer application. An economic analysis described by Heady (1956) was used to compute optimum N rates under different degreed of soil water deficit. Water deficit was defined in terms of stress days, computed by summing the term (1-E/E) over daly intervals, where E is daily evapotranspiration rate an E is the daily potential evapotranspiration rate above the plant canopy. Cumputer simulation of soil water (...).
This study examines the interactions between nitrogen and the ecosystem and discusses nitrogen fertilization practices around the world. Simulation models that play an important role in determining the dynamics of source-sink relationships are presented, helping to pinpoint inefficiencies and develop strategies to synchronize nitrogen supply and demand.
The book deals with agroecological aspects of nutrients essential to crop production. A new concept termed 'AGROSPHERE' has been introduced in the book. A brief description about agrosphere, its expanse, contrasting features and interactions with other ecospheres, global nutrient dynamics and food production trends within various agro ecosystems fo
From the beginning of agriculture until about 1950, increased food production came almost entirely from expanding the cropland base. Since 1950, however, the yield per unit of land area for major crops has increased dramatically. Much of the increase in yields was because of increased inputs of energy. Between 1950 and 1985, the farm tractor fleet quadrupled, world irrigated area tripled, and use of fertilizer increased ninefold. Between 1950 and 1985, the total energy used in world agriculture increased 6. 9 times. Irrigation played a particularly important role in the rapid increase in food production between 1950 and 1985. The world's irrigated land in 1950 totaled 94 million hectares but increased to 140 million by 1960, to 198 million by 1970, and to 271 million hectares in 1985. However, the current rate of expansion has slowed to less than 1 % per year. The world population continues to increase and agricultural production by the year 2000 will have to be 50 to 60% greater than in 1980 to meet demands. This continued demand for food and fiber, coupled with the sharp decline in the growth rate of irrigation development, means that much of the additional agricultural production in future years must come from cultivated land that is not irrigated. Agricultural production will be expanded in the arid and semiarid regions because these regions make up vast areas in developing countries where populations are rapidly rising.
Plant Nutrition - From Genetic Engineering to Field Practice, the 12th International Colloquium on Plant Nutrition, is the latest in a series which began in 1954. Early meetings were mainly concerned with the practical problems of soil fertility, with soil assessment, fertilizer requirements and methods of analysis. As the colloquia have progressed, the emphasis has slowly changed. The practical problems are still important, but there is increasing emphasis on plant physiology, plant biochemistry, membrane biochemistry, and even on the chemistry of genes which control the proteins which transfer nutrient ions to the inside of cells. The meetings therefore provide a valuable opportunity for each half of the science of plant nutrition to interact with, and learn from the other half. This volume begins with five papers which review current knowledge in important fields: the rhizosphere, molecular biology, electron microscopy, location and function of elements in vivo, and modelling nutrient responses in the field. These themes are continued in groups of shorter papers which follow. In addition, there are sections on nutrient dynamics and partitioning, diagnostic techniques, plant survival strategies, mycorrhizas, and on nutrients such as P, N, S, K, Ca, Mg, and micronutrients. A large section is devoted specifically to boron - reflecting the considerable current interest in this element. In total there are 177 refereed papers providing both a broad overview and a detailed picture of the latest developments in pure and applied plant nutrition.