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This volume was first published in 1981. The history of man's use of arid lands is a sad record of deterioration of the natural resource base and of low and declining living standards for the 300 million people who live in them. One prerequisite to meeting the challenge of reversing the deterioration and of raising living standards is a sound knowledge of the natural ecosystems.
Offers various directions for both research and management.
A system may be studied by distinguishing its major components, characterizing the changes in them by differential equations that form their simplified representa tions, and then interconnecting these representations to obtain a model of the original system. Developing the model is the systems synthesis phase. The behaviour of the model may now be studied and compared with experimental results obtained from the system. This research method is called systems analysis and simulation. Systems analysis and simulation can serve to make predictions, to improve the insight in systems, and to test knowledge on consistency and completeness. Predictive models are rare in ecology, simply because the underlying processes which form the basis of the models are seldom well known. A successful example of a predictive model was the work of van Keulen (1975). He showed that under semi arid conditions, where water is the main factor controlling primary production, the simulation technique could predict the production of natural grasslands. Fair predicti ons could also be made for the Sahelian pastures (Penning de Vries & Djiteye, 1982). Predictive models of populations of different pest and disease organisms are being used in biological control systems (Zadoks et aI., 1984).
Offers a treatment of modern applications of modelling and simulation in crop, livestock, forage/livestock systems, and field operations. The book discusses methodologies from linear programming and neutral networks, to expert or decision support systems, as well as featuring models, such as SOYGRO, CROPGRO and GOSSYM/COMAX. It includes coverage on evaporation and evapotranspiration, the theory of simulation based on biological processes, and deficit irrigation scheduling.
Throughout history, man has, by over-use, consistently reduced the productive capacity of dry lands. This degradation of one-third of the land area of the globe is, unfortunately, increasing. In recent years, world interest has turned to the problems of pollution of the environment and the impending food shortage as world population grows explosively. Thus the attention of international and other agricultural bodies has turned to the need for preserving and developing more effectively the agricultural potential of these areas.This book provides a comprehensive review of present knowledge of the agriculture of dry lands, with special emphasis on measures for conserving their natural resources. Management practices are described which aim at optimizing productivity of rainfed and irrigated agriculture without adverse effects on sustainability. Land use in the dry regions, and its evolution throughout history is described and analysed, and the lessons to be learnt from destructive technologies are stressed. In particular, current proposals for an alternative agriculture are discussed and their justification is questioned. This is a generalist work, which specialists can also find interesting, not only in their own discipline but as a concise way of acquainting themselves with the state-of-the-art in associated fields. Increasing specialisation with each discipline using its own vocabulary leads inevitably to communication problems, and the need for multi-disciplinary teams makes inter-discipline communication indispensible.
ILCA's policy towards modelling in the framework of livestock systems research; models and the analysis of productivity in extensive livestock systems in Israel; prediction of actual primary production under nitrogen limitation; behavioural aspects of intake at pasture in ruminats; prediction of feed intake in ruminats; relationships between chemical composition and voluntary intake of feeds by sheep and cattle; the effect of breeding season duration on production and feed consumption in grazing beef cattle in the south of Israel; adaptation of the Kahan model for a mixed farming system in southeastern Asia; appraisal of the ILCA cattle herd dynamics model using data from pastoral systems in mali and kenya; moddeling pastoral livestock production: problems and prospect; analysis of management impact in semi-arid agropastoral systems; modelling economic outcomes of livestock production systems; selection of sheep husbandy techologies under single and multiple goal constraints; types, purposes and users of models; problems related do intake.
Agricultural water management includes many topics: farm-level and regional water management, irrigation, drainage, and salinity management of cultivated areas, collection and storage of rainfall in relation to soil properties and vegetation; the role of groundwater and surface water in nutrient cycling, exploitation and protection of water resources, control of flooding, erosion, and desertification. This book presents leading-edge research from around the world.