Crop Growth And Soil Water Balance Modeling To Explore Water Management Options

The study was on the performance of the decision support system for agrotechnology transfer (DSSAT) and the soil water atmosphere plant (SWAP) under an acid sulphate soil. The comparison of these models was done as a prerequisite to the selection of an appropriate model, which is capable of simulating water management scenarios, water balance and crop growth, to be coupled with an adaptive optimization algorithm that can be used to explore water management options.

The first premise of this book is that farmers need access to options for improving their situation. In agricultural terms, these options might be manage ment alternatives or different crops to grow, that can stabilize or increase household income, that reduce soil degradation and dependence on off-farm inputs, or that exploit local market opportunities. Farmers need a facilitating environment, in which affordable credit is available if needed, in which policies are conducive to judicious management of natural resources, and in which costs and prices of production are stable. Another key ingredient of this facilitating environment is information: an understanding of which options are viable, how these operate at the farm level, and what their impact may be on the things that farmers perceive as being important. The second premise is that systems analysis and simulation have an impor tant role to play in fostering this understanding of options, traditional field experimentation being time-consuming and costly. This book summarizes the activities of the International Benchmark Sites Network for Agrotechnology Transfer (IBSNAT) project, an international initiative funded by the United States Agency for International Development (USAID). IBSNAT was an attempt to demonstrate the effectiveness of understanding options through systems analysis and simulation for the ultimate benefit of farm households in the tropics and subtropics. The idea for the book was first suggested at one of the last IBSNAT group meetings held at the University of Hawaii in 1993.

A clear understanding of the current water balance is required to explore options for water saving measures. However, measurement of all the terms in the water balance is infeasible in terms of spatial and temporal scale, but hydrological simulation models can fill the gap between measured and required data. For a basin in Western Turkey, simulation modeling at three different scales, field, irrigation scheme and basin scale, was performed to obtain all terms of the water balance. These water balance numbers were used to calculate the Productivity of Water at the three spatial levels distinguished to assess the performance of the systems.

Water a key natural resource, fundamental to life, livelihood, food security and sustainable development is rapidly becoming scarce and limited. Agriculture is the major water user in our country utilizing nearly 70-80 per cent of all the utilizable water resources of the country. Therefore, Agricultural Water Management (AWM) interventions aim at enhancing per capita benefits, while preventing the degradation of natural resource bases of land, water and ecosystem services. Evidence shows that AWM interventions have increased yields, which has helped areas with low productivity. In recent past a large number of new techniques and advanced tools have been invented in recent past which can enhance the water productivity in agriculture to a very high level. Knowledge adoption and extensive use of these tools and techniques needs proper dissemination. There is a dearth of ample number of technically trained manpower to undertake the work of On-farm AWM. Therefore, the present book has been organized with following specific objectives: i) to impart the advanced knowledge of On-farm water management using modern concepts, tools and techniques for assessing, planning and designing the AWM (irrigation and drainage) systems and to disseminate these techniques for enhancing crop water use efficiencies; ii) to train the readers in designing, installation operation and automated operation, controls and management of high-tech irrigation water management systems; and iii). to provide the participants an opportunity to discuss and exchange the new ideas/knowledge with experts/resource persons who have contributed substantially in Agricultural Water Management (AWM). The book has a very wide spectrum covering almost all topics pertaining to advanced concepts and methods of modern Agricultural Water Management. The present book will provide to the readers an in-depth understanding of various related topics pertaining to highly efficient irrigation water management for crop production and enhancing agricultural water productivity such as scientific design and layout of farm irrigation and drainage, soil water content measurement using TDR/Neutron Moisture meters/Soil moisture probe, geophysical techniques of groundwater exploration etc. It will elaborate the concepts and methodology of using modern instruments and systems of irrigation such as drip, sprinkler, rain gun, level basin system etc. that would be an added benefit. Applications of modern techniques such as GIS and remote sensing applications for enhancing water resources use efficiencies in irrigation project, sensor based weather data collection and automated irrigation management and control systems under open field and covered cultivation have been explained in depth. The book shall impart the comprehensive knowledge on advanced concepts in Soil-Plant-Climate interactions, scientific estimation of crop water demand, various irrigation scheduling criterions and application of modern tools and techniques such as; application of computer softwares (such as EQUITA/DRIPD/CROPWAT/AQACROP/IMPASSE/USAR etc.) for irrigation planning and management; under different water supply scenarios in a lucid manner.

This volume is an analytical summary and a critical synthesis of research at the International Water Management Institute over the past decade under its evolving research paradigm known popularly as 'more crop per drop'. The research synthesized here covers the full range of issues falling in the larger canvas of water-food-health-environment interface. Besides its immediate role in sharing knowledge with the research, donor, and policy communities, this volume also has a larger purpose of promoting a new way of looking at the water issues within the broader development context of food, livelihood, health and environmental challenges. More crop per drop: Revisiting a research paradigm contrasts the acquired wisdom and fresh thinking on some of the most challenging water issues of our times. It describes new tools, approaches, and methodologies and also illustrates them with practical application both from a global perspective and within the local and regional contexts of Asia and Africa. Since this volume brings together all major research works of IWMI, including an almost exhaustive list of citations, in one single set of pages, it is very valuable not only as a reference material for researchers and students but also as a policy tool for decision-makers and development agencies.

This publication comes with computer software and presents a comprehensive simulation model designed to predict the hydrologic response, including potential for surface and groundwater contamination, of alternative crop-management systems. It simulates crop development and the movement of water, nutrients and pesticides over and through the root zone for a representative unit area of an agricultural field over multiple years. The model allows simulation of a wide spectrum of management practices and scenarios with special features such as the rapid transport of surface-applied chemicals through macropores to deeper depths and the preferential transport of chemicals within the soil matrix via mobile-immobile zones. The transfer of surface-applied chemicals (pesticides in particular) to runoff water is also an important component.

This work presents models that characterize the relationships between quantity and quality of irrigation water application, and agricultural production and the environment. A comprehensive modeling approach addressing both the benefits of irrigation and the potential negative effects is introduced. Physical-biological concepts are combined with economic and engineering principles to demonstrate the usefulness of the model for analyzing various water management and policy issues. Decision makers on all levels should find the modeling approach interesting and useful in the management issues from the farm to national levels.

Mankind has manipulated the quantity and quality of soil water for millennia. Food production was massively increased through fertilization, irrigation and drainage. But malpractice also caused degradation of immense areas of once fertile land, rendering it totally unproductive for many generations. In populated areas, the pollutant load ever more often exceeds the soil’s capacity for buffering and retention, and large volumes of potable groundwater have been polluted or are threatened to be polluted in the foreseeable future. In the past decades, the role of soil water in climate patterns has been recognized but not yet fully understood. The soil-science community responded to this diversity of issues by developing numerical models to simulate the behavior of water and solutes in soils. These models helped improve our understanding of unsaturated-zone processes and develop sustainable land-management practices. Aimed at professional soil scientists, soil-water modelers, irrigation engineers etc., this book discusses our progress in soil-water modeling. Top scientists present case studies, overviews and analyses of strengths, weaknesses, opportunities and threats related to soil-water modeling. The contributions cover a wide range of spatial scales, and discuss fundamental aspects of unsaturated-zone modeling as well as issues related to the application of models to real-world problems.