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Analysis and Evaluation of Tillage on an Alfisol in a Semi-arid Tropical Region of India

出版	na, 1983
URL	http://books.google.com.hk/books?id=0ezMWvSzjpUC&hl=&source=gbs_api

註釋To put the experiments into perspective, a general review is given in chapter 2 on the environment of the semi-arid tropics, its problems and the research related to agricultural production. Rainfed agriculture has failed to provide a stable and sufficient food supply for the populations of many developing countries. An important reason is the severe physical constraint to agricultural production imposed by the harsh climate. Water is the key factor and though the average total precipitation appears to be sufficient for cropping, its distribution is highly erratic. Much of the rain falls in high intensity storms, resulting in uncontrolled runoff and erosion. Thus a high proportion of the water is lost for crop use.The majority of as much as 500 million people living in the world's semi-arid tropics, depend on agriculture for income, food and shelter. During the last three decades, populations have doubled in many of the 48 countries which are at least partly located in the semi-arid tropics.Since the indigenous production systems are characterised by stagnant yield levels, hitherto stable forms of agriculture came under immense pressure by the attempt to continue to provide sufficient amounts of food and fiber for the rapidly growing populations. The farmers were compelled increasingly to expand their agricultural activities to more marginal lands.Consequently, the production potential of the resource base is threatened seriously and vast areas already have been damaged permanently further destabilizing agricultural production.To improve a situation of recurrent food shortages, governments tended to concentrate their resources on improving agriculture in water- assured areas. With the advent of high yielding varieties of wheat and rice, this strategy proved succesfull.In India it was realised that continuing such a policy would further widen the gap with dryland farmers, as it creates 'islands of prosperity in a sea of poverty'. Furthermore, there is a physical limit to the area that potentially can be irrigated. A high proportion of the nation's food requirements would still have to be met by rainfed agriculture. So, unless yield levels and stability are improved in this segment of farming, a few poor monsoons in succession would still lead to serious food problems.Therefore, research on dryland agriculture was revived, but met with limited and varying results. Either too much emphasis was given to genetical improvement of the seeds, or major attention was given to soil and crop management aspects. The proposed technologies did not fit well into the farmers traditional cropping systems, in which crop yield security is important.In 1972, ICRISAT started to work on the improvement of dryland crops. From the outset, it was recognized that the lack of a suitable technology for soil and water management and crop production systems, was a primary constraint to agricultural development in rainfed farming. A farming systems research program was developed. A so-called watershed based research program evolved, wit' the underlying filosophy that the only water available to the common farmer comes from rain falling on a limited area. Therefore, small natural watersheds comprising several field-scale units, became the testing ground for promising new technologies.During the first period, attention was focussed on developing improved soil and water conservation and cropping systems suitable for deep Vertisols.