Land husbandry [antikvár]

Foreword Since the 1939 work of Bennett, the father of soil conservation, the world has seen a host of erosion control manuals, most of them in English or Spanish and describing practical experience, technical principles, mechanical (and sometimes biological) methods to be used, and a series of practical recipes that have been adopted with varying degrees of success in specific regions. However, there have been few authors who, having seen at first hand the relative ineffectiveness of the generally recommended techniques, have been ready to re-examine the erosion control principles that Bennett developed for the very specific environmental, social and economic conditions of the large-scale, mechanized cropping of groundnut, cotton, tobacco and cereals, all providing little ground cover, that the European immigrants introduced into the semi-arid Great Plains of the United States of America during the Great Depression of the 1930s. Bennett's approach to soil conservation (based on draining runoff water from cultivated fields along gently sloping channels to designated outlets) was then applied, with no prior testing, in totally different circumstances (for example among small subsistence farmers in tropical upland areas) with the very indifferent results that have been seen by all. Science has made giant strides since Bennett's day. Firstly, it has been discovered that the kinetic energy of raindrops can lead to degradation of cuhivated soils. Risks of ranoff and erosion can therefore be cut by introducing production systems that provide better ground cover (Ellison 1944, Stallings 1953, Wischmeier and Smith 1960 and 1978, Hudson 1973, Roose 1977a, etc.). Secondly, people have realized that there are many different processes in soil degradation and erosion, with a variety of causes - and a similar variety of sometimes contradictory factors involved in any action to alter them. Treatment of sheet erosion has, for instance, sometimes increased the risk of landslides (as can happen with marls). Tliirdly, differences in physical landscapes and in the social and economic conditions of effective application of erosion control methods are better analysed today. The erosion crises facing large-scale, modern landowners in temperate zones are no longer treated in the same way as the subsistence problems of poor, densely-populated communities clinging to tropical hillsides. Instead of simply describing schemes that have worked in one specific place, today one has to learn to assess different conditions and work with, rather than against, the forces of nature; for example, by progressively modifying the slope of a hillside by slowing down sheet runoff and using farming techniques that will gradually terrace the land, instead of tearing at mountains with powerful bulldozers to produce often unstable and expensive-to-maintain infrastructore. The author would like to remind agricultural experts that erosion control is not the exclusive domain of specialists working to rehabilitate land degraded because it has been more mined than farmed, but must incorporate the viewpoints of the land-use planner responsible for water and soil fertility management in the development of cropping systems that are profitable, sustainable, and safe for rural and urban environments.