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This Bulletin is the joint effort of three authors: Professor C.J. Pearson of The University of Queensland, Gatton College, who wrote the first five chapters and Professor D.W. Norman of the Department of Agricultural Economics, Kansas State University, and Dr J. Dixon of FAO, Bangkok, Thailand, who wrote the final chapter 6. Professor Pearson wrote his contribution in 1992 during a short stay at FAO, Rome. It reflects his personal views and experience acquired over the years. His conclusions on which issues need urgent consideration, however, largely emerged during writing. While there are sections which he would now phrase or emphasize differently, the editor has restricted changes to some references to recent work.

The main themes of the Bulletin are that management of soil productivity is central to sustainable dryland cropping and that successful management depends on understanding the mechanisms underlying soil productivity and on the recognition of non- technical factors such as human goals. It follows that its conclusions are not prescriptive. Rather it aims to encourage researchers and policy-makers to work jointly with farmers to develop better cropping systems and devise locally acceptable indicators of sustainability.

The text is illustrated by numerous figures and tables and is supported by a substantial list of recent references. It does not, however, pretend to be a comprehensive review of sustainability, soil processes and cropping systems.

Readers will note that soil characteristics are described in Chapters 2 and 3 in an unconventional sequence. This emphasizes the characteristics we think are important for crop growth, and should encourage scrutiny of some of the present trends in soil research. Our knowledge of quantitative relationships between soils and crops is sparse, and that of soil biology and weed ecology is rudimentary. In contrast, we no longer emphasise work on mineral nutrition and crop fertilizer responses. We are concerned that resources continue to be spent on fertilizer experiments that are economically irrelevant and, in the absence of soil data may not be transferable to other situations.

It is significant that many of the key issues identified are social, policy and economic, rather than technical. Chapter 5 also recommends that care should be given to the process of identifying key indicators of sustainability. It follows, since involvement of farmers is essential, that urgent consideration be given to surrogate measures of soil sustainability, and to the balance between farmer-participatory and more detached research. The Bulletin questions the conventional view of the benefits from fallow in crop rotations. It may be rewarding also to look at management of soil, weeds, livestock etc. during the fallow as critically as we look at the crop phase.

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