Abstract
Agriculture in the tropics is complex and diverse, encompassing plants and soils, climate and people, trade and survival. It can be very diverse biologically, as in mixed gardens; elsewhere, one species can dominate vast areas of land. Several widespread subsistence crops such as potato, and certain cereals including wheat and barley, are common throughout temperate agriculture and also occur widely in tropical latitudes, usually at high altitude where it is cooler. Indeed, staples such as potato and some cereals originate from high altitude tropical regions and, although much land is cultivated using hoes and ploughs, the management of these crops in many tropical locations is little different to that in temperate regions. Nevertheless, the principles advanced in this book should be relevant to a wide range of plants, husbandry and regions that fit the loose term "tropical". The examples described in this book are primarily of tropical species grown under low input husbandry, or in plantations, in low latitude regions of Africa, Asia and South America. The rest of this book examines the way knowledge of flux currencies can be used to inform agronomic practice. The sequence of chapters argues that choices and operations in management can be separated into 2 broad groups. In the first are those that govern what, when and how to sow a crop; factors that all farmers must decide around the time of sowing. They require decisions about the genotypes to be grown, the time of sowing and of other operations, and the intended configuration of the stand as influenced by the population density and species composition. The second group of factors includes operations that are not always done, such as applying fertilizer, water harvesting techniques and irrigation, and reducing competition from weeds. Inevitably, several subjects are covered only briefly or have been omitted. These include the effects of pests and diseases, and localized soil problems such as salinity, waterlogging and the effects of acid sulfates and peats. In practice, knowledge of the flux currencies could help to elucidate any of these problems. The wider implications of the approach are explored and areas where progress and deeper understanding is needed are also explored.