11. The physiology of tropical production.
CAB INTERNATIONAL, UK.; ISBN 0-85198-677-3; 1990, paperback, £13.95
This is an excellent book that examines the way the physiological processes of tropical crops are influenced by environmental factors, namely solar radiation, temperature, photoperiod, saturation deficit, soil water and nutrients.
The effects of plant population density are also considered. The work is based largely on the research funded by the UK Overseas Development Administration which examined the physiological control of yield of pearl millet, grain sorghum and groundnut by temperature and drought.
The subject matter in this book is extended to cover more physiological processes and environmental factors (e.g. nutrients) and more tropical crops (including maize, sugarcane, pigeon pea, cassava, tea and oil palm). To keep the book to a workable size, the research presented is selective, with examples largely from developing countries in the tropics. This does not detract from the value of the book, and it is a valuable contribution to tropical crop physiology.
The physiology of yield is examined in terms of four types of process - development, expansion, productivity (both in terms of solar radiation intercepted and water transpired) and partitioning of dry matter.
Throughout the text, the effects of solar radiation, temperature, water and nutrients on these processes are examined in terms of a duration and a mean rate. For example, leaf canopy development is examined in terms of an expansion rate governed largely by temperature and a duration governed largely by temperature and photoperiod. Then, restrictions to the rate and duration of leaf canopy development due to solar radiation, saturation deficit, water and nutrient supply are considered.
The first five chapters of the book consider the key physiological processes. The chapter titles are: 1. Control of Development; 2. The Leaf Canopy and Root System; 3. Dry Matter Production by Interception and Conversion of Solar Radiation; 4. Transpiration and Dry Matter Production; and 5. Partition of Assimilate. The final chapter (6. Environmental and Physiological Control of Yield) attempts to draw together the responses of crops to environment and cultivation. Yield is analysed in terms of supply-limitation (water-limited) and demand-limitation (radiation-limited). Then, the physiological responses to nutrients, plant population density and mixed cropping are considered, and finally, species are compared in terms of their main physiological attributes.
Perhaps one disappointment with the book is its lack of application of the physiological understanding to the solution of agricultural problems. The main value of the physiological understanding, described so well in the book, is in the development of crop growth simulation models. Given that most crops in the tropics are grown under variable and relatively unpredictable environmental conditions, it is impossible to sample sufficient growing seasons to obtain the mean response and assess the climatic risk to production, using conventional field experimentation. Consequently crop physiologists should view crop simulation as an adjunct to field experimentation. It would have rounded the book off nicely if a final chapter had been devoted to the application of this physiological knowledge.
Abstract by R.C. MUCHOW, shortened
1101 92 - 4/144
Asia, Indonesia, study, cropping systems, labour requirements, mulch rotation system, sustainable systems, deforestation
LORENZ, C. and A. ERRINGTON
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