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The AEZ study methodology is capable of estimating the production potential of any crop in any part of the world. Initially, crop adaptability, the range of climatic conditions required by a crop, was analysed for more than 70 crops. These crops were divided into five groups according to their photosynthetic requirements. Each group responds to solar radiation and temperature in different ways, and these responses determine productivity. (Group V, a rather special group that includes pineapple and sisal, is not considered further in this publication because it does not include any of the major crops considered in the study.)
The 11 major crops in the developing world in 1988
The information gathered was used to help define the temperature regimes of the 14 major climates used in the study. Thus almost from the start of the study, the crops and climates were matched, and it was possible to determine which crops could be grown in which climates, and which could not. For example groups I and IV, which include wheat and potato, cannot be grown in the warm tropics (see diagrams below).
Photosynthesis and temperature requirements:
optimum temperature for photosynthesis (°C)
Because the AEZ study could not conveniently handle as many as 70 crops, 20 were initially selected for study on the basis of the area of the crop harvested in the developing world. Crops not commonly grown throughout the developing countries, such as barley, oats, groundnuts, rye, peas, chickpeas, grapes and rapeseed, were then dropped from the list. Sugar cane was also dropped because its production potential is highly dependent on factory management. This left 11 crops:
• five grain crops (wheat, rice, maize, pearl millet and sorghum);
• three root crops (white potato, sweet potato and cassava);
• two legumes (phaseolus bean and soybean); and
• one cash crop (cotton).
The AEZ study thus analysed 22 alternative land uses-production with low or high farming inputs for each of 11 major crops.
The soil requirements of the 11 crops were analysed in terms of factors such as soil drainage, fertility, acidity, salinity, stoniness, texture and slope.
The way in which these climatic and soil factors are applied in the AEZ study are described on pages 16/17.
STEP 1
