Importance of multiple cropping in increasing world food supplies

Multiple cropping is widely used by farmers in the warmer parts of the world at all levels of agricultural technology, although the exact form varies from area to area depending on the farmers" total resources. The patterns of multiple cropping reflect two basic practices: simultaneous cropping, (growing crops in mixtures), and successive cropping, (growing crops in sequence). Intercropping, mixed cropping, and strip cropping are "simultaneous," while double (and triple, etc.), relay, and ratoon cropping are "successive." In vast areas of rain-fed agriculture where full irrigation is an economic impossibility, the extent of crop growth is limited by the duration of the wet season moisture supply. The simultaneous patterns of cropping aim at using both extra time and the spatial arrangements of component crops. In a successful mixture of similar and different maturities, the sum of the inter-crop competition should be less than the sum of the intra-crop competition of the component crops when grown sole. Gains from crop mixtures are due to the fact that individual plants yield more or that higher total plant population densities are possible. Successive cropping is possible in climatic areas where conditions for plant growth exist beyond the duration of one early maturing crop. Successive patterns of cropping aim at multiplying the net return per unit area by growing extra crops. The breeding of high yielding, early maturing crop cultivars has greatly contributed to the flexibility of such cropping patterns. Maximum cropping should be obtained with sequences of high yielding crops in compatible mixtures