Crop Production In Dryland Regions

Cereal yields in dryland regions, particularly when produced without irrigation, are low because of the lack of water. As already stated, high-yielding varieties, fertilizers, pest control, and irrigation have been mainly responsible for large increases in worldwide food and fiber production. When irrigation is not available in dryland regions, the lack of water limits production, and the benefits of the other technologies are largely muted. FAO (1996) reported that the 1988-1990 average yield of wheat in developing countries in semi-arid regions was 1100 kg ha-1 for wheat, 1130 kg ha-1 for maize, and 650 kg ha-1 for sorghum (Sorghum bicolor). In contrast, the worldwide average yields were 2561 kg ha-1 for wheat, 4313 kg ha-1 for maize, and 1439 kg ha-1 for sorghum. Only about 10% of wheat, 8% of maize, and 35% of sorghum grown in developing countries were produced in semi-arid regions (FAO, 1996).

The worldwide average wheat yield has increased 2.5 times during the past four decades, and maize yield has increased 2.2 times. These crops are mostly grown in the more favored areas or under irrigation. While statistics are not available for worldwide yields when these crops are grown in dryland areas, it is well known that average yields have not increased dramatically because of low and erratic precipitation. Worldwide yields of sorghum, which is grown more widely in dryland regions, have increased only 1.6 times during the past four decades. The yield of millet (Panicum mill-aceum), grown almost entirely in dryland regions, has increased only 1.26 times during the same time period. It is well understood and documented that the large benefits from technologies such as fertilizers, high-yielding varieties, and pest control have largely occurred under irrigation or in the more-favored precipitation regions. Figure 14.1 illustrates the small gains from technology inputs under limited water

Organisation Agri Imags

— Irrigated HYV — Irrigated low input —High input rainfed — Low input rainfed

Figure 14.1 Effects of added inputs on the water use efficiency of cereal production. (From Koohafkan, P. 2000. Food Security, and Sustainable Development in the Middle East Region. Food and Agriculture Organization, Rome.)

— Irrigated HYV — Irrigated low input —High input rainfed — Low input rainfed

Figure 14.1 Effects of added inputs on the water use efficiency of cereal production. (From Koohafkan, P. 2000. Food Security, and Sustainable Development in the Middle East Region. Food and Agriculture Organization, Rome.)

conditions in comparison to the large gains obtained when water is not limiting.

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