Crop Yield Response to Deficit Irrigation: Report of an FAO/IAEA Co-ordinated Research Program by Using Nuclear Techniques(84 Developments in Plant and Soil Sciences)

The increasing global demand for food and other agricultural products calls for urgent measures to increase water use efficiency which is, with plant nutrient availability, one of the two main limiting factors in crop production. Although only 20% of all cultivated land in the world is under irrigation, it provides 35-40% of all crop production. Because of higher yields under irrigated agriculture, investments for irrigation are usually a top priority. However, it has become a matter of serious concern in recent years that, despite their high co~ts, the performance of many irrigation projects has fallen short of expectations as a result of inadequate water management at both farm and system levels. Crop production increase has been well below the project targets. The greatest potential for increasing food and other agricultural products is the more efficient use of naturally occurring precipitation in conjunction with improved soil fertility management. Until recently, regardless of the amounts and distribution of rainfall, irrigation practices were used almost exclusively to supplement the amount of soil water stored in the root zone to such an extent that the available soil water never allowed the crop to suffer from water stress throughout the growing season. As a result, even today farmers still tend to over-irrigate to ensure a bountiful amount of water stored.

Table of Contents:
1. Water, no longer a plentiful resource, should be used sparingly in irrigated agriculture.- 2. Yield response of cotton, maize, soybean, sugar beet, sunflower and wheat to deficit irrigation.- 3. The response of winter wheat to water stress and nitrogen fertilizer use efficiency.- 4. Improving irrigation management practices with water-deficit irrigation.- 5. Field estimation of water and nitrate balance for an irrigated crop.- 6. Water and nitrogen use efficiency under limited water supply for maize to increase land productivity.- 7. Water balance and nitrate leaching in an irrigated maize crop in SW Spain.- 8. Nuclear techniques to evaluate water use of field crops irrigated in different growth stages.- 9. Effects of water stress imposed at different plant growth stages of common bean (Phaseolus vulgaris) on yield and N2 fixation.- 10. Yield response of groundnut grown under rainfed and irrigated conditions.- 11. Sugarcane yield response to deficit irrigation at two growth stages.-12. Contribution to improve sugar beet deficit- irrigation.- 13. Water stress effect on different growing stages for cotton and its influence on yield reduction.- 14. Some studies on pre-planned controlled soil moisture irrigation scheduling of field crops.- 15. Optimum irrigation schedules for cotton under deficit irrigation conditions.- 16. Field response of potato subjected to water stress at different growth stages.- 17. Crop yield response to deficit irrigation imposed at different plant growth stages.- 18. Soil spatial variability considerations in salt emission and drainage reduction.- 19. Summary by the Editors.- 20. List of Contributors.