Water and nitrogen use efficiency under limited water supply for maize to increase land productivity

In as much as drought is the main environmental factor limiting productivity, the study of plant response to water deficit has been a major research topic. Increasing maize evapotranspiration ET does not always mean increasing efficiency because a large ET value does not always mean a large grain yield value. Mechanisms relating grain yield to ET are complex. The amount of rain and its distribution during the reproductive stage is the main meteorological factor influencing yield. In our study 1991, high soil water content caused a reduction of maize grain yield in the wet years owing to excessive water under irrigation conditions. As a result of insufficient oxygen for respiration and lack of nitrate formation, excessive water normally limits root development. The yield response of different hybrids to water deficit is of major importance in production management. The available water supply should be directed towards fully meeting the water requirements of hybrids having large values of their yield response factor ky. For hybrids having smaller values of ky, overall production will increase by extending the area under irrigation without fully meeting water requirements, provided water deficits do not exceed critical values. (author). 5 refs, 3 figs, 4 tabs