DROUGHT INFLUENCES ON GRAIN-YIELD OF BARLEY, WHEAT, AND MAIZE

The response of three grain crops to drought was determined in a serie s of experiments in a mobile rainshelter at Lincoln, Canterbury, New Z ealand. For winter wheat and spring barley, the critical potential soi l moisture deficit (D-c) beyond which yield was affected was independe nt of drought timing, but was much smaller for barley than wheat. Both crops showed similar yield responses to drought above their D-c. In c ontrast, D-c for maize increased as the season progressed, and yield w as much less sensitive to drought once D-c was exceeded. Although yiel d response was mostly associated with grain number in wheat and barley , mean kernel mass was also reduced as drought stress increased. Grain yield in maize was correlated with mean kernel mass, and uncorrelated with grain number.