Abstract

Abstract Under controlled irrigation, corn plants grown in large containers were subjected to water deficits in one of nine periods during each of two growing seasons. The first experiment (1965) differed from the second (1966) by somewhat different timing of treatments and by limiting soil fertility conditions. A significant grain yield reduction (12 to 15%) was observed after stress during the vegetative period at early ear shoot and ovule development in 1966. A 53% grain yield reduction was associated with stress at 75% silking in 1965. In the 3‐week period after silking, water deficits consistently reduced yields approximately 30% in both years. Significant reductions in kernel numbers were associated with yield reductions from stress before or during silking and pollination. Kernel weights were significantly reduced by stress during or after silking. Trends in the percentage of developed kernels in each of three ear sections indicated that the ability of kernels to compete for products of photosynthesis correlated with the comparative age of the ovule or kernel at the time of water deficit.