Yield, Yield Components, and Nutrient Content of Corn Grain as Influenced by Post-Silking Moisture Stress

Sensitivity of corn (Zea mays L.) grain development to moisture stress is related to the physiological stage of development when stress occurs. For this reason the time when moisture stress occurs is important in determining final grain yield; hence, timing of precipitation or irrigation becomes an important economic factor in corn production. The primary objective of this work was to determine the effect of successive, repetitive moisture-stress treatments on yield and yield components. To accomplish this goal, experiments were conducted in the movable rain shelter facility at Ames, Iowa, during the summers of 1976 and 1977. With this facility, different soil-moisture conditions were imposed simultaneously with plants growing under similar conditions of atmospheric demand. Corn plants were grown in containers with 100 liters of a Nicollet loam soil (an Aquic Hapludoll, fine-loamy mixed mesic). Single and multiple periods of moisture stress were imposed after silking in one, two, or three successive stress cycles to study their effect on grain yield and yield components (kernels/plant and masskernel). Successive respective stress treatments on the same plants were included to observe plant response to moisture stress after sink size (kernel number) was altered because of previous stress. Grain yield reductions of up to 33% depended primarily upon severity and duration of soil-moisture stress. Additional stress cycles did not always cause an additive reduction in grain yield. Moisture stress that occurred within 2 weeks after silking reduced the number of kerneldplant by about 15% with little influence on final mass/kernel. Additional stress cycles had only minor effects on kernel number. Plants that were stressed shortly after silking and suffered reduction in kernels/plant had shorter, but uniformly filled ears, suggesting that stress-inhibited development of kernels at the tip of the ear. Moisture stress influenced masskernel in a complex fashion. Decreases up to 20% were observed. The observed pattern for mass/kernel depended on the timing of stress in relation to silking date and previous moisture-stress history of the plant. Moisture stress increased % N in the grain from 1.7% in controls to 1.8 and 1.9% in one and two repeated stress cycles, respectively, but did not significantly influence % P or % K in the grain at harvest.