Agronomic responses of corn to stand reduction at vegetative growth stages

The current standard for assessing corn (Zea mays L.) yield loss due to stand reduction from hail assumes that remaining plants lose the ability to compensate for lost plants by mid-vegetative growth. From 2006 to 2009, experiments were conducted over 12 site-years in Illinois, Iowa, and Ohio to determine the agronomic responses of corn to stand reduction at the 5, 8, 11, and 15 leaf collar stages (V5, V8, V11, and V15, respectively), and whether these responses vary between uniform and random patterns of stand reduction with differences in within-row interplant spacing. When compared to a control of 88,900 plants ha^-1, grain yield decreased linearly as stand reduction increased from 16.7 to 50%, but was not affected by the pattern of stand reduction. This rate of yield loss was greatest when stand reduction occurred at V11 or V15, and least when it occurred at V5. With 50% stand loss, yield was 83 and 69% of the control when stand loss occurred at V5 and V15, respectively. With 16.7% stand loss at V5, V8, or V11, yield averaged 96% of the control. Per-plant grain yield increased when stand loss occurred at earlier stages and was more severe. With 50% stand loss at V11 or V15, per-plant grain yield increased by 37 to 46% compared to the control. These results show that corn retains the ability to compensate for lost plants through the late vegetative stages, indicating that current standards for assessing the effect of stand loss in corn should be re-evaluated.