Growth and Yield of Maize as Affected by Early‐Season Defoliation1

Abstract

AbstractComplete defoliation of maize (Zea mays L.) at the five‐leaf stage has been reported to increase the grain yield of early‐season hybrids in the northern U.S. corn belt while similar treatments have generally reduced yields of full‐season hybrids. The objective of this study was to extend this research to the central corn belt by measuring the effect of defoliation at the five‐leaf stage on grain yield of maize hybrids differing in maturity. Yield responses were related to growth characteristics. Field experiments conducted at two Illinois locations during a 2‐year period indicated that defoliation reduced average grain yields 10 to 13% regardless of maturity class. Defoliation also reduced plant height, leaf number, leaf area, and percentage grain protein. Defoliation delayed pollen shed and silking but did not change the pollen shed to silking interval. In some experiments lower grain yields from defoliation were associated with a slight decrease in plant population, but reduced ear size was the primary factor causing the decreases in yields. Reduced leaf area probably decreased the supply of photosynthate resulting in smaller ear weight.