Defoliation Affects Grain Yield, Protein, and Oil of TopCross High-Oil Corn
2003
Thomison, Peter R. | Nafziger, Emerson D.
The TopCross grain production system, in which about 90 percent of the plants in a corn (Zea mays L.) field are male-sterile and the remainder serves to transmit the high-oil character through pollen, is widely used to produce high-oil corn (HOC). In the TopCross system, two types of corn are planted as a physical mixture (a TC Blend). It is not known whether defoliation by hail or other factors affects yield of TC Blends the same as it does normal hybrids, nor whether defoliation affects grain quality, particularly oil content, on which premiums are based. In studies conducted over two years in Ohio and three years in Illinois, grain yields decreased as leaf removal increased in severity, and as time of defoliation neared tassel emergence. The greatest yield reductions caused by defoliation occurred at or near flowering, with complete defoliation at flowering reducing yields by 95 percent or more. Grain oil content was usually less affected by defoliation than grain yield, and it typically required defoliation sufficient to reduce yield by more than 50 percent, and sometimes as high as 70 percent, in order to decrease oil content. Grain oil content was reduced as much as 30 to 40 percent with complete defoliation during late vegetative, flowering, and early grain fill, whereas protein content was increased as much as 50 percent. High-oil corn TC Blends and a conventional hybrid counterpart exhibited similar responses to defoliation for grain yield, and oil and protein content in the Ohio study. Since premiums for contract production of HOC are based on grain oil concentration, the lower oil content caused by severe defoliation may result in reduced premiums.
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