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Double Cropping Corn on the Coastal Plain of the Southeastern United States¹

Asbtract: The adoption of doublecropping systems involving corn, Zea mays L., following corn in the same year would greatly improve the efficiency of land utilization in areas where the practice is possible. A study was conducted to determine if such a system would be useful in the southeastern U. S. where many locations have more than 240 frost-free days during the growing season. Growing two crops during the same season would also help alleviate the feed-grain deficit of states in the southeastern area. Our objectives were to determine which maturity Combinations could be expected to perform best and produce the greatest return when grown for gain or forage. We also wanted to determine whether there was an advanlage in using hybrids with tropical germplasm for the summer crop. Two locally recommended hybrids and two hybrids containing exotic germplasm, each pair having one early-maturing and one late-maturing hybrid, were evaluated on the coastal plain of Gmrgia at Tifton in 1976 and 1977. The spring planting, consisting of the two recommended hybrids only, was harvested as grain; the summer planting, having all four hybrids, was harvested for grain and forage. The spring planting was effectively a 24-replicate test to provide space for the six-replicate summer planting which included all hybrid combinations. The experiments were planted as a split-plot design, with the two hybrid adaptation types (exotic and recommended) providing the split, and maturity (late and early) combinations being randomized within each adaptation split. Early frost in 1976, hot weather in 1977, and an unusually heavy insect population during both years resulted in low grain yields for the summer planting each year. Overall performance levels were slightly better in 1976 than in 1977, but relative performance of the various hybrid and maturity combinations of the doublecropping system was similar for both years.

Double cropping of corn might be a viable option on the coastal plain of the southeastern U. S. if the second crop were taken as forage rather than as grain. Grain yields of the summer crop were all less than 40 q/ha, and the early hybrids could not compete with late hybrids in forage production. Among maturity combinations, a recommended early hybrid, grown for grain as the spring crop, followed by late-maturing hybrids, produced the highest ($957 to $1308/ha) average economic return. We suggest that some benefit may be obtained from using a hybrid with exotic (tropical or subtropical origin) germplasm for the summer crop and future testing of corn double-cropping systems should include hybrids of this type.

Key Words: Maize • Multiple cropping • Fall armyworm • Silage • Grain • Zea mays L

² Research geneticist and research entomologist, respectively, USDA. SEA, Titton, GA 31794.

Received for publication January 8, 1979.