Comparative Yields of Ratoon Cropped Temperately and Tropically Adapted Grain Sorghum Hybrids¹

Abstract

With a growing season of + 230 frost‐free days and the need for additional double‐cropping alternatives in a subtropical environment, 10 tropically adapted (TA) and 10 temperately adapted (TE) sorghum [ Sorghum bicolor (L.) Moench] hybrids were evaluated for ratoon cropping (two grain harvests from a single planting) performance in the southeastern USA from 1981 to 1983. The field study was conducted on a Greenville sandy clay loam (Rhodic Paleudults) and involved planting the crop in early April, harvesting the first grain crop in late July or early August, removal of the remaining stubble with a silage chopper, and harvest of the ratoon grain crop in early December. Tropically adapted hybrids produced 610 and 620 kg ha ‐1 higher grain yields on the planted crop and on total combined yields, respectively, than TE hybrids. Ratoon‐crop yields were not significantly different between TA and TE hybrids, indicating that the adaptation characteristic was not a factor in ratoonability. Northrup King ‘Savanna 5’ (TE) and Douglass King ‘DK 788’ (TA) produced the greatest yields for the planted crop, ratooned crop, and total crop. However, the majority of hybrids apparently were not well adapted to ratoon cropping, and breeding efforts will be needed to stabilize yields in this alternative double‐cropping program, particularly for ratoon‐crop grain yields.