THE INFLUENCE OF RATOON CROPPING ON SWEET SORGHUM YIELD, SUGAR PRODUCTION, AND INSECT DAMAGE

Abstract

As multiple cropping practices continue to spread in the southeastern U.S.A., ratoon cropping (two harvests from a single planting) provides an additional double-cropping scheme for farmers. Fourteen sweet sorghum (Sorghum bicolor (L.) Moench) cultivars were evaluated in a ratoon double-cropping system at two locations during 1980 and 1981. Significant cultivar × location interactions were detected both years. Environmental conditions (particularly air and soil temperatures) and genetic capability governed performance of cultivars in the ratoon cropping system. The Coastal Plain location provided a more stable environment for ratoon cropping of sorghum than the Piedmont location and this production dependability was attributed to warm temperatures during April–May and October–November coupled with at least 230+ frost-free days. Total whole-plant green weights were 36% higher in the Coastal Plain than in the Piedmont. Percent sugar concentration was 15% higher on the first crop and 9% higher on the ratoon crop in the Piedmont than in the Coastal Plain. Calculation of total sugar yield per hectare revealed that the cultivars produced 43% more sugar when grown in the Coastal Plain than in the Piedmont. Roma was the best cultivar in the Coastal Plain while Brandes, Wray, and Keller were the best cultivars in the Piedmont. MN 960 and Ramada should be avoided when ratoon cropping. Insect damage was significantly greater on the ratoon crop than on the first crop. Fall army worm (Spodoptera frugiperda (J. E. Smith)) larvae caused the major foliar damage on the ratoon crop. Genetic improvements are needed in sweet sorghum cultivars used in ratoon cropping to increase total plant weight productivity (especially on the ratoon crop), sugar accumulation in the stem (particularly on the first crop), tillering capability in the ratoon crop, germination and seedling vigor in cool soils, and disease and insect resistance.Key words: Sorghum bicolor (L.) Moench, double cropping, cultivar by location interaction, Spodoptera frugiperda (J. E. Smith), Heliothis zea (Boddie)