Sweet sorghum planting effects on stalk yield and sugar quality in semi-arid tropical environment

Abstract

Sweet sorghum [Sorghum bicolor (L.) Moench] has potential as a bioenergy crop for producing food, fiber, and fermentable sugar. Unlike dryland grain sorghum, little information is available on the influence of staggered planting and genotypes, especially in semiarid tropical environments. The objectives of the present study were (i) to quantify the effects of planting time and genotype on stalk and biomass yields, juice sugar quality, and (ii) to identify the most productive genotypes and planting windows for sustainable feedstock supply. Four commercial sweet sorghum genotypes (SSV84, SSV74, CSV19SS, and CSH22SS) were planted on five planting dates (1 June, 16 June, 1 July, 16 July, and 1 August) during the rainy (June–October) season of 2008 and 2009 in Hyderabad (17°27´ N, 78°28´ E), India. Planting in early and mid-June produced significantly (P ≤ 0.05) higher fresh stalk yield and grain yield than later planting dates. Commercial hybrid CSH22SS produced significantly more stalk, grain, sugar, and ethanol yield over genotypes SSV84 or SSV74. Based on the stalk yield, juice sugar quality, sugar, and ethanol yields, the optimum planting dates for sweet sorghum in semiarid tropical climate is early June to early July. Planting sweet sorghum during this time allows more feedstock to be harvested and hence extends the period for sugar mill operation by about 1 mo, that is, from the first to the last week of October.