INCREASING MILLABLE CANE YIELD OF SWEET SORGHUM THROUGH ALTERED NITROGEN, POPULATION LEVEL AND PLANT GROWTH REGULATORS SPRAY

Abstract

Sweet sorghum (Sorghum bicolor) has the potential to become a multipurpose feedstock for large-scale ethanol production from stem juice, cellulose/hemicellulose from stalks, and starch from grain. Maximizing the feedstock yield is the first step for large-scale production of ethanol. Feedstock yield in sweet sorghum can be improved by various nitrogen levels, spacing and plant growth regulators. Field experiments were conducted to evaluate the responses of sweet sorghum to nitrogen levels (60, 120 and 180 kg N ha^-1), populations (21.7, 10.9 and 7.2 plants m^-2), plant growth regulators (Naphthalene acetic acid; NAA 40 ppm and salicylic acid 200 ppm) and pollen sterilants spray (ethrel 200 ppm, p-coumaric acid 400 ppm and deheading) on millable stalk yield and brix value. Increased millable stalk yield was observed in 120 kg N ha^-1. However, maximum brix value was recorded in 180 kg N ha^-1. Increased millable stalk yield and brix value (%) was recorded in 7.2 plants m^-2 and it could be due to less competition between the plants for the resources. Naphthalene acetic acid (NAA) application increased brix, sucrose content and theoretical ethanol yield compared to control and it could be due to enhanced sugar mobilization from the leaf to the stem. Ethrel 200 ppm sprayed plants had higher stem girth, millable stalk yield, brix value and sucrose content and this may be due to increased pollen sterility percentage. The study revealed population of 7.2 plants m^-2, nitrogen level of 120 kg N ha^-1, NAA 40 ppm spray at booting stage and ethrel 200 ppm spray at anthesis stage resulted in higher millable stalk yield and brix value.