Irrigated sweet sorghum yield as affected by plant spacing and row width

Greater plant spacing and row width than is commonly used in sweet sorghum [Sorghum bicolor (L.) Moench] can reduce lodging and facilitate the use of a sugarcane harvester in the case of greater row width. The hypothesis for this study is biomass and theoretical sugar yield are more tolerant of greater distance between plants and wider row spacing in the desert Southwest than other climatic regions with less insolation. The study was conducted with the sweet sorghum variety ‘M81E’ in 2010 and 2012 at the Campus Agricultural Center in Tucson, AZ, on a Gila very fine sandy loam (coarse-loamy, mixed, superactive, calcareous, thermic Typic Torrifluvents). The treatments consisted of five within-row plant spacings (20, 25, 51, 102, and 203 cm) at 102 cm row width and two row widths (102 and 203 cm) at 20 cm plant spacing. The highest biomass yield was at the closest three spacings in 2010 and the closest four spacings in 2012. The highest theoretical sugar yield was at the closest four spacings both years. The yield of the 203 cm plant spacing compared to the others averaged 59% for biomass and 64% for sugar. Row width did not affect biomass or theoretical sugar yield. Stalk diameter, leaves per stalk, weight per stalk, stalks per plant, and juice extraction increased in response to greater plant spacing and row width. Biomass and theoretical sugar yield were more tolerant of greater distance between plants and wider row spacing than has been reported in other regions.