Developing Row Spacing and Planting Density Recommendations for Rainfed Sweet Sorghum Production in the Southern Plains

Abstract

Sweet sorghum [Sorghum bicolor (L.) Moench] is gaining in popularity as an alternative biofuel feedstock. The potential of sweet sorghum for low nutrient and water requirement appears to fit well within the Southern Plains arid climate. The objectives of this project were to determine the optimum row spacing and plant population for sweet sorghum production in the Southern Plains. Three locations in Oklahoma were established, ranging in in‐season precipitation from 240 to 500 mm west to east, respectively. Soils at locations ranged from silt loams to loams. At each location two separate studies were conducted: row spacing and planting density. To determine the effect of row spacing on sweet sorghum production two varieties, Topper and M81, were evaluated in spacings of 20, 38, and 76 cm. To determine optimum plant density, plots were arranged in a randomized complete block design and seeded at rates of 74,100 to 172,900 seeds ha−1 in 20 and 76‐cm row spacings using one cultivar, M81. Plots were harvested at soft dough stage to obtain fresh yield. Samples were pressed to determine juice yield and brix values. Using a row spacing of <76 cm is advantageous under average to high yield potential (>60 t ha−1), while in extremely high yield potential areas (>100 t ha−1) a row spacing of 20 cm would be better suited. For row spacings of 20 and 76 cm a wide range of planting densities would be acceptable due to sweet sorghums’ ability to tiller.