The Effect of Row Spacing and Seeding Rate On Biomass Production and Plant Stand Characteristics of Non-Irrigated Photoperiod-Sensitive Sorghum (Sorghum bicolor (L) Moench).

To evaluate the effect of row spacing and seeding rate on yield and plant stand characteristics of high-biomass sorghum, a photoperiod-sensitive sorghum cultivar was sown at three different row spacings and seeding rates for four site-years from 2009 to 2010 in Alabama and Arkansas, USA. Measurements included above-ground dry matter production, plant height, plant population, and stem diameter. Narrower row spacing (i.e. 19 cm) produced the highest biomass yields for all site-years. In contrast, increasing seeding rate did not affect yield for three of the site-years, and significantly decreased yield for one site-year. The 19 cm row spacing produced the highest plant populations for all site-years. Plant height increased with increasing seeding rates at one site and decreased with higher seeding rates at another site. At one location, stem diameter declined as seeding rates and plant populations increased. It is concluded that narrower row spacing (19 cm) provides the maximum yield benefit by significantly improving stand establishment, and low seeding rates (4.48 kg ha^-1) are preferable because higher seeding rates do not positively affect yield and in some instances, cause morphological changes (i.e. taller plants with thinner stems) conducive to lodging.