Seeding rate is an important factor in optimizing dry matter yield of biomass sorghum Sorghum bicolor (L.) Moench. It is vital to understand how seeding rate (S rate) varies across environments, planting dates, and whether optimum S rate changes by date of harvest in the Mid-Atlantic region. From 2017 to 2019, a study was conducted at Virginia Tech’s Tidewater Agricultural Research & Extension Center in Suffolk, VA, across two locations (Holland and Hare) with six seeding rates (120, 160, 200, 240, 260, and 310 thousand seeds ha− 1), two planting dates early planting (EP) date as in a full season cropping system versus late planting (LP) mimicking a double-crop system and three harvesting dates (August – October) to determine the economic optimum seeding rate of biomass sorghum. Dry matter yield, plant height, stem diameter, disease, and lodging severity were evaluated. Results showed that compared to LP, EP increased dry matter yield by 69%, plant height by 21%, and stem diameter by 15%. Dry matter yield decreased with higher S rates under EP, whereas under LP, higher S rates increased yield in 3 of the 6 environments. In contrast, plant height and stem diameter consistently decreased with increase in S rate. In general, a S rate of 120,000 ha− 1 was optimum under EP, and 310,000 ha− 1 under LP, when considering the disease and lodging resistance as well as economics. An October harvest always had greater yield than August or September. Planting biomass sorghum at these recommended S rates and harvesting in October could improve farm profitability while decreasing disease and lodging susceptibility.
Koduru et al. (Sat,) studied this question.