Nitrogen Fertilization Effects on Yield and Nutrient Removal of Biomass and Sweet Sorghum

Abstract

Core Ideas During the 4‐yr period of this trial, N fertilization increased dry matter yield in 2 out of 4 yr for biomass sorghum and there was no effect on dry matter yield of sweet sorghum. High DM yield supports sorghum as a bioenergy crop, however, the relatively low nutrient removal rate may limit its utilization in nutrient‐rich environments such as spray fields. Greatest dry matter yields achieved were ∼18.5 Mg ha−1 at a N fertilization rate of 67 kg N ha−1 yr−1 for biomass sorghum. Sorghum [Sorghum bicolor (L.) Moench] can be used as bioenergy crop for either biomass or sugar yield. Dry matter (DM) yield and nutrient removal information is needed if sorghum is to be planted in high‐nutrient receiving areas such as swine (Sus scrofa domesticus) spray fields. The objectives of this 4‐yr experiment (2012 through 2015) were to determine the effect of five N fertilization rates (0, 67, 134, 201, and 268 kg N ha−1 yr−1) on DM yield and nutrient (N, P, and K) removal of cultivars Blade ES5200 (biomass) and M81‐E (sweet). The DM yield of ES5200 plateaued at 18.5 and 18.9 Mg ha−1 in 2012 and 2014, respectively, when N rate was 67 kg ha−1. There was no N fertilization effect on DM yield of M81‐E, which were 11.1 and 15.0 Mg ha−1 in 2012 and 2014, respectively. Early season excess rainfall in 2013 and 2015 negatively affected yield of both sorghums. Nutrient removal for ES5200 was 87 to 139 kg N ha−1, 20 to 23 for kg P ha−1, and 187 to 205 kg K ha−1. For M81‐E, nutrient removal was 52 to 118 kg N ha−1, 8 to 20 for kg P ha−1, and 92 to 156 kg K ha−1. Sorghum cultivars responded differently to N fertilization. High DM yield supports sorghum as a bioenergy crop, however, the relatively low nutrient removal rate may limit its utilization in nutrient‐rich environments such as spray fields.