Nitrogen Uptake and Biomass and Ethanol Yield of Forage Crops As Feedstock for Biofuel.

Ethanol production is projected to increase with the utilization of forage crops for biomass production. Nitrogen fertilizers are extensively used to enhance the growth of biomass crops, but the current trend towards greater sustainability in agriculture is leading towards increased research to reduce the use of fertilizers. This study was conducted to determine the forage crop that produces the most biomass that can be utilized for bioenergy and to determine the effect of different levels of nitrogen fertilizer on biomass yield and nitrogen uptake in the different forage crops. The effects of nitrogen fertilization on the nitrogen uptake and the biomass yield of forage sorghum [Sorghum bicolor L. Moench], sudangrass [Sorghum sudanense (Piper.)], reed canarygrass [Phalaris arundinacea L.], and kenaf [Hibiscus cannabinus L.] were investigated at the North Dakota State University research sites in Fargo and Prosper, ND. The experimental design in both locations was a randomized complete block design with a split-plot arrangement with three replicates. The different crops constitute the main plots and the nitrogen rates were regarded as subplots. The independent variables in this study were the four biomass crops and the five levels of N fertilization (0, 75, 100, 150, and 200 kg N ha^-1). Soil samples were taken for analysis in the spring before the crop was planted and in the fall immediately following harvest. Soil samples from both 0 to 15 cm and 15 to 60 cm were taken from each subplot and analyzed for N, P, K, OM, and pH. Aboveground portions of whole plants were collected at three developmental stages: vegetative (V8), flowering (VF), and right before harvest for plant NO₃-N determination. Biomass yield, forage quality, estimated ethanol yield, and nitrogen uptake was recorded. An economic analysis will be conducted as well. In 2010, the plant NO₃-N levels increased for all crops as N rates increased. Forage sorghum was expected to uptake the highest amount of nitrogen out of the soil because of the highest biomass yield. Forage sorghum had the greatest dry matter biomass yield (21.28 Mg ha^-1) whereas reed canarygrass had the least biomass yield (8.35 Mg ha^-1). Estimated ethanol yield was highest for forage sorghum (3381 L ha^-1) at the 150 kg N rate. The results indicate that forage sorghum has greatest potential as a feedstock.