Optimal Nitrogen Fertilizer Rates for Ethanol Production From Sweet and Photoperiod Sensitive Sorghum.

Sorghum (Sorghum bicolor L) grown in the Texas High Plains is mainly grain sorghum and the balance is forage sorghums. In this region, there is little information available on N fertilizer requirements for the ethanol production from these sorghums. This study was conducted in 2008 and 2009 on an Acuff sandy clay loam at Texas A&M AgriLife Research and Extension center farm near Lubbock. The total dry matter (TDM), total N uptake, juice yields, juice ethanol, cellulosic ethanol and total ethanol yields were higher in 2009 than in 2008. In 2009, TDM was in higher forage sorghum than in sweet sorghum cultivars. In 2008 N application did not increase juice ethanol yields, but in 2009, cultivar M81E showed N response. As expected, cellulosic ethanol yield was higher in forage sorghum cultivars than sweet sorghum cultivars in 2009. In 2009, sweet sorghum cultivars, especially M81E, had the highest total ethanol yield than the forage sorghum cultivars. The optimum N fertilizer rate for ethanol and TDM across all four sorghums was 107 kg ha-1 and 108 kg ha-1 respectively in 2009.