Sweet Sorghum: Effect of Nitrogen on Biomass, Juice Content and Juice Quality.

The increasing frequency of dry and hot conditions, and population-driven demand for food is bound to affect corn use for bioethanol production. Under these conditions, population-driven demand for food is bound to reduce corn use for bioethanol. Therefore a need exist for heat and moisture stress tolerant crops to substitute corn for bioethanol production. Sweet sorghum, a warm season annual crop whose stems is loaded with simple sugars is a viable option. A study is underway at Virginia State University to evaluate sweet sorghum varieties for their response to nitrogen (N) fertilizer. The experiment consist of five sweet sorghum varieties (Dale, Theis, Topper 76-6, M81-E, and CHR-SW8) and four N rates (0, 40, 80, or 120 kg ha^-1) replicated three times.

Initial result indicate that except for CHR-SW8 which produced the lowest fresh stem (Stem + sheath) biomass of 72 tons ha^-1, all other varieties showed comparable biomass averaged at 79 tons ha^-1. Nitrogen application increased fresh stem yield and at 120 kg N ha^-1 yield was increased by 41 %. Juice yield varied between 11300 and 14890 Lha^-1 among the varieties and increased with N application. Topper 76-6 showed the highest brix value at 17.53 compared to all others that averaged 15.87. Similarly, Topper 76-6 showed the highest concentration of sucrose in its juice (4.88%) that was similar to that of CHR-SW8 and M81-E but higher than that of dale and Theis that averaged 2.79%. Dale and Theis had the lowest sucrose levels but relatively higher levels of fructose and glucose. Detaching the inflorescence at beginning of dough stage increased brix and sucrose but had no effect on fructose and glucose content in the juice. There is great potential for sweet sorghum production in southeast Virginia. Seeking non-seed forming (sterile) varieties may be important to increasing juice sugar content in sweet sorghums.