Effect of Tillage and Fertilization on Agronomics and Nutrient Uptake of Sweet Sorghum.

The use of sweet sorghum [Sorghum bicolor (L.) Moench] as a biofuel feedstock has garnered attention in recent years. Currently, little is known about the nutrient demand for sweet sorghum or how it responds agronomically under differing tillage systems. The objectives of this study were to: 1) evaluate the effects of tillage on sweet sorghum agronomics and 2) to determine total uptake and partitioned nutrient content of sweet sorghum. A two-year field study was conducted at the LSU AgCenter Rice Research Station, near Crowley, LA. A randomized complete block design with four replications was used to evaluate two tillage practices (conventional tillage and no-tillage) under two nutrient management practices (without and with K and P fertilization) on productivity of ‘Durasweet’ sweet sorghum. Plant samples were collected from head grain, stalk, green and brown leaves at the soft dough stage of development. Samples were dried, ground, and analyzed for total elemental concentration. There was not a significant tillage or nutrient management effect on total biomass production. Mean total biomass ranged from 76 and 82 Mg ha^-1across tillage and nutrient management treatments. Total P and K uptake was not significantly different across tillage or nutrient management practices. The greatest percentage of N, P and K absorbed by plant at the soft dough stage of development was contained in the stalk. In the decreasing order,  the percentage of total N, P and K uptake in sweet sorghum at the soft dough stage of development was stalk>green leaves > head > brown leaves.