Effect of Tillage and Fertilization on Agronomic 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 three-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 (CT) and no-tillage (NT)) under two nutrient management practices (without (NMF) and with “maintenance fertilization” (MF)). MF represented that application of phosphorous (P) fertilizer (45 kg P₂O₅ ha^-1) and potassium (K) fertilizer (67 kg K₂O ha^-1) 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. When pooled over three years, the agronomics analysis results showed that plant height, fresh stalk biomass, and total fresh biomass were significantly affected by MF. Additionally, plant tiller percentage was significantly impacted by tillage management. Total plant K and stalk K concentrations (based on whole dry plant and stalk) were significantly higher with MF as compared to NMF. Stalk K concentration (based on dry stalk) was also significantly affected by CT. However, plant P concentration was not affected neither under different tillage practices nor fertilization managements. Therefore, plant’s K distribution could be estimated from these results, and the efficiency of K fertilizer on sweet sorghum would be improved for different harvesting styles.