Rotation, Fertility, and Residue Effect On Yield, Nutrient Uptake, and Soil Quality In Bioenergy Sorghum Production Systems In Texas.

Soil is the fundamental resource in agricultural systems and maintaining soil quality is key to ensuring sustainable production. Productivity and soil quality may be affected by cropping sequence complexity, fertilization, and residue removal. The goal of this research was to optimize the efficiency of crop management and soil and environmental quality in high biomass (bioenergy) sorghum systems. The two-year field study took place in College Station and Weslaco, Texas, utilizing several management systems for bioenergy sorghum. The study utilized a complete factorial design with four replications of the following factors: Rotation: continuous biomass sorghum vs. biannual rotation with corn; Stover Return: 0, 25, 50% of the sorghum biomass and all corn stover; and N Rate: 0 vs. non-limiting N. The bioenergy sorghum used in all studies was a high-yield photoperiod-sensitive hybrid. All other inputs and practices were those commonly used in the respective areas. Sorghum was harvested for yield and total concentrations of C, N, P, K, and other selected nutrients were determined. Soil samples were taken at the beginning of the study, with additional samples being collected before the second growing season. Samples were analyzed for soil quality parameters including total organic and inorganic carbon and nitrogen, residual nitrate and other available nutrients. Rotation, fertilization, and residue return affected yields, plant growth, and soil quality (p <0.05). Total yields, C, N, P, and K uptake in sorghum were significantly increased by rotation and N fertilization both years, while 25% residue return significantly increased sorghum yield and N uptake at College Station the first year (Fisher’s LSD <0.05). At Weslaco, C and N uptake were increased by N fertilization. Continuous sorghum increased soil near-surface C and N more than rotated sorghum, but depleted more soil nutrients. Residue return compensated somewhat for this depletion.