Performance of Annual and Perennial Biofuel Crops: Nutrient Removal during the First Two Years

Nutrient removal is an important factor that must be considered in lignocellulosic fuel production. This study was conducted to determine the macronutrient (N, P, and K) composition of grain and stover, as well as the nutrient removal in grain, stover, and total biomass of annual and perennial C4 crops in northeast Kansas in 2007 and 2008. Crops studied were corn (Zea mays L.) grown continuously or rotated with soybean [Glyane max (L.) Merr]; five sorghum [Sorghum bicolor (L.) Moench] cultivars, brown midrib (bmr), photoperiod sensitive, sweet, and two dual-purpose forage cultivars; and three perennial warm-season grasses, switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and Miscanthus (Miscanthus x giganteus). Perennial grass yields were from the first two harvests after establishment. Yields and total nutrient removal rates were greater for annual crops than for perennial grasses. Perennial grass nutrient concentrations were greatest in the establishment year (2007). Perennial grass yields increased from 2007 to 2008, but nutrient removal was not affected by the yield increase. Grain nutrient removal rates were greatest for corn even though nutrient concentrations were less than or equal to those for sorghum grain. Total nutrient removal rates were most affected by biomass yield and soil test P levels. Total K removal was greatest for the photoperiod-sensitive, sweet, and dual-purpose forage sorghum cultivars. These results indicate that higher annual crop yields will remove more nutrients than perennial grasses during the grass establishment period.