Fertilizer Nitrogen Rate Effects on Nutrient Removal by Corn Stover and Cobs

The harvest of corn (Zea mays L.) stover and cobs for cellulosic ethanol production will likely accelerate the depletion of soil N, P, K, and S, thus increasing nutrient replacement costs. Fertilizer N rate is a management variable that may influence N, P, K, and S removed by corn cellulosic materials. The effects of fertilizer N rate on grain and cellulosic biomass yields have been reported for the Upper Midwest, but no information exists regarding its effects on stover and cob nutrient removal across a range of rates in diverse environments. Experiments were conducted in eight environments in Minnesota to determine the effect of fertilizer N rate on N, P, K, and S removal by corn stover ( leaves, stalks, husks, shanks, and tassels) and cobs. Removal of N, K, and S by stover and cobs generally increased as fertilizer N rate increased, although the response oft en differed among environments. Removal of P by stover and cobs decreased or did not change as fertilizer N rate increased. Harvesting 7.5 Mg ha(-1) of corn stover removed on average 46, 3.5, 76, and 3.7 kg ha(-1) of N, P, K, and S, respectively, while harvesting 1.5 Mg ha(-1) of cobs removed 6.1, 0.37, 9.5, and 0.38 kg ha(-1) of N, P, K, and S, respectively. The harvest of solely corn cobs would remove 9 to 12% less N, P, K, and S, and thus deplete soil nutrient pools at slower rates compared with the harvest of both stover and cobs.