Nutrient Management of Elephantgrass for Biomass Production Using Municipal Biosolids.

High energy prices have directed attention to bioenergy, including the production of lignocellulosic feedstock. Adequate nutrient supply is necessary to meet the requirements of high-yielding bioenergy crops, while minimizing environmental impact and production costs are critical. This study evaluated the effect of applying municipal biosolids (MBS) and NH₄NO₃  fertilizer at differing proportions on dry matter (DM) production and N and P removal by elephantgrass (Pennisetum purpureum Shum.). Ratios and total amounts of MBS and N fertilizer applied were chosen to bracket the range of expected P removal by the crop. Treatments were four percentages of MBS surface-applied (100, 67, 33, and 0% of N provided by MBS) for a total N application of 350 kg ha^-1 yr^-1. Two additional treatments were: 100% MBS with MBS incorporated, and twice the rate of the 100% MBS treatment surface-applied. Treatments were equally split-applied in spring and after a first harvest in August. Total DM yield decreased linearly (23.2 to 17.5 Mg ha^-1) as proportion of MBS increased from 0 to 100. Herbage DM yield was greater for 100% MBS when MBS was incorporated vs. surface-applied (23.6 vs. 17.5 Mg ha^-1). Thus, yields were similar between 100% MBS incorporated and 100% NH₄NO_3, and greater than surface-applied 100% MBS.  There was no treatment effect on herbage N concentration. Herbage P concentration increased linearly as the proportion of MBS increased from 33 to 100 (1.4 to 1.8 g kg^-1). N and P removal followed the same general pattern as DM yield. Incorporation of MBS had a positive effect on DM production, N, and P removal. The 33% MBS treatment most closely matched the P removal rate with the amount of P applied. Results suggest that MBS is a viable nutrient source, and that incorporation should be encouraged in order to maximize nutrient uptake and crop yield.