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Incorporation of municipal biosolids affects organic nitrogen mineralization and elephantgrass biomass production

Abstract:

Municipal biosolids (MBS) represents an alternative source of nutrients for the production of bioenergy crops like elephantgrass (Pennisetum purpureum Schum.). Two experiments were conducted during 2 yr in Florida to evaluate the effect of soil incorporation vs. surface application of MBS on: (i) elephantgrass dry matter (DM) yield, tissue N and P concentration and removal, and soil C and P (Exp. 1); and (ii) organic N mineralization and DM decomposition rates of MBS measured in the field using a litter bag incubation technique (Exp. 2). In Exp. 1, three treatments supplied 350 kg total N ha-1 yr-1 from surface-applied municipal biosolids (MBSSA), soil-incorporated municipal biosolids (MBS-INC), and surface-applied ammonium nitrate (NH4NO3). A fourth treatment provided 700 kg total N ha-1 yr-1 from MBS-SA (double rate of municipal biosolids, 2x-MBS). In Exp. 2, MBS was field incubated in litter bags placed on the soil surface or at a 5-cm soil depth. Elephantgrass DM yield, and N and P removal were greater for MBSINC than MBS-SA. Dry matter yield for MBS-INC was not different than for NH4NO3 fertilizer (22.5 vs. 24.3 Mg ha-1). Removal of N and P increased 39 and 10 kg ha-1 yr-1, respectively, for MBS-INC and MBS-SA. Total organic N mineralized was greater for MBS-INC (386 g kg-1) than MBS-SA (308 g kg-1). Incorporation of MBS increases elephantgrass DM yield and nutrient removal compared to surface application and allows MBS to replace a greater proportion of inorganic N fertilizer. © 2011 by the American Society of Agronomy.