Nitrogen Fertilization and Legume Proportion Affect Grassland Litter Deposition and Decomposition.

Legumes are an alternative to fertilizer for providing N to grasslands, but legume presence may affect nutrient cycling. The research objective was to quantify litter deposition and decomposition of bahiagrass (BG; Paspalum notatum)-based pastures as affected by N fertilizer or proportion of ‘Florigraze’ rhizoma peanut (RP; Arachis glabrata). Two pure BG treatments, receiving 0 or 60 kg N ha^-1, were replicated three times along with six plots of RP–BG mixtures for 2 yr. Proportion of RP ranged from 6 to 55% and 42 and 78% in 2015 and 2016, respectively. Herbage (litter) was collected to ground level, separated, and incubated over 128 d. Existing litter (EL) was collected twice a year per plot, and deposited litter (DL) was collected from the same quadrats 14 d later. Litter deposition rate (DR) was calculated based on DL corrected for decomposition. Extent and rate of losses in biomass and N increased with increasing proportion of legume and were greater for mixtures when compared with pure BG. This was probably due to the increase in N concentration (23 and 29 g N kg OM^-1 in RP–BG litter compared with 16 and 20 g N kg OM^-1 in pure BG in 2015 and 2016, respectively), although greater microbial diversity in mixed-species litter probably had a positive effect on decomposition. Nitrogen became increasingly more unavailable as decomposition advanced. Extent of decomposition was greater in 2015 compared with 2016 (53 and 71% for mixtures and 57 and 80% for pure BG, respectively) due to more frequent rainfall and greater temperatures in 2015. Litter DR was similar across treatments. More EL accumulated in BG relative to mixtures, and at lesser compared with greater RP proportions because of differences in decomposition rates. Legume inclusion in grasslands is a sustainable alternative to provide N to grassland systems.