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Legume Proportion in Grassland Litter Affects Decomposition Dynamics and Nutrient Mineralization

M. Kohmann,L. Sollenberger,J. Dubeux,M. Silveira,L. S. Moreno

Published 2019 in Agronomy Journal

ABSTRACT

The impact of legume inclusion on the decomposition of aboveground plant litter in grasslands is not well understood. Our objective was to quantify litter decomposition and nutrient disappearance from ‘Pensacola’ bahiagrass (Paspalum notatum Flugge) as affected by N fertilizer or proportion of ‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) in litter. Five litter treatments (unfertilized bahiagrass [BG], bahiagrass receiving 60 kg N ha–¹ [BGN], rhizoma peanut and bahiagrass mixtures in 33–67% and 67–33% proportions [RP33 and RP67, respectively], and pure rhizoma peanut [RP]) were incubated for 128 d during each of 2 yr. Decomposition followed a logistic curve with a linear decay between initial and final lag phases. Litter treatment did not affect decomposition rate, but RP33 litter decomposed to a greater extent than BG (35 and 43% remaining biomass, respectively) due to a longer linear decay period for RP33. At the end of incubation, only 25% of the initial rhizoma peanut component litter mass remained for RP33, whereas 35 and 39% remained for RP67 and RP. Bahiagrass decomposition was not affected by the presence of legume. Bahiagrass monocultures showed δ¹³C depletion, and all legume-containing treatments showed δ¹³C enrichment during incubation. After incubation, there was less N in legume litter treatments despite similar chemical characteristics to BGN, indicating that other factors, such as microbial diversity, affected mixture decomposition. Recalcitrance of C and especially N increased during decomposition. We conclude that N return from mixed legume–grass litter is superior to that of unfertilized grass and equal or superior to that of moderately N-fertilized grass.

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