Legume Proportion in Grassland Litter Affects Decomposition Dynamics and Nutrient Mineralization

• Published in: Agronomy journal Vol. 111; no. 3; pp. 1079 - 1089
• Main Authors: Kohmann, Marta M., Sollenberger, Lynn E., Dubeux, Jose C.B., Silveira, Maria L., Moreno, Leonardo S.B.
• Format: Journal Article
• Language: English
• Published: The American Society of Agronomy, Inc 01.05.2019
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2018.09.0603

Core Ideas Grass reduced lag phase and increased legume decomposition in mixtures relative to monocultures. Factors besides litter chemical composition, such as microbial diversity, affected decomposition. Legume treatments were enriched and grass monoculture depleted in δ13C during decomposition. Availability of C, and to a greater extent N, decreased during decomposition. 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 Flügge) 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.