Litter mass, deposition rate, and decomposition in nitrogen-fertilized or grass-legume grazing systems

Plant litter deposition and decomposition play important roles in grassland nutrient cycling. The objective was to evaluate plant litter responses and estimate the N returns via plant litter in contrasting grazing systems, since legume inclusion is hypothesized to result in similar quantities of N return compared with N-fertilized grass systems. Systems were (a) N-fertilized bahiagrass (Paspalum notatum Flugge) during summer with a mixture of N-fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N); (b) bahiagrass (no N fertilizer) during summer and a rye-oat-clovers (Trifolium spp.) mixture + N in winter (Grass+Clover); and (c) bahiagrass (no N fertilizer in summer) with strip-planted rhizoma peanut (Arachis glabrata Benth.) during summer with a rye-oat-clovers mixture + N during winter (Grass+CL+RP). Litter mass was greatest for Grass+N during October (4,430 kg organic matter [OM] ha(-1)) and least for Grass+CL+RP in June (490 kg OM ha(-1)). Litter N concentrations were greatest in Grass+N (16 g kg(-1)), with similar N concentration for Grass+Clover and Grass+CL+RP litter (14 g kg(-1)). Contribution of C-3 species to litter mass increased from May to July but decreased thereafter. Overall, there was a net return of 47 kg N ha(-1) yr(-1) via litter across the three systems, and litter decomposition was similar in the three systems. Inclusion of forage legumes during cool and warm seasons in grazing systems has the potential to return similar amounts of N through plant litter deposition as grasses receiving moderate levels of N fertilizer.