Litter Deposition and Decomposition Under Grass-Legume Mixed Systems.

Litter quality plays an important role in nutrient cycling in C4 grassland ecosystems since litter is typically of poor quality. Incorporating legumes into these grassland systems should increase the overall litter quality, which is beneficial for overall nutrient return to the system. The study was conducted in three contrasting grazing systems, consisting of 1) N-fertilized bahiagrass (113 kg N ha^-1; Paspalum notatum Flügge) in the warm-season and overseeded with a mixture (45 kg ha^-1 each) of FL 401 rye (Secale cereal L.) and RAM oat (Avena sativa L.) in the cool-season; 2) rhizoma peanut (Arachis glabrata Benth germplasm Ecoturf) strip-planted into bahiagrass in the warm-season, and overseeded with similar rye/oat mixture with 34 kg N ha^-1 plus a mixture of clovers (Trifolium spp.) in the cool-season; 3) unfertilized bahiagrass in the warm-season, and overseeded with similar rye-oat and clover mixture previously mentioned during the cool-season. Litter deposition was evaluated every 5wk from May-November 2016 by harvesting plant litter within six 0.25-m² quadrats placed in each paddock. Litter decomposition was evaluated using nylon bags, placed in exclusion cages within each paddock, covered with existing litter material and collected on 4d, 8d, 16d, 32d, 64d, 128d, and 256d after placement. Response variables included litter mass, decomposition rate, and chemical composition (ADF, NDF, N, C, and C:N ratio). Fertilized pastures showed greater litter mass (P=0.01), with 1580 kg OM ha^-1, while grass-legume pastures showed the least at 805 kg OM ha^-1. Litter C:N ratios had a treatment by evaluation interaction (P = 0.02), in which all treatments exhibited increasing patterns throughout the evaluation period due to the seasonality of bahiagrass growth. NDF contents were greater (P = 0.01) in the fertilized and unfertilized treatments (73% both), while bahiagrass-rhizoma peanut treatments had 71% NDF contents.