Grazing Intensity and Nitrogen Fertilization Affect Litter Responses in ‘Tifton 85’ Bermudagrass Pastures: I. Mass, Deposition Rate, and Chemical Composition

Abstract

Plant litter deposition and composition affect nutrient cycling and sustainability of grazed grasslands, but the effect of management practices on litter responses has not been fully investigated. The objective of this study was to determine the effects of grazing intensity (postgraze stubble height, SH) and N fertilization on existing litter mass, litter deposition rate, and litter chemical composition in rotationally stocked ‘Tifton 85’ bermudagrass (Cynodon spp.) pastures. Three levels of SH (8, 16, 24 cm) were compared at the same interval between grazing events (28 d) and amount of N fertilization (250 kg N ha−1 yr−1). Three levels of N fertilization (50, 150, and 250 kg N ha−1 yr−1) were compared when SH (24 cm) and regrowth interval were constant (28 d). Existing litter mass (1730–2510 kg ha−1) and litter deposition rate (10–30 kg ha−1 d−1) increased as SH increased, but N fertilization had no effect on litter mass or deposition rate. Increasing SH from 8 to 24 cm resulted in lower existing litter N (20.5 vs. 19.2 g kg−1) and lignin (186 vs. 148 g kg−1) concentrations and a greater C/N ratio (24 vs. 26). Increasing N fertilization increased litter N concentration from 11.5 to 19.2 g kg−1 and decreased C/N ratio from 43 to 26, but N had no effect on lignin and acid detergent fiber (ADF) concentrations. Bermudagrass litter quantity was affected more by grazing intensity than by N fertilization, but N fertilization had a greater impact on litter composition than did grazing intensity.