Grazing Intensity and Nitrogen Fertilization Affect Litter Responses in 'Tifton 85' Bermudagrass Pastures: II. Decomposition and Nitrogen Mineralization

In many grassland ecosystems, nutrient cycling via plant litter is important for plant growth and persistence. Understanding dynamics of litter decomposition and nutrient release under different management practices is critical to understanding nutrient cycling in grasslands, but this topic has received relatively little attention in C-4 grass pastures. The objective of this study was to determine the effects of grazing intensity (defined as postgraze stubble height, SH) and N fertilization on litter decomposition and N release in 'Tift on 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). Loss of litter mass was most rapid early in the decomposition period. Pasture SH had no effect on decomposition of litter mass, but increasing N fertilization increased decomposition rate. Immobilization of litter N began almost immediately aft er placement in the field regardless of treatment, did not reach its maximum for up to 60 d, and lasted more than 128 d for most treatments. Increasing SH and N fertilization increased N immobilization in plant litter. Nitrogen immobilization in bermudagrass litter occurs across a wide range of pasture management practices, impacting N availability for plant growth.