Litter decomposition and mineralization in bahiagrass pastures managed at different intensities

Plant litter is an important nutrient pool in grassland ecosystems. Management practices affect litter quality and may affect nutrient dynamics in pastures by altering the rates of nutrient mineralization and immobilization. The effect of management intensity on litter decomposition and nutrient disappearance was evaluated in a litter bag study on continuously stocked 'Pensacola' bahiagrass (Paspalum notatum Flugge) pastures growing on Pomona and Smyrna sands. Treatments were three management intensities: Low (40 kg N ha(-1) yr(-1) and 1.3 animal units [AU, one AU = 500 kg live weight] ha(-1) stocking rate [SR]), Moderate (120 kg N ha(-1) yr(-1) and 2.7 AU ha(-1) SR), and High (360 kg N ha(-1) yr(-1) and 4.0 AU ha(-1) SR). Litter relative decomposition rate (k) was greater for High (0.0030 g g(-1) d(-1)) than Low (0.0016 g g(-1) d(-1)). Litter N, acid detergent insoluble N (ADIN), and lignin concentrations were greater for High than the other intensities at the end of the 168-d incubation period because of faster decomposition of soluble compounds. Across management intensities, approximately one-half of litter N remaining at the end of the incubation period was bound to acid detergent fiber (ADF). Net N mineralization through 128 d of incubation was only 200 to 300 g kg(-1) of total N. Increasing management intensity resulted in faster litter turnover and greater nutrient release, but nutrient release from litter was small and significant quantities of nutrients were immobilized even under the most intensive management.