Grazing Intensity and Nitrogen Fertilization Effects on Litter Decomposition and Mineralization on Tifton 85 Bermudagrass Pastures.

    Plant litter is an important nutrient pool in grassland ecosystems. Nutrients in plant litter are released by litter decomposition and mineralization, processes that are related to litter quality. Litter quality is affected by pasture management, and in this experiment a litter bag technique was used to investigate how pasture grazing intensity and fertilization affected litter decomposition and mineralization. This study was conducted in 2006 and 2007 on a loamy, siliceous, hyperthermic Grossarenic Paleudult soil in northern Florida. There were five treatments in two replications of a randomized complete block design. Three treatments reflected varying grazing intensities, with rotationally stocked pastures grazed every 28 d to 8-, 16-, or 24-cm post-graze stubble heights (SH). These pastures all received 250 kg N ha^-1 yr^-1 in five applications of 50 kg N ha^-1. The fourth and fifth treatments were grazed to a 24-cm SH every 28 d, but they received 50 and 150 kg N ha^-1 yr^-1, respectively, providing three levels of N fertilization within a single grazing treatment. After a 128-d incubation period, litter disappearance was greater on pastures grazed to 16- and 24-cm SH (486 and 479 g kg^-1) than 8-cm SH (409 g kg^-1). Litter in pastures receiving 250 and 150 kg N ha^-1 had greater decomposition rates than those receiving 50 kg N ha^-1 (0.00459 and 0.00424 vs. 0.00304 g g^-1 d^-1). These data show that in addition to their effects on herbage accumulation and nutritive value, pasture fertilization and grazing management affect extent and rate of litter decomposition.