Spatial heterogeneity of herbage response to management intensity in continuously stocked pensacola bahiagrass pastures

Redistribution of soil nutrients often occurs on grazed swards, but the effect of these changes on herbage response is not well understood. This 3-yr study evaluated the effects of a wide range of management intensities on patterns of herbage and soil nutrient responses in continuously stocked 'Pensacola' bahiagrass (Paspalum notatum Fifigge) pastures growing on Pomona and Smyrna sands. The three management intensities were: Low (40 kg N ha(-1) yr(-1) and 1.4 animal units [AU, one AU = 500 kg live weight] ha(-1) stocking rate [SR]), Moderate (120 kg N ha(-1) yr(-1) and 2.8 AU ha(-1) SR), and High (360 kg N ha(-1) yr(-1) and 4.2 AU ha-(1) SR). Responses were measured in three zones based on distance from the watering point (Zone 1, 0-8 m; Zone 2, 8-16 m; Zone 3, > 16 m). Herbage accumulation rate increased as management intensity increased from Low to Moderate in 2 of 3 yr (14 vs. 41 kg ha(-1) d(-1) in 2002 and 17 vs. 42 kg ha(-1) d(-1) in 2003) but was not greater for High than Moderate in any year. Herbage accumulation rate was greater in Zone 1 than 3 (40 vs. 20 kg ha(-1) d(-1) kg ha(-1) d(-1)). Herbage mass was lower in Zone 1 than in Zones 2 and 3 during 2 of 3 yr. Herbage nutritive value increased with management intensity and was greatest in Zone I for Low, but not for the other intensities. Soil P, K, and Mg accumulated in Zone 1 of all management intensities. Across management intensities, soil nutrient concentration and productivity of continuously stocked bahiagrass pastures was greatest in the zone including shade and watering locations, but zonal heterogeneity in nutritive value occurred only in the least intensively managed pastures (Low).