Submitted to: American Society of Animal Science Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/13/2006
Publication Date: N/A
Technical Abstract: To evaluate cattle grazing effects on the potential for sediment and nutrient loading of surface waters, forage cover, sward height, and mass and manure cover were measured in pastures with different grazing management systems. Six 12.1-ha cool-season grass pastures were assigned one of three treatments; continuous stocking with unrestricted stream access (CSU), continuous stocking with stream access only at a reinforced crossing (CSR), or rotational stocking (5 paddocks; RS). Pastures were stocked with 15 fall-calving Angus cows (615 kg) from May through October, 2005. Forage sward height, determined with a falling plate meter (4.8 kg/m2), and mass, determined by clipping a .25-m2 area, and the proportions of bare and manure-covered ground, determined by a point line procedure over 16.1 m, were measured monthly from open and congregation sites on the stream banks and at distances of 0 to 33.5 m, 33.5 to 67 m, and greater than 67 m from the stream banks. The proportion of ground that was bare (P<0.05) was greater in congregation than open areas in July through October. The proportion of ground covered with manure was greater (P<0.05) in congregation than open areas in August through October. Forage mass was lower (P<0.05) in congregation than open areas in June and August through October. Pastures with CSU had greater (P<0.05) proportions of bare soil in October, greater (P<0.05) manure cover on the banks and 0 to 33.5 m from the banks, lower (P<0.05) sward heights on the banks in June and October and lower (P<0.05) forage masses on the banks and 0 to 33.5 m from the banks in October than CSR pastures. In October, RS pastures had greater (P<0.05) proportions of manure-covered ground and lower (P<0.05) forage sward heights and masses on the banks and 0 to 33.5 m from the banks than CSR pastures. Results imply that limiting access to streams to stabilized crossings or using rotational grazing may decrease the potential for sediment and nutrient loading to surface waters.