Spatial Distribution of Inorganic Nitrogen in Pastures as Affected by Management, Landscape, and Cattle Locus.

Abstract

Uneven spatial distribution of soil N in conventionally managed pastures is a function of various biotic and abiotic factors and results in poor land use efficiency. In this study, we measured soil inorganic N (at depths of 0-5, 5-10, and 10-20 cm) in a 50-m grid and specific areas of interest from eight conventionally managed beef pastures (∼17 ha each), four near Eatonton and four near Watkinsville in the southern Piedmont of Georgia, USA, to assess the effects of management, landscape, and cattle locus in spatial distribution of soil inorganic N. Significant spatial autocorrelation was observed in the soil inorganic N indicating that the regions of high inorganic N deposition were near (within 91 m of) one or more pasture equipage (hay, shade, and water). In the Watkinsville pastures, inorganic N was 65% higher within 5 m of shade than the rest of the pastures, down to a 10-cm soil depth. In the Eatonton pastures, inorganic N (0-5 cm) was 22% higher within 30 m of a hay-feeding areas than the rest of the pasture. Cattle locus calculated as cattle density (cow ha yr) was a function of pasture equipage and had a significant positive relationship with soil inorganic N. Landscape parameters (slope and elevation) significantly affected inorganic N distribution; however, the effect was small and was masked by management factors. Our results suggest that strategic placement of pasture equipage (hay, shade, and water) can effectively distribute N where needed in beef pastures, thereby increasing land use efficiency.