Agronomy and Horticulture Department


Date of this Version



Published in Agronomy Journal 96:547–555 (2004).


Legumes establish and persist on backslope landscape positions but fail on summits and toeslopes in southeastern Iowa pastures, suggesting that these pastures be managed site specifically. Visual delineation of landscape positions, however, can be difficult, and char- acterization of spatial variability through soil sampling is expensive. Creation of digital elevation models (DEM) and apparent soil electrical conductivity (ECa) mapping are inexpensive alternatives to de- scribing field conditions. Our objective was to examine the relationships of DEM-derived slope, soil ECa, and legume distribution in pastures.We examined these relationships across four 1.4-ha pastures. Each pasture was divided into 0.46-ha plots that were assigned one of three stocking treatments: continuous, rotational, and nongrazed. We found that legumes, as a percentage of pasture cover,were greatest at 15 to 20% slopes and intermediate values of soil ECa. The absolute ECa value at which legumes were maximized varied by plot within each stocking system and year ECa was measured. When ECa was standardized by pasture and year, however, a nonlinear response curve explained 23 to 42% of the variation of legume cover across the plots. Grazing reduced competition from smooth brome (Bromus inermis Leyss.) and reed canarygrass (Phalaris arundinacea L). These grasses dominated at 0 to 8% slopes and where ECa was either low or high in value. We concluded that slope and soil ECa data are useful in identifying sites where legumes are successful in pastures and showed potential for use in site-specific management of pastures.