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Distribution of Legumes along Gradients of Slope and Soil Electrical Conductivity in Pastures
Author(s) -
Guretzky John A.,
Moore Kenneth J.,
Burras C. Lee,
Brummer E. Charles
Publication year - 2004
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2004.5470
Subject(s) - bromus inermis , grazing , agronomy , pasture , phalaris arundinacea , environmental science , stocking , legume , festuca arundinacea , soil science , poaceae , biology , ecology , zoology , wetland
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 characterization of spatial variability through soil sampling is expensive. Creation of digital elevation models (DEM) and apparent soil electrical conductivity (EC a ) mapping are inexpensive alternatives to describing field conditions. Our objective was to examine the relationship of DEM‐derived slope, soil EC a , 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 EC a . The absolute EC a value at which legumes were maximized varied by plot within each stocking system and year EC a was measured. When EC a 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 EC a was either low or high in value. We concluded that slope and soil EC a data are useful in identifying sites where legumes are successful in pastures and showed potential for use in site‐specific management of pastures.