HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Guretzky, J. A. Articles by Brummer, E. C. Search for Related Content PubMed Articles by Guretzky, J. A. Articles by Brummer, E. C. Agricola Articles by Guretzky, J. A. Articles by Brummer, E. C. Related Collections Grazing Management Other Forage Crops Crop Ecology Site-Specific Analysis Spatial Distribution

PASTURE MANAGEMENT

Distribution of Legumes along Gradients of Slope and Soil Electrical Conductivity in Pastures

Dep. of Agron., Iowa State Univ., Ames, IA 50011-1010

^* Corresponding author (John.A.Guretzky{at}erdc.usace.army.mil).

Received for publication May 7, 2003. 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.

Abbreviations: AUM, animal unit month • DEM, digital elevation model • EC_a, apparent electrical conductivity • GIS, geographic information system • GPS, global positioning system