SOIL SAMPLING PROCEDURES FOR MONITORING POTASSIUM DISTRIBUTION IN GRAZED PASTURES

Nutrient redistribution in grazed pastures occurs primarily via deposi tion of excreta by animals. Because this redistribution is generally n ot uniform, a composite sample of randomly collected soil cores may no t reflect the nutrient status of much of the pasture. To address this limitation, zonal soil sampling, with zones determined by distance fro m shade, water, and supplemental feeders (lounging areas), has been pr oposed as an alternative sampling strategy. This experiment was conduc ted to evaluate the potential of zonal soil sampling for monitoring ex tractable K distribution in grazed pastures. Utility of the zonal appr oach was evaluated by comparing it with a more rigorous, but less prac tical transect sampling procedure. Rotationally and continuously stock ed bermudagrass [Cynodon dactylon (L.) Pers. 'Callie'] pastures were u sed in the study. Ranges of extractable K within a pasture were as gre at as 13-fold (14-181 mg kg-1) after 2 yr of grazing. Extractable K co ncentration was greatest in the one-third of the pastures closest to l ounging areas regardless of grazing method. Data from zonal soil sampl ing described this distribution of soil K. Kriged contour maps constru cted using data from transect soil sampling supported the conclusions made using zonal sampling. We conclude that zonal soil sampling is a u seful and practical tool for describing K redistribution in pastures a nd for improving the utility of soil test results and ferlilizer recom mendations for grazed swards.