Spatial Distribution of Soil Carbon and Nitrogen Pools under Grazed Tall Fescue

Cattle ( Bos taurus ) behavior may be an important variable controlling the spatial distribution of soil C and N pools in long‐term, grazed pastures. Shade and water sources are more frequented areas of a pasture that can also serve as camping areas where excreta are deposited. We sampled a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludult) under tall fescue ( Festuca arundinacea Schreb.) at distances of 1, 10, 30, 50, and 80 m from permanent shade or water sources at the end of 8 and 15 yr of grazing. To a depth of 75 mm, soil bulk density was 1.15 Mg m −3 at 1 m and averaged 1.00 Mg m −3 at other distances from shade or water. To a depth of 300 mm, soil organic C was 4.6 kg m −2 at 1 m, 4.3 kg m −2 at 10 m, and ≈4.0 kg m −2 at distances of 30, 50, and 80 m from shade or water. Particulate organic C averaged 1.53 kg m −2 at distances of 1, 10, and 30 m and 1.30 kg m −2 at distances of 50 and 80 m from shade or water. Soil microbial biomass C, basal soil respiration, and net potential N mineralization were also greater nearer shade or water than farther away. Although lateral distribution effects were most dramatic at a depth of 0 to 25 mm, similar effects were observed even at a depth of 150 to 300 mm. Long‐term cattle grazing in relatively small paddocks (0.7–0.8 ha) with permanent shade and water sources resulted in significant lateral and vertical changes in soil organic C and N pools.