U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
2011
Citation
Renewable Agriculture and Food Systems: 27(4); 256–265 doi:10.1017/S1742170511000378
Abstract
Surface-soil structural condition in perennial pastures is expected to be modified by how forage is (a) harvested through haying or grazing and (b) stimulated through source of nutrients applied, as well as by compactive forces, e.g., grazing cattle or hay harvest machinery. Changes in surface-soil condition can affect hydrologic processes that have important implications for plant growth, greenhouse gas emissions and off-site water quality. We determined the effects of harvest management and nutrient source on the rate of ponded water infiltration and penetration resistance in a bermudagrass [Cynodon dactylon (L.) Pers.]/tall fescue (Lolium arundinaceum Schreb. S.J. Darbyshire) pasture on a Typic Kanhapludult in Georgia. During a period when soil was wet (61% water-filled pore space), the rate of water infiltration was 2.8±1.5 times greater when forage was left unharvested as when hayed or grazed (mean ± standard deviation among nine nutrient sourcerharvest management comparisons). During a subsequent period, when soil was dry (28% water-filled pore space), the rate of water infiltration followed the same treatment pattern, but was not statistically different among harvestmanagement practices (1.5 ± 0.4 times greater between unharvested and other systems). Penetration resistance of the surface at 10 cm depth followed the order: unharvested (62 J) < hayed (100 J) < low grazing pressure (119 J) < high grazing pressure (137 J). Water infiltration during the wet period was negatively related (P ≤ 0.01) to soil-water content (r = -0.57), penetration resistance at 0–10 cm depth (r = -0.50) and bulk density at 3–6 cm depth (r = -0.53), but was positively related to surface residue C (r = 0.47) and soil organic C concentration at 12–20 cm depth (r = 0.42). These results suggest that complex soil physical (i.e., aggregation, penetration resistance and infiltration) and biological (i.e., plant growth, surface residues and soil organic matter) interactions occur in pastures. We conclude that well-managed grazing systems with excellent ground cover should have adequate hydrologic condition to promote pasture productivity and limit environmental contamination from runoff. Further work is needed to understand the linkages between field- and watershed-scale hydrology in perennial pastures and their implications on water quality.
Comments
U.S. Government Work