Soil nitrate leaching in silvopastures compared with open pasture and pine plantation

Wide acceptance of silvopasture as an alternative sustainable agricultural system in the southeastern United States will depend on an improved understanding of the tree-forage interactions and recognition of its environmental benefits. The objective of this study was to evaluate differences in soil nitrate leaching in different land-use systems, in north Florida. An 18-yr-old loblolly pine (Pinus taeda L.) plantation was thinned in the summer of 2002 to create a fifth-row thinned, nontraditional intensive pine plantation (FO), silvopastures (HE = fourth-row conventionally thinned with random tree distribution and DO = double-row sets of trees with 15-m wide alleys), and an open pasture (PA). 'Argentine' bahiagrass (Paspalum notatum Flügge.) was established as understory vegetation in HE, DO, and PA. From 2004 to 2005 soil nitrate leaching was sampled and compared in the DO, HE, PA, and FO systems at 0.3 and 1.2 m depths after fertilizer application. Significant nitrate peaks were observed at 0.3 m depth after N fertilizer application in all systems. At the 1.2 m depth, the maximum nitrate concentrations were 67, 18, and 8 mg L(-1), in the forest plantation, open pasture, and both silvopastures, respectively. In general, reduced nitrate leaching at 1.2 m depth was observed in silvopastures compared with other land-used systems. These results are not intended to have a direct bearing on traditional pine plantation management, but rather support the potential role of silvopasture systems in reducing nitrate losses from the soil.