Bambo Susan K, Nowak Jarek, Blount Ann R, Long Alan J, Osiecka Anna
Rm. 303S Perry-Paige Building, Florida A&M Univ., Tallahassee, FL 32307, USA.
J Environ Qual. 2009 Jul 23;38(5):1870-7. doi: 10.2134/jeq2007.0634. Print 2009 Sep-Oct.
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.
在美国东南部，要让林牧复合系统作为一种替代性可持续农业系统被广泛接受，将取决于对树木与牧草相互作用的深入理解以及对其环境效益的认识。本研究的目的是评估佛罗里达州北部不同土地利用系统中土壤硝酸盐淋失的差异。2002年夏天，对一片18年生的火炬松（Pinus taeda L.）人工林进行间伐，形成了第五行间伐的非传统集约型松树林（FO）、林牧复合系统（HE = 第四行按常规间伐且树木随机分布，DO = 双行树带，行距15米宽）以及一片开阔牧场（PA）。在HE、DO和PA中种植了‘阿根廷’雀稗（Paspalum notatum Flügge.）作为林下植被。2004年至2005年，在施肥后，对DO、HE、PA和FO系统中0.3米和1.2米深度的土壤硝酸盐淋失进行取样并比较。在所有系统中，施肥后0.3米深度处均观察到显著的硝酸盐峰值。在1.2米深度处，森林人工林、开阔牧场和两个林牧复合系统中的最大硝酸盐浓度分别为67、18和8毫克/升。总体而言，与其他土地利用系统相比，林牧复合系统在1.2米深度处的硝酸盐淋失减少。这些结果并非旨在直接影响传统松树林的管理，而是支持林牧复合系统在减少土壤硝酸盐流失方面的潜在作用。
