|MACKOWN, C - Retired ARS Employee|
Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2011
Publication Date: 6/6/2013
Citation: Burner, D.M., Pote, D.H., Mackown, C.T. 2013. Short-term soil responses for an emulated loblolly pine silvopasture. Communications in Soil Science and Plant Analysis. 44(11):1708-1721.
Interpretive Summary: Long-term (more than 50 years) land use practices can affect soil properties, but changes may be less evident during shorter time intervals. Integrative land use practices like agroforestry are generally thought to maintain or improve soil quality compared to some conventional agricultural practices like, for example, row cropping. The relevance of short-term changes becomes important when land use practices change more often than every 50 years. ARS scientists at Booneville and El Reno studied if fertilization of a grass-pine agroforestry practice affected properties of a Leadvale soil in the short-term (3 years). Compared to an unfertilized treatment, commercial fertilizer increased soil acidity while poultry litter increased soil phosphorus. Fertilization caused transient change in soil nitrogen. The study also documented how properties of this agriculturally important (1.31 million ha) Leadvale soil changed with depth. Growers with similarly overstocked pine stands probably should apply nitrogen only when foliar levels fall below the critical level needed for pine growth, plus additional nitrogen to support growth of alley crops, if any. These results further our understanding of the nutrient dynamics during alley cropping of an upland soil, and should interest land use advisors and professionals as they provide insight into fertilization impacts for pine agroforestry practices.
Technical Abstract: Pine (Pinus spp. L.) stands are often overstocked early in the tree rotation, prior to initial thinning. While pre- and/or post-thinning fertilizer applications are best management practices to optimize growth of southern pines, fertilization has questionable economic value due to poor N utilization and adverse environmental impacts. Our objective was to determine short-term (3-year) soil responses of an emulated loblolly pine (P. taeda L.) silvopasture which received a single application of commercial N-P-K fertilizer (CF) or pelletized poultry litter (PPL) applied at about mid-rotation (12 years post-planting). Compared to the control, CF decreased soil pH at 0-10 and 10-30 cm depths, and PPL increased extractable P at 0-10 cm. Fertilizer responses were found for extractable NH4-N, and NO3-N, mineral N, pH, and Mehlich 3 available P, but not for diel CO2-C flux, total C, and total N. Total soil C, total soil N, pH, and Mehlich 3 available P decreased with depth, while mineral N and 1 M KCl extractable Al increased with depth. These results further our understanding of the nutrient dynamics during alley cropping of an upland soil, and demonstrate the challenge in detecting short-term responses with fertilization.