Short-Term Soil Responses for an Emulated Loblolly Pine Silvopasture

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, there can be poor nitrogen (N) utilization and adverse environmental impacts associated with fertilization. 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–phosphorus (P)–potassium (K) fertilizer (CF) or pelletized poultry litter (PPL) applied at about midrotation (12 years postplanting). Compared to the control, CF decreased soil pH at depths of 0–10 and 10–30 cm, and PPL increased Mehlich 3 available P at 0–10 cm. Fertilizer responses were found for soil extractable ammonium (NH₄ ⁺)-N, and nitrate (NO₃ ⁻)-N concentrations, mineral N ha⁻¹, pH, and available P but not for diel carbon dioxide–carbon (CO₂-C) flux, total C, and total N. Total soil C, total soil N, pH, and available P decreased with depth, whereas mineral N ha⁻¹ and 1 M potassium chloride (KCl)–extractable aluminum (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.

Keywords:

• Alley crop
• Pinus taeda L.
• plantation design
• silvopasture
• soil nutrients

Acknowledgments

The authors appreciate the efforts of Henry Pearson (USDA-ARS, retired) who designed and planted this experimental area. Perdue AgriRecycle LLC, Seaford, Delaware, USA, donated the Microstart60 pelletized poultry litter. Technical expertise was provided by S. Haller, K. Chapman, J. Whiley (USDA-ARS, Booneville, Ark., USA), and J. Weik (USDA-ARS, El Reno, Okla.). Tom Sauer (USDA-ARS, Ames, Iowa) and Ranjith Udawatta (University of Missouri, Columbia) provided helpful review comments. USDA is an equal opportunity provider and employer. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA.

Notes

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