Short-Term Soil Responses for an Emulated Loblolly Pine Silvopasture

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.