Seasonal soil and foliage nutrient dynamics of a juvenile loblolly pine plantation: Impacts of fertilizer formulation and vegetation suppression

Understanding soil and foliage nutrient dynamics can enhance effectiveness and sustainability of forest nutrition improvement practices. Monthly soil and foliage nutrient concentrations were measured in a juvenile loblolly pine (Pinus taeda L.) plantation in southeastern Oklahoma, USA, in response to: untreated control, herbaceous vegetation suppression (VS), urea and diammonium phosphate (DAP), urea and DAP with VS, and coated urea fertilizer (CUF) with VS. Fertilization treatments persistently increased soil NO3− and foliage N concentrations. All fertilization treatments also reduced foliage P:N and K:N ratios below optimum levels, suggesting that the fertilizer treatments used in this study (which are conventionally applied to mid-rotation loblolly pine plantations of the region) did not adequately match the nutrient demands of this juvenile plantation. Herbaceous vegetation suppression prolonged soil and foliage N increases, prolonged declines in P:N ratios, and increased foliage B and P concentrations in the second year of the study. Fertilizer formulations yielded similar foliage and soil N and P concentrations.