Characterization of Foliar Macro- and Micronutrient Concentrations and Ratios in Loblolly Pine Plantations in the Southeastern United States

Abstract

Abstract Foliar nutrient concentration data collected from pretreatment foliage samples in regional trials extending across the southeastern United States provided a large data set useful for characterizing baseline loblolly pine nutrition for the native range of this species. The range and distribution of the foliar nutrient concentrations and their ratios to nitrogen (N) were characterized using descriptive statistics and frequency distributions. Data were collected from a total of 2,663 measurement plots from 110 studies. Manganese (Mn) was the most variable element (coefficient of variation [CV] = 52%), and N exhibited the least variability (CV = 11%). Nitrogen, phosphorus (P), potassium (K), magnesium (Mg), sulfur (S), copper (Cu), and the ratios P:N, K:N, calcium (Ca):N, Mg:N, S:N, and zinc (Zn):N were normally distributed. Calcium, Mn, Zn, boron (B), and the ratios Mn:N, B:N, and Cu:N were significantly non-normal, with positively skewed distributions. Baseline N, P, and S concentrations and the P:N and S:N ratios were considered potentially limiting to growth, as only the upper quartile of studies achieved the currently accepted adequate values for loblolly pine. Boron could be interpreted as being in sufficient supply or potentially limiting to growth, depending on the adequate value used for comparison. The remaining elements and their ratios to N were within the range of sufficiency reported for other conifers. Target concentrations for S and B and their ratios to N require further investigation, as the recommended values for loblolly pine may be too high.