Evaluation of Soil Testing Methods for Predicting Growth and Response of Pinus elliottii to Phosphorus Fertilization

Abstract

Soil tests were evaluated as methods for predicting height growth or increased height growth due to P fertilization of Pinus elliottii var. elliottii Engelm. on acid Coastal Plain soils. Growth and response parameters were obtained from field and greenhouse trials fertilized at time of planting with N and P. Field trials were measured 1, 3, and 5 years after planting and the greenhouse trial, which involved unfertilized soils collected from the field trials, was measured 1 and 2 years after planting.The amounts of P extracted by H2O or NH4OAc (pH 4.8) were the most closely correlated with height growth and response to P fertilization after 1 year of growth in both the greenhouse and field. The effectiveness of these methods declined after longer growth periods. Methods which extracted larger amounts of P—0.5M NaHCO3; 0.05N HCl + 0.025N H2SO4; 0.03N NH4F + 0.025N HCl—were more effective predictors of response to P fertilization over growth periods of 3 and 5 years in the field. Phosphorus extracted by 0.03N NH4F + 0.025N HCl was the most closely correlated with response recorded after 5 years (r2 = 0.778).Concentrations of P in the tops of greenhouse‐grown pine seedlings after both 1 and 2 years growth were most closely related to P removed by the stronger extractants. The r2 values for the relationships between soil test values and both concentrations of P in seedling tops after 2 years and in foliage of field trees at age 4 were almost identical.

The North American long-term soil productivity experiment: Findings from the first decade of research

“…With few exceptions (Ballard and Pritchett, 1975;Burger and Kelting, 1999;Froehlich and McNabb, 1984;Gale and Grigal, 1988;Powers, 1980), correlations between soil monitoring variables and potential productivity tend to be anecdotal or regionally restricted in North America, and others used by the Forest Service are mainly conceptual. Because they are conceptual and somewhat subjective, they can be challenged as being too lenient or too stringent.…”

Forest fertilization: Trends in knowledge and practice compared to agriculture

“…Pfertilizer is needed at planting (Pritchett et al 1961), and thereafter a combination of N and P is far better than either nutrient alone (Amateis et al 2000). The concentration of P in an acid extract (Bray2-P) best discriminated between responsive and non-responsive sites at planting (Ballard and Pritchett 1975). Once established, leaf area index (LAI) is the main diagnostic.…”

Assessment of P availability in heavily fertilized soils using the diffusive gradient in thin films (DGT) technique

“…These measurements of immediatelyavailable P fail with plants having high P requirements (Ballard and Prichett, 1975). Under these conditions, the soil's ability to buffer the concentration of P in solution becomes important.…”