Determining Available Soil Phosphorus in Nova Scotia Blueberry Soils

Abstract

A project was initiated to determine the best predictor of plant-available phosphorus (P) for the Nova Scotia lowbush blueberry (Vaccinium angustifolium Ait.) from the following extractants: Mehlich 1, Mehlich 3, Bray 1, modified Morgan, and the anion exchange membrane. The study was initiated in 1999 with three newly established sites; two loamy soils located in South Branch (South Branch and White Fields) and one sandy loam soil in Debert. An established long-term experiment located at the Nova Scotia Wild Blueberry Institute on a sandy loam soil was also used. Soil samples were taken in the spring and at tip dieback (July) or harvest (August) from all sites during the 1999 and 2000 growing seasons. Tissue samples were obtained, with the July and August soil samples, to enable correlation of extracted soil P with the P present in the tissue. Results indicate that at all sites, except the White Field site, correlations between the five extractants and plant tissue were not significant in either year. However, correlation between the individual extraction methods at each site indicates that, with the exception of the South Branch site, all correlation coefficients were significant in both years. These conflicting results show that it would be misleading if a soil P testing program for blueberries was based solely on comparison with a previous soil P extraction method. This would result in a program that was incorrectly predicting the P requirements of the blueberry. Further work on the uptake of P by the blueberry plant under conditions of low and high levels of extractable P is required.