Phosphorus Forms for Cranberry Production

Abstract

Commercial cranberry (Vaccinium macrocarpon Ait.) soils are high in iron and calcium and have low pH. This soil chemistry causes conditions where phosphorus is tightly bound and is, to a large extent, unavailable to the cranberry plants. In theory, P forms that directly enter the plant (foliar), or that do not quickly dissolve to become rapidly immobilized (organic, slow-release, other insoluble forms) could be more efficient for cranberry production. To test this hypothesis, two separate sets of field plots, one comparing 19 kg P/ha from sole P sources (all received 22 kg·ha–1 each N and K2O as ammonium sulfate and potassium sulfate) and the other comparing “complete” N–P–K fertilizers containing P, were established at six locations on three cranberry cultivars. Experiment #1 showed that, over all locations, there were no differences in mean yield for plots fertilized with triple super phosphate (current practice), foliar, or rock phosphate. However, fruit rot levels differed by treatment. In Experiment #2, organic forms (except bone meal) gave the lowest yields, while rock phosphate plots had the greatest yields. These field studies indicated that, while some organic P sources may not be suitable for cranberry production, low-leaching P forms such as bone meal and rock phosphate were as effective for cranberry production as the more-soluble triple super phosphate.