Phosphorus Mobility in Low pH Soils Used for Lowbush Blueberry Production.

Chemical fertilizers containing P are commonly applied to lowbush blueberries to increase fruit yield. This has led to an accumulation of P in these soils and concerns about P leaching into nearby waters. Blueberries are grown in acidic soils but much of what we know about P leaching applies to soils with higher pHs. The goal of this research was to determine the leachability of P in acidic soil (pH 4.5) taken from the Nova Scotia Wild Blueberry Institute. A column study was conducted using soil with a history of either no (control), moderate (46 kg/ha-1), or high P fertilization (92 kg P2O5 / ha–1). One experiment simulated 1000 mm of precipitation over 30 days. The leachate was analyzed daily for soluble reactive P using Ion Exchange Chromatography. No phosphate was detected in any of the leachates. In another experiment, P solutions (50 to 100 mg/L) were added to the columns for 90 days. No phosphate was consistently detected in the leachates. Therefore, P leaching will not likely be a problem in acidic blueberry soils, regardless of the level of P input. Soil before and after the experiments was analyzed for P sorption and Mehlich 3 extractable P. Both methods confirmed that added P was concentrated within the top 5 cm of soil, with little accumulation lower in the soil columns. This indicates that P losses from surface erosion could be a concern in these soils.