Sources, Transport, and Management of Phosphorus Loss during the Cranberry Harvest

Abstract

Wet (flood) harvesting is essential to commercial cranberry (Vaccinium macrocarpon Ait.) production in Massachusetts, where one‐fifth of the US cranberry crop is produced. However, periodic flooding may lead to impaired water quality in lakes that receive harvest flood discharges. In this study, harvest flood inputs and outputs of P were measured to determine the net flux of P (Mnet) from a 19.2‐ha cranberry bog and its five bog units. Results showed that the cranberry bog was a source of dissolved P (DP) (Mnet = 0.32 kg P ha−1) and a minor sink of particulate P (PP) (Mnet = −0.03 kg P ha−1). For the five bog units, values of Mnet were highly variable, ranging from −0.49 to 1.48 kg P ha−1 with a coefficient of variation of 223% for DP. Variation in Mnet was not strongly related to P fertilizer rate, soil test P, or flood holding time, but was inversely related to the water flux from the cranberry bog to the underlying aquifer. Groundwater concentrations of DP were not statistically different before, during, or after the harvest flood, suggesting minimal subsurface leaching of P to shallow groundwater. Collectively, these findings point to soil P retention in some cranberry bogs, as might be expected in natural wetlands. Although there is potential for subsurface P leaching, the use of select cranberry bogs as filter beds of high‐P floodwater may help to curtail surface water export of P from cranberry agriculture.Core Ideas Wet (flood) harvested cranberry bogs may contribute to water quality problems. Harvest flood P losses varied from 0.49 to 1.48 kg P ha−1 for five cranberry beds. Harvest flood P losses were not related to P fertilizer, soil P, or flood length. Rather, the best indicator of harvest flood P loss was groundwater recharge. Groundwater recharge may facilitate P sorption and reduce harvest flood P losses.