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 (M net ) 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) (M net = 0.32 kg P ha −1 ) and a minor sink of particulate P (PP) (M net = −0.03 kg P ha −1 ). For the five bog units, values of M net 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 M net 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.

Amounts, forms, and management of nitrogen and phosphorus export from agricultural peatlands

“…Mean TP and DRP concentrations of surface water discharge were 2 and 7 times higher than hydrological inputs, respectively. These results aligned with those from focused investigations of the winter and harvest floods, which showed higher TP concentrations in surface water discharge compared with incoming floodwaters (Kennedy, ; Kennedy et al, ).…”

“…Although incomplete release of the winter flood seems possible, it is more likely that positive differences in Q gw + Δ S for April and May were due to regional patterns of elevated spring groundwater discharge to the cranberry farm (Li, Rodell, & Famiglietti, ). In contrast, the highly negative difference in Q gw + Δ S for October was consistent with harvest floodwaters as sources of groundwater recharge (Kennedy, ; Kennedy, ; Masterson, Carlson, & Walter, ).…”

“…Soils are mapped mostly as Freetown coarse sand and muck (dysic, mesic Typic Haplosaprists; Natural Resources Conservation Service, ), with soil test P of 25.9 to 46.8 mg of P kg −1 (Mehlich‐3) and total N of 0.2 to 0.8 g of N kg −1 at the 0 to 15‐cm depth (Table 1; Kennedy, unpublished data). Soil P saturation (i.e., P/[Al + Fe]) ranges from 9 to 10% for the unrenovated farm units and 15% for the renovated unit FF7 (Kennedy, ). Soils are planted with native cultivars 'Early Black' and 'Howes' with the exception of a 3.16‐ha field, which was replanted with the 'Ben Lear' variety in 2007.…”

“…Hydrological inputs and outputs were identified based on earlier studies of the cranberry farm (Kennedy, ; Kennedy, Jeranyama, & Alverson, ; Kennedy, Kleinman, & DeMoranville, ) and measured or estimated between 1 May 2017 and 30 April 2018. Daily precipitation data were obtained from a National Weather Service gauge (site 192451) at the University of Massachusetts Cranberry Station in East Wareham, Massachusetts.…”

“…We collected monthly samples from the lake and retention pond by manually dipping a sample bottle at roughly the depth of the pump intake screen. For floodwater, we collected three lake water samples during the harvest flood and another three samples prior to the winter flood, based on the relatively low nutrient variation of the incoming floodwaters (Kennedy, ; Kennedy et al, ). We collected samples of surface water discharge as surface (<15‐cm depth) grab samples on a weekly basis, with more frequent sampling during flood discharges (66 samples in total).…”