Phosphorus Export In Cranberry Floodwaters.

In Massachusetts, wet harvesting of cranberries has been implicated as a major source of P in surface water requiring TMDL implementation.  A widely adopted industry practice, wet harvesting is an efficient means of harvesting cranberries by using a temporary flood, but also represents a significant export of total P (TP) to surface water, with values as high as 2 kg TP ha^-1.  The variation of P export in cranberry floodwaters tends to be related to the to the age and substrate of the bog, with recently renovated mineral bogs generally exporting less TP compared to older organic bogs.  The mechanisms that contribute to higher P export in organic bogs are currently under investigation, but preliminary results suggest elevated soil P and poor drainage as contributing factors.  One characteristic that is consistently observed in both mineral and organic bogs is a peak in TP concentration toward the tail end of the flood release.  Management strategies targeting reduction in floodwater P during these peak times are currently under development with results showing promise in gypsum as a floodwater amendment and in re-routing these high P waters through off-farm filter beds.