An Alternative to Flooding for the Winter Protection of Cranberries in ME
The usual practice, for winter protection of cranberries in Maine, is to flood the bogs following harvest, a few inches of water and ice being sufficient to protect them from the cold and drying winter winds.
There wasn’t enough precipitation during the summer of 1998, however, to provide adequate water for flooding. This prompted Bert-Sid to look around for alternate means of protection. Together with Charles Armstrong of Univ. of Maine Cooperative Extension, he designed an experiment to test whether snow could serve as well as flooding for a winter cover.
They laid out eight plots in Bert-Sid’s bog, each measuring 6 feet by 6 feet. Three plots (A) were flooded, according to the usual practice, and three others (B), located on a slight rise which put them above the floodwater, were covered with snow—natural snow, if it fell, and manufactured snow if it didn’t. The two remaining plots (C) were left untreated and unflooded, and received only such natural precipitation as fell from the sky. In the spring buds were examined and the survival rate determined.
The experiment was run for two successive winters, 1998-9, and 1999-2000. As it happened, both winters were exceptionally warm and dry, which meant that the B plots had to be repeatedly covered with artificial snow. It also meant that there were substantial differences between conditions on the B and C plots; the latter went through both winters with little protection. During a “normal” snowy winter, the B and C plots would have experienced identical conditions.
Percent of buds surviving undamaged until May, when the sampling was done, is given below:
Treatment 1998-99 1999-2000
A – flooded 93% 90%
B – snow 76% 84%
C – natural 48% 79%
The differences in survival for the winter of 1998-9 are significant at the 95% confidence level; i.e. we can definitely say that that year flooding was substantially more effective than snow, which in turn was better than doing nothing at all.
The following year the differences are smaller, and only that between flooding and no treatment is significant at the 95% confidence level. Why, in particular, the untreated C plots fared so much better the second winter than they did the first, is not clear.
We may conclude, then, that in the absence of sufficient floodwater, some years it will help to cover the bogs with snow, and some it won’t make much difference. Bert-Sid however warns that using an artificial snowmaking machine to keep the bogs covered during warm spells is highly labor-intensive. Using a blanket of snow to protect the bogs appears to be feasible only if sufficient snow falls from the sky, so that none has to be manufactured, the weather stays cold enough that what falls doesn’t melt, and equipment is available to move the snow to where it is needed.