Latent Heat of Fusion

Last night was a "frost night" on the bogs. The tiny buds have swollen and begun the process of elongation, indicating a tolerance just below 30 degrees Fahrenheit. New Bedford had a record low temp of 34, while the bogs got down to around 21. Brrr. So what is a lonely cranberry farmer to do in the night as he watches the mercury (actually it is colored mineral spirits in todays orchard thermometers) dip towards damaging degrees? It is all in the magic of water. Ah yes, the mysterious and wonderful properties of our abundant water resource. We start the irrigation pumps, and begin the process of building a nice coat of ice on our little vines. It seems ironic, I know, but it works quite well. Many farmers use this technique to protect spring plants from unexpected cold snaps, yet some do not understand why exactly. I saw on strawberry grower profess the ice was an insulating layer. I beg to differ! The protection comes from the water changing its state from liquid to solid. This process gives off what is referred to as the latent heat of fusion, as water changes from a higher energy state to a lower one, latent heat is released, and the temperature should not dip below 32. Now the only trick for the cold, damp grower is to ensure that pump continues to run through the night, because if the water is shut off, then the process will stop and temperatures will drop back towards the critical tolerance. The greater danger is a breeze picking up, and moving across the ice surface, potentially evaporating the precious ice. That can have dire consequences, as this would be an instant hop back up two states, having the reverse effect of fusion, thus robbing our farmers precious plants of their hard earned heat. Alas, it is a long night we have survived again, always followed by beautiful high pressure days. Until next time, keep drinking our tart gift to the juice aisle!