Before and after: remember the photo on the left (top) from just 3 weeks ago (scroll down if you don’t)? The first organic greenhouse tomatoes (in greenhouse 13) are coming along very nicely.
…And how about the early corn we seeded two weeks ago!
We have been covering fields and irrigating during the early morning hours to protect the crops in the fields from the frost.
Those of you driving by our frozen lower strawberry fields next to Route 5 in the morning have probably wondered, “Why do they irrigate the field and make “plant-cicles”? We spray water on the berry plants to protect them from frost and freezing.
There are three ways that water can transfer heat to protect plants from frost. The first mode is radiation. Water pumped from the pond (river) is warmer than the surrounding air temperature. As the water cools, it transfers energy to the surrounding air, warming it, keeping the temperature around the plants warmer. The second mode is conduction. Conduction is similar to radiation except that, instead of the water radiating its energy to the atmosphere, the energy is transfered directly to the plant. Warmer water spayed on cooler plants creates a temperature gradient between the two. The energy from the warmer water moves to the plant and that increased energy results in an rise in the plant’s temperature. The third and most efficient mode is latent heat. Latent heat is the heat that is either absorbed or given off during the change of water from a liquid to a solid. During this change, 80 cal per gram of water (about 1200 BTUs per gallon) are given off with no change in the water’s temperature (this is due to the decrease in potential energy as the molecules lock into position in the crystal structure of the solid (Miller, 1977)). As water is sprayed onto the plants it freezes, changing phase from liquid to solid and liberating the latent energy which keeps the plants warm!
The greenhouses officially open for the season today and we are all looking forward to a fun, warm, sunny and busy day!
After leaving them to suberize and sprout in the greenhouse for a week, we planted the early poatoes today into the fields. It took the collaborative efforts of Jake, Bill, Charlie (the tractor driver), Mike C., Kristin and Scott to complete the operation over the course of a couple of days.
