Hmmm that sounds like a great idea, but might be a little expensive for large areas. Interestingly, this time of the year, the dew that forms in the early morning can keep crops alive, but only just enough if it rains to wet the soil. The water from the dew must get absorbed through the leaves and maybe wets the soil a little for the surface roots to soak up a little moisture before it evaporates. I have an Oat Crop that was sown when the soil was moist enough back a few months ago, and they get the dew every morning, and they are doing ok. Where these photos were taken, they have not even had a chance to sow seed. If your suggestion is viable and affordable, it could be a good solution though, as long as the crops grown would help pay back the capital cost.