Walls of water time again

Last year I used my walls of water to get a head start on the warm season tomato plants. This season I am starting several weeks earlier than last year, but I have put up the walls of water first to warm the soil above the current 49* F, then I will plant in a few days. I also read that tomato plants appreciate egg shells for their calcium to prevent blossom end rot. I did not have a problem with blossom end rot, but decided to save and freeze egg shells for three months then put them in the soil before planting tomatoes this season. I sprinkled crushed shells in a trench before I set up the walls of water.