Summer may seem an odd time to use cover crops because it is the time when the main crops are growing. But summer may be the right opportunity to improve fields with a cover crop. If the soil is wearing out, summer is when a soil-building crop can be a lot more beneficial. Also, if the crop rotation leaves an opening in the summer, using a short cycle cover crop is much better than leaving the field subject to rain erosion and weeds that are going to seed.