Complex sentence: Summer fallow, sometimes called fallow cropland, is cropland usually in semi-arid regions that is purposely kept out of production during a cropping season mainly to conserve moisture for the next season.
Split into simpler sentences: Summer fallow, sometimes called fallow cropland, is cropland that is purposely kept out of production during a regular growing season. Usually this is done in semi-arid regions in order to conserve moisture for the next season.