Cover crops are not planted for harvest and consumption by people (though some cover crops are excellent sources of nutrients for livestock), but for a variety of beneficial purposes such as suppressing weeds, protecting against erosion, adding organic matter and building soil fertility. Because city farmers often cannot leave land fallow for extended periods, and do not have access to tractors or other mechanized equipment, the best cover crops for urban environments are annuals that can be easily incorporated into the soil, through winterkill or hand-powered methods of tilling, such as oats, field peas and buckwheat.
The Cornell University Garden Ecology Project, a community-research partnership based in New York City, provides an information sheet specifically for New York City and Tompkins County/upstate NY gardeners, but pertinent to all urban farmers, on cover crops for urban environments, available for download from the project website at http://blogs.cornell.edu/gep/.
The Sustainable Agriculture Research and Education (SARE) publication, Managing Cover Crops Profitably (3rd Edition), edited by Andy Clark, 2007, has general information on using cover crops for different purposes and includes and charts and profiles of many cover crops with information on planting and management. This publication is available for download or purchase at http://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition.
Cornell University’s “Cover Crops for Vegetable Growers” provides a Decision Tool to help farmers decide which cover crop best suits their needs at http://covercrops.cals.cornell.edu/decision-tool.php.