Most sandy soils in the southeastern US have low water and nutrient retention capacity and are prone to nitrogen (N) leaching. Use of leguminous cover crops (CC) may enhance soil quality, reduce N-fertilizer requirements, and enhance water and nutrients retention, thereby decreasing nutrient loading on groundwater resources. The effects of CC crops on crop N requirements, yield, weed control, soil quality and N leaching were studied for different production systems and locations. Sunn Hemp performed well across environments and produced 7-12 MT/ha in 12-14 weeks. In S-Florida, on-farm trials showed that following Sunn Hemp directly with either tomato or pepper crop provided 100-144 kg N/ha thereby reducing crop N-requirements by 50-75%. It also increased overall tomato yield by 27 to 44%. In N-Florida, up to 80-90% of the N from Sunn Hemp was lost within 2-4 weeks. Using a Hairy Vetch/Winter Rye CC mix resulting in a biomass production 5.5 and 11.5 Mt/ha during 2004 and 2005, respectively. Although following Sunn Hemp with a winter CC may reduce N losses, net N benefits were only 45 kg N/ha. Based on these results we redesigned our system and followed summer CC directly by a commercial fall crop. Pearl Millet and Cowpea generated 6 and 4 Mt/ha, respectively and these crops were followed with Broccoli supplemented with 0, 67 and 100%N. In the absence of inorganic fertilizer, Cowpea stimulated initial growth where as Pearl Millet appeared to enhance nutrient retention and it's use increased crop yield and reduced N requirements by 33%. Use of CC did not greatly enhance Soil Organic Matter but increased Particulate Organic Matter and C:N ratio values. Use of cover crops reduced weed growth by up to 90% with a combination of Winter and Summer CC being the most effective in providing consistent weed control.