The Mid-Atlantic region of the United States is a world leader in no-till and cover crops, two major soil health practices. Cover crops are one of the main tools used to promote improved soil health because they not only add above and below ground carbon to the soil ecosystem during the off-season when otherwise the soil would be bare, cover crops also protect the soil from erosion and introduce a much higher level of plant biodiversity than would be possible for most market-oriented commodity farming systems. In Maryland, cover cropping is incentivized to reduce nitrogen (N) loading and estuary eutrophication. Most N leaching occurs during November–May when evapotranspiration is low. Here we describe a decade of research to enhance cover crop effectiveness in reducing nitrogen leaching. Early on, we found an average of 250 kg N/ha of soluble nitrogen entrained in cropland soils after the main cropping season and recognized that deeper soil nitrogen was more susceptible to over-winter leaching. Studies using buried K15NO3 proved that cover crops obtained nitrogen from 2 m depth and transferred some of it to the subsequent cash crop. Evidence showed that cover crop biomass and nitrogen uptake in fall, rather than spring, drive reductions in nitrate leaching. We found that high N uptake in fall prior to winter dormancy requires early planting, which can be achieved by seeding into maturing cash crop canopies using high-clearance equipment or airplanes. The resulting extra 2–3 weeks of warm weather for fall cover crop growth more than compensated for less reliable stand establishment with this method. Policies now incentivize farmers to manage cover crops according to these principles.