Nitrate Leaching from Winter Cereal Cover Crops Using Undisturbed Soil‐Column Lysimeters

Cover crops are important management practices for reducing nitrogen (N) leaching, especially in the Chesapeake Bay watershed, which is under total maximum daily load (TMDL) restraints. Winter cereals are common cool‐season crops in the Bay watershed, but studies have not directly compared nitrate‐N (NO3–N) leaching losses from these species. A 3‐yr cover crop lysimeter study was conducted in Beltsville, MD, to directly compare NO3–N leaching from a commonly grown cultivar of barley (Hordeum vulgare L.), rye (Secale cereale L.), and wheat (Triticum aestivum L.), along with a no‐cover control, using eight tension‐drained undisturbed soil column lysimeters in a completely randomized design with two replicates. The lysimeters were configured to exclude runoff and to estimate NO3–N leaching and flow‐weighted NO3–N concentration (FWNC). The temporal pattern of NO3–N leaching showed a consistent highly significant (p < 0.001) effect of lower NO3–N leaching with cover crops compared with no cover but showed only small and periodically significant (p < 0.05) effects among the cultivars of barley, rye, and wheat covers. Nitrate‐N leaching was more affected by the quantity of establishment‐season (mid‐October to mid‐December) precipitation than by cover crop species. For example, compared with no cover, winter cereal covers reduced NO3–N leaching 95% in a dry year and 50% in wet years, with corresponding reductions in FWNC of 92 and 43%, respectively. These results are important for scientists, nutrient managers, and policymakers because they directly compare NO3–N leaching from winter cereal covers and expand knowledge for developing management practices for winter cereals that can improve water quality and increase N efficiency in cropping systems. Core Ideas Nitrate‐N leaching was lower with winter cereal cover crops than without covers. Nitrate‐N leaching was similar among the cultivars of barley, rye, and wheat. Fall rainfall quantity had larger effects on NO3–N leaching than cover crop species. Winter cereal covers reduced NO3–N leaching 95% in a dry year and 50% in wet years.