Brassica Cover Crops for Nitrogen Retention in the Maryland Coastal Plain

Abstract

The Brassica cover crops, forage radish (Raphanus sativus L. cv 'Daichon'), oilseed radish (Raphanus sativus L. cv 'Adagio'), rape (Brassica napus L. cv 'Dwarf Essex'), and cereal rye (Secale cereale L. cv 'Wheeler') were examined for ability to decrease mineral N losses and influence organic N cycling at two Maryland Coastal Plain agricultural sites. Brassicas were similar or superior to rye regarding N uptake and soil profile NOsub3-N depletions (105-180 cm depth). Rape and rye maintained soil porewater NOsub3-N below 3 mg L to the minus 1 throughout spring while radish performed similarly on fine-textured soil, but caused porewater NOsub3-N > 10 mg L to the minus 1 on coarse-textured soil. Dissolved organic N averaged 51% of total N in porewater, but was unaffected by cover crops. Brassicas were as effective as rye in minimizing mineral N losses, but the role of cover crops in managing organic N was unclear.