Nitrogen and phosphorus leaching under the potential biennial oilseed plant Lepidium campestre L. in a field trial

Domestication of biennial Lepidium campestre L. offers possibilities for more varied crop rotations in cold regions, with increased crop cover during winter. In the first winter after sowing, L. campestre can reduce nitrogen (N) leaching before harvesting in the second year. In this system no soil tillage is needed during the first year, unlike in systems with annual crops. A three-year leaching study on loam soil in southern Sweden revealed significantly (p?<?0.05) lower flow-weighted mean total nitrogen (TN) concentration in drainage water under L. campestre (5.8 mg TN L^?1) compared with a control treatment (no catch crop and autumn mouldboard ploughing) (9.6 mg TN L^?1). In two years of observations, Lepidium campestre had lower flow-weighted mean TN concentration (6.2 mg L^?1) than a mixed Vicia villosa L. (hairy vetch)/Secale cereale (winter rye) catch crop (10.2 mg L^?1) and rather similar concentration to a Raphanus sativus (oilseed radish) catch crop (5.7 mg TN L^?1), both sown after harvest of the main crop. However, L. campestre appeared to have a negative effect on total phosphorus (TP) leaching, with TP concentration in drainage of 0.05 mg L^?1 compared with 0.01–0.02 mg L^?1 for the other catch crops and the control.