Nitrogen Dynamics Affected by Management Practices in Croplands Transitioning from Conservation Reserve Program

Management practices are needed to reduce N losses from croplands converted from Conservation Reserve Program (CRP). We evaluated the effects of irrigation, tillage, cropping system, and N fertilization on surface residue N, soil total nitrogen (STN), NH 4 –N, and NO 3 –N at the 0‐ to 85‐cm depth in a sandy loam from 2005 to 2011 in croplands converted from CRP in western North Dakota. Treatments were two irrigation practices (irrigated vs. non‐irrigated) and six cropping systems (CRP, conventional till malt barley [ Hordeum vulgaris L.] with nitrogen fertilizer [CTBN], conventional till malt barley without nitrogen fertilizer [CTBO], no‐till malt barley–pea ( Pisum sativum L.) with nitrogen fertilizer [NTB–P], no‐till malt barley with nitrogen fertilizer [NTBN], and no‐till malt barley without nitrogen fertilizer [NTBO]). Surface residue N was greater in non‐irrigated CRP than irrigated and non‐irrigated CTBN, CTBO, and NTBO and non‐irrigated NTB–P. Soil total N at 0 to 10 cm was greater in irrigated CRP, but at 0 to 85 cm was greater in non‐irrigated NTBN than irrigated CRP, CTBN, CTBO, and NTBO and non‐irrigated NTB–P. Soil NH 4 –N content at 0 to 20 cm was also greater in irrigated CRP than irrigated and non‐irrigated CTBO, NTB–P, and NTBO. Soil NO 3 –N at 0 to 85 cm was greater in NTB–P than CRP, CTBO, and NTBO. Because of increased soil N sequestration and NO 3 –N level, irrigated NTB–P may be used to reduce soil N losses and optimize N availability compared to other treatments in croplands converted from CRP.