The rotational effects and economic potential of incorporating fall-seeded pea ( Pisum sativum L.) and lentil ( Lens culinaris Medik) into conventional wheat ( Triticum aestivum L.)-based cropping systems in the northern Great Plains are not well understood. Two 2-yr crop rotation experiments were conducted in central Montana to investigate how winter pea hay, lentil green manure, and lentil grain affects subsequent winter wheat yield and protein content, as well as the economic returns of the systems under no-till conditions. In Exp. 1, a winter pea hay-winter wheat (WP-WW) rotation was compared to fallow-winter wheat (FW-WW) and spring wheat-winter wheat (SW-WW) rotations. In Exp. 2, a winter lentil for green manure-winter wheat [WL(m)-WW] rotation was compared to a winter lentil grain-winter wheat [WL(g)-WW] rotation. Four different rates of N were applied to the winter and spring wheat. Winter wheat yield in the WP-WW rotation was 2193 kg ha -1, which was equivalent to the yield in the FW-WW rotation (2136 kg ha -1), and much greater than the SW-WW rotation (1155 kg ha -1). Averaged over all N rates, the WP-WW, FW-WW, and SW-WW systems had $196, $116, and $41 ha -1 net return, respectively. In Exp. 2, the WL(m)-WW rotation produced greater grain yield and protein content at lower N input levels, indicating a greater N benefit. Nevertheless, the WL(g)-WW system generated $213 ha -1 net profit while the WL(m)-WW system produced $92 ha -1. Therefore, the winter pea cover crop, used for livestock feed, improves the system profitability.
