Pulse – Wheat Systems Are Economically Superior to Wheat – Only Systems At Reduced N Fertilizer Rates.

Montana cropping has long been dominated by wheat-only systems. Diversifying with water-use-efficient pulse crops may lead to increased net returns while improving soil nitrogen supply. A crop rotation experiment was begun at Bozeman in 2003 to measure change in soil nitrogen and carbon over time, and to make economic comparisons among wheat-only and diversified cropping systems. Seven comparable cropping systems include tillage-based and no-till fallow – wheat systems as well as five annually cropped systems; three of which are alternate year pea – wheat systems. Spring and winter growth habits are included equally in 4-yr rotations and each system is split into full (5 and 6.5 kg per 100 kg of targeted wheat and oilseed yields, respectively) and half recommended rates of N fertilizer. Potentially mineralizable N was measured in 2009; wheat-only systems were 25% lower than pea – wheat systems, but no difference was found between N fertilizer rates. Here we present economic results from the most recent 4-yr cycle (2009-2012). Crop prices and wheat protein premium/discount schedules were considered on a 3-yr running market average preceding harvest. All fertilizer was priced according to a moving 24-month purchasing window prior to seeding. Seed costs were based on industry quotes and machinery and pesticide costs were based on the most recently available price schedules published by NDSU. The pea – wheat system had the greatest total net returns for 4 yr at both N rates ($1,788/ha) but the mean of three wheat-only systems did not differ from the mean of three pea-wheat systems at the full rate of N fertilizer. At half recommended N fertilizer, the three pea-wheat systems averaged $565/ha greater total net returns for 4 yr than wheat-only systems. Soil N supply was enhanced by repeated cycles of pea which protected wheat yield and protein at reduced N fertilizer rates.