Short-Term Economics of Late-Seeded Cover Crops in a Semi-Arid Environment.

While cover crops have many potential benefits, it is important to understand how they can be produced most cost-effectively. A field study was conducted from 2008-2011 to investigate the productivity, soil impacts, and economic performance of cover crop treatments seeded after dry pea (Pisum sativum L.) harvest near Mandan, North Dakota. The cover crop treatments included seven crops in monoculture and in mixtures, and one treatment serving as a no cover crop control. In the year following the cover crop treatments, four response crops [spring wheat (Triticum aestivum L.), corn (Zea mays L.), soybean [Glycine max (L.) Merr.] and dry pea] were seeded in strips across each of the cover crop treatments to measure potential short-term yield impacts of cover crop treatments. This sequence was repeated on three sites with the same soil type.

Costs for establishing cover crops were calculated based on seed costs, along with the cost for no-till planting the treatments. Cover crop establishment costs ranged from $53 to $106 ha^-1. Response crop results showed no impact of cover crops on yields, implying no short-term direct economic benefit, but also no added cost through negative production effects. Consequently, economic analysis focused on the most cost effective treatment producing the most aboveground cover crop biomass per unit cost. Apparent NO₃-N uptake by each cover crop treatment was correlated with biomass production (r=0.74) though apparent NO₃-N uptake and biomass production varied widely among years. Economic analysis of N uptake also identified the most cost efficient treatments for NO₃-N retention. Overall, purple top turnip (Brassica rapa L.) resulted in the lowest average cost per unit biomass and lowest cost per unit N uptake, at $42 Mg^-1 biomass and $2.70 kg^-1 N respectively.