Spring‐planted cover crop effects on weed suppression, crop yield and net returns in no‐tillage dryland crop production

Integrating cover crops (CCs) into dryland crop rotations could provide options for herbicide-resistant (HR) weed control in no-tillage (NT) systems. Field experiments investigatedweed suppression potential of spring-planted CCs and their effects on plant available water, crop yields, and net returns. The CC treatments were implemented during the fallow phase of NT wheat (Triticum aestivum L)-sorghum (Sorghum bicolor Moench)-fallow rotation at two locations: Brownell and Colby, over 3 yr in western Kansas. Treatments were oat-triticale (OT), oat-triticale-pea (Pisum sativum; OTP), spring pea, and fallow. Spring pea aboveground biomass was 3,290 kg ha-1, whereas OT produced 5,640 kg ha- 1 and OTP produced 5,260 kg ha-1. Regardless of location, weed biomass was reduced between 86 and 99% with CCs relative to weedy fallow. Cover crops reduced plant available water at winter wheat planting in three out of the six site-years. Averaged across years, CCs reduced winter wheat yields by 18% compared with fallow at Brownell but not at Colby. Replacing fallow with spring pea increased gross revenue but generated negative net returns because of high cost of herbicide and pea seed. Net return with OT or OTP CCs were negative in four out of six site-years when used strictly for weed suppression. However, net returns were mostly positive when OT ($110-876) or OTP (-$ 110-832) CCs were used as forage. Our results showed replacing fallow with spring-planted CCs for weed suppression in dryland cropping system is profitable only when the CCs are used for forage.