Cover Crop Management Options to Improve Weed Control, Crop Yield and Soil Health

View the project final report

Commodities

• Agronomic: hay, sorghum (milo), wheat

Practices

• Crop Production: conservation tillage, cover crops, cropping systems, no-till
• Education and Training: extension, on-farm/ranch research, workshop
• Production Systems: dryland farming
• Soil Management: soil quality/health

Integrating cover crops (CC) into dryland crop production in the semiarid central Great Plains (CGP) can provide several benefits. This includes reduced soil erosion, improved nutrient cycling, suppression of herbicide resistant (HR) weeds, enhanced crop profitability and improved soil health. Despite these benefits and grower interest in using CC to improved soil health and suppress HR weeds, CC adoption is slow and not widely popular in the CGP because CC utilizes water that otherwise would be available to the subsequent cash crop. Grazing or haying CC can provide economic benefits to offset revenue loss associated with decreased crop yields when CC are grown ahead of a cash crop. This approach could provide an opportunity for dryland producers to build soil health and produce harvestable forage for the region’s livestock. Limited information exists on impacts of utilizing CC for forage on soil health and crop yields in semiarid dryland (non-irrigated) systems. This research and education project was conducted to the fill the critical knowledge gap and provided immediate information needed to address producer questions on sustainable use of CC for forage while maintaining soil health in our semi-arid dryland environment. Field experiments were conducted both on-farm and Kansas State University experimental farms (near Brownell and Garden City) from 2018 to 2022 to investigate forage production potential, water use, weed suppression and cash crop yield penalties associated with growing CC in place of chem-fallow. Treatments at university farms consisted of oats (Avena sativa L.)/triticale (×Triticosecale Wittm.) CCs grown in place of fallow, which were hayed, grazed by yearling heifers, or left standing. Additionally, a flex-cover crop treatment was included where a CC was planted only when soil water content was adequate, and the precipitation outlook was favorable. The on-farm study evaluated effects of grazing CCs on soil bulk density, aggregate stability, and soil chemical properties on three producer fields with paired grazed and non-grazed CCs from 2018 to 2021. Results showed CC productivity varied from year to year. For example, at K-State HB ranch near Brownell, KS, non-grazed CC biomass ranged from 1900 lb/a in 2020 to 3280 lb/a in 2018. Averaged across the study years (2018 to 2022), hayed and grazed CCs removed 63 and 32% of available CC biomass. Across seven on-farm site-years, CC residue after grazing averaged 2210 lb/a compared to 3475 lb/for the non-grazed CCs, representing a 36% decrease in CC biomass with grazing. Grazing days across farms ranged from 25 to 54 days with an average daily gain of 1.2 to 3.11 lb per day. Cover biomass after grazing were not different from biomass measured before grazing, suggesting significant regrowth from the cool season CCs species used in the study. Growing a CC decreased weed biomass by 70 to 98% compared to fallow. Cover crops reduced winter wheat yields compared to fallow in 2- out of 5-years. However, wheat yields were not different among treatments when averaged across the 5-yrs at Brownell, KS. Bulk density, penetration resistance, aggregate size distribution, and mean weight diameter (MWD) of water stable aggregates were not different between grazed and non-graze CCs. Soil pH, soil organic carbon (SOC), nitrate, and phosphorus concentrations did not differ between grazed and non-grazed CCs.  Cover crops tended to increase SOC concentration compared to fallow or initial SOC concentration in some site-years. For example, SOC measured at the surface 0 to 2-inch depth near Hays, KS in spring 2019 was 1.4%, which was significantly less than 2.1% SOC measured in 2021 after two cycles of grazing CCs at this location. Penetration resistance measured after grazing in 2021 averaged 0.36 and 0.34 MPa for the grazed and non-grazed CCs at Marquette, KS. Similarly, penetration resistance averaged 0.52 MPa with grazed and non-grazed CCs at Alexander, KS. The penetration resistance measured across locations and CC management strategies was below the threshold of 2 MPa that will limit root growth. Furthermore, flex-hayed CCs maintained winter wheat yields and significantly increased residue cover and MWD of water stable aggregates compared to fallow. Findings of this research showed CCs can be grazed or hayed in no-tillage (NT) dryland cropping systems with no negative effects on soil properties, wheat and grain sorghum yields compared to standing CCs or fallow.  Therefore, grazing of CCs enrolled in National Resource Conservation Service (NRCS) cost-share programs may be a management strategy for farmers to integrate CCs in dryland cropping systems to balance profitability, increase CC adoption and improve soil health in water-limited production systems. Results of this project provided timely information to western Kansas farmers integrating CCs to grain-based production systems to increase profitability and soil health. Results were shared through four field days at near Brownell and Garden City, KS (> 350 participants), at two on-farm field days (>150 participants). Results were also shared through ten media interviews and 20 research and extension reports (> 3500 downloads New Prairie Press).

1. Determine forage production potential of cover crops in dryland systems.
2. Quantify impacts of removing cover crops for forage on weed suppression, crop yields and soil health
3. Conduct on-farm research to quantify the impacts of grazing cover crops on weeds, crop yields, soil health and profitability in dryland systems.