Comparing methods for overseeding winter rye into standing soybean

Authors: WILSON, MELISSA - THE COMMUNITY COLLEGE OF BALTIMORE COUNTY; BAKER, JOHN; ALLAN, DEBORAH - UNIVERSITY OF MINNESOTA; PAGLIARI, PAULO - UNIVERSITY OF MINNESOTA

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2019
Publication Date: 7/1/2019
Citation: Wilson, M., Baker, J.M., Allan, D.L., Pagliari, P.H. 2019. Comparing methods for overseeding winter rye into standing soybean. Agrosystems, Geosciences & Environment. 2(1):1-7. https://doi.org/10.2134/age2019.04.0023.
DOI: https://doi.org/10.2134/age2019.04.0023

Interpretive Summary: There is great interest in the use of winter cover crops as a conservation tool in the US Corn Belt, but they can be difficult to establish because there is often little time between fall harvest and the onset of winter. Aerial seeding prior to harvest is one option, since it permits the planting of a large number of acres in a short period of time. However, aerial seeding often results in poor stands, so we conducted a field study to determine which factors have the greatest effect on the success of aerial seeding. We aerially seeded 31 sites in southern MN in late summer of 2009, 2010, and 2011 and measured a number of properties at seeding time, as well as the amount of cover crop biomass collected prior to soil freezing. A second study was conducted in the laboratory to determine the sensitivity of the germination of surface-applied seed to soil moisture levels and soil temperature for three different soil types. For the aerially seeded field sites, precipitation during the week following seeding was the most important factor affecting fall biomass production, although it explained only 43% of the variation among sites. The germination study showed that for seed scattered on a soil surface, germination was sensitive to water potential in a sandy loam, but for the finer textured silt loam and clay, water content was more important, with germination decreasing substantially when soil moisture was below a threshold of 0.083 g g-1.The key conclusion is that aerial seeding of winter cover crops will have the greatest chance of success if the seed is applied just prior to a rain event.

Technical Abstract: Establishing cover crops in the corn-soybean (Zea mays - Glycine max) rotation in northern climates can be difficult due to the short time between harvest and freezing temperatures. Aerial seeding into standing crops is one way to increase time for germination and growth. Field studies were conducted to characterize the physical and chemical properties that affect successful winter rye (Secale cereale L.) establishment in corn and soybeans, while a germination experiment was designed to determine optimal temperature and surface soil moisture content needed for successful germination. In the field study, 31 field-scale sites (22 corn and 9 soybean) were aerially seeded in southeastern Minnesota during late-August to early-September of 2009, 2010, and 2011. Above-ground rye biomass was collected prior to ground-freeze and multiple regression analysis was used to relate biomass to multiple soil and weather conditions. Total N uptake was also determined. Overall, precipitation the week after seeding was the most important factor in determining rye establishment, although our model accounted for only 43% of the variation in biomass. The germination study characterized winter rye germination on the surface of three different soils equilibrated to -50, -200, and -500 kPa water potential placed in three low-temperature incubators at 10°C, 18°C and 25°C. Total germination was decreased by decreasing water potential in the sandy loam, but not the clay or silt loam, suggesting that moisture content may be more important than water potential at the soil surface. In general, germination was drastically reduced below a moisture content of 0.083 g g-1.