|WILSON, MELISSA - University Of Minnesota|
|ALLAN, DEBORAH - University Of Minnesota|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2013
Publication Date: 10/4/2013
Publication URL: https://handle.nal.usda.gov/10113/59528
Citation: Wilson, M., Baker, J.M., Allan, D.L. 2013. Factors affecting successful establishment of aerially seeded winter rye. Agronomy Journal. 105(6):1868-1877.
Interpretive Summary: Winter cover crops are recognized as a valuable tool for protection against erosion in annual cropping, but they can be difficult to establish in the northern Corn Belt, due to the brief period between fall harvest and winter. Aerial seeding prior to harvest, either by airplane or helicopter, has been proposed as a way to obtain earlier germination and growth of the cover crop, but success has been mixed. A series of field trials was conducted over a 3 year period in multiple fields in southern MN. A range of variable was measured in 31 fields that were aerially seeded, in an attempt to determine which factors were most correlated with successful etablishment of winter rye. Rye biomass at the time of ground freezing was measured in all fields. Of all other variables measured, the amount of precipitation in the week after seeding was found to be the best predictor of success in establishing the cover crop, although even it only accounted for 43% of the variation in biomass. A separate laboratory test was conducted to determine the optimum moisture level for rye germination in three different soil textural classes. It showed that total germination decreased with decreasing water potential in a sandy loam, but in the finer textured clay an dsilt loam, germination was more sensitive to water content than water potential, suggesting that hydraulic conductivity was the limiting factor. Overall, we conclude that practioners of aerial seeding of winter cover crops will have the best chance of success if seding is timed just before expected precipitation.
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.