Update:
On the sites with a larger cover crop, corn yields were higher, the soil was better protected, and soil moisture was higher. Soil moisture was substantially higher on the treatments where the cover crop was killed late. The yields on the loamy sand where the cover crop was killed early were significantly lower than the yields for the late killed cover crop, but not on silt loam soils.
The soybean experiment at Beltsville provided important insight for cover crop interseeding in winter 2018. Fall 2018 had very high rainfall, which provided good conditions for interseeded cover crops, but poor conditions for drilling a cover crop. Under these conditions, the differences between treatments were dramatic. Results indicate that it is possible to interseed a cover crop too early in the year and that planting in October after harvest resulted in substantially lower cover crop biomass than interseeding prior to harvest. Earliest interseeding results showed that there was an ideal planting window likely between the 8/24 and 9/22 dates, when soybean leaves are all yellow, but before they begin dropping. As of March 2019, biomass was harvested from field sites at Beltsville and the Eastern Shore, but the kill date treatments had not yet been applied. Research in 2019 includes harvesting cover crop biomass from each treatment in the first week of April 2019, followed by herbicide application on early killed treatments and harvesting from late killed treatments in the first week of May 2019, followed by herbicide treatment and corn planting.
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