Effect of Length of Interval Between Cereal Rye Cover Crop Termination and Corn Planting on Seedling Root Disease and Corn Growth.

Cereal rye cover crops terminated immediately before corn planting can sometimes reduce corn population, early growth, and yield. We hypothesized that cereal rye may act as a green bridge for corn pathogens and may increase corn seedling root disease. A field experiment was conducted over two years to determine whether the length of the interval between cereal rye termination and corn planting affected incidence of seedling root disease and reduced corn population, growth, and grain yield. A cereal rye cover crop was terminated 25, 14, 10, or 3 days before planting or 1 day after planting and was compared with corn without a rye cover crop preceding it. Measurements of plant population were taken at multiple dates until emergence was complete. At fourth or fifth leaf stage corn plants were dug up and evaluations of root infections and fungal pathogens were made. Additionally at plant maturity plant population and number of barren plants were determined. Whole plant samples were also taken for total plant weight and yield parameters. Corn was harvested in October with an instrumented combine to determine grain yield. Some of the results from the first year follow. Grain yield of the rye treatments terminated 3 days before corn planting (DBP) and 1 day after planting (DAP) were significantly less than the no cover crop treatment. Rye terminated 10, 14, or 25 DBP did not significantly reduce yield. The rye treatment terminated 1 DAP also had fewer plants and ears at harvest (Pr < 0.10). Early plant samples taken at 5th leaf stage showed that corn shoot height, shoot dry weight and radicle length were reduced (P <0.10) following rye compared to no rye. Radicle disease incidence, radicle disease severity, and Pythium incidence were greater (P <0.01), while the incidence of Fusarium did not differ, in corn following rye compared to no rye. Radicle infection and Pythium incidence were reduced in treatments where rye was terminated 21, 14 and 10 DBP compared to 3 DBP, and 1 DAP. Fusarium incidence was less in most treatments than where rye was terminated 1 DAP. The length of the time interval after cereal rye cover crop termination impacted quite a few of the parameters measured and seems to be related to root infection and pathogen presence. Understanding how rye termination date affects corn seedling disease and yield will enable improved management practices to ensure optimum use of cover crops in a corn farming system.