Interseeding Grass and Legume Cover Crops into Early Vegetative Stage Corn

Aug 2019


Three main areas of cover crop interseeding (cover crop species selection, establishment timing, and seeding method) need further research to understand how they interact with modern corn hybrids under Iowa climate and soil conditions. Further exploration of these factors will fill a knowledge gap to guide best management practices for interseeding cover crops into a corn cash crop.


This project will evaluate the effects of interseeded cover crop species, establishment timing and seeding method on corn productivity, to help help clarify treatment effects on:

  • cover crop establishment, biomass accumulation and nutrient uptake;
  • corn growth, productivity and nutrient uptake; and
  • weed community and diversity.


A comprehensive field study will be conducted at the ISU Northwest Research and Demonstration Farm, Sutherland, Iowa, and the Armstrong Research and Demonstration Farm, Lewis, Iowa. Three cover crop species will be used (winter rye, annual rye grass and red clover) with three establishment timings and two seeding methods (drilled or broadcast). Crop growth and development, nutrient uptake, crop reflectance and grain yield will be evaluated.

Researchers will conduct 5 to 10 on-farm trials using a subset of the treatments from the research farm trials that match farmers’ interests and farm suitability. The on-farm trials will compare no interseeding with 1 or 2 additional treatments in a replicated strip trial design throughout the field. Crop growth and grain yield will be evaluated.

Project Updates

December 2019

Field plot layouts have been developed and research farm managers are identifying plot space. Adjustments to the interseeder are being finalized and arrangement made for transporting to research and on-farm locations. A project meeting is being planned for early 2020 with the farm managers to begin the process of identifying on-farm locations and finalizing field plans for the growing season.