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Home > Protecting Our Lands & Waters > Clean Water Fund > Clean Water Research Program > Optimizing Establishment of Cover Crops

Optimizing establishment of corn in cover crops and living mulches to maintain yield while reducing nitrate losses

Principal Investigator: Julie Grossman 
Organization: University of Minnesota, Department of Horticultural Science
Sponsor: Clean Water Fund
Award Amount: $232,244
Start Date: 5/9/2014 | End Date: 6/30/2017
Project Manager: Heidi Peterson

Project Summary Tractor is performing rotary tillage in a cover crop of clover to create rows for planting corn. Alternating strips of tilled soil and clover remain.

This project will test three methods of field preparation for corn with the goal of developing more effective methods to establish corn in cover crops and living mulches. The objective is to reduce negative effects that cover crops and living mulches may have on the early growth of corn seedlings. The three methods include: no-till, strip till, rotary zone till (a novel strip till that is wider but shallower than traditional strip till), and both strip till units together.

Research will focus on eliminating the yield gap between conventional corn and corn produced in a perennial living mulch system. This research will be conducted over two or three growing seasons at the University of Minnesota’s Research and Outreach Centers in Rosemount and Waseca.


Use of winter cover crops can decrease soil erosion, suppress weeds, and minimize the amount of runoff leaving a field. Cover crops have also been shown to improve soil health. However, less research has focused on living mulch systems where the perennial legume cover, such as kura clover or alfalfa, is not completely terminated; rather, strips for planting the cash crops are created either chemically with herbicides or physically with strip tillage. Perennial legumes provide all the environmental benefits of a traditional winter cover crop, but also promote nitrogen fixation and increase the overall amount of nitrogen in the system.

Any plant material grown in the same field as a row crop has the potential to negatively affect crop yield. The goal is to overcome these hurdles and capture the environmental benefits of cover crops and living mulches by understanding and eliminating the mechanism of yield loss.

Project Description

The Rosemount site focuses on an established kura clover living mulch system, while research at Waseca focuses on winter annual cover crops with an emphasis on a cereal rye/hairy vetch mixture. Living mulches are not terminated at the time of row crop planting; instead, strips for planting are created either with herbicides or cultivated. The cash crop is planted directly into the strip.


The general hypothesis is that rotary zone tillage will produce both higher yields and greater environmental benefits than current practices.

Specifically, novel rotary zone tillage will:

  • provide more rapid nitrogen mineralization for the subsequent corn crop,
  • maintain lower nitrate leaching losses,
  • increase active soil carbon pools and microbial activity (both proxies for soil health),
  • provide a more favorable light environment for cash crop seedlings,
  • provide earlier and more consistent emergence, and  
  • result in higher corn yields.

Methods and Data Collection


The following items will be delivered within two years:

  • Results guiding whether to accept or reject the hypothesis regarding the water quality benefits and effectiveness of the cropping systems tested.
  • An extension bulletin providing guidelines for growing living mulch and cover crop systems for corn.
  • Two peer-reviewed journal articles focused on 1) agronomic considerations and 2) environmental benefits (or ecosystem services).

Outreach and Education


  • The University of Minnesota Research and Outreach Centers at Morris, Lamberton and Waseca will host field days focusing on the dual-purpose cropping system.
  • Development and distribution of a dual-cropping system grower’s guide.


  • Support of two graduate students, a postdoctoral research associate, and an undergraduate researcher who are directly involved in the dual-purpose cropping system research.


  • Development of peer-reviewed journal articles
  • On-campus seminars
  • Field days focusing on dual-purpose cropping systems

MDA Contact

Margaret Wagner
Clean Water Technical Unit Supervisor
Margaret.Wagner@state.mn.us ~ 651-201-6488