Weed Management

Weed Management

March 30, 2007

Tips for No-tilling Corn on Corn

1. Using residue as a mulch. An advantage of no-till corn on corn is that the residue acts as a mulch and reduces weed emergence, which may reduce the need for herbicide applications. Tillage “plants” surface weed seeds and volunteer corn into the soil. Seeds left on the soil surface are less likely to grow and more likely to be eaten by wildlife.

2. Preplant weed control. Any growing weed is using water and nutrients that could be used by the crop. Scout fields after harvest to determine the need to treat winter annuals. If weed pressure is heavy, fall applications are generally more effective and simplify spring operations. Scout again in early spring to determine if treatment is needed. (See this week's CropWatch story, Controlling Winter Annual Weeds.) Especially in dryland production, use early preplant herbicides to conserve soil moisture. In dry springs this can have a large impact on crop emergence. Many weeds provide habitat for insects such as cutworms that are drawn to green vegetation to lay their eggs.

3. Herbicide resistance management. It's easy to use glyphosate too frequently in a continuous no-till corn system because it may be applied as a burndown as well as a postemerge product. Rotate herbicide modes of action over time or use multiple modes of action in a single application to reduce the chances of weeds developing resistance to herbicides. Spray at label rates, especially paying attention to weed size and additives with postemerge products, to reduce weed escapes and resistance development. Using low rates on large weeds selects a population of weeds that are relatively more tolerant to the herbicide.

4. Consider ridge planting and timely cultivation. The residue clearing devices on the planter can be used to remove most of the weeds and many of the weed seeds from the row and cultivation will clean up the row middles. This mechanical weed control reduces herbicide costs, aids in herbicide resistance management and is popular for organic production. To reduce problems with furrow irrigation, some producers are no-tilling on top of the ridge, reducing the amount of residue moved to the furrow. Timely cultivation will control early season weeds and create loosened soil for rebuilding the ridge later.

5. Consider grazing corn stalks to clean up harvest losses to reduce volunteer corn, particularly if using Roundup-Ready corn. However, livestock may bring in some weed seeds in their digestive systems if they grazed weedy areas in the previous few days. If necessary, put the livestock on a drylot or a “clean” pasture for a few days before turning them into the corn stalks to reduce this problem.

6. Consult UNL Extension EC130, Guide for Weed Management in Nebraska, for recommendations, attributes, and weed responses for herbicides labeled for use in Nebraska and for information on how to plan and implement an integrated weed management strategy, including resistance management.

Mark Bernards
Extension Weeds Specialist - Irrigated Production
Robert Klein
Extension Cropping Systems Specialist
Paul Jasa
Extension Engineer

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