ASK Jeff: The Rodale Institute’s farm manager, Jeff Moyer, answers your hardcore farming questions

How do I manage the velvet leaf in my corn?

Posted March 23, 2004

Dear Jeff,

Enjoy your posts at New Farm. I am looking into getting certified organic, but one concern is that of velvet leaf in our corn. I know the problem is related to some other problem in our soil. Any suggestions?

Thanks,
Roger

Hi, Rodger,

Velvet leaf is not a big problem for me in corn; I do have some spots where I see it but not too much. I tend to see it more often in soybeans. It is a large-seeded weed that germinates from deeper in the soil profile than most annual weeds do, making it more of a challenge than other annuals. The best result I’ve had is by rotating annual crops with hay or forages and by hand-pulling the bad spots to prevent seed from re-infesting the location. It’s one of those weeds where depleting the seed bank is an issue. I’ve copied others here at The Rodale Institute® with this answer in the hopes that they may also have some comments for you. I thank you for reading The New Farm® and my brief articles and wish you the best with your transition to organic.

If I can be of any help, email me again and I’ll do my best.
Jeff

Rodger and All,

Paul Hepperly here, the research manager at The Institute. Just had an additional thought to complement Jeff's comments:

Jeff is getting some real good results with no-till corn and soybean on rolled-down rye and/or vetch. These systems change the weed composition significantly.

For instance, we had a lot of ragweed in our no-till, and in our tilled soybeans we had a lot of foxtail. Generally, the ability of the mulch to control certain weeds in particular and weeds in general is quite amazing.

You may want to experiment with a rye/vetch mixture as a way of getting a good increase in soil nitrogen and stimulating a weed control that requires less cultivation. We are pretty encouraged at the progress in this area.

Sincerely,
Paul

Hi Roger,

Dave, here—one of the researchers at The Rodale Institute®. I’d like to add some more detail to the discussion. There are typically two types of weed control in organic systems: preventive and reactive).

If the velvet leaf weed is already an established problem, then the reactive measure Jeff mentioned is an appropriate control (actively hand cutting areas where the weed infestation in the field is the worse, to keep the plant from producing new seed). This type of control is often overlooked because it is labor intensive, but sometimes it is required. Cutting weeds before they go to seed will greatly reduce future weed problems.

Since velvet leaf is a summer annual, germinating in the spring, a rotary hoeing regime and a spring tine weeder are initial tools for mechanical weed control early on. Pre-plant tillage will promote the annual weed seeds to germinate by exposing dormant seeds to oxygen and sunlight. A pre-plant tillage timed 1 to 2 weeks before planting reduces the weed pressure by stimulating weed growth 1 to 2 weeks before planting and then killing the weeds with a second tillage operation immediately before planting the corn. Sometimes this pre-plant tillage is referred to as "false seedbed" or "stale seedbed tillage" Some use a rod weeder or light harrow for this. A rotary hoe, chain harrow or finger weeder can also be used effectively. If there is a lot of stubble in the field, a disk can be used.

After the corn is planted, pre-emergent tillage (blind harrowing) is done after the corn seed has sprouted but not yet emerged from the soil. The field is harrowed to kill the weeds which have already sprouted, then the corn will emerge soon afterwards. This lets the corn gain a competitive edge on the next germinating generation of weeds. This is effective on annual broadleaf weeds like velvet leaf. The timing of this is usually 3 to 4 days after planting. Ideally, blind harrowing should be done 24 hours before crop emergence. This works best on dry loose soil. During a rainy spring weather spell it's not so good.

The above methods get the weed seed close to the soil surface. The weed seeds that germinate from deeper in the soil have to be managed with inter-row cultivation. This will uproot the small weeds and cut off the larger ones.

If a particular field has a widespread problem, it is probably best to rotate that into a grass or clover hay. When considering and planning your rotation for organic corn, weed seed bank populations are dramatically reduced with rotations that have a higher proportion of grass or clover in the rotation. Depending on your farm rotation plan either a rotational pasture if you have animals or a rotational hay crop worked into the rotation will work. Rotations that have grass in them have been shown to have a 68 percent reduction in the weed seed bank. On the other hand, rotations that don't have grass in them have a 59 percent increase in the weed seed bank.

So the planning of the grass/clover hay or pasture into a rotation is one of the best preventive measures. Using perennial phases in crop rotations combined with mowing or intensive grazing to control perennials and to interrupt the life cycles of annual weeds in cultivated crops is a strategy that helps to maintain weed control in organic rotations. Also managing the frequency that a particular crop is grown within a rotation affects the population of certain weed species. Spread your rotation out as much as possible.

If there is a particular field that has problems with any weed, take it out of production, if you can afford to, and put it into summer fallow. Then, perform frequent tined cultivations during the hot summer months. This strategy can result in desiccation of the weeds and reduction in the population and seed bank. Summer tillage should be as shallow as possible to avoid bringing new weed seeds to the surface. It may be used to control perennials and some deep seeded later germinating summer annuals. Tillage is most effective when the soil surface is dry and the air temperature is high. Summer fallow is typically considered a "last resort" method. Where soil erosion is a high risk, tillage should be integrated with other methods to protect the soil.

If you plan a small grain into the rotation, then inter-sowing and under-sowing with clover in the cereals can also reduce weed growth.

To expand on what Paul suggested: We’ve found a cover crop/no-till scenario to be very effective for weed suppression. In the no-till scenario, the cover crop growing in the field that is then rolled and killed as a weed suppressing mat gives early weed control.

Spring tillage can stimulate the germination of annual weed seeds. With the organic no-till, since there is no disturbance of the soil, many of the typical weeds that show up because of spring tillage are not present. With the rye and hairy vetch cover crops, we obtained early weed control in our no-till corn for 16 days. After that time, the weed pressure from in the slits in the cover crops where the corn was planted became more pronounced. Fortunately, the early weed suppression achieved by the mat of the rolled cover crop was sufficient and did successfully suppress weeds during the most critical period--the early stages of crop growth until canopy formation. After that, you still can go in and cultivate if need be. We’re still working to perfect this "organic no-till," and will keep you informed about new innovations and new results.

Dave

Have some questions to Ask Jeff? E-mail him directly at jeff.moyer@rodaleinst.org.