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Study: Buckwheat cover suppresses weed growth
By KEVIN WALKER
Michigan Correspondent

 
ITHACA, N.Y. — Weeds are a continual problem for growers, and scientists are always on the lookout for better ways to control them.
A recent study published in the latest issue of Weed Science provides more evidence that buckwheat used as a cover crop is effective at controlling certain weeds without harming the crop.

Buckwheat cover cropping can reduce both the emergence and growth of weeds, thereby presenting an easy and economical alternative to herbicides, according to the study, called Suppression of Powell Amaranth, Shepherd’s Purse, and Corn Chamomile by Buckwheat Residues: Role of Nitrogen and Fungal Pathogens.

“In terms of just weed suppression, it’s a good thing to do,” said Robin Bellinder, one of the authors of the study and a professor in the horticulture department at Cornell University. “You just have to be careful of what you plant behind it, especially if it’s vegetables. Grains aren’t a big concern.”

According to the study, initial low nitrogen (N) availability after crop incorporation is one possible mechanism of weed suppression. Buckwheat can take up N during growth and immobilize N after incorporation, thus reducing soil N. Initial low N availability during the early life stages of plant development might inhibit the growth of weeds more than crops, because germination and early growth of many weeds is stimulated by N. Many crops, however, have larger seeds, which contain enough N to establish themselves at low soil N levels.

In addition, incorporation of buckwheat residues may stimulate fungal pathogens that may selectively attack weed seeds and seedlings.

In studying three weed species, the researchers – including graduate student Virendar Kumar, Professor Dan Brainard of Michigan State University and Bellinder – found that buckwheat induced changes in N accounted entirely for the suppression of weed growth. Suppression of weed emergence, however, varies by species.

Bellinder pointed out growth of weeds is one thing in the study, emergence quite another. Thus, fungal and N effects accounted for suppressed emergence of corn chamomile and shepherd’s purse, but the mechanism of suppression for Powell amaranth emergence remained unclear.

The same authors did a similar study two years ago, that time looking at the effects of buckwheat residue and several other cover crops on hairy galinsoga and several vegetable crops. Hairy galinsoga is a problematic weed in New York.

“In this study, we saw significant suppression of both galinsoga and vegetable crops, although snap beans were only minimally affected,” Brainard said. “For most vegetables, delayed planting would therefore be recommended. In other work with buckwheat, we’ve seen no suppressive effect on yields of wheat planted into soil with buckwheat residue.

“As with herbicides, the effects of buckwheat are selective. Our continued research aims to understand which weeds are most sensitive and which crops are least sensitive, so that we can successfully integrate buckwheat into vegetable production systems.”

According to Brainard, their work has shown some crops may be adversely affected by using buckwheat as a cover crop, especially if it’s sown into freshly incorporated residue. He said it’s best to wait at least a week for some crops, or not use it at all for others; for example, peas.

To see the most recent study online, download www.allenpress.com/pdf/i0043-1745-56-2-271.pdf

This farm news was published in the April 9, 2008 issue of the Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.
4/9/2008