Reestablishing the use of buckwheat as a precise weed control tool

2007 Annual Report for LNE05-214

Project Type: Research and Education
Funds awarded in 2005: $103,235.00
Projected End Date: 12/31/2008
Region: Northeast
State: New York
Project Leader:
Dr. Thomas Bjorkman
Cornell University

Reestablishing the use of buckwheat as a precise weed control tool


Buckwheat is a traditional tool for weed control, but knowledge of how to use it effectively is being lost. Current guidance is overly general, missing important details needed to incorporate it effectively into farming systems. Through this project, more growers will use buckwheat effectively by knowing the situations where is works best and detailed procedures to succeed.
We will provide the needed information through four approaches.

First, we will document traditional knowledge of the art of weed control with buckwheat through interviews and gray literature. Second, we will identify the questions growers most need answered to try the method, and do field trials to provide answers with the degree of detail expected of other weed control methods. These include the target crop, the weeds that are controlled and not controlled, seeding rates, and the timing of use relative to the climate and to weed and crop development. Third, we will engage about 60 growers to test and demonstrate the effectiveness. Finally, we will produce a definitive grower-friendly information set for the Northeast that will be in archival form so that it is available indefinitely. It will be promoted through field days, grower conferences, mailings, and publications in trade magazines and extension newsletters.

We are examining the following best uses:

Bringing abandoned land or old pasture into production using buckwheat to suppress summer annuals and to make the soil friable.

Before a late-summer seeding of alfalfa or alfalfa/grass to suppress quackgrass and winter annuals, and to leave a weed-free friable soil for rapid establishment of small alfalfa and timothy seeds.

Between early-harvested vegetables and overwintered crops to suppress annual weeds and maintain tilth.

Before strawberries, in which weed control is a great expense. Used with a winter grain to disrupt perennial weeds, to suppress annuals, and to reduce the weed seed bank.

The performance target is to have 100 growers in the Northeast using buckwheat as a cover crop successfully in situations where they did not use it previously by the 2008 growing season.

Objectives/Performance Targets

The performance target is to have 100 growers in the Northeast using buckwheat as a cover crop successfully for weed management in situations where they did not use it previously by the 2008 growing season.


1. Five Core Advisors and 150 prospective Intensive Engagement growers consulted. (winter-spring 2005)

Completed and reported in 2006.

2. Five Core Advisors and 60 Intensive Engagement growers have identified unknowns. (Spring 2005)

Completed and reported in 2006.

3. Answers to growers key questions discovered through field trials (summer 2005- Fall 2006)
Most reported in 2006, but some trials were extended into 2007.
Issue 1. What is the effective range of seeding times?
The range of planting dates over which buckwheat cover crops can be established was tested by making sequential plantings every 2 weeks from May 15 to September 15. Early seeding resulted in slow initial growth, with initial growth increasing in each successive planting until mid-August. Ground cover at 3 weeks increased from 50% in the first planting to 85% in the last. Seeding from mid-June through mid-August produced maximal buckwheat biomass. Planting in mid-August resulted in good early growth, but plants stopped growing in September. One June planting did poorly because the soil was too dry for germination. Therefore, buckwheat cover crops can be planted to control weeds any time from late May until mid-August. If it is used as part of full-season cover cropping, June planting is ideal.
Issue 2. What is the necessary field preparation to obtain good growth and weed suppression?
Trial A. Establishment of alfalfa/timothy. For the second year, replicated randomized complete block trial was established to test buckwheat before alfalfa/timothy. The treatments are with and without buckwheat before seeding, and also buckwheat sown as a nurse crop and killed by frost. Buckwheat treatments inhibited fall growth of the forage crops by 50 to 80%, and provided no better weed control in the fall than treatments without buckwheat. Establishing a stale seedbed with herbicide was superior for crop growth and for weed suppression. Replacing the herbicide with tillage or with buckwheat stimulated subsequent weed growth. Following the stale seedbed with a buckwheat nurse crop only inhibited crop growth but not weed growth. Where weeds had been managed by cultivation before seeding, a buckwheat nurse crop did suppress fall weeds. If the forage species catch up in the spring, a buckwheat nurse crop may be useful for growers who control weeds with cultivation rather than herbicides before planting their forage. First-cutting hay data will be collected this summer. However, buckwheat has no benefit when grown before seeding alfalfa and timothy.

Trial B. Establishment after early vegetables.

i. How much tillage is necessary? Incorporating crop residue with a disk was necessary and sufficient tillage. No-till planting stunted the buckwheat.

ii. How long after incorporating the crop residue must one wait to sow the cover? In the dry years (2005 and 2007) sowing immediately after incorporation was too soon, resulting in a low population and spaces where weeds could grow. One week was enough of a wait, less may be all right. In the wet year (2006), no wait was necessary. Waiting more than one week was undesirable, because it allowed weeds to germinate.

iii. How much weed control can be achieved? A good buckwheat stand eliminated all weeds. Where the ground was disked, then planted after 1 week, weed biomass was reduced by 99% (dry year) or 90% (wet year) relative to the weedy control. The wet year (2006) had about 4 times as heavy weed pressure.
Issue 3. Which herbicides carry over to injure buckwheat?
Field trial. Buckwheat was seeded after spraying the soil with 13 different herbicides used in early vegetables. Carryover was simulated by waiting seven weeks after spraying, lighly disking the soil and sowing to buckwheat. The amount of stunting of buckwheat was measured one and two weeks after sowing, and the dry weight at 2 and 4 weeks measured. Buckwheat was not stunted significantly by carryover of ten of the herbicides. It was stunted severely by Refex, Sandea and Pursuit.
Trials by others. Carryover problems can be expected with same-season use of Command.
Issue 5. Which weeds are suppressed, and which weeds escape?
Over three years of trials, we found that purslane and nightshade were completely suppressed. Galinsoga suppression was complete in some trials and poor in others. The first weeds to escape where the buckwheat stand was weak were redroot pigweed, lambsquarters and barnyardgrass. Ragweed suppression was excellent, yet populations were high in the subsequent crop.
The only weed suppressed after buckwheat incorporation is Powell amaranth, perhaps by allelochemicals.
One concern we discovered was that summer pea emergence was suppressed if sown immediately after incorporation of buckwheat.
Trial D. Weeds observed in buckwheat stands were primarily lambsquarters in stands planted before late July; in later plantings, pigweed and grasses became more common.
Issue 6. Management of volunteer buckwheat.

4. Intensive Engagement group tries buckwheat cover crop and reports reasons for success or failure, and identifies new information needs. (Ten in 2006 and 30 in 2007).
One tried buckwheat in 2005. Ten tried buckwheat and our draft instructions in 2006. Six vegetable, two strawberry and two idle.

Thirty four growers participated in 2007. Their evaluations are being returned during winter 2008.

5. Five hundred growers have heard about project through early publicity (Fall 2006)
We reported previously about 350 farmers reached by 2006, and now reached at least 150 more through newsletter articles and presentations during 2006.

6. 2000 have heard about project results. Definitive literature is generally available in grower homes, extension and consultant offices, libraries and online archives. (Fall 2007)
Project results were presented in a workshop at the NOFA-NY Winter meeting (70 growers, Jan 2007), and the NY Fruit and Vegetable Expo (50 growers, Feb 2007), the New England Vegetable and Fruit conference (200 growers, Dec 2007), the Empire State Fruit and Vegetable Expo (70 growers, Jan 2008).
Articles were published in extension newsletters throughout the Northeast in late spring and early summer 2007 reaching 500 to 1000 growers.

Literature is nearly ready for mailing.

7. 100 growers in the Northeast use buckwheat as a cover crop successfully for weed management in situations where they did not use it previously (Summer 2008)

An aggressive publicity campaign in the winter and spring 2008 with targeted information should meet this goal.

Impacts and Contributions/Outcomes

Forty one Northeast growers have used buckwheat as a cover crop in a situation where they have not tried it before.

Additionally, this project has lead to the funding of cover crop research (including buckwheat) from the New York Farm Viability Institute and from the USDA Risk Assessment and Mitigation Program. those projects will allow continuing development and outreach of production practices to address specific management goals.


Robin Bellinder

Cornell University
Department of Horticultre
134a Plant Science
Ithaca, NY 14853
Office Phone: 6072557890
Russell Hahn

Associate Professor
Cornell University
Department of Crop and Soil Sciences
238A Emerson Hall
Ithaca, NY 14853
Office Phone: 6072551759