Evaluation of Annual Legumes as Alternatives to Red Clover for Use as Cover Crops
We initiated a two-year study of annual legumes in summer 2007. The legumes are to be used as green manures, supplying nitrogen (N) to the following corn crop. As a group, they are being compared to medium red clover which has been our cover crop of choice for the last ten years. Although extremely reliable and productive, red clover has some drawbacks including difficulty of terminating the stand before corn and limited potential for harvest as dry hay should additional forage be needed on the farm. The annuals will winterkill, eliminating the need for herbicide to terminate the cover crop before planting corn, and should be harvestable as dry hay.
Annual legumes (berseem clover, annual sweetclover and chickling vetch) were no-till established into wheat stubble in early August alongside medium red clover which had been frost seeded into wheat the previous spring. The experimental design is a randomized complete block with four replicates and individual plots measuring 75 x 75 feet. Aboveground biomass was measured in early November, following a killing frost. At that time, one half of each plot was harvested as dry hay, and forage quality measured. Growing season measurement taken include:
-Western corn rootworm (WCR) beetle abundance in August (this estimates the attractiveness of the legumes to variant WCR during egg laying, and thus the need for rootworm control the next year if the treatment threshold is exceeded.
-Plant height 60 days after planting.
-Biomass and forage yield after killing frost.
-Observations on harvestability (cutting/conditioning, raking and baling) and animal acceptance.
Legume performance data is presented in the accompanying table. [Editor’s Note: For a copy of the table, please contact NCR-SARE at: email@example.com or 1-800-529-1342.] Ample rainfall in August (11.04”) got the legumes off to a fast start and resulted in very high productivity. Precipitation in August averages 3.00” so these results may not be representative for the long-term, but certainly demonstrate potential productivity.
As a group, the annual legumes were less productive (forage and N yield) than red clover as indicated by contrasts. However, both berseem clover and annual sweetclover were productive enough to make them acceptable, and forage quality of both exceeded that of red clover. The N yield estimates include only herbage. Past experience with clovers indicates that substantial N is contained in roots (up to 50% of total). Both berseem clover and annual sweetclover N yields approach the 120 lb needed to optimize corn yield on this soil type if root contribution is 40% of total. We will measure this in 2008 and planned added N response trials will examine this in following corn this year.
While all legumes displayed acceptable harvest qualities, chickling vetch was difficult to rake because the vines tangled on the tines, creating uneven and scattered windrows. Red clover also dried to a higher final moisture content (data not shown) and long-term storage without molding may be difficult. When fed to sheep, all legumes were readily accepted.
Finally, no difference in attractiveness to rootworm beetles was measured, and numbers were well below treatment threshold. 2007 in general had lower populations than in the past.
WORK PLAN FOR 2008
We will repeat what we did in 2007, adding root measurements. In corn following the 2007 trail, we will measure response to several levels of added N to determine sufficiency and/or N credits. This will take place in both harvested and unharvested portions of the plots.
I conduct an annual cover crop workshop for the Michael Fields Agricultural Institute on our farm. In 2007, 12 individual attended and viewed the legumes in the trial. Data was given to select UW-Extension educators at their request and has been incorporated into the master UW-Extension cover crop database, compiled by Kevin Shelley, Regional Agronomist with the UW Nutrient and Pest Management Program and myself. Our intent is to revise older publications with current data to promote the practice of cover cropping Statewide.
In 2008, I will again host the MFAI cover crop workshop. In addition, Dr. Peg Reedy, UW-Extension Agricultural Agent in Walworth County and I are setting up a summer field day to highlight this work.
We have a collection of digital images documenting the project that will be submitted with the final report.