Feature Articles

Will cover crops work for Ontario producers?

November 21, 2006:

Farmers harvest sunshine. After the wheat crop is harvested, there is at least two months of brilliant sunshine still to come. Yet often this sunshine falls on bare soil. There must be a way that farmers could harvest this sunshine, to improve their soil and bottom line!

Three years of trials (2003-2005) in south western Ontario have shown that cover crops after wheat can produce significant plant biomass. These plots showed various cover crops captured significant nitrogen in their plant material, and greatly reduced late fall soil nitrogen levels. All the soil health parameters should improve: increasing organic matter, water infiltration and water holding capacity, and reducing soil erosion potential.

Eighteen research/demonstration plots were established following winter wheat harvest (late August) over this 3-year period. Cover crop species included: annual ryegrass, buckwheat, oats, oilseed radish, and peas. Red clover was evaluated at several of the sites. Manure (swine, liquid dairy, or solid cattle manure) and non-manure treatments were evaluated at each site.

>MP David Anderson, fifth from left, posed for photo with CAAPAS delegates following breakfast meeting
Significant growth can occur with late summer planted cover crops.

In the absence of manure, oats performed better than annual ryegrass, buckwheat and oilseed radish, while peas and red clover out paced oats for biomass production. Oats produced two tonne per hectare (t/ha) of biomass on average (annual ryegrass 1.25 t/ha buckwheat and oilseed radish 1.75 t/ha, peas and red clover 2.2 t/ha) without manure. Manure applications increased growth by 50 percent or more, except for the pea cover crop. Oats averaged just over 3.0 t/ha while annual ryegrass, buckwheat and red clover averaged 2.5 t/ha and peas 2.25 t/ha.

The oat cover crop contained about 40 kg/ha of nitrogen in the plant biomass without manure and 75 kg N/ha with manure. Without manure, the peas had the highest levels of plant biomass nitrogen (80 kg N/ha), significantly higher than oilseed radish (40 kg N/ha) or oats. With manure the peas showed little increase in plant biomass nitrogen (85 kg N/ha), but the oilseed radish (80 kg N/ha) and oats had significant increases in plant biomass nitrogen.

Cover crops, especially the non-legume ones were able to reduce soil nitrogen levels in the fall. The value of the cover crops was most evident where manure was applied. The soil nitrogen levels where no cover crop was planted showed significantly more fall soil nitrogen available than where any of the cover crops were established. The oats and oilseed radish reduced the late fall soil nitrogen levels significantly, by 45 and 50 kg soil mineral N/ha respectively. Peas did not draw down soil residual nitrogen levels (10 kg/ha reduction) like the other cover crops likely due to its nitrogen fixing abilities as a legume crop.

Cover crops are excellent at capturing nitrogen and building biomass. The final piece of this puzzle: does a cover crop increase yield, or reduce nitrogen requirements, in the following corn crop? The jury on these questions is still out. With harvest of the corn plots from our sites in 2006, we hope to have the answer, which we will report in a future issue of this publication!

This project was funded by Agriculture and Agri-Food Canada via the Greenhouse Gas Mitigation Program for Agriculture, administered by the Soil Conservation Council of Canada.

The project was a cooperative effort between the University of Guelph and Ontario Ministry of Agriculture, Food and Rural Affairs crops staff, in conjunction with Ontario Soil and Crop Improvement Association and Innovative Farmers Association of Ontario.

(This article produced by Ken Janovicek, Bill Deen of University of Guelph and Greg Stewart, Ian McDonald, Peter Johnson, Adam Hayes of the Ontario Ministry Agriculture Food and Rural Affairs originally appeared in the August 2006 issue of Top Crop Manager, Easter edition.)

For more information contact Adam Hayes, OMAFRA, (519) 674-1621 adam.hayes@omafra.gov.on.ca.

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