Cover crops is a topic with a lot of ink spilled in many farm publications in recent years. Some scribblers seem to imply that a farmer is a laggard and an environmental hazard if she/he is not using cover crops on a regular basis.
Cover crops actually include a wide variety of cropping sequences, and many do have positive effects. We usually think of the “shoulder” season as the main target for cover cropping. The shoulder season is the time after crop No. 1 is harvested and crop No. 2 is planted.
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For decades now, I have been a member of the U.S. Tri-Societies: the American Society of Agronomy, the Crop Science Society of America and the Soil Science Society of America, with the Soil Science Society as my main allegiance.
In recent years, I have paid the extra fee (very reasonable) to have open access to all of the scientific journals of the society plus books published by Wiley. Just weeks ago, I was able to download a PDF of the new book Cover Crops and Soil Ecosystem Services by Humberto Blanco, published by the Tri-Societies under the Wiley banner.
This book by Blanco runs to 16 chapters. Each chapter has a long list of references to original works, so it is a great source of information for a current hot topic.
Benefits
The Blanco book lists erosion reduction, nutrient retention, weed suppression and carbon sequestration as benefits of cover crops. One major problem listed is excess water use by the cover crop in dry areas where lack of moisture puts a lid on crop yields.
On the nutrient retention topic, on my bookshelf I just stumbled on an old newsletter from the then-IPNI (International Plant Nutrition Institute). That piece provided data from Maryland to show that a rye cover crop soaked up the extra soil nitrate left behind after a dry year for a corn crop. Thus, nitrate loss by leaching or denitrification was avoided.
Blanco also points out that the benefits are often “blown up” while the challenges are underemphasized. The results of cover cropping are also site-specific. Degraded soils low in organic matter and subject to erosion may benefit the most from cover cropping but not always. Soils “degraded” by soil salinity will not benefit from cover cropping but can benefit greatly from establishing a permanent stand of salt-tolerant grass like Saltlander Green Wheatgrass.
In the Palliser Triangle
The Palliser Triangle of central and southern Saskatchewan and southeast Alberta is prone to drought. Water is often the factor determining how hard the trucker must work in the fall.
By the time the crop is off, the topsoil is often dry and there is little time to seed and establish a cover crop. Our “cover crop” is the stubble of the previous zero-till crop. If any plant has nerve enough to grow we spray it out, so it does not use up the moisture for next year’s crop.
We cannot take practices that seem to work in the Corn Belt with long rains and short winters, like Des Moines, Iowa, and expect them to work in dry and short-season Saskatchewan with long winters with no winter growing days. Much of the U.S. Corn Belt has temperatures that permit fair plant growth in October and November, but that is not the case in the Palliser Triangle. Annual precipitation is 15 inches at Swift Current, Sask., and 39 inches at Des Moines.
In the Canadian Prairies there is often little or no time to plant a cover crop after the main crop has been harvested. In many areas and years, surface soil moisture will not be adequate for germination and early growth. A winter annual like rye could work in some years but not consistently.
So, enough already about cover crops! For the most part, in the Palliser Triangle, they are a non-starter.
University of Manitoba survey
The University of Manitoba has recently conducted a survey of cover crop adoption in the Prairie provinces. It shows the adoption is quite widespread. The report is a good source of information on cover crops and the range of farm types and crops that are included in the practice.
Intercropping
The practice of planting two crops in the same field in the same year is advancing slowly and has much to offer. The practice really goes back to the 1970s when peaola was a unique intercrop. Early pea varieties tended to fall down when ready to harvest, so canola was used to provide the pea crop something to climb on.
The peas were planted as normal and then canola was broadcast and harrowed. In those days, canola seed did not cost $500-plus per bushel, so 10 pounds per acre could be broadcast without upsetting the crop budget. At that time, the crop was harvested and hauled straight to the elevator where the peas and canola were separated, and the farmer was paid for each crop minus the separation cost.
Lana Shaw at the Southeast Research Farm at Redvers, Sask., has conducted many experiments with the practice and is the best source of information. Colin Rosengren, a farmer from Midale, Sask., has many years of experience with intercropping.
I think intercropping is what we should concentrate on. For years, I have stated that we are painting ourselves into a corner with herbicide-resistant weeds. Two crops in the same field leave very little space for weeds to get a foothold.
By the time you read this, winter will be in full force. Enjoy the farm shows, meetings and information gathering for the 2024 crop.
