There are a variety of options to use when cover cropping. A cover crop can be grown with the grain crop to provide additional shade and competition for weeds (legume and cereal). Cover crops can be seeded late in the summer or early in the fall. These cover crops will grow until winter competing and suppressing fall annual and perennial weeds (tillage radish). The cover crop then dies over winter and provides organic matter and nutrients to the soil for the following years. Cover crops can also be perennials (alfalfa) and grown for a couple years and then tilled under, mowed, baled, or removed as silage.
Cover crops provide many advantages to the soil when used in a crop rotation including increasing organic matter and nutrient content in the field, reducing wind and water erosion, enhancing soil structure, increasing biological activity, and supressing weed growth by shading and disrupting germination and competing for nutrients (Mutch, 2010). Cover crops are also quite cheap to grow as seed and the cost of seeding (and plowing if required) are the only costs associated with growing them. Disadvantages can include the opportunity cost of not growing a cash crop for one or multiple years and residue problems if not managed properly before seeding of the new crop.
I think cover crops are a good idea in an agronomic and soil science perspective. They provide organic matter back to the soil which is important for future crop growth. When alfalfa is grown for multiple years it is effective in reducing annual weed populations and is especially effective when the weed seeds have short seed dormancy as they will no longer be viable when a grain crop is grown. I think tillage radish also has a place when compaction is an issue or a field cannot be seeded in the spring due to excess moisture. In an economic perspective I do not know if it makes sense to not grow a cash crop on a field for multiple years in a row.
Reference
Mutch, D. 2010. Cover Crop Overview. Michigan State University. Available online: http://www.covercrops.msu.edu/general/general.html (Accessed on March 11, 2014).
________________________________________________________________________________________________________
Cover Crops – Garth Stang
Cover Crops
Introduction – Controlling weeds in the crop during the growing season in an organic system can be very tricky. By growing another crop with the main crop to cover the ground and prevent weeds from getting to big is an effective way to decrease weed pressure and is known as cover cropping. There are many options to use for a cover crop, but the most common are winter cereals, legumes, and tillage radish®. The cover crop is grown with the main crop, but does not compete with the crop too much. The cover crop is usually short, and spreads out, covering the grounds and weed seedlings, preventing them from competing and reproducing.
Fine Tuning – Cover cropping can be very complex and the ideal system depends on the crop being grown, the cover crop being used, what and how many weeds are being controlled, and environmental conditions.
Considerations – You must be careful that the cover crop does not compete with the crop too much, or act as a vector for disease. Harvest can be more difficult if the cover crop is high enough and not dead yet. Seeding may have to be done in more than one pass to seed the cover crop, if it is not grown with the seed.
Costs – The seeds for the cover crop can cost a fair bit, and you’re not harvesting anything with them, so that can seem like a loss. The cover crop will compete with the main crop at least a little bit, so there will be a slight yield loss, although this may be a benefit compared to the yield loss caused by weeds.
Personal opinions – I think this technique can be very valuable in controlling weeds during the growing season, and it can have many applications and benefits if used properly.
Sources – http://www.tillageradish.com/, http://www.organicgardening.com/learn-and-grow/pay-dirt-fewer-weeds-less-labor, http://www.umanitoba.ca/outreach/naturalagriculture/weed/files/singleseason/cover_crops_e.htm, http://www.covercrops.msu.edu/general/general.html, http://www.agr.gc.ca/eng/about-us/offices-and-locations/pest-management-centre/pest-management-centre-publications-and-document-archive/sustainable-crop-protection-factsheet-series/field-vegetable-production-using-cover-crops-for-weed-management/?id=1304452312132.
_________________________________________________________________________________________________________
Cover Cropping- Garrett Foley
Cover cropping can help manage weeds in several ways. Cover crops provide weed control by competing with weeds for light, moisture, nutrients, and space. This is important in suppressing winter annual weed growth or certain cool-season perennials. Cover crops and their residues also can act as mulches or physical barriers by smothering weeds, suppressing weed seed germination and growth, and lowering soil temperatures. In general, the larger the cover crop and greater the biomass or dry matter production, the greater the impact on weeds. Cover crops can and often are used in a large scale in organic production in Saskatchewan; cover crops can also be used in a variety of crops. Each crop would need a different cover crop depending on its fertility needs, growing season, and competitive ability. If there is a limited amount of a resource cover crops may actually harm your crop by using essential nutrients, moisture, and light. To avoid these problems operators should not choose to use this system in drier years, or to choose cover crops that will out compete the crop. There are also additional costs than normal cropping practices some of these include the cost of the cover crop seed, labor and time for planting, alternative equipment may be needed to handle the greater amounts of residue present in no-till systems. Even though there are several risks and disadvantages to a cover cropping system I feel that it would provide a great opportunity to control problematic weeds and possibly improve soil.
References
http://smallfarms.cornell.edu/2013/09/04/organic-cover-crop-workshop-and-tour/
http://www.agriculture.gov.sk.ca/Default.aspx?DN=f28ca162-3ee3-4619-bec8-2a51cb86e62b
http://www.umanitoba.ca/outreach/naturalagriculture/weed/files/singleseason/cover_crops_e.htm
___________________________________________________________________________________________________________
Cover Cropping as a Weed Management Technique – Kali Kasper
Cover crops like fall rye and sweet clover can be successful competitive methods to choke out persistent weeds.7 A positive aspect of using cover crops, is the advantage of fitting them into a rotation that suits the timeline of a specific piece of land. If a sufficient amount of moisture is available for this organically approved practice; spring cover crops, fall, and cover crops that take place in rotation instead of fallow, are all great options in Western Canada.
If a fall rye cover crop is sown, producers have the option of intercropping soybeans (or other crops similar in size) into the living rye crop the following spring. The fall rye can then be mowed some time later, as it will stand over the canopy of the second crop that was seeded. This provides a sustainable means of weed control that is environmentally friendly.
On the negative side, high costs can be associated with killing cover crops. Herbicide use for cover crop kill is, on average, cheaper compared to mowing, while conventional tillage has the lowest cost per acre.8 This being said, the indirect impact of herbicides are not something that is easily measured, considering the high negative environmental costs of chemical use.
There are other uses for cover crops and many other benefits. Vetch, clover and rye are often used in cover crop rotations. As seen in this video with the link posted below, there is a wide variety of crops than can be sown together. Grazing can aid the termination of cover crops, while grazing also provides another means of organic nutrient capture.
With time will come more weeds that are insensitive to herbicides and cultural practices, like cover cropping will be heavily relied on. This is a great means of weed control that has low environmental costs and it could potentially save Western Canadian producers in the future.
Sources
7) Organic Crop Production: Weed Management. 2009. Government of Saskatchewan. http://www.agriculture.gov.sk.ca/Default.aspx?DN=f28ca162-3ee3-4619-bec8-2a51cb86e62b
8) Field Vegetable Production: Using Cover Crops for Weed Management. 2011. Agriculture and Agri-Food Canada. http://www.agr.gc.ca/eng/about-us/offices-and-locations/pest-management-centre/pest-management-centre-publications-and-document-archive/sustainable-crop-protection-factsheet-series/field-vegetable-production-using-cover-crops-for-weed-management/?id=1304452312132