19 Jan What information can you give me on cover crops for vegetable production that can be grazed by livestock?
S.M.ColoradoAnswer: I am pleased to provide you with information on cover crops that will act as a cover crop for your vegetables as well as provide winter grazing for your hogs and sheep. Your question is a bit difficult to answer, as there really isn’t a perfect crop to meet all of the criteria you are looking for. There are several tradeoffs that you will need to make in the system you describe. While the crop must compete with weeds, it also must not be so competitive that it decreases your vegetable yields. In addition, while you need a spring-seeded variety with prostrate growth profile, you also need a long-standing perennial with fall and winter grazing potential. Together, all of these criteria make for a very interesting research topic!In your first inquiry, you had mentioned rye as a potential cover crop. This might work, but be aware of the pros and cons. Rye is very cold and drought tolerant and requires the least fertility of all grain crops. In addition, rye will be very competitive with the weeds. But it may be so competitive that is hurts your vegetable yields. There is some debate on the allelopathy of rye. Some say that rye inhibits weeds by exuding chemicals from its roots, while others suggest that rye chokes out weeds because of its rapid structural root growth. (Stoskopf, Canadian Organic Growers) Either way, it’s safe to say that rye could be a real problem for your direct-seeded vegetables. In Montana, rye is rarely grown as a cash crop for this very reason. Once it is planted into a field and is allowed to mature, it is nearly impossible to get it out in following crop years. It becomes a major weed problem in subsequent wheat or barley crops. I would recommend barley as a better option in your case. I had a chance to speak with Bruce Bosley at the CSU Logan County extension office, and he agreed with this idea. Barley will germinate at 35F, and in your area can be planted in February, and no later than March 15th. Barley is fairly tolerant to low-fertility, drought, and saline soils. You can plant it early and it will bring nice, lush growth for grazing. In addition, the cost of seed is very reasonable. You might want to experiment on your seeding rate. The SARE manual recommends “25 to 50 pounds per acre if overseeding as a companion crop or a higher rate (140 pounds) for very weedy fields,” which is a very wide range. Make sure you use a winter variety of barley. Typically, winter barley is planted in the fall, overwinters, and then sets seed and is harvested the following summer. In your case, you do not want the barley to set seed. You want to control its growth so that it doesn’t compete too much with your vegetable plants. Planting a winter variety in the spring means that the barley will put out lush vegetative growth and not put out a seed head. If you notice the barley grows taller than 6 inches, you may need to consider mowing or grazing the plant to control its growth. Researchers in North Dakota did some interesting research on spring barley and hairy vetch as a cover crop in an irrigated vegetable system. In these studies, they found that the barley needed to be kept between a height of 6 and 14 inches in order to allow for good vegetable growth. You can view their findings at: http://www.ag.ndsu.nodak.edu/oakes/covcrop.htmIn the North Dakota study, the barley was planted on the same date as the direct-seed carrots (May 16). Then in June and July, a mix of vetch and clover was planted. In your case, you are planting your cover crop first and it will get a head start on your vegetables. You will need to be very careful that your cover crop don’t take too much water, nutrients, and sunlight away from your vegetable crop.Planting a winter cereal in the early spring should give you some weed competition and grazing forage for the first part of the year. The drawback is that the crop will die off after a few months, which doesn’t help you during the fall and winter months. I spoke with Dr. Phil Bruckner, the winter wheat breeder here at MSU to confirm some of the science behind keeping a winter cereal in its vegetative state by planting in the spring. For your situation, you will need to keep in mind the idea of vernalization. Vernalization is the requirement of a winter cereal before flowering. It needs a certain length of cold temperatures for flowering to occur. Winter wheat in Montana generally needs soil temperatures less than 40F for a period of 5 or 6 weeks. At your location, this will probably not be an issue. However, if you get an unseasonable long cold snap after seeding, your cereal cover crop may go to seed later in the season. Dr. Bruckner said some of this ability will depend on the variety you select. There are some varieties that require more vernalization than others before flowering can occur. He also noted that he will be traveling this week with Dr. Scott Haley, the winter wheat breeder in Colorado and will chat with him about your situation.In order to get the perennial qualities you are looking for, you might want to consider establishing a legume along with your annual cereal. There are two options that might be well-suited for your situation: black medic and cicer milkvetch. Black medic is very well suited to our northern plains climate of harsh weather and low rainfall. Farmers in Australia have used it for many years in their ley farming system of rotational grazing and cropping systems. For an in-depth article on black medic, look at The Sustainable Agriculture Network publication Managing Cover Crops Profitably, 2nd Edition (2001) which has an entire chapter on using black medic as a cover crop. This publication can be downloaded from the SARE website as a PDF file. This is the most comprehensive book ever published on the use of cover crops to sustain cropping systems and build soil.The advantages of black medic are several. It grows low to the ground, competes with weeds, and fixes nitrogen. While it is an annual, it has a high reseeding rate and produces abundant amounts of hard seed.The disadvantage of black medic is that it has the same bloat potential as alfalfa for grazing sheep. (Conversation with Dennis Cash, MSU extension forage specialist, assuming grazing a stand of 100% black medic.) However, proper management of your grazing should prevent this from being a problem. Linda Coffey, the ATTRA small ruminant specialist compiled some information on grazing black medic to avoid bloat in sheep. 1. Purdue article on grazing legumes to prevent bloat in sheep. 2. Information from Oregon State: Annual medics are excellent winter forages for domestic livestock and wildlife. In the Midwestern USA annual medics are being evaluated as a summer annual as intercrops for small grains and corn.Anti-quality: Often times, the annul medics will have a higher protein content and a lower fiber content that clovers, and this contributes to a potential for bloat if over consumed. However this can be overcome by proper management of livestock and providing other forage to the grazing animals such as frosted mature grass, hay, or planting ryegrass or small grains with the medic.3. Western SARE research on grazing cattle on black medic in MontanaIn addition, Linda would recommend offering dry hay along with the pasture. A producer in AR was grazing alfalfa with his cattle and had great success, but then one morning he turned them out while the dew was still on and the cattle were very hungry. He lost several animals to bloat that day. He advised giving them something else to eat first and then turning them on to the alfalfa. I have found various opinions regarding the vigorous nature of black medic. Dr. Dennis Cash of MSU commented that black medic can often become a weed. However, he was assuming you would be growing a different crop the next year in a large scale operation. In contrast, Dr. Merle Vigil of the USDA-ARS station at Akron, CO commented that black medic isn’t very vigorous and will take some time to establish. Dr. Vigil’s opinion may be more correct for your situation, as his experience with the crop was closer to your location. The key to growing a good stand of black medic is to not graze the plant during seed set in September. Make sure enough seed has dispersed before grazing.Another legume option for your situation is cicer milkvetch. Dr. Merle Vigil (Vee-hill) in Akron, CO suggested this crop for your situation and offered to speak with you if you’d like more information. His phone number is (970) 345-0517. Cicer milkvetch is well-adapted to your area and was the research object of a local scientist for over 20 years. At the Akron station, they have an experimental plot that is over 15 years old. Dr. Vigil suggested you drive up to the station if you would like to look at this plot.Like black medic, cicer milkvetch is an annual that can be managed as a perennial, due to its ability to reseed itself. The disadvantage compared to black medic is its growth habit. Cicer milkvetch grows more upright, with the seedheads at the very tip of the plant. This makes the seedhead more likely to be eaten during grazing. However, the advantage of cicer milkvetch is that it is bloat-free. Less management care is needed when grazing this crop. With both black medic and cicer milkvetch, you may find that seed is difficult to find and expensive. Please feel free to contact me if you need help finding a reliable seed source for either of these crops. As with any legume, remember to select the correct Rhizobium for the species you are planting. In summary, you will want to look at all of these resources and decide which option will work best for your system. For this spring, I would recommend planting a mixture of barley and a legume as soon as you can. Make sure the growth of the barley doesn’t get too out of hand to out compete with your vegetables. You might want to look into strip tilling for the vegetable rows. Make sure you plant 2 to 3 weeks after the strips are tilled in order to allow enough time for the crop residue to break down in the soil.After you harvest your vegetables in the fall, wait until the legume has gone to seed before turning in your livestock for grazing. At this point, you could consider overseeding another grass crop in the fall, such as annual ryegrass, or wait until the spring and plant another winter cereal. This may take some trial and error to figure out what works best for your system. I would be very interested in hearing back from you on what you try and what the results are. Please feel free to call me directly if you would like to follow up with this information. You have a lot of competing criteria, which has made this case challenging, as well as fun, to research.Resources:The Sustainable Agriculture Network. 2001. Managing Cover Crops Profitably, 2nd Edition.Stoskopf, Neal. 1995. Cereal Grain Crops. Reston Publishing Co.Canadian Organic Growers. 2001. Organic Field Crop Handbook, 2nd Edition.