CRAWFORD COUNTY - More than 40 producers and an all-star agricultural cast were on hand on an overcast, cool morning on Friday, August 11 for the last cover crop field day in the 2017 series presented by Crawford, Vernon and Grant/Lafayette County UW-Extension, Crawford and Vernon Land Water Conservation Departments, and USDA-NRCS.
The third event was dedicated to a discussion of year-one results of research around using a red clover cover crop, interplanted with a cash crop, to earn nitrogen credits. The research will continue for two more growing seasons.
Another highlight was a talk by UW-Extension Specialist in organic and sustainable cropping systems with UW-Madison, Dr. Erin Silva. Her topic was use of the roller crimper technology.
To kick the field day off, Ted Bay, the UW-Extension Agent for Grant and Lafayette counties, asked farmers to name the benefits of using cover crops in their farming systems. Weed suppression, soil building, erosion control and nitrogen credits were chief among the benefits listed.
N credit research
Jay Aspenson is a grain farmer who farms just outside of Mt. Sterling in Crawford County. He has been a cooperator with the county cover crop program for multiple years.
Aspenson is collaborating in cover crop research with Ted Bay and Dan Smith, from the UW-Extension Nutrient and Pest Management Program.
Bay and Smith conducted a replicated study on Aspenson’s farm to test the level of nitrogen available from the red clover for the corn crop that Jay planted after establishment of the red clover. They used the Pre-Sidedress Nitrate Test (PSNT) for this evaluation.
The field where the research is being conducted was planted in winter wheat in the fall of 2015. In March of 2016, it was frost seeded with red clover at the rate of 12 pounds per acre. Getting the clover to establish well in the autumn is critical in the process. In the spring, the rule of thumb is that it should yield an 80-pound nitrogen credit if the stand is 6-12 inches high, and a 40-pound credit if the stand is less than 6 inches high.
The red clover established, and did not compete with the wheat or become a problem weed. Once the wheat was combined, the red clover came back and flourished.
In spring of 2017, the clover was burned down with herbicides and planted into corn. Prior to planting, the field had received nitrogen applications except for six test plots in the field, which were protected by tarps to allow comparison of corn yields with and without added nitrogen.
The goal of the research is to compare yield levels to determine if yields from the red clover without added nitrogen compare favorably (same or better) to yields with added nitrogen.
“Of course, the gold standard comparison and bottom line is always going to be yield,” Bay explained. “Our rule of thumb is you have to try anything three times before you can feel confident in your results – we’re working on this with our research.”
Initial research results
Year-one results were not quite what Aspenson, Bay and Smith had hoped to see. Results of the testing indicated no nitrogen available at a level that could be taken as a nitrogen credit for the corn crop. This is quite unusual and not typical for red clover, which most often can be found to provide a nitrogen credit from 40-80 pounds per acre.
Interpreting the results of the PSNT, a result of less than ten indicates there is ‘no nitrogen credit.’ The results in the three test plots in Aspenson’s cornfield came in at 4.7, 8.2, and 9.0.
The results of the test assist the producer in determining how much added nitrogen it is necessary to apply to his fields. If a good nitrogen credit is yielded from use of the cover crops, this can result in a considerable cost savings to a producer, and help to reduce runoff of nutrients into surface waters as well.
The final conclusion on the nitrogen credits for the 2017 growing season will be determined when they take corn grain yield measurements on the replicated study during fall’s grain harvest. Actual grain yields will confirm if the lack of nitrogen credits carried through the entire growing season.
The two will continue the same test next year, including a check plot with no red clover, to allow them to determine a better or more complete picture of nitrogen fixation and thus nitrogen credit from red clover.
What happened?
Bay attributes the results to the fact that 2017 was an unusual year with seemingly unceasing rains in the planting season in May. He thinks the main problem in the field this year was nitrogen leaching. He emphasized that every field, and every growing season is a unique puzzle of varying conditions that the grower has to learn to work with.
“No two fields, and no two years, will be exactly the same,” Bay explained.
Crawford County UW-Extension Agent Vance Haugen elaborated on Bay’s point.
“Success of the cover depends in part on the density of the stand,” Haugen explained. “You have to achieve good levels of germination. Red clover as a cover can be visually deceiving because of the size and density of the foliage, and sometimes it can look better than it is.”
“One thing that is critical with cover crops, especially for weed suppression which is critical in organic cropping systems, is that you need a high seeding rate of at least three bushels per acre,” Dr. Silva pointed out. “For erosion control with winter rye, you need at least one to one-and-one half bushels per acre.”
Dan Smith reminded participants that a sample captures only a moment in time, and that in reality the nitrogen levels in the field will fluctuate.
Bay described a different result at Driftless Organics where hairy vetch, winter pea and red clover had been used as cover crops.
The PNST results for the hairy vetch plots came in at 0, 10, 160; for the winter peas at 35, 0; and for the red clover at 60, 10, 10.
Smith went on to explain that with a seeding rate of 120 pounds per acre of winter rye, planted in the fall, his research has reliably demonstrated a 10-85 percent suppression of weeds, depending on the variety. He said the covers had proven especially useful in suppression of giant ragweed, dandelion and giant foxtail.
Use of roller crimper
Dr. Erin Silva, gave a presentation on her experience and results from use of the roller crimper technology in no-till conventional and reduced-till organic cropping systems.
Silva’s research has focused on use of the roller crimper in soybean fields, which she explained seem to work better with the crimper than corn.
Silva elaborated that the planting dates for the cash crop and the maturity dates for the cover crop to be crimped need to be carefully managed. In the typical scenario of a fall-planted winter wheat, and spring-planted soybeans, if you crimp the rye when the beans are at the V1 or V2 stage they tolerate the crimping very well.
“With corn there are more management risks,” Silva said. “Success is very dependent on conditions which will vary from year to year.”
The scenario is to seed in the winter rye no later than September 30, then plant the beans in mid-May, and finally, roll the rye at the end of May.
Silva uses the roller crimper model developed by the Rodale Institute in Pennsylvania. This is also the model being manufactured by Chaseburg Manufacturing in Coon Valley. The device is currently being used in both conventional and organic cropping systems.
The implement is set up for 30-inch rows, and the drum is reversible to be used on the front or the rear of your planter. Using the device, a cover crop can be crimped at the speed of about five miles per hour. Efficiencies are achieved when the device is front-mounted, and used to crimp and plant all in one pass.
Chaseburg’s roller crimper, available for purchase at a cost not to exceed $5,300, is also available from the Vernon County Land Water Conservation Department for a ‘try before you buy’ daily rental fee of $100.
Cover crop termination
Silva explained that she has her own organic research fields, and in addition has worked extensively with conventional farmers in Illinois growing soybeans with a red clover cover crop.
“The combination in a conventional soy bean field of a red clover cover, roller crimping and use of glyphosate has yielded very good results, and with half the amount of glyphosate,” Silva said.
Silva shared an example of one of her research fields where she had planted beans following winter wheat. The whole field was covered in giant ragweed. After a fall seeding of red clover, there was no giant ragweed the following year.
With mechanical termination such as the roller crimper, she explained that there are several different varieties of winter rye that can be used. The choice of which to use involves tradeoffs. With the varieties that mature earlier, you may sacrifice biomass and density.
Planting dates can also be a consideration. Often, a later planting date is okay in an organic system, but bad in a conventional system.
“One option,” Silva explained, “is to plant green in the middle of May. You need to find a way to balance your planting date with achieving the maximum weed suppression.”
Another aspect of weed suppression from cover crops is allopathic, according to Silva. Winter rye is especially effective for this, as is triticale. Triticale is a low-growing, leafy plant that grows quickly and shades out other weeds. Newer varieties of triticale have improved winter hardiness, and improved feed value for forage.
Silva cautioned that winter rye can be difficult to manage in a wet spring, and can quickly get away from you. By contrast, triticale is not as fast growing in the spring. Some farmers prefer triticale on wetter ground, and also with wheat.
Silva also shared an experience she had with insects. In this particular case, armyworms were attracted to the chemicals from the decaying residue after use of the roller crimper.
“In a conventional system, it would probably work better to terminate early and let the cover dry down,” Silva said.
Dan Smith pointed participants to online resources for information on use of herbicides with cover crops. Producers can go to the UW-Extension Integrated Pest Management (IPM) website and it can be a good resource for them. Smith said that some of the You Tube videos available there are particularly helpful.
Smith also cautioned that in some cases, because of herbicide persistence, depending on the half-life of the herbicide, the soil pH, the amount of organic matter in the soil, and the rate of use, an herbicide could suppress growth of a cover crop. For example, corn herbicides are often detrimental to establishment of cover crops, and this can limit your choices of cover crop species.
Equipment essential
“It is essential when using cover crops and the roller crimper that you optimize your equipment, and are using the right equipment,” Silva cautioned.
Silva explained that you need to optimize and adjust your seeder to plant into the rolled debris, and you also must adjust your closing wheel.
“Soybeans can be amazingly resilient,” Silva shared, “even when you don’t get perfect row closure.” Silva also shared that she sometimes bumps up seeding rates to 225,000 seeds per acre to optimize emergence.
