As Nebraska State SARE Coordinator, the use of cover crops is an important initiative that I am focused on. Cover crops have been used for a number of years particularly in organic cropping systems. They have been a source of nitrogen, organic matter and other nutrients when incorporated as green manures in these systems. Cover crops have also been planted as forage crops for livestock for grazing or hay for many years. In recent years there has been increased interest in the use of cover crops in conventional cropping systems. The USDA NRCS (Natural Resource Conservation Service) has promoted cover crops and provided cost-share programs for farmers to encourage their use to help improve soil health and reduce erosion and degradation of soils.
Cover crops have many potential benefits. Legumes fix (N) nitrogen from the atmosphere which is a source of N for the subsequent crops. Biomass from the cover crops adds carbon and organic matter to the soil. A primary function of cover crops is prevention of erosion with their roots holding soil in place and reducing impact of rain drops by covering the soil. Other benefits include: improve water infiltration, scavenge nutrients, weed suppression and forage for livestock. A number of farmers across Nebraska and in other states have utilized cover crops for several years and are seeing benefits. The University of Nebraska has conducted research and is conducting research to evaluate how cover crops can best be utilized in crop and livestock systems in Nebraska. Nebraska Extension is also cooperating with farmers using cover crops to document impact on soil and subsequent crops.
In Nebraska there are also many questions and challenges with the incorporation of cover crops in cropping systems. Probably one of the primary questions and challenges is how to successfully plant and establish cover crops in a timely manner in corn/soybean crop rotations? Another challenge is developing a herbicide program that allows you to plant and graze cover crops successfully without impacting the previous cash crop of corn or soybeans. A final challenge is balancing the use of cover crops to reduce the impact on the previous and subsequent crops. These are questions currently being addressed by Nebraska Extension, other universities, agri-businesses and farmers across the Midwest.
Diversified multi-species cover crop mixes are used by some farmers. These mixes are generally more expensive, but they have a number of different types of plants which can impact the biology of the soil, attract different pollinators and beneficial insects. They also provide excellent multi-species forage for livestock and nutrients for the diversified microorganisms in the soil as the forages are broken down.
Cover crops can be used for specialty crops, like apples in orchards. Cereal rye was planted in the fall of 2014 on land that was going to be planted to apple trees. The rye was shredded after it had headed out and made seed in the summer of 2015. The cereal rye re-seeded itself in the fall of 2015 and had an excellent stand. This spring at Union Orchard, near Nebraska City, NE; apple trees are planted in rows after the rye was knocked down with a shredder. According to Vaughn Hammond, orchard manager, this field was solid weeds before the rye was planted into it. As you can see, the cereal rye successfully suppressed weeds. Research has documented the weed suppression attributes of cereal rye which has been confirmed by farmers in different cropping systems.
Apple trees will be planted in this cover crop of clover and grass at Union Orchard in southeast Nebraska in the future.
A cover crop of field peas was planted in the summer of 2015 to provide nitrogen for vegetables at Shadowbrook Farm near Denton, NE.
Kevin Loth of Shadowbrook Farm uses oats as a cover crop. Here he shows where oats have been plowed down. With their dairy goat herd, oats has the potential to being used as an excellent forage.
These three images illustrate how erosion had a major impact in southeast Nebraska in 2015. With torrential rains, even no-till cropped fields showed significant erosion.
This field of terminated cereal rye from the spring of 2015 illustrates how erosion can be prevented with the use of cover crops. Notice the rill erosion in the soybean field in the background. This field is only a few miles from the first image (shown above) of the eroded corn field planted in the soybean stubble. These areas received 5-8″ of rain in one day in May 2015. The cover crop held the soil very well. This field also had tillage radish which can help break up compaction and increase soil water infiltration rates.
With all of the rain in 2015, there were several prevented planted acres in southeast Nebraska. Here is a prevented planted field of oats that winter-killed. If you are just starting to investigate using cover crops, oats is a good one to try because the seed is cheap and you do not have to worry about terminating it in the spring before next year’s crop. Many people have planted oats following corn silage when beginning to use cover crops. This field above will be planted to corn or soybeans in 2016.
This field of cereal rye was terminated with chemicals and will be planted to soybeans this spring. The challenge is to terminate the rye crop to get the most benefit from the root growth without impacting the subsequent crop. Cereal rye can tie up nitrogen and also use valuable moisture impacting the following crop.
This field of cereal rye was planted following corn silage harvest. This photo was taken in mid-April. It will be terminated soon and planted to soybeans.
Field of cereal rye in mid-March that was drilled in the fall, mid-October. This field will probably be grazed by cow/calf pairs this spring before it is terminated. Notice the irrigation in the background. This can take a lot of the risk out of allowing cover crops to put more growth on in the spring either for forage or as a method of improving soil health. Soil water that is depleted by the cereal rye crop can be replaced through irrigation.
Cow/calf pairs graze cereal rye in mid-March under a center pivot. Rye can provide a significant amount of forage for cattle, especially in the spring. It is probably the most common cover crop used in southeast Nebraska.
The cereal rye on the right was planted in mid October, 2-3 weeks earlier than the rye on the left. The earlier planted rye benefits from warmer days and put on more growth.
Some farmers have cereal rye aerially seeded from mid-August from mid-September into standing corn or soybeans. In 2015 excellent late summer rains benefitted this field of cereal rye. It was grazed in late fall and again this spring into early May. The soybeans will be planted into this field later this spring and the cereal rye will be terminated.
This is a field of a cover crop of brassicas. Several farmers are also using brassicas for grazing, i.e. tillage radish, turnips and rape. Seed corn producers overseed or aerial seed brassicas into their seed corn fields in August. Tillage radish is used to break up compaction, increase pore spaces which will improve soil water infiltration, scavange excess nitrogen and help recycle other nutrients, besides providing excellent forage for cattle. Nebraska research has shown cattle gain 1.5 – 2.0 lbs/hd/day grazing a cover crop consisting primarily of brassicas.
This is a photo taken in May 2015 of a field of terminated cereal rye and tillage radishes that winter killed. Notice the large holes in the ground. These are left after the carcasses of the tillage radish decompose. This provides an excellent water storage reservoir in the top 6-12″ of soil which helps reduce runoff and potential erosion during large rainfall events like we saw in the spring of 2015.
This is a photo of our probe truck taking soil samples in Elbon Cereal Rye down to 8′ on Prevented Planted Acres on the Jon Keithley farm in Richardson County in southeast Nebraska. This rye was planted in late August, 2015. Growing roots of the cereal rye were found at almost 7′ in the soil core taken on April 15, 2016.
Here is a soil pit dug down to about 8′ under the Elbon cereal rye from the previous photo. The Elbon cereal rye was almost 3′ tall above ground. Next to this plot was VNS (Variety Not Stated) Cereal Rye planted which was only 18″ tall. It has growing roots down to over 6′ though. There was also Annual Ryegrass planted in these plots. It was only 12″ tall, but it also had growing roots down to over 6′. This indicates there may be much more biomass below the ground then what we see above the ground which should benefit the soil in the long term. This project is part of a Nebraska NRCS Innovative Grant Nebraska Extension and several farmer cooperators received in 2014. We conducted a field day at this site on April 18th. this was one of 4 field days and 5 workshops that have been or will be held to provide education on the use of cover crops and understanding soil health.
This is the side of soil pit in the Elbon cereal rye. See the fibrous roots growing in the top 12″ of soil with single roots going down much deeper. This field has been in no-till about 10 years, but only the first year with cover crops.
As part of a SARE Research and Education Grant the University of Nebraska-Lincoln is evaluating cover crops in crop/livestock systems on farms at different locations across Nebraska. Here soybeans planted on May 8th are emerging through the cereal rye. As part of this project in Nemaha County in southeast Nebraska, we have treatments of a control with no cover crop, a cover crop grazed and a cover crop ungrazed treatment which are replicated three times.
Dr. Humberto Blanco, Soil Scientist at the University of Nebraska and project leader takes penetrometer readings in the cover crop plot. Several measurements will be taken over the 3 year period of the grant including soil physical, chemical and biological properties, crop yields, cover crop biomass production, livestock carrying capacity and performance and economics of the systems evaluated.
Soil temperature at 2″ and 6″ depths is one of the several soil measurements that will be collected throughout this research project.
I have just scratched the surface in regards to cover crops. I hope I have provided you with a glimpse of how some producers in Nebraska are using cover crops and some of the research and education that is taking place in Nebraska and in other states to determine how cover crops can best be utilized in agriculture today and in the future. There are a number of excellent resources where you can learn more about cover crops and soil health. Here are a few publications and links you may want to investigate.
Cover Crop Resources
http://www.mccc.msu.edu/ Midwest Cover Crop Council Field Guide
http://beef.unl.edu/a75cc51e-22d6-4767-b09d-5e025cf8f3ca.pdf Dryland Cover crops as a grazing option for Beef Cattle
http://beef.unl.edu/cattleproduction/covercrops Cover Crops following weather damaged bean and corn harvest.
http://www.rma.usda.gov/help/faq/covercrops2016.html 2016 Cover Crops Insurance and NRCS Cover Crop Termination Guidelines
http://www.ars.usda.gov/Services/docs.htm?docid=20323 USDA Cover Crop Chart
http://www.mccc.msu.edu/ Midwest Cover Crop Council