5 Lessons Learned with Rye Cover Crops

Here at Iowa Learning Farms, we’ve been working with cereal rye cover crops since 2008. That’s not nearly as long as our good friend and colleague Tom Kaspar with USDA-ARS, but we can certainly say that, with our partners in the Iowa Cover Crop Working Group, we’ve been exploring and promoting cover crops long before they were cool!

Our longest ongoing study involves the use of cereal rye as a winter cover crop in on-farm trials within corn/soybean cropping systems across the state of Iowa. Over the years, twelve farmers have participated as partners in this project, with each demonstration site featuring field-length replicated strips with a cereal rye cover crop as well as replicated strips without a cereal rye cover crop.

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In our eight years of on-farm cover crop demonstrations, what have we learned?  Here are our Top 5 takeaways regarding cereal rye cover crops:

1. Rye cover crops are largely yield neutral.
In the vast majority of this study (55 of 59 site-years), farmers found that a properly managed cereal rye cover crop had little to no negative effect on corn and soybean yields. Soybean yield actually increased in 7 site-years and corn yield increased in 2 site-years. There can be a learning curve up front, but in the long run, this study’s findings dispel the myth that rye negatively impacts crop yields (especially corn yields) in the following season.
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2. Cover crops require active management.
Additional considerations/management factors when using a rye cover crop include seeding rate and method in the fall, and then cover crop termination and adjusting planter settings to accommodate additional residue in the spring. In the few cases of this study where crop yields were negatively impacted, farmers identified insufficient cover crop termination and improper planter settings as reasons for the few years where there were crop yield reductions.

3. Spring growth is key to realizing rye’s benefits.
Unlike winter wheat, oats, radishes and turnips, cereal rye survives over winter and continues its growth into the spring months. Large amounts of spring over crop biomass can be produced – variable to location and termination date.
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4. Soil health is hard to define and even harder to measure.
Five years into the study, we found no measurable differences in soil health variables (soil organic matter, total carbon, total nitrogen, pH, infiltration and runoff) between the strips with and without the cereal rye cover crop at individual locations. A much greater intensity of sampling and additional time (years) may be required to quantify significant changes. Plus many of Iowa’s soils have relatively high levels of organic matter to begin with, so detecting very small changes can be challenging.

5. Earthworm numbers have increased with a cereal rye cover crop. Looking at the common nightcrawler (Lumbricus terrestris), our 2016 midden count data indicate a statistically significant difference of 38% more earthworms with a cereal rye cover crop. Earthworms can serve as tangible, early biological indicators of soil health.
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These findings and more will be highlighted at ISU’s Soil Health Conference coming up later this week. Stop by and see our poster, and let’s talk cover crops – we hope to see you there!

Ann Staudt

 

Additional information on our work with rye cover crops:

ILF Cover Crop Research webpage
Additional ILF Cover Crop Resources
Earthworms, Cover Crops and Soil Health

The Iowa Cover Crop Working Group is a collaboration of Iowa Learning Farms and the following organizations:

  • Practical Farmers of Iowa
  • Iowa State University Extension and Outreach
  • Iowa Dept. of Agriculture and Land Stewardship
  • USDA-Agricultural Research Service, National Laboratory for Agriculture and the Environment
  • USDA-Natural Resources Conservation Service
  • Midwest Cover Crops Council

Funding for this demonstration project has been provided by Iowa’s State Soil Conservation Committee, Iowa Department of Agriculture and Land Stewardship, Leopold Center for Sustainable Agriculture, Iowa State University Extension Water Quality Program, and NRCS Conservation Innovation Grant 69-6114-15-005.

What happens to all of that cover crop biomass?

This has been an amazing fall (and winter) for cover crops! Driving around the state, it makes my day to see those lush fields of green. In an earlier blog post titled The weather outside is frightful, but the cover crops are oh SO delightful!, we showed you some of the beautiful cover crop growth that was achieved at the ISU Armstrong Research Farm near Lewis in southwest Iowa, as documented when we were there collecting fall biomass samples in late November.

Once the biomass is collected, what happens next? Let’s go on a bit of a behind-the-scenes tour documenting the next steps in the processing and analysis of the cover crop biomass.

When sampling the cover crop biomass in the field, all of the above-ground biomass from each PVC frame is harvested and transferred to a brown paper bag.

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Once we’re back to campus, the bags are transported to the porous media lab in Sukup Hall, part of the brand new Biorenewables Complex that houses Iowa Learning Farms and ISU’s Department of Agricultural and Biosystems Engineering. Each individual bag is opened up immediately and allowed to start air drying; it is important to start the drying process right away to prevent wet samples from molding or any other sample degradation.

With 6 research farm sites and 10 on-farm demonstration sites (each with multiple replicated treatment strips) where cover crop biomass was collected, you can imagine that we have collected quite a few bags of cover crop biomass by the end of the season!

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SORTING of the biomass comes next. The goal is to collect just the above ground cover crop biomass, so the first step is sorting out any non-cover crop material from the bag – including soil, corn stalks, soybean residue, and trimming off any cover crop roots that may have been collected.

Since many of our demonstration projects involve cover crop mixtures, then we begin sorting the biomass by species in order to determine how much growth was achieved by each of the species in the mixture. This sorting is done visually, using photographs of the individual cover crops to identify and sort the cover crop biomass on a species basis.

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Here, intern Kayla Hasper sorts a cover crop mixture that includes radish, hairy vetch, and oats. The biomass from each species is put on its own pile, and once fully sorted, each individual species is transferred into its own brown paper bag.

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Samples are dried at low heat (60C) for 48 hours to remove any remaining water. Each individual species sample is then weighed. Knowing this dry weight measurement as well as the size of the PVC frame used for sampling, we can calculate the amount of biomass grown in the field on a lb/acre basis… per species, as well as the total lb/acre for the mixture. We’ll do the same thing in the spring to see what kind of growth is achieved then.

Finally, the biomass samples are submitted to ISU’s Soil Processing Lab in the Agronomy Department to determine the Total Carbon and Total Nitrogen makeup of the plant biomass. These numbers can then be related to the Total Carbon and Total Nitrogen in the soil, the nitrate concentrations found in the water samples collected from each plot, and the crop yields in each plot… each individual piece of data helps us gain a better understanding of the big picture in terms of the numerous benefits of cover crops integrated into corn and soybean cropping systems!

Ann Staudt

New! Iowa Cover Crop Research and Demonstration Directory Now Online

Cover crops are an important tool in the Iowa Nutrient Reduction Strategy that can help meet the goals of reduced nutrient loss from the state.  From the ability to protect the soil from erosion when the fields are typically brown to cycling nutrients and improving soil, cover crops can provide many benefits.

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Cover crop mixture demonstration site in Madison County fall 2015. Photo credit: Anna MacDonald

However, there are still many questions that come into the Iowa Learning Farms about cover crops.  Most asked questions include: what kinds of plants can be used, when and how to seed and when and how to terminate. With help from fellow Iowa State University, Practical Farmers of Iowa, USDA-ARS-National Laboratory for Agriculture and the Environment researchers, ILF strives to help farmers, and other interested people, find the answers to these questions and more through ongoing cover crop research and demonstration projects.

Now available on the ILF webpage is a directory of 60+ cover crop projects led by ISU and colleagues.  This sortable file contains brief descriptions of the projects, as well as contact information to learn more about each one.   Also available, is a list of cover crop research and demonstration projects in Iowa compiled by Clean Water Iowa through the Iowa Department of Agriculture and Natural Resources.

Liz Juchems

It’s Alive!

As the harvest season continues, fields across the state are beginning to come alive with cover crops. The Cover Crop Working Group mixed species demonstration site in Nashua is among those fields coming alive this fall – just in time for Halloween!

During a visit to the site in early October, the cover crops had begun germinating even before the corn and soybeans had been harvested. In the upcoming weeks, the team will be heading out to evaluate the cover crop stand and collect soil samples for total nitrogen, total carbon, pH and total organic matter. Check out photos from Nashua below and read our earlier post To Mix or Not to Mix My Cover Crop Species for more information about the project.

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Rye before soybeans in the single species trial
October 2, 2013

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Rye, radish and rapeseed before soybeans in the mixes trial
October 2, 2013

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Oats before corn in the single species trial
October 2, 2013

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Oats, radish and hairy vetch before corn in the mixes trial
October 2, 2013