Exploring whether cover crop mixtures make sense on Iowa farmland

Last week I had the opportunity to attend the Soil and Water Conservation Society’s 72nd Annual Conference in Madison, Wisconsin.  In addition to attending some great sessions, meeting fellow conservationists, and exploring Madison, I participated in the Conservation Innovation Grant Showcase poster exhibition.  On display were early results from our cover crops mixtures project that began in 2013.

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 Some preliminary observations from the study: 

  • Achieved more biomass from the single species (oats or rye) than mixtures
  • Oats and rye resulted in the majority of biomass from the mixtures
  • Cereal rye was the only species to over-winter consistently
  • Generally lower pore water nitrate concentrations following rye and mixture of rye, radish and rapeseed

As we continue to analyze the data collected, the project indicates:

  • Cereal rye and oats establish readily and provide the most biomass growth when seeded on their own.
  • Cover crops can offer some water quality benefits, reducing nitrate concentration in pore water.
  • Rye and oats provide the best biomass return on seed investment! Single Species are the way to go in Iowa for corn and soybean producers.

Be sure to subscribe to our blog and check back for updates on the project, including analysis on crop yields.

Liz Juchems

 

 

Now Available! Evaluating Cover Crop Seeding Techniques Publication

Seeding Tech LocationsThe Iowa Cover Crop Working Group (ICCWG) has wrapped up a two-year study evaluating planting techniques for the successful establishment of cover crop mixtures and single species in Iowa. We are grateful to our partners: Hagie Manufacturing Company, famer partner Tim Smith, and Iowa State University Northern Research and Demonstration Farm.

Replicated cover crop strips were established in fall of 2014 and 2015 to compare three different seeding techniques:

Evaluation was completed through fall and spring biomass collection and crop yield. A no cover crop plot was included in the replications as a yield comparison check strip.

The mixtures species were selected based on the upcoming crop and their winter hardiness. Because the species seeds are different sizes, a goal of one million seeds per acre was used for seeding calibration to provide a fair comparison between treatments.

Seeding Mixtures

Oats and rye win the day

Results show that earlier seeding with the high clearance interseeder resulted in more cover crop biomass, both fall and spring, than the later seeding with a drill. For Iowa, oats and rye work better than any other species tested at this time. The single species (oats and rye) resulted in more total biomass than the mixtures providing better soil erosion protection. Oats and rye were also the predominant species in the mixtures, accounting for the majority of the biomass.

Seeding Tech Biomass

There are no statistical differences in corn or soybean yields across the different cover crop treatments and no cover check plots. This yield neutral response following a cover crop is consistent with a long term ICCWG cereal rye cover crop project now entering its ninth year.

The publication is now available online and at upcoming ILF field days.

This research project was made possible with a State Conservation Innovation Grant through the Iowa Natural Resource Conservation Service.

The ICCWG includes core members from: Iowa Learning Farms, Practical Farmers of Iowa, Iowa State University Extension and Outreach, USDA-Agricultural Research Service, Leopold Center for Sustainable Agriculture, Iowa Department of Agriculture and Land Stewardship.

Fields of Green: Fall Cover Crop Biomass Sampling

An unseasonably warm fall has made an excellent year for cover crop growth! The ILF team has been traveling across the state and has seen some beautiful, green cover crop fields. With more growing degree days this fall, it has been a good year for radishes in the southern portions of the state. Check out this growth on radishes at Crawfordsville!

If you have cover crops and are interested in measuring the amount of biomass growing in your fields, follow along with our methodology in this blog. Check out the end of the blog for a summary of how you can apply this research to your own farm.

As part of our National Conservation Innovation Grant/Cover Crop Mixtures demonstration project, we are interested in learning if more biomass can be generated by seeding a single species of cover crop in a plot versus a mixture of cover crop species. To see which treatment yields more biomass (pounds per acre), we collected biomass in the fall and spring from six research sites throughout the state.

To sample biomass, we start with a frame that we constructed out of PVC piping. Our frame measures 19.2 inches x 30 inches (about four square feet). We toss the frame randomly into our test plots. Wherever the frame lands, we sample the cover crop biomass to the soil surface within the frame. We use clippers to cut the cover crop biomass, and we do not include soil, cash crop residues, or weeds in the sample. We try to only capture cover crop biomass and then place it in a labeled paper bag that tells us which test plots the sample came from.

We walk to a different portion of the plot and repeat the process. We always use a different paper bag for each sample and make sure to close the bag after sampling so that sampled biomass cannot escape. We go through the same process in all of our cover crop plots.

We take our biomass samples back to a lab on campus at Iowa State University within the Department of Agricultural and Biosystems Engineering and immediately open the bags the allow them to start air drying. This can prevent sample degradation, like molding on wet samples, from occurring.

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We then sort our samples from each plot by species. For the mixture plots, sorting helps us separate the biomass generated by each cover crop species. For all plots, it ensures that crop residue and other items can be separated from the sample before it is dried and then weighed.

Sorted samples are then placed into their own paper bag and dried in a drying oven at low heat (104 degrees) for at least 48 hours to remove any remaining water. We weigh the samples to get the dry measurement of the biomass. For our demonstration project, the last stop for our samples is the ISU Soil Processing Lab in the Agronomy Department. The samples are analyzed for Total Carbon and Total Nitrogen of the plant.

On-farm Research: If you’re interested in measuring the biomass growing on your own farm, here’s a summary of steps you can follow to make it happen.

Step 1: Create your frame (as long as you know how many square feet are within your frame, the math will work).

Step 2: Take samples in your field and place the samples in separate paper bags. We recommend taking at least eight square feet of samples to get a representative average for the field.

Step 3: Dry the biomass (about 104 degrees for 48 hours). Regional ISU Research Farms may have facilities for you to dry your samples.

Step 4: Calculate total biomass. Weigh the sampled biomass with a scale with two decimal precision (ounce or gram). Also weigh the paper bag by itself.

 

biomass

Average the total biomass from all of your samples to get an average biomass for the field. Convert results to appropriate lbs/acre using unit conversions.  1lb = 16 ounces = 453.592 grams, 1 acre = 43,560 sq. ft.

And finally, always expect surprises! We found a few purple top turnips mixed into our mix of oats, radish, and hairy vetch.

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Julie Whitson

 

Let it GROW, let it GROW!

The mild fall and winter gave cover crops across the state a great start. Now it’s time to begin thinking about plans for spring management and termination. However, when preceding soybeans, hold off on cover crop termination as long as possible… later spring termination dates can offer outstanding environmental benefits!

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recently released study by Iowa State University describes the impacts of winter cereal rye cover crop termination dates preceding a soybean crop. Side-by-side trials were carried out in which the cereal rye termination date was varied – the early termination date coincided with termination before planting a corn crop, while the later termination date was delayed three weeks (one day before planting the soybean crop). Researchers found amazing differences in those extra three weeks of growth!

KeyFindingsISU Associate Professor of Agronomy Mike Castellano summarized the project’s findings as follows:

“At the present time, we can say with confidence that we can retain a lot more nitrogen in the system and lose less to the environment with increased biomass production. In the short term, that’s a great benefit for water quality challenges. In the long term, adding that biomass and keeping that nitrogen in the system will build soil health.”

Read more about this Iowa State University Extension and Outreach project and its findings at Research Shows Extra Cover Crop Growth Prior to Soybeans Provides Benefits.

Ann Staudt

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

The weather outside is frightful… but the cover crops are oh SO delightful!

 

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If there was ever a picture perfect fall season for cover crops, 2015 would absolutely be it! Rainfall was timely – there was sufficient precipitation in August and September – to help the freshly seeded cover crops germinate and kick start their fall growth. Beyond that, we’ve had beautifully mild temperatures for the majority of October and November.

While many parts of the state experienced freezing conditions back in October, cover crops are quite hardy – just one cold night that drops below the freezing point is not enough to knock them out! So as the fall marched on, the cover crops grew and grew…

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However, winter-like weather has arrived this week, which meant it was high time for the Iowa Learning Farms team to get out there and take care of our fall field work responsibilities. As part of our National Conservation Innovation Grant/Cover Crop Mixtures demonstration project, we were collecting fall cover crop biomass at each of our demonstration sites across the state. In order to obtain the most accurate cover crop growth data, the collection of cover crop biomass is ideally done as close as possible to the time of an extended hard freeze – which is now looming very near. So Iowa Learning Farms team members have been “on the clock” this week trying to complete all of our fall field work and sampling before the cold is here to stay!

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Included below are a number of photographs from our cover crop mixture plots at the ISU Armstrong Research Farm near Lewis in southwest Iowa. These photographs were all taken on Wednesday, November 18. We hadn’t been back to the Armstrong Farm since the cover crops were seeded in early September, so it was thrilling to see the beautiful growth that has been achieved!

In the plots that had soybeans in ‘15 (going to corn in ’16), the cover crop treatments included:

Single species cover crop (oats)

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Cover crop mixture (oats, hairy vetch, and radish)

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Now in the third year of this project, this is the first time that we really definitively saw strong growth of all species in the mixture!

While there is no denying the amount of intrigue in using radishes as a cover crop, we typically have not seen as much success with it in Iowa when compared to other states, due to our shorter window of opportunity for fall growth. This year is turning out to be a good year for the radish, as well. Healthy radish growth was found throughout our mixture plots, with many radishes forming tubers around 1/2” in diameter. However, there were a few big boys that just went crazy…

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Moving across the farm to our corn plots (going to beans in ’16), the cover crop treatments included:

Single species cover crop (cereal rye)

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Cover crop mixture (rye, rapeseed, and radish)

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While the dates of cover crop planting and growing conditions (temperature, precipitation, sunlight – as related to leaf drop/canopy opening with the cash crop) certainly vary across the state, it is exciting to see such vibrant cover crop growth this fall.

How are the cover crops looking in your area? We’d love to see any photographs that you may have. Send them to us at ilf@iastate.edu, or share with Iowa Learning Farms on social media (we’re on Facebook and Twitter).

Ann Staudt

Another month of growth…

Over the last two weeks, Iowa Learning Farms team members (with help from our friends at Practical Farmers of Iowa) have been visiting ISU Research and Demonstration Farms statewide, checking up on our cover crop mixture plots planted as part of the National Conservation Innovation Grant.   Our visits to the six sites include collecting fall above-ground biomass from each of the cover crop plots, the final water sampling of the season, and winterizing the suction lysimeters until sampling resumes in spring.

In a previous blog post, I shared photos from the Armstrong Research and Demonstrations Farm in Southwest Iowa from our trip there at the end of September.   After another month-plus of growth, the cover crops are flourishing!  So for comparison purposes, let’s take a look post-harvest:

Treatment #1: Single Species Cover Crop (rye pictured here in corn plots)

Treatment #1: Single Species Cover Crop (Rye in corn plots, 9/26/2014)

Treatment #1: Single Species Cover Crop (Rye in corn plots, 11/5/2014)

And how about those mixtures?

Treatment #2: Cover Crop Mixture (Blend of rye, radish, and rapeseed shown here in corn plots)

Treatment #2: Cover Crop Mixture (Blend of rye, radish, and rapeseed in corn plots, 9/26/2014)

Treatment #2: Cover Crop Mixture (Blend of rye, radish, and rapeseed in corn plots, 11/5/2014)

And a few views from the soybean plots:

Cover Crop Mixture used in Soybeans (Blend of oats, radish, and hairy vetch)

Cover Crop Mixture used in Soybeans (Blend of oats, radish, and hairy vetch, 9/26/2014)

Cover Crop Mixture used in Soybeans (Blend of oats, radish, and hairy vetch, 9/26/2014)

Collecting water samples from suction lysimeter in Cover Crop Mixture plots (Blend of oats, radish, and hairy vetch, 11/5/2014 – All species present, but definite frost damage observed here)

Two sets of biomass samples are collected in each plot:

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Biomass Sampling in Progress: All cover crops within the quadrant are cut at ground level, collected in bags, and brought back to ISU for analysis to determine the amount of cover crop growth (# biomass/acre) and well as total carbon/total nitrogen content of the cover crop biomass collected. Biomass is collected in the fall (as close to hard freeze as possible) and in the spring (as close to termination as possible).

 

Want to learn more?   Join us for one of our upcoming November field days!   Detailed information for each is available on the Iowa Learning Farms website.

Nov. 12, 10:30 am-12:30 pm
Wallace Learning Center at Armstrong Research Farm
Lewis

Nov. 18, 10:30 am-12:30 pm
Borlaug Center at Northeastern Research Farm
Nashua

Nov. 19, 10:30 am-12:30 pm
Fire Department building
Kanawha

Nov. 20, 10:30 am-12:30 pm
Rob Stout farm, Washington Co.

Nov. 25, 11 am-1 pm
Truro Lions Club, Madison Co.

Ann Staudt