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

 

 

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.

 

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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

 

Research Rocks!

Hi! I am Emily Rehmann, and I am one of the high school interns for Water Rocks! and Iowa Learning Farms this year. I will be a freshman at Washington University in St. Louis next year, and I am excited to start a new adventure there.

MeetTheInterns-EmilyThis is my second year interning with Water Rocks!, and while I enjoyed a second season of counting middens and attending fairs with the Conservation Station, I also wanted to try something new: data analysis. I had already experienced collecting water samples in the field from lysimeters, and now I wanted to take it further and see the results of the project and finally the implications of the results and the effects that they could have.

In the most recent blog post, Getting Dirty and Getting Samples, Mary described how the water samples from lysimeters are collected. Where she left off, Jessica, another high school intern and my sister, and I come in.

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The Rehmann sisters out and about with the Conservation Station — Emily is on the left and Jessica (who blogged earlier this summer) is on the right!

We have been working on analyzing the lysimeter project data from 2014 and 2015. Lysimeters collect groundwater samples, which are sent to the lab and analyzed for nitrate. The Iowa Learning Farms team is comparing the amount of nitrate in the subsurface water for corn vs. soybeans, and single cover crop vs. a cover crop mixture vs. no cover crop.

There are five sites where the Iowa Learning Farms team has collected water quality data for three years now: ISU Research Farms at Lewis, McNay, Crawfordsville, Kanawha, and Nashua. Each site has 24 plots (and thus 24 lysimeters), with 12 plots each for corn and soybeans. Within each cropping system, there are three treatments: plots with no cover crops, plots with a single cover crop (oats before corn; rye before soybeans), and plots with a cover crop mixture (oats, hairy vetch, and radish before corn; and rye, rapeseed, and radish before soybeans).

 Data are collected about eleven times per year from each lysimeter (from approximately April through November, as the weather allows). This all adds up to a lot of data to analyze–almost 800 samples per year!

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We had ten of these big spreadsheets, plus summary sheets, by the end of the process!

Jessica and I compared the lysimeter results from one plot with itself throughout the year, from one plot with a certain treatment to other plots with the same treatment, as well as comparisons between treatments. We also looked at precipitation data and the volumetric water content at 12 and 24 inches deep in the soil, measured at each site (from Iowa State Agclimate Automated Weather stations). We lined up the data from the lysimeters with the precipitation and volumetric water content data at each site to look for patterns and correlations.

Analyzing data was a fun and challenging experience. It was fun to figure out how what would be interesting to look at and compare, and how to best present the data. As we worked through the data, we kept coming up with more ideas for what to do with it and what graphs to make.

Our preliminary results indicate a positive water quality benefit comes from using a cereal rye cover crop ahead of soybeans. Cover crop mixtures can also help, but so far, across multiple sites, we have found that having a single species cover crop of rye ahead of soybeans is the most effective treatment for having a low amount of nitrates leaving the field. Preliminary results from Kanawha are shown below as an example. Since I do not know what a statistical difference between measurements would be, I cannot claim any definite results of the data yet.

Kanawha Preliminary ResultsThe water quality trends were less clear with corn. While a single species cover crop (oats) is also the most effective for corn, it is far less effective than rye is for soybeans. The cover crops used ahead of corn (oats, hairy vetch, and radish) all either die off over the winter OR yield very little spring growth. The biggest difference in the soybeans was the use of cereal rye and its winter hardiness — the spring cover crop growth made a huge difference in terms of water quality benefits! As the rye on the soybean plots has more to time grow in the spring, it uptakes more nitrate. Corn is planted earlier in the season, so if rye were growing prior to corn, it would have to be terminated earlier, yielding less benefit for the nitrate uptake by the cover crop.

Ideally, the amount of nitrate leaving the field (represented by the water that a lysimeter collects) would be low. Nitrate is most useful on the farm field, as it is dangerous in high concentrations to humans and pollutes water. Depending on the final results of the data, this research could potentially be used to show how and which type of cover crops are most effective in holding the nitrate in place without letting it move into water sources.

IowaNutrientReductionStrategyThis research and its results are important for water quality across the state of Iowa. The Iowa Nutrient Reduction Strategy aims to reduce nutrients in water coming from point sources, like wastewater treatment plants, and nonpoint sources, like farms. A high concentration of nutrients can cause hypoxia, a condition of an area of water that cannot support marine life because it does not have enough oxygen. Hypoxia is a problem in the Gulf of Mexico, and currently the states along the Mississippi River have (or are working to develop) nutrient reduction strategies to help solve this.

This research is made more relevant with the current lawsuit between Des Moines Water Works and three Iowa counties. The Des Moines Water Works uses the Raccoon River for their half million consumers, and they want the amount of nitrates coming from farms in the counties to decrease.

Farmers can make a huge impact on the amount of nitrate in water. I attended a meeting of the Ames City Council in the spring, and the Water and Pollution Control Administration presented to the Council. They could put $36 million into reducing nitrate leaving their facility, but there would be little overall effect. Since farms contribute 92% of the nitrogen load, while municipalities only contribute 8%, we need to consider how much focus there is on reducing the contribution from the point source pollution sources in the municipalities as well as on farms. The research that we are doing will hopefully help show farmers that cover crops are a great way to reduce the amount of nitrate leaving their fields, while also helping to build soil health and protect our soil from erosion.

Overall this internship has been very influential in what I am interested in. I am undecided on what I would like to major in at WashU, but I know that I would like to continue studying science and the environment, including taking a class on environmental science. I care about protecting the water, soil, and climate, and this internship has helped me to realize that.

Emily Rehmann

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

Friday Photos: Cover Crops Thriving!

ILF staff visited the Armstrong Research and Demonstration Farm in Southwest Iowa earlier today, and we were pleased to find some good growth in our recently-seeded cover crop plots.   As part of a National Conservation Innovation Grant looking at cover crop mixtures, these plots involve an investigation of three different cover crop treatments:

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 #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 #3: No Cover Crop (in some very nice looking no-till!)

Treatment #3: No Cover Crop (in some very nice looking no-till, 9/26/2014)

 

The crops are looking great in SW Iowa, as are the cover crops.  However, when walking through the plots, beware of badger holes!

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One very ambitious badger makes its home in our corn plots at the Armstrong (SW) Research and Demonstration Farm.

The cover crop species in our plots are different based on whether they are planted into standing corn or soybeans.  The above images all come from standing corn.   Here’s a view from the soybean plots, as well:

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)

How are your cover crops looking this fall?  We’d love to see any photographs you may have, and will share them in future blog posts. Send them to us at ilf@iastate.edu.

Ann Staudt