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

 

 

Cover crop researcher Tom Kaspar receives Spencer Award

Congratulations to our friend and collaborator, Dr. Tom Kaspar, on receiving the Spencer Award for Sustainable Agriculture yesterday!

Long regarded as the grandfather of cover crops here in the state of Iowa, USDA-ARS plant physiologist Tom Kaspar is certainly one of the leading voices on cover crops across the Midwest.  He was one of the “founding fathers” of the Midwest Cover Crops Council, and his collaborative work over the years has investigated and documented the benefits and challenges of cover crops in corn and soybean cropping systems, ranging from impacts on water quality, soil health, nutrient cycling, and more.

We are grateful to Tom for serving as a guest speaker at countless Iowa Learning Farms field days and workshops over the years, sharing his findings with farmers, landowners, and other ag partners across the state. We are also grateful for his efforts in guiding the work of the Iowa Cover Crop Working Group, including our long-term on-farm rye study and our study of earthworms and cover crops.

Kaspar has amassed years of experience investigating not only soil health and cover crops, but also connections with no till, minimum tillage, climatic variations, disease, pathogens, and more. To hear some great perspectives from the man himself, check out Episode 6 of the Conservation Chat podcast, in which host Jackie Comito talks cover crops with Dr. Tom Kaspar.

Kaspar was also featured in our August 2015 Iowa Learning Farms webinar, presenting on Reaching the Full Potential of Cover Crops in Iowa.  Stay tuned to the blog, as well — we’ll be highlighting some of Kaspar’s cover crop findings here in the next week or so.

In the meantime, congratulations to Tom for an honor that is very well deserved!

Ann Staudt

 

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.
springbiomass

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.

Earthworms serve as Indicator of Soil Health

A friend of the farmer, gardener, and angler alike, the earthworm may help to unlock the secrets of the soil by serving as an early indicator of soil health!  Anecdotally, farmers have expressed benefits to using cover crops and noted improvements to their soil, but quantifying changes in soil health can be complex to measure (and require years of intensive sampling). That’s where earthworms come into play!

Thanks to funding from a USDA-NRCS Conservation Innovation Grant, the Iowa Learning Farms team is studying the common nightcrawler, Lumbricus terrestris, and investigating its population dynamics in agricultural ecosystems.

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In particular, we are conducting midden counts at seven sites across the state (6 on-farm demonstration sites, 1 research site), all managed as a no-till corn/soybean rotation.

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Within that system, we are evaluating earthworm populations on side-by-side strips with and without cereal rye cover crops.  Read more about the study in our earlier blog posts Guest Blog: Digging for Worms and Midden Madness.

What have we found?

The midden counts conducted in June 2016 indicate that on each site, strips with a cereal rye cover crop have comparable or higher earthworm counts than those without a cereal rye cover crop …

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Looking at all sites together across the board, we see statistically significant differences between the strips with a cereal rye cover crop and those without. Based upon this preliminary data set, we are seeing 38% more earthworm middens with a cereal rye cover crop!

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If you’d like to learn more, I just gave a webinar earlier in the week on this topic. The archived webinar can be viewed on the Iowa Learning Farms webinar page (along with all of our previous webinars). Click on the November 16 webinar to view Earthworms and Cover Crops: Unlocking the Secrets in Soil!

Ann Staudt

This material is based upon work supported by the Natural Resources Conservation Service, U.S. Department of Agriculture, under NRCS Conservation Innovation Grant 69-6114-15-005.

Cover crops key to N retention + soil health, especially before soybeans

How can we increase nitrogen retention and soil health in Iowa’s corn and soybean cropping systems? There is not just one single quick fix, but Dr. Mike Castellano, William T. Frankenberger Professor of Soil Science and Associate Professor in the Department of Agronomy at Iowa State University, made the strong case for cover crops in last week’s Iowa Learning Farms webinar.

Castellano framed the webinar with a discussion of nitrogen budgets. As he put it, we don’t typically think about financial management without a budget – nutrient management is the same way! He then explored the potential of cover crops, especially cereal rye, to aid farmers in retaining nitrogen (via the cover crop plant biomass) and building soil organic matter. Watch the full archived webinar on the Iowa Learning Farms website: https://connect.extension.iastate.edu/p6kfk1qr4te/.

OR, if you’d like the CliffsNotes version, here are the Top 5 key take home points that jumped out at me…

cc-top5takehomepoints-iiAgain, you can check out the full presentation on the Webinar Archives page of the Iowa Learning Farms website.

Save the date…
The next Iowa Learning Farms webinar will be Wednesday, October 19 at 1:00 p.m., featuring our own Dr. Matt Helmers. He will be addressing common questions and misconceptions regarding cover crops, drainage, and more … think Mythbusters meets water quality! It’s sure to be a lively conversation.

Ann Staudt

 

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.

ConservationStation-Emily&Jessica

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

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!

LetItGrow

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