Impact of cover crops on weed management

Dr. Bob Hartzler, professor of agronomy and an extension weed specialist, and Meaghan Anderson,  field agronomist in central Iowa posted this recent Integrated Crop Management blog on the impact of cover crops on weed management.

LichtBlog-02One benefit of planting cover crops is their contribution to weed management.  While several factors contribute to the inhibition of weeds by cover crops, the physical barrier of cover crop residue on the soil surface is most important.  Research has shown a strong relationship between the amount of cover crop biomass at termination and the level of weed control provided by the cover crop.

Because of the importance of cover crop biomass, it is essential to manage the cover crop to maximize growth when using cover crops to aid weed management.  The following practices have a major influence on cover crop biomass:

1) Planting and termination date.

2) Cover crop species.

Due to the risk for negative effects of cover crops on corn yield, there is greater potential for using cover crops for weed suppression in soybean.  The longer termination is delayed, the greater accumulation of biomass, and the more benefit in suppressing weeds.  In most years, delaying termination until mid- to late-May will allow sufficient biomass for consistent weed suppression.

Increasing the seeding rate of cereal rye above recommended rates generally has little impact on the quantity of biomass when termination is delayed, except in cases of very late planting. The tillering ability of rye is responsible for the lack of responsiveness to seeding rate.  Higher seeding rates may result in more rapid ground coverage in the fall and early spring, but the impact of seeding rate on biomass is diminished when termination is delayed until stem elongation.

Be sure to read the full blog here to learn more about potential reductions in herbicide use and allelopathy considerations.

Finding the right seeding method – which option is best for you?

ILFHeaderJust ask Clayton County farmers Mark Glawe, Dan Keehner and Brian Keehner! Each have explored different seeding methods and shared their tips for successful cover crop management at our field day on November 29th in Luana. Although their soil types, crop rotations and seeding method vary, they share similar goals for using cover crops in their operations – improved soil health and reduced nutrient losses.

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Left to Right: Farmer Panelists Dan Keehner, Brian Keehner, Mark Glawe, and Eric Palas, Clayton County SWCD Project Coordinator

Mark Glawe began using cover crops in his no-till system near Elkport in 2006 to address soil erosion concerns on his steep slopes. In early September, he seeded about 2/3 of his acres aerially with oats, rye, radishes and rapeseed. These acres are grazed by his cattle herd following harvest and again in the spring. This year, Mark turned his cattle out in October and estimates his additional forage value at $35/acre. In addition to the aerially seeded acres, Mark’s son follows the combine on the remaining acres to drill cereal rye to keep the steep slopes covered between crop seasons.


Dan Keehner first started with aerially seeded cover crops in 2013 on his ground near Monona. Noting disappointment with the consistency of the stand, he hired the cereal rye cover crop to be drilled after harvest in 2014. Similar to this fall, harvest was delayed and the drilling wasn’t completed until mid-November. With limited fall growth but more consistent stand, Dan decided to set up his own cover crop seeding rig for 2015.

Using his vertical tillage implement, Dan mounted an air seeder to seed the cover crop himself following harvest and has covered all of his acres with a cover crop since 2016. He uses both cereal rye and winter wheat to keep the ground covered until planting of his cash crop in the spring.

“I love seeing one crop (cover crop) go down and another (corn/soybeans) come up. You know when you get the rains, that soil is protected,” stated Dan.


Similar to his cousin, Brian Keehner has tried multiple seeding methods but wasn’t satisfied with the results. Through custom innovation, and discussion with a cover crop user in Indiana, Brian has modified his combine with an air delivery system on his corn and soybean heads to seed the cover crops while harvesting. This method fits the needs of his operation by saving time, labor and fuel by combining passes. His next goal for the system is to increase his seed carrying compacity to reduce the number of refill stops.

Regardless of how they seeded their cover crops, all three producers reported 0.5-1.2% increases in their soil organic matter over a five year time-frame. The combination of no-till and cover crops has led to the retention and building of soil organic matter on their lands. The building of organic matter helps improve water holding capacity and retention of soil micro-nutrients needed for crop production. With healthier soils, we have healthier crops and water!

Liz Juchems

Conservation: Investing in the Land for Years to Come

Farmers and landowners pulled in to West Iowa Bank in Laurens earlier this week for a cover crop + conservation field day.  Wait, a field day at a bank?!  That’s not a typo.

A regular trip to the bank might involve a deposit transaction, reflecting how we invest our money.

This trip to the bank was all about how we invest in the future of our land—reflecting how conservation practices are an investment in our land and our water for generations to come.

Cover crops and no-till, in particular, were at the heart of the conversation during the field day. Out in the field, after lunch, we saw some nice fall growth of cereal rye, thanks to host farmer Dick Lund.

 

Back to thinking in terms of investments, that theme ran deep as area farmers shared the following thoughts in the farmer discussion panel:

 

Investing in conservation practices like no-till can mean saving money, too:

This field day was a collaboration of Soil Health Partnership, Practical Farmers of Iowa, Iowa Farmers Union, Iowa Seed Association, Iowa Department of Agriculture and Land Stewardship Clean Water Initiative, Iowa Corn, Iowa Soybean Association, Iowa Agriculture Water Alliance, and Iowa Learning Farms.

Iowa Learning Farms has a handful of additional field days still coming up this month, now that harvest is just about wrapped up. Visit our events page to find one near you and RSVP today!

Ann Staudt

Grass species most popular cover crops among Iowa farmers

Grasses, brassicas, legumes – oh my! With so many cover crop species to choose from, how does one decide?

One way is to look at what the producers in your area are using and observe how well those species will help reach the goals you have for your land. Here are some examples of cover crops by group:

  • Grasses = cereal rye, oats, wheat, triticale, barley
  • Brassicas (plants producing a tap root) = radishes, rapeseed, mustards
  • Legumes = red clover, crimson clover, hairy vetch, peas

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To help identify what cover crop species are being used across the state, we asked our 2017 field day attendees.  Responses to our 2017 Field Day Evaluation Report are similar to our conclusions of what works best in our cover crop species research projects. Grasses are the best choice of cover crops for a corn/soybean system. Cereal rye was the mostly widely used species, with 85% respondents listing it as what they seeded in 2017. Reported brassica and legume usage is down overall compared to 2016 data.

Cover Crop Species

For those looking to get started with cover crops, we recommend the following:

Oats Before Corn & Cereal Rye Before Soybeans

These cover crop species are relatively inexpensive, readily available and easy to establish. Oats will winter kill whereas cereal rye is winter hardy and requires spring termination. That is why we recommend using it before soybeans to provide the best opportunity for first time cover croppers to learn how to manage the cereal rye and minimize negative yield impacts.

Liz Juchems

Farmer Profile: Ben and Andy Johnson

Ben and Andy Johnson_cropCLLThe Johnson brothers farm in Floyd County where they grow corn and soybeans and manage a ewe flock and feeder lamb operation. The duo are no strangers to conservation and trying new practices. They began no-tilling soybeans over fifteen years ago and have nearly ten years of experience strip-tilling corn. Other conservation methods they have employed on their farm include buffer strips, prairie CRP, pollinator habitats, field windbreaks, a pheasant safe program and cover crops.

Ben began using cover crops in 2013 when a wet spring delayed planting on hundreds of acres until it was too late to plant a cash crop. Not wanted the fields to remain empty all year, Ben planted oats and radishes for the first time. As to why he does it, Ben explained, “I want all my black soil still on top of my hills and not at the bottom of all of them, not in my road ditches and not in the Cedar River.” Within his no-till system for soybeans and strip-till system for corn, he found that using cover crops helped control erosion and improved organic matter and overall soil structure.


“I want all my black soil still on top of my hills and not at the bottom of all of them, not in my road ditches and not in the Cedar River.” – Ben Johnson


In 2016, Iowa Learning Farms approached Ben and Andy to be a part of a new Conservation Learning Labs* (CLL) project that is studying changes in nitrogen and phosphorus loss at the delivery scale. The Johnsons farm near an existing Conservation Reserve Enhancement Program (CREP) wetland in Floyd County that has measured water quality for about three years.

Using the CREP wetland monitoring system, the project will be able to measure changes in water quality after cover crops are planted in the project area over the next three years. The Johnsons agreed to participate in the CLL project, and in fall of 2017 they seeded cover crops on over 54% of the nearby research watershed acres.

Ben says, “The easiest place for somebody to start is no-tilling their beans. They don’t really seem to respond to tillage and it’s such a labor and money eater. That’s the biggest reason we switched. The most precious resource on my farm is time.”

Ben Johnson and his wife Amy have two sons, Jackson and Riley. Andy Johnson had his wife Abbie also have two young sons, Kyle and Carter. Ben was featured in our Conservation Chat podcast – listen to the episode to hear more about his operation and what drives his conservation ethic.

Julie Winter

*The Conservation Learning Labs project is funded by the Iowa Department of Agriculture and Land Stewardship (IDALS) and the United States Department of Agriculture – Natural Resources Conservation Services (USDA-NRCS) of Iowa.

Reducing Soil Erosion with Cover Crops: New Infographic

Iowa Learning Farms is pleased to announce the release of a new infographic publication titled Reducing Soil Erosion with Rye Cover Crops.

This visually engaging document highlights one of the biggest benefits of cover crops — the ability to significantly reduce soil erosion. Based upon long-term cover crop work conducted by Korucu, Shipitalo, and Kaspar, colleagues at the USDA-ARS National Laboratory for Agriculture and the Environment here in Ames, this study looks specifically at one of Iowa’s most popular cover crops, winter cereal rye.

The USDA-ARS team conducted in-field simulated rainfall studies on plots with and without cereal rye cover crops, and their findings are powerful in terms of quantifying erosion reduction – 68% less sediment in surface runoff water with a rye cover crop. Further, the amount of surface runoff water decreased, while the amount of water infiltrating was found to increase with the cover crop.

This study was conducted in central Iowa, in the heart of the Des Moines Lobe, on land with a 2% slope. Substantial erosion reductions were found here with rye cover crops — consider the benefits of cover crops to reduce erosion on more sloping lands across the state!

The full infographic is available as a free PDF download on the Iowa Learning Farms website. Clicking on the image below will also take you right there.

Ann Staudt

Do cover crops reduce phosphorus loss?

Cover crops are proven to reduce nitrate loss and decrease soil erosion on our agricultural landscape, but field scale studies on phosphorus loss are still in their infancy. Drs. Antonio Mallarino, Matt Helmers, Rick Cruse, John Sawyer with Iowa State University and Dan Jaynes with National Laboratory for Agriculture and the Environment have completed two years of a long-term field study and have released their preliminary results.

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The Hermann farm site south of Ames allowed Mallarino’s team to observe the effects of cover crops on phosphorus in the runoff study funded by the Iowa Nutrient Research Center.

The study is located at south of Ames on Iowa State’s Hermann Farm. The study includes replication on 12 areas ranging from one to three acres in a field that tested very high in soil phosphorus and is managed with a corn and soybean rotation. The study compares the use of winter cereal rye cover crops with and without tillage.

After two years, Dr. Mallarino observed:

“It is confirmed that cover crops reduce soil loss with tillage or no-till but mainly with tillage. Results also show that with tillage a cover crop reduces phosphorus loss. But it is not so clear that with no-tillage management a cover crop reduces phosphorus loss,” Mallarino said. “With no-tillage, there seems to be a small reduction in particulate phosphorus loss, but an increase in dissolved phosphorus loss.”
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Surface runoff at the testing site is evaluated for total solids and several forms of nutrients.

Why the focus on dissolved phosphorus? The Iowa Nutrient Reduction Strategy is a technical, scientific and voluntary approach to reducing the loss of nitrogen and phosphorus to our waterbodies and the Gulf of Mexico that is home of a large hypoxic or dead zone.  Both particulate and dissolved phosphorus are part of the reduction goal, however dissolved phosphorus is responsible for algae blooms and has a visible impact on aquatic ecosystems.

Caution should be taken when drawing conclusions from only two years of data. Environmental factors play a role in nutrient dynamics with surface runoff, and during the two years of the study, major rain events at the test site had been minimal with very low runoff.

“We can’t make a strong conclusion from these two years of data. There needs to additional data collection from this site and better science-based projecting so we can encourage the addition of cover crops for the right reasons,” Mallarino said.

Click here to read the full article and learn more about project.

Questions about the project contact:

Antonio Mallarino, Agronomy, 515-294-6200, apmallar@iastate.edu

 

Liz Juchems