Research and Field Crops Director
Stefan Gailans joined Practical Farmers of Iowa in August 2013. An agronomist by training, Stefan's primary responsibility is to manage the Cooperators' Program, Practical Farmers of Iowa's vehicle for conducting on-farm research on the issues and concerns deemed most important by our members. He also coordinates field days, conference sessions and work shops for PFI's field crops program.
Stefan grew up in southeast Wisconsin and gained an appreciation for the environment after spending many hours hunting and fishing with his family. This appreciation for the environment birthed a curiosity in the intersection of the natural landscape and the ever-present agricultural landscape. Stefan pursued this curiosity, receiving his BS degree in Crop Sciences from the University of Illinois in 2005 and an MS in Sustainable Agriculture and Crop Production & Physiology from Iowa State University in 2010. In 2013, he completed his course work for a PhD in the Agronomy Department at ISU. His primary research interests were cover crops, third crops and alternative crop rotations.
Stefan enjoys calling Ames (and Iowa!) his home and looks forward to working with farmers across the state and addressing their research concerns. When he’s not thinking about crops, Stefan enjoys listening to music, seeing local bands with friends, listening to the radio, reading science fiction novels that envision interesting (and intriguing) futures, spending time outdoors, and cooking & eating quality local food.
Cover crops are typically either aerially seeded into standing crops around the time of physiological maturity in late summer or drilled immediately following crop harvest in the fall. However, on occasion time does not permit one to get a cover crop seeded in the fall or the cover crop fails to establish.
In 2017, farmer-researchers Jeremy Gustafson and Chris Teachout evaluated spring cover crops that were seeded in March approximately 50 days before planting soybeans later in the spring.
Read the full report here: Spring-Seeded Cover Crops Ahead of Soybeans.
How Was the Trial Conducted?
Jeremy Gustafson conducted a trial in one field where he seeded oats. Chris Teachout conducted trials in two separate fields where he seeded two different cover crop mixes. See the table below for cover crop and soybean management at the two farms.
Aboveground biomass of the cover crop mixes was sampled the day before termination on May 27 at Gustafson’s and amounted to 1,537 lb/ac. Teachout did not collect biomass samples but reported that the mix in Field 1 was 6-10 in. tall at termination on May 19 and the oats+barley in Field 2 was 8-10 in. tall at termination on May 19. He also noted far less weed growth in the cover crop strips compared to the no-cover strips in both fields (weed biomass or weed counts were not collected, though).
Soybean yields at Gustafson’s (one field) and Teachout’s (two fields) are shown in the table below. In all three fields, the spring-seeded cover crop had no affect on soybean yield compared to no-cover crop.
Because they saw no reduction in yield, both farmers are considering using this practice in the future. “I will use this practice [in the future] in the case of no fall seeded cover crops,” Teachout said. “The next steps are to see if spring-seeded covers can be grown with early planted soybeans as a beneficial nurse crop.”
For more details on this trial, read the full report here: Spring-Seeded Cover Crops Ahead of Soybeans.
This project was supported by the Walton Family Foundation.
In Iowa, cover crops are typically either aerially seeded into standing corn around the time of physiological maturity in late summer or drilled immediately following corn harvest in the fall. However, the earlier one can seed a cover crop, the more potential for growth and biomass production. An earlier seeding date also opens up the opportunity for more diverse cover crops like brassicas and legumes that need more time and heat units to grow than common cover crops like cereal rye.
Farmer researchers Jack Boyer and Jeremy Gustafson interseeded cover crops (cowpeas, annual ryegrass, rapeseed) into corn at the V4 stage in June. Corn hybrids chosen exhibited vertical and horizontal leaf orientations to test whether more light penetrating the corn canopy would encourage successful cover crop establishment and growth.
Read the full report here: Corn Leaf Architecture for Interseeded Cover Crops.
How Was the Trial Conducted?
- Corn planting date (both hybrids): Boyer = Apr. 25; Gustafson = May 5
- Cover crop mix interseeding date: Boyer = June 14; Gustafson = June 16
- Cover crop mix seeding rates: Cowpeas (60 lb/ac); annual ryegrass (22 lb/ac); rapeseed (7 lb/ac)
- Corn harvest date (both hybrids): Boyer = Nov. 4; Gustafson = Oct. 25
Aboveground biomass of the cover crop mixes was not sampled but photographic evidence shows that cover crops persisted beneath the corn canopy into early fall at both farms.
Corn yields at Boyer’s were affected by the hybrid (horizontal leaf architecture vs. vertical leaf architecture) and the interseeding. See figure below.
At Jeremy Gustafson’s, corn yields were not affected by hybrid or planting population. All strips were interseeded. See figure below.
“The seed germinated well,” Gustafson said, seeing mostly cowpeas by mid-September. “Not much made it into fall, though. Leaf architecture didn’t seem to matter and lack of rain really played havoc with this trial.”
“This technique requires more testing before wide spread adoption,” Boyer said. “I need to understand what caused the yield hit. The cover crop species I interseeded worked with both corn varieties, so I will probably try another interseeding with just one variety.”
For more details on this trial, read the full report: Corn Leaf Architecture for Interseeded Cover Crops.
This project was supported by the Walton Family Foundation.
A roller-crimper presents farmers the opportunity to mechanically terminate cover crops without chemicals or tillage. This method is dependent on a large amount of cover crop growth and the cover crop reaching the flowering stage before crimping. A roller-crimper is a large, metal cylinder with “chevron” pattern blades that simultaneously lays the cover crop flat on the ground and crushes the stem in several places. Successful termination of a cover crop with the roller-crimper is dependent on the cover crop being at the anthesis (flowering) stage at the time of rolling. For cereal rye, this flowering stage is likely to occur in late May in Iowa.
Farmer-cooperator Tim Sieren compared soybean seeding dates relative to cover crop termination (before and after) as well as cover crop termination techniques (chemical vs. roll-crimp). “If I can manage a roller-crimper system in soybeans, while maintaining yields,” Sieren said, “I could drastically reduce herbicide use.”
Read the full report here: Roll-Crimping Cover Crops and Soybean Seeding Date.
How was the trial conducted?
This trial was conducted by Tim Sieren of Green Iron Farm near Keota in Washington County. Treatments included:
- Plant-then-spray: plant soybeans (Apr. 24), then spray the cover crop (May 5)
- Spray-then-plant: spray the cover crop (May 5), then plant soybeans (May 7)
- Plant-then-roll: plant soybeans (May 7), then roll the cover crop (May 30)
- Roll-then-plant: roll the cover crop (May 30), then plant soybeans (May 30).
Soybean yields were mostly affected by cover crop termination date (table below). Regardless of soybean seeding date, yields were greater on average by 10.5 bu/ac when the cover crop was terminated with herbicide on May 5 compared to roll-crimping the cover crop on May 30.
Roll-crimping the cereal rye cover crop proved to be a challenge. “The rye needs to be roll-crimped before the planter goes through, not after,” Sieren said. “I didn’t have a heavy enough stand to crimp down, and stay down (possibly due to the May 17 hailstorm). It didn’t kill all the rye, and after 2 weeks, you couldn’t tell it had been crimped, and it stayed greenish until I finally hit it with glyphosate 2 weeks later. Then it died and the beans finally acted like they wanted to grow.”
When Sieren waited to roll-crimp the cover crop on May 30, soybean yields were similar between the May 7 and May 30 seeding dates, but they were also less than when the cover crop was chemically terminated on May 5. With the May 30 cover crop termination (roll-crimp), Sieren achieved yields equivalent to his county’s average with only a single in-season herbicide application on June 27.
For more details on this trial, read the full report: Roll-Crimping Cover Crops and Soybean Seeding Date. This project was supported by the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation.
How does a cover crop affect corn and soybean yields? Winter Cereal Rye Cover Crop Effect on Cash Crop Yield: Year 9 is now available! This is a long-term project being conducted by Iowa Learning Farms and Practical Farmers of Iowa. Between 2009 and 2017, 12 farmer-cooperators have contributed to 63 site-years of on-farm research to investigate what effect a cereal rye cover crop might have to yields of corn and soybeans.
Over the course of this project, farmers reported that in 59 of 63 site-years, properly managed cover crops had no negative effect on corn and soybean yields. Of those 59 site-years, soybean yields were improved by cover crops in 8 instances and corn yields were improved in 2 instances (both occurring in 2016).
How the Study was Conducted
This long-term study employs a “paired strips” design. Cooperators established and maintained replicated strips of “cover” and “no cover” that run the length of their field for the duration of the study in corn-soybean rotations. Cooperators were allowed to manage their cover crops and cash crops however they saw fit. The table below shows how the five farmer-cooperators who participated in 2017 managed cover crops and cash crops during the growing season.
Corn and Soybean Yields 2015 – 2017
In the past three years, corn yields at locations have mostly been at or above 200 bu/ac (Fig. 1). In 2016, corn yields were improved by the cover crop at West Chester and New Market. At New Market, an especially wet year reduced corn yields overall but the cover crop appeared to soften that blow.
Soybean yields have been near 60 bu/ac the past three years with improvements from the cover crop being observed at New Market, West Chester and Kalona in 2015 and New Market again in 2017 (Fig. 2).
Over the course of this project, 35 site-years have been dedicated to determining the effect of the cover crop on corn yields and 28 site-years have been dedicated to determining the effect of the cover crop on soybean yields. In the majority of cases, yield were not affected by the cover crop. Read the full report here.
For more information on this study, contact Stefan Gailans at [email protected]
This project has been made possible by funds provided by the State Soil Conservation Committee, the Iowa Department of Agriculture and Land Stewardship, NCR-SARE, the Walton Family Foundation and Iowa Learning Farms.
Successfully raising corn after a cover crop requires timely cover crop termination and N fertilization. Commonly, farmers terminate a cover crop 2-3 weeks prior to planting corn but generally do not need to apply any more N than if they did not use a cover crop. Last year, PFI farmer-cooperator Dick Sloan attempted “planting green”: planting his corn into a cereal rye cover crop that was terminated just two days prior. In Sloan’s case, he saw a 5 bu/ac yield reduction compared to where he terminated the cover crop two weeks prior to planting corn yet stands were equal between the two treatments (Cover Crop Termination Date Ahead of Corn). This past growing season, farmer-cooperators Dick Sloan and Tim Sieren compared terminating their cover crops approx. 3 weeks prior to planting corn with terminating their cover crops within 3 days of planting corn. They also investigated N fertilizer timing and rates across the cover crop termination dates.
You can read the full report of this project here: N Fertilizer Strategies for Corn Following Cover Crop.
How was the trial conducted?
This study was conducted by Dick Sloan in two fields near Rowley in Buchanan County and Tim Sieren in one field near Keota in Washington County.
Cover crops used
- Sloan, corn following corn field: winter wheat, oats, winter barley and rapeseed
- Sloan, corn following soybeans field: winter wheat, winter barley and cereal rye
- Sieren: cereal rye
In addition to comparing cover crop termination dates before corn planting, Sloan compared “low” and “high” N rates in both of his fields (Table 1) while Sieren assessed N application timing and form (applying 140 lb N/ac in each of his treatments) (Table 2).
At either farm, when the cover crops were allowed to grow until the May 5 termination (1-3 days before planting corn on either farm), the cover crops produced over twice as much aboveground biomass as the cover crops terminated on Apr. 17 (Figure 1).
“I was amazed at how well the corn planted into tall, thick covers,” Sloan said.
Across both farms, terminating the cover crop near the time of corn planting (3 or 1 DBP) often resulted in a yield reduction compared to when the cover crop was terminated about 3 weeks prior to corn planting (21 or 19 DBP) (Tables 3, 4 and 5). Higher N rates or varying the N strategy at the farms did not appear to overcome the yield reducing effects of terminating the cover crop near corn planting. The exception came where Sloan followed corn with corn and applied fall hog manure in addition to applying N fertilizer at corn planting and side-dress (Table 3). In this instance, terminating the cover crop three days before planting corn resulted in no yield drag compared to when he terminated the cover crop 19 days before planting corn.
Sieren applied 140 lb N/ac to all treatments but varied when he applied and in what form. Regardless of N strategy, he scored top returns when he terminated the cover crop 19 DBP (Table 5). Sieren saw greatest returns to N fertilizer strategy when the cover crops were terminated 19 DBP and yields were also greatest. Nitrogen costs were greatest and returns on investment were least when the cover crops were terminated 1 DBP.
“I really expected that this would be an example of ‘Don’t do stupid stuff’, which it kind of is!” Sloan said. “Just the physical environment those young plants grew out of, the shading and crowding of all that residue standing there for weeks, it’s not something a farmer would do. But it was a much closer competition than I expected. The corn after corn plot (Table 3) did not have the same level of competition between covers and corn (Figure 1), so it’s not the cover crop termination date, it’s the amount of cover crop biomass you’re planting into.” The cover crop in the corn-following-corn field at Sloan’s was comprised of winter wheat, oats, winter barley and rapeseed. The lack of cereal rye in that mix may have contributed to the less amount of biomass produced than in the corn-following-soybean field where the cover crop was winter wheat, winter barley and cereal rye.
For more details on this trial, read the full report: N Fertilizer Strategies for Corn Following Cover Crop. This project was supported by the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation and the Natural Resources Conservation Service of the USDA.
Cover crops are gaining new attention for their ability to reduce weed pressure in soybeans. Specifically, when seeding soybeans directly into a thick cover crop. In the past two years, farmer-researchers Jeremy Gustafson and Jack Boyer have documented reduced herbicide use when planting soybeans into a tall, thick cereal rye cover crop that they chemically terminated near the time of soybean planting (Cereal Rye Cover Crop Termination Date Ahead of Soybeans). In this new project, farmer-cooperators Jack Boyer and Scott Shriver investigated the effect of row-width on soybean yields when rolling a cereal rye cover crop. Boyer rolled select strips after terminating with an herbicide; Shriver used a roller-crimper to terminate his cover crop.
You can read the full report of this project here: Rolling Cover Crops and Soybean Row-Width.
How was the trial conducted?
This trial was conducted by Jack Boyer near Reinbeck in Tama County and Scott Shriver (certified organic) near Jefferson in Greene County. At both farms, treatments were replicated four times in side-by-side strips running the length of the field. Cereal rye cover crop was drilled on Oct. 1, 2016 at a rate of 50 lb/ac at Boyer’s and on Oct. 11 at a rate of 160 lb/ac at Shriver’s.
Treatments at Boyer’s:
- Soybean row-width: 10-in. vs. 30-in. Seeded 5 days prior to cover crop termination.
- Cover crop termination: Spray, then roll cover into flat mulch vs. Spray, then let cover stand.
Treatments at Shriver’s:
- Soybean row-width: 7.5-in. vs. 15-in. vs. 30-in. Seeded 5 days prior to roll-crimping cover crop.
At Boyer’s, drilling the soybeans in 10-in. rows scored top yields regardless of whether the cover crop was rolled or not. “In general, I did not see a benefit from rolling the rye when using my usual seeding method of drilling,” Boyer said. “I believe that this is partially due to the harrow behind the drill performing some of the same effects as rolling.” Drilling soybeans in 10-in. rows and not rolling the terminated cover crop also netted Boyer the greatest returns on investment from the cover crop (less passes across the field!). In-season weed control was achieved entirely with the cover crop mulch (either rolled or left standing). In other words, after terminating the cover crop, Boyer did not need to spray again for weeds.
Boyer did experience some difficulty while harvesting the soybeans in 30-in. rows where the cover crop was not rolled. “The rye was standing between the rows and had a tendency to bunch up and create a blockage [while combining],” he said. “In the 10-in. rows the drill apparently laid the rye down enough that it was not as much of a problem.” Boyer also estimated that the final stand in the not-rolled, 30-in. row-width treatment was approximately 30% lower than the other treatments.
Shriver also saw his best yields with the narrowest row-width he used: 7.5-in. Soybean plant populations and yields were drastically reduced with the 15- and 30-in. row-widths. He noted some difficulty planting into very thick cover crop residue (15,165 lb/ac) in early June (i.e., closing the seed trench). “I had an overall problem in the field of getting the soybeans to grow and I think it was mostly due to poor planting (open seed trench, planter penetration, seed to soil contact, etc.) heightened by lack of rainfall,” he said. Shriver accomplished the different row-widths by offsetting his planter with auto steering and making multiple passes over the same area to get the 15- and 7.5-in. row-widths. “I believe these multiple passes helped the previous passes with their poor planting issues. Therefore, I do not believe we can conclude that the yield differences are solely from the different row spacings.”
For more details on this trial, read the full report: Rolling Cover Crops and Soybean Row-Width. This project was supported by the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation.
Cover crops in Iowa are typically seeded in late summer or fall. The most common cover crops are winter small grains like cereal rye or winter wheat. But farmers are increasingly interested in diversifying the cover crop portfolio in Iowa. In this trial, cooperators wondered: Can frost-seeding small-seeded brassica species into crop residue be an effective spring cover crop strategy? Because mustard and rapeseed have relatively small seeds, some have wondered if frost-seeding these into crop residue in the early spring could be an effective 40- or 50-day cover crop strategy. Read the new report here: Spring-Seeded Brassica Cover Crops.
How was the trial conducted?
Three PFI farmer-cooperators participated in this project: Steve McGrew (Emerson, SW Iowa); Jeremy Gustafson (Boone, central Iowa); Chad Ingels (Randalia, NE Iowa). In the early spring, cooperators hand-seeded brassica cover crops into soybean stubble in small plots measuring 7.5 ft x 25 ft. McGrew screened Trophy rapeseed, Daikon radish and Pacific Gold brown mustard. Gustafson and Ingels evaluated Dwarf Essex rapeseed, Kodiak brown mustard and Purple Top turnip. All cover crops were seeded at a rate of 5 lb/ac at each location.
Before terminating the spring cover crops, cooperators evaluated each species for the amount of groundcover provided.
At McGrew’s, the Pacific Gold mustard provided nearly 25% groundcover which was significantly greater than the Trophy rapeseed (11%). The Daikon radish did not establish. At Gustafson’s and Ingels’s, Kodiak mustard was the top performer. There were no differences between the Dwarf Essex rapeseed or Purple Top turnips, though. The cover crops at McGrew’s and Gustafson’s provided approximately twice as much groundcover as those at Ingels’s.
Not surprisingly, more GDD were accumulated in the southwest (McGrew) and center (Gustafson’s) than in the northeast (Ingels) and this translated into more groundcover by the cover crops at McGrew’s and Gustafson’s.
“I might try this on a larger scale and try to plant [the cover crop] sooner,” McGrew says. “[This technique] might fit where the [fall-seeded] broadleaf cover crops don’t overwinter well. I am considering planting a winter-kill grass like oats or barley and then maybe mustard and rapeseed broadcast during the winter before corn.”
Continuing work from the previous two years, Practical Farmers of Iowa and partners conducted another round of oat variety trials in 2017. Fifteen varieties were screened at two Iowa State University research farms (Kanawha, Nashua) and one PFI farmer-member farm (Wayne Koehler, Charles City) Find the new report here: Oat Variety and Fungicide Trials 2017.
- The variety Antigo had the highest test weight at each location (>38 lb/bu) but was also among the lowest yielding varieties. Reings scored a test weight of 38 lb/bu at Kanawha
- Application of fungicide did not improve oat yield or test weight for the four varieties tested at Nashua
Learn more about this project below.
Varieties Included in 2017
Oat Yields at Kanawha
Natty and Betagene were the top yield performers at Kanawha with Antigo scoring the highest test weight.
Oat Yields at Charles City
Saber and Reins were the top yield performers at Charles City.
Oat Yields at Nashua
Hayden and Deon were top performers at Nashua in terms of both yield and straw.
Fungicide Trial at Nashua
Fungicide application had mostly no effect but did appear to increase straw yields, particularly for Shelby 427.
Previous oat variety trials can be accessed here:
Thank you to our partners:
- General Mills
- Grain Millers, Inc.
- Albert Lea Seed House
- Sustainable Food Lab
- Welter Seed and Honey Co.
- Wisconsin Crop Improvement Association
And our participants:
- ISU Northern Research Farm (Kanawha)
- ISU Northeast Research Farm (Nashua)
- Wayne Koehler (Charles City
For those who missed the field day on soil regeneration hosted by Chris & Janenne Teachout near Shenandoah on Aug. 29, or for those who want to re-acquaint themselves with some of it, check out the “highlight reel” we’ve compiled below. The video features Chris, as well as Dr. Jill Clapperton, discussing cover crop practices and benefits to soil health.
Find more images from this excellent field day below.
Thank you to our partner organization for this field day, Green Cover Seed, as well as field day sponsors North Central SARE, Iowa Farmers Union and Page County SWCD for their support and help putting on this event.
In Iowa corn-soybean production systems, cover crops are typically aerially seeded into standing crops around the time of physiological maturity or drilled immediately following corn or soybean harvest. Previous on-farm research conducted by Jack Boyer has shown that seeding cover crops earlier in the fall can translate to greater fall and spring biomass. This may present the opportunity for more diverse cover crop species selection. With this in mind, farmer-cooperator Jon Bakehouse wanted to investigate how he could seed cover crops earlier than normal in a corn-soybean system and more successfully include a diverse array of cover crop species. To accomplish this, Jon planted early maturing varieties of corn (104- or 105-day) and soybean (1.0 group) in an attempt to harvest earlier in the fall and seed cover crops earlier in the fall.
You can read the full research report here: Accommodating Cover Crops with Early Maturing Corn and Soybeans.
The table below shows how Jon conducted the trials in 2015 and 2016 on his family’s farm near Hastings in Mills County in southwest Iowa. The late maturity system includes corn and soybean varieties of typical maturity groups in the region. The early maturity system includes corn and soybean varieties that would mature and be harvested earlier than the typical varieties in the region. In both systems, a cover crop mix was seeded immediately after corn harvest and a cover crop of cereal rye was seeded immediately after soybean harvest.
Cover crops seeded after soybeans were cereal rye (30 lb/ac); hairy vetch (5 lb/ac); Austrian winter pea (8 lb/ac) in 2015 (ahead of 2016 corn). Cereal rye (55 lb/ac) was seeded after corn in 2015 (ahead of 2016 soybeans). In the fall of 2016, cover crops seeded after soybeans were cereal rye (25 lb/ac); hairy vetch (5 lb/ac); rapeseed (3 lb/ac). Cereal rye (55 lb/ac) was seeded after corn.
- Planting early maturing varieties of corn and soybean generally did not result in yield drag compared to the late maturing varieties typically grown in southwest Iowa. The exception was in 2015 when the early maturing soybeans yielded less.
- Cover crop biomass produced tended not to differ between the early and late maturity corn-soybean systems. Seeding cover crops earlier in the fall, following the early maturing corn and soybean varieties, proved to be a challenge. “The cover crop could have been planted on Sept. 22 following the harvest of early maturing corn in 2015,” Jon says, but rain immediately after harvest prevented this. “Also, the early maturing soybean was ready for harvest by Sept. 28, and the cover could have been planted as well if soil conditions would have allowed,” he adds. “My takeaway: drilling cover after soybeans in September is possible.”
Conclusions & Next Steps
“Can early maturing corn and soybean varieties facilitate cover crops?” Bakehouse asks. “I think the answer is, ‘probably not’ unless a grower is willing to get down to an 80-day corn variety. The early maturing soybean could possibly work, though I think we’ve confirmed that group 1 soybean grows better when planted in early to mid-May, at which point there probably isn’t going to be much difference in the fall between a late-planted group 1 and an early-planted group 3.”
“I also think letting the cover grow in spring is just as important (or maybe even more important) than a few extra days/weeks [in the fall] from earlier planting,” he says. “Earlier planting in the fall naturally facilitates better spring growth, but I think having soil cover during spring rains is essential.”
For more details on this trial, read the full report: Accommodating Cover Crops with Early Maturing Corn and Soybeans. This project was supported in part by the Walton Family Foundation and the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation.