Refining the potential for interseeding cover crops in corn

Final Report for ONE12-172

Project Type: Partnership
Funds awarded in 2012: $14,703.00
Projected End Date: 12/31/2012
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. Gregory Roth
Penn State University
Expand All

Project Information


In this project, we evaluated the Penn State Cover Crop Interseeder on three farms in replicated trials and on one farm as a non replicated demonstration. The trials were designed to evaluate a legume and Italian ryegrass mixture compared to an Italian ryegrass seeding with or without a seed treatment designed to improve establishment. Establishment in the three replicated trials was less than desired in most cases and the seed treatment had little effect on improving establishment. Cover crop plant establishment averaged 4.1, 5.2 and 3.3 plants/sq. ft in the three trials. In the fall biomass yields average 923, 864 and 265 lbs DM per acre at the three sites. We interseeded annual ryegrass in border areas of each study and this consistently established better than the Italian ryegrass. We also noted significant recovery late in the season at most of the sites which demonstrated that with even low establishment plant counts, significant cover crops can establish in the fall. At the demonstration site, establishment was much better including with some of the alternative species we evaluated such as tillage radish. We conducted several outreach activities in the fall showcasing the trials and the some of the insights we gained into interseeding and are using the results as a steppingstone to future work with the interseeders. We estimated a potential economic advantage of interseeding, provided we could achieve a good establishment of clover/ryegrass mixture to be $41/acre in the first year and $83 acre in subsequent corn years that this system was used.


Authors: G.W. Roth, C.D. Houser, C.S. Dillon, M.M. Madden and W.C. Curran, Penn State University

Previous studies have demonstrated that interseeded cover crops or “relay crops” could have some potential for establishment of cover crops without impacting the yield and growth of the primary crop. Researchers from Cornell (Scott et al., 1987) have reported successfully seeding cover crops during the late spring in fields that were tilled with minimal residue on the soil surface with no impact on crop yields. They determined that annual ryegrass and red clover were the most effective of several cover crop species evaluated. In this system, cover crop seeds were broadcast on the soil surface and incorporated using a row crop cultivator. A second study showed that this system could be used in soybean production as well (Hively and Cox, 2001). Canadian researchers have reported the effective use of seeding devices that can establish cover crops in a standing crop of corn in a tilled seedbed (Walters, 2004) however this machine is not adequate for use in no-till systems. Their experience and others in Europe, however, has demonstrated the potential utility of this in season cover crop or “relay crop” system as a part of corn production. In New York, a more recent study by Kleinman et al. (2005) showed that establishing a red clover or ryegrass cover crop at planting showed great potential for reducing non point P runoff from corn fields, but the ryegrass seeded at planting tended to reduce corn yields.

We have developed a system that could be a breakthrough in interseeding cover crops under a range of conditions, including no-till fields, and greatly expand cover crop adoption, but needs a bit more evaluation and demonstration in the field. We developed a machine in conjunction with Penn State Agronomy Research Farm in 2010 to facilitate interseeding in no-till and reduced tillage corn crops. The machine uses coulter tillage in the row to prepare a shallow seedbed followed by packing wheels and a drag chain to incorporate the seed. Since interseeding often coincides with sidedressing and postemergent herbicide applications, we added the capability of applying N fertilizer next to the corn row and applying herbicide to the machine. Our goal with the design of the interseeder was to develop an affordable machine that could do the interseeding effectively as well as improve the application of the fertilizer and herbicide.

Project Objectives:

The objective of this study was to assess the potential of a seed treatment to improve the interseeding establishment of Italian ryegrass and also to evaluate a mix of clover and ryegrass compared to a single ryegrass intereseeding. We were also interested in identifying any issues that could help to improve the potential of interseeding cover crops in corn.


Click linked name(s) to expand/collapse or show everyone's info
  • Cinda Corl
  • Dan King
  • Ron Kittle


Materials and methods:

Replicated trials were established at three locations in Bradford and Counties, PA. These were located on the Ron Kittle farm in Sylvania, the Dan King Farm in Milheim, and the Cinda Corl farm in Pine Grove Mills, PA. Each consisted of four treatments and three replications. Treatments consisted of Green Spirit Italian Ryegrass, Green Sprit Italian Ryegrass with a “Yellow Jacket” seed treatment, and the PSU mix from Kings Agriseeds, a mix of red, white, crimson, and yellow sweet clover along with the Green Spirit Italian ryegrass. Seeding rates were 10 lb/acre for all seeds. The Yellow Jacket seed coating is a proprietary product sold by Barenburg that consists of a corn starch based superbsorbent material designed to promote germination with less water.

Interseedings were done at approximately V6 to V8 at each location in mid to late June. Each plot consisted of four rows, approximately 500 feet long at each location. Stand counts were made at each location in early August and silage corn yields were estimated in early September by harvesting 2 1/1000 acre subsamples from each plot. In early November biomass samples were collected from each location. At two of the locations, soil samples were collected at the same time. At the Kittle location soils samples were not collected then and the field was manured before they could be collected. Soil and plant samples were then analyzed to assess nutrient content. At each location, the borders were seeded to an annual ryegrass, DH3, so that we could make some evaluation of its potential. We also established a fourth demonstration site near the Bradford County site, in Sullivan County, PA so that we could conduct a field day if the opportunity developed. At this location we included some additional species including tillage radish, rye and oats.

Research results and discussion:

A short term drought occurred across much of the region during late June and early July and this caused establishment to be more erratic than anticipated in some of the trials.

At the Kittle farm, we found that the Green Spirit ryegrass averaged 5.2 plants/sq. ft. in the control and 3.5 plants/sq. ft. in the Yellow Jacket seed treatment (Table 1). There was little clover establishment at this site. The PSU mix averaged 2.8 plants/sq. ft. We concluded that there was no benefit to the seed treatment at this site. Corn yields were not different among the treatments and despite the dry weather yielded about 8.3 tons of DM/acre. There were no differences in biomass accumulation but the interseeded treatments averaged 923 pounds DM/acre and the control had 300 pounds per acre. The forage quality of the ryegrass at this location (Figure 1) in the fall was excellent, with crude protein levels above 20% and NDF levels below 40%. By converting the protein content to N (3.4%) we were able to estimate the ryegrass contained 32 pounds of N in the fall. Overall we felt establishment in this field was a bit variable and would have liked to see about twice the ryegrass establishment and biomass accumulation. We found that the annual ryegrass (Variety DH3) we used in the border at this location had better establishment and this suggests that it might be more tolerant of the mid-season drought conditions.

At the Corl Farm, results were similar to the Kittle farm (Table 2). Establishment here was also limited by the dry conditions, and mostly ryegrass was established. The Green Spirit averaged 5.6 plants/sq. ft and the Yellow Jacket seed treatment averaged 5.4 plants. The PSU mix averaged 3.4 ryegrass plants/sq ft. and 1.2 clover plants/sq ft. There was no impact of the seed treatment on establishment. Corn yields were not impacted by the interseeding and were slightly higher than the Kittle Farm, averaging 8.8 tons DM per acre. Biomass yields averaged 864 lbs/acre for the cover crop treatments and 161 lbs/acre for the control. Forage quality was also excellent at this site as well with crude protein levels averaging 18.1% from all interseeding treatments. These were slightly lower than the Kittle farm and represented about 25.0 lbs N/acre in the ryegrass following corn harvest. At this location, we measured the soil nitrate levels and found relatively low soil nitrate levels in all treatments. After the study concluded the plot area was grazed with the Corl’s Angus cow/calf herd (Figure 2). We also noticed at this location that the annual ryegrass in the borders had generally better establishment than the Italian ryegrass we had selected for the study.

At the third location, the King farm, establishment was more erratic than the other sites. We found it to be acceptable in some areas of the field and nonexistent in others. Even so in the fall, after the farmer Dan King had sowed no-till cover crop rye, the interseeding appeared to be superior to the rye (Figure 3). In this study, ryegrass was again the primary species to establish, with 3.7 plants/sq ft with the Green Spirit treatment and 3.5 plants/sq ft with the Yellow Jacket treatment (Table 3). For the mix, total plant establishment was 2.8 plants/sq ft, with 1.9 plants/sq ft as ryegrass. Corn yields were lower here, averaging 7.2 tons/acre and showing no difference due to the interseeding. Cover crop biomass in this field averaged about 265 pounds per acre, likely due to the variable establishment. Forage quality of the interseeded ryegrass that was present was also high at this location. Soil nitrates were measured at this location and were generally high, averaging 23.9 ppm with little impact from the cover crop. This site is an example of why fall cover crops would be important to reduce overwinter N leaching.

Based on the results from the three study sites, we concluded that the seed treatment had no effect on establishment, and that ryegrass often established better than the ryegrass clover mixture. We also noticed that with the heavier Green Spirit seeding rate in the ryegrass treatments compared to the mixture, we achieved better stands. This could suggest that even better establishment could have benn achieved with higher seeding rates. We used a seeding rate of 10 pounds per acre, and this was very economical so there could be potential to increase this in future studies. We also noticed the more consistent establishment of the annual ryegrass in the border areas, so we would like to evaluate that more in future studies.

We also established a demonstration site at another location as part of this study to use as a backdrop as a field day. At the demonstration site, we generally had good cover crop establishment of the species used in the trials. We also included some other species in this demonstration, including the popular tillage radish, which established quite well. We found that the tillage radish did not form the deep taproots in the corn canopy as it often does in late summer seedings. (Figure 4). At this demonstration, the corn population was lower than the other sites, so this suggests that slightly lower corn populations might improve interseeding success.

Research conclusions:

We obtained some valuable feedback from the study we will incorporate in future work. We see potential for annual ryegrasses, and possibly higher seeding rates. We did not see any effect from the seed treatment. We also noticed at the end of the season that the Italian ryegrass had some significant recovery in the fall, as we had seen in the past. Italian ryegrasses have performed better in some of the cooler environments where interseeding has been successful in other regions. At the end of the trial, our cooperator Cinda Corl, in Centre County, grazed the corn stubble and cover crops with an Angus cow calf herd and we were able to obtain some good photographs for future use. This also validated the concept that there is a large potential value for forage to offset interseeding costs. So despite the inconsistent establishment, we feel we learned some ideas that could be useful for the future. Following the study, we interviewed each of the participants. Each felt the concept has merit if we can develop tactics to improve the consistency of establishment. Ron Kittle has agreed to participate in another study of the interseeder in 2013.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

Because of the less than ideal establishment we decided to forgo the idea of having field days at the sites, except for the demonstration site where we had a small field day with farmers and several industry seedsmen from Cover Crop Solutions. This was a great opportunity to discuss the concept and exchange ideas for future development. We were also invited to the Cover Crop Solutions field day in Lancaster to discuss the interseeder where over 200 folks attended.

We developed a handout (Figure 5) on the project and distributed it to participants. This led us to be invited to a meeting with Homestead Nutrition, a Cover Crops Solutions dealer, where we shared the potential of the interseeder with over 150 attendees. We also reported on the interseeder project in the Field Crop News ( (Figure 6), a Penn State electronic newsletter that is distributed to over 1000 farmers and crop advisors. We also tweeted images from each of the sites and at least one of these was retweeted by several others, to more than 400 twitter subscribers. An example of one of the tweets and images can be found here: . We also posted the work we did on our website ( ), where it can be part of the record of our work with interseeding. So despite the inconsistent establishment in some of our trials, we were able to generate some good publicity for the project and NESARE and identify some potential strategies for improving our success with the interseeder in the future.

Project Outcomes

Project outcomes:

We conducted an economic analysis based on the experience at the Corl farm. We used a partial budget (Table 4) approach compared to conventional corn production. We made the following assumptions. In the first year an interseeding operation would cost $20/acre and seed would cost an additional $20/acre. The preemergent herbicide would be reduced by $10/acre, and costs of sidedressing at $10.90/acre and postemergent spraying would be reduced by $10/acre since these would be done with the interseeder. The result of the interseeding would be approximately 1000 pounds of high quality forage valued at $100 ton. The net impact in the first year would be $41.60/acre.

In the second year, we made all of the same assumptions, except that corn yields could be improved by 5% or 7 bu/acre by a partial rotation effect from the ryegrass. This caused the net impact in the second year to be $83.60/acre. Thus, it could be possible to achieve positive economic returns with the modest establishment success in these systems.

If establishment could be improved to achieve yields of 1 ton per acre in the fall, valued at a conservative $100/ton, then returns to interseeding would increase to $91.60 in the first year and $133.60 in the second year.

Farmer Adoption

Since the initiation of this study, two farmers have purchased interseeders for evaluation on their operations. Many others have expressed an interest in evaluating interseeders in conjunction with extension or researchers. In 2013 evaluations are planned in PA, VT, NY, and MD. We anticipate 10 to 15 farms in the region will be participating in interseeder evaluation and development work in 2013.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Several management issues need further study. These include varieties of ryegrass and seeding rates. Also alternative legume species should be considered, perhaps with some hard seeded legumes that could germinate later in the season. We also might consider earlier interseeding to provide some crop establishment before drought stress and corn competition become problematic.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.