Evaluating the perennial living mulches in a silage corn production system in the Northeast

Final report for ONE17-299

Project Type: Partnership
Funds awarded in 2017: $15,000.00
Projected End Date: 02/29/2020
Grant Recipient: University of Vermont
Region: Northeast
State: Vermont
Project Leader:
Dr. Sid Bosworth
University of Vermont
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Project Information

Summary:

We proposed to explore corn silage production systems that employ perennial living mulches to protect surface water and improve soil quality. For this project, our goal was to introduce and evaluate potential perennial legume cover crops and test their feasibility as a living mulch in corn silage.  It is too cost prohibitive for farmers to take a year out of production in order to establishment perennial legumes for living mulch.  An alternative approach is to inter-seed the cover crop into corn.  Our experience has been that inter-seeding success can be quite variable. It was our goal to test different cover crops and management practices that could enhance the success of inter-seeded legume cover crops.

In the first year of our project, we seeded a four replicated strip trial of four perennial legumes (crownvetch, birdsfoot trefoil, white clover and kura clover). The site was part of a corn field that had been tilled the previous fall.  The intent was to get the stand established and no-till corn into the strips in 2018.  Even though the plots were clipped twice during the summer to suppress weeds, we were still unsuccessful in effectively establishing these slow emerging legumes to get a successful stand.  The farmer decided not to continue the project with a reseeding.

In a field scale study the first year, we planted a 5 acre field to corn to be harvested for silage with an underseeding of Kura Clover.  The corn was planted with a four row planter and the Kura clover was then drilled in with a no-till seeder on the same day.  The corn was a Clearfield hybrid so that Pursuit herbicide could be applied since Kura clover is tolerant of this product. Pursuit was applied in June.  The Pursuit herbicide was only partially effective in weed control and the Kura clover was fairly sparse in germination and establishment.  Also, the farmer felt that the extra weeds significantly hurt his yield. By the end of August, there were sections of the field with some Kura clover in the under story; however, by the time the corn was harvested, there was very little visible clover. The farmer decided not to continue this demonstration field the next year since it would have required another Clearflield hybrid and the same herbicide both of which he was disappointed in.

After the failures in 2017, we focused on a different approach in 2018 and 2019.  First, we wanted to use cover crops, methods and products that are readily available to farmers and avoid having to use any special hybrids or products. Our focus was using a Roundup Ready corn hybrid with only glyphosate as our weed control. Both of these are common practices that conventional farmers use; therefore, we thought if this method works, we’d have a better time getting farmers to try it.

In our evaluation of different legumes, we found alfalfa to be the most successful in germination and seedling development when planted in corn at the 2-leaf or 4-leaf stage of maturity. However, we found that it did not persist well by the time the corn was harvested most likely due to shade intolerance from the corn.  I observed that by August, when the corn was at its maximum height, the alfalfa became tall and thin (etiolated), thus, weakening it.  Recent research in Wisconsin has shown that a growth regulator applied to the alfalfa was important in assisting this crop to thrive when seeded with corn. Red and white clover was moderate in success in second year when there was adequate rainfall, but in the first year, they did poorly in dry conditions.  Kura clover never germinated or developed well for us when inter-seeded in corn.

We found in our studies that glyphosate applied at the 2 to 3 leaf stage followed by a second application at the 4 to 5 leaf stage provided better weed control compared to a one time application at the 2 leaf stage. In 2018, we also found a higher yield due to the better weed control but we were unable to measure yields in 2019 to test these treatments. However, we found that herbicide application timings had no impact on late season percent cover. Also, we found that lowering the corn population by 4,000 ppa did not make any difference in cover crop development or percent cover.

Overall, we were disappointed in our attempts to inter-seed perennial legume cover crops for the purpose of a living mulch.  However, more research is needed to evaluate other practices that we did not look at such as different corn hybrids that may vary in late season completion and light patterns, timing of seeding, seeding rates, use of growth regulators, etc.

Project Objectives:

Building on past work done by researchers in other states and incorporating relevant technology, we propose to
explore corn silage production systems that employ perennial living mulches (PLM) to protect surface water and
improve soil quality. Our goal is to increase the percent of in-season and post-harvest vegetative cover of corn
silage fields in the Northeast.

Questions we wish to answer include:
1) to what extent (if any) do PLM impact corn silage yield an area of the Northeast where rainfall tends to be
consistently higher and better distributed during the growing season than other regions of the U.S.
2) at critical times of year do PLM cover the soil significantly more than approaches (i.e. cereal rye planted after
corn harvest) currently used?; and
3) does current locally available technology allow for efficient establishment and management of PLM systems?
Our objectives are to:
1) describe the impact of PLM on corn silage yield compared to two controls;
2)describe the functionality (i.e., ability to cover the soil) of PLM compared to two controls; and
3) determine if locally available technology is sufficient for establishing and managing PLM in corn silage.

Introduction:

Research on living mulch systems has been conducted since the 1975, with soil stability, nutrient scavenging, and biological nitrogen fixation being primary drivers. Other benefits cited include: increased soil quality; reduced soil losses; weed suppression; and pest (insect, weed, disease) management via competition, obstruction, and/or promotion of beneficial insects. Systems in which living mulches can fit include vineyards, orchards, and row- and vegetable crop production fields. 

The most visible sets of research on the subject of living mulches in corn cropping systems have been generated by Nathan Hartwig (Penn State - emeritus), Ken Albrecht (University of Wisconsin), and Nick Hill (University of Georgia).

Challenges that those researching living mulches are trying to overcome include:
1. The living mulch becoming excessively competitive with the crop. Assuming that an appropriate PLM species is chosen and is adequately suppressed to prevent light competition, water competition/use is the biggest challenge, especially in dry areas/years. A kura clover living mulch had a minimal impact on corn yield in years where soil moisture was adequate leading up to canopy closure, but detrimental to yield in years where rainfall leading up to canopy closure was deficient.
2. Establishment or persistence of the living mulch species. While the persistence and glyphosate tolerance crownvetch and kura clover seem to be excellent PLM candidates, they can be difficult and slow to establish. While white clover establishes relatively quickly and thrives Northern regions, winter stolon injury is often severe, resulting in slow spring recovery. All of these challenges can be managed to varying degrees, depending on the environment.
3. Suppressing the living mulch without killing it. Albrecht, Hartwig, and Hill have each spent considerable time developing protocols that can reliably suppress the living mulch while the corn is being established, yet that without reducing the functionality or survival of the living mulch. Albrecht (et al.), Hartwig, and Hill have each developed herbicide suppression + no-till corn planting protocols that are effective for suppressing PLM in their environments.

Even with perfectly balanced suppression of the living mulch corn production system, water competition can limit corn yield.  In Georgia’s climate, this would happen every year, so Nick Hill’s research is conducted under irrigation. In Wisconsin, heat/drought problems are occasional and, given that few acres are irrigated in Wisconsin, yields can be significantly reduced in dry years. 

Rainfall in Northeast and Central Vermont is typically abundant and regular during the growing season. Given these conditions and the existing living mulch suppression approaches developed by Albrecht, Hartwig, and Hill, we believe that one or both of these systems will be adaptable to high-rainfall areas of the Northeast. With locally available band-spraying and no-till technology, we believe that these systems will be adoptable by many farmers.

Cooperators

Click linked name(s) to expand
  • Steve Stocking (Educator and Researcher)
  • Stephen Carson

Research

Materials and methods:

2017 Carson Farm Strip Trial - On May 4, 2017, we seeded a four replicated strip trial (20' by 40' per plot) of four perennial legumes (crownvetch, birdsfoot trefoil, white clover and kura clover) at the Carson Farm in Newberry, VT.  We used a walk behind Carter small plot seeder to plant each plot  The site was part of a corn field that had been tilled the previous fall. The intent was to get the stand established and no-till corn into the strips in 2018. Plot were clipped twice during the summer to suppress weeds.

2017 Stocking Farm Field Demonstration - In May of 2017, Steve Stocking and Dan Hudson planted a 5 acre field to corn to be harvested for silage with an underseeding of Kura Clover. The corn was planted with a four row planter and the kura clover was then drilled in with a no-till seeder on the same day. The corn was a Clearfield hybrid so that Pursuit herbicide could be applied since Kura clover is tolerant of this product. Pursuit was applied in June.

2018 Stocking Establishment Trial - After the failures in 2017, we focused on a different approach to establishing perennial legumes as an under story in corn grown for silage.  First, we wanted to used cover crops, methods and products that are readily available to farmers and avoid having to use any special hybrids or products.  Our focus was using a Roundup Ready corn hybrid with only glyphosate as our weed control.  Both of these are common practices that conventional farmers use; therefore, we thought if this method works, we'd have a better time getting farmers to try it.

The corn was grown for silage and planted on May 14th at a population target of 32,000 plants per acre. Treatments included five perennial legumes interseeded (broadcast followed by light raking) in combination with four seeding time/herbicide treatments. Cover crops included alfalfa, kura clover, subterranean clover, white clover, red clover and a control of no cover crop.   We had three cover crop planting times: 1) at time of corn planted, May 15, using no herbicide, 2) when the corn was in 2 leaf stage, May 30 (using glyphosate to kill any emerged weeds), and 3) when the corn was at the 4 leaf stage, June 20 (again using glyphosate to kill emerged weeds).  An additional fourth treatment included planting at the 4 L stage but using a repeated application of glyphosate (once when corn was at 2L and again when corn was at 4L).

2019 Stocking Establishment Trial - In 2019, we decided to focus on corn planting populations as well as herbicide timing as variables in the establishment of perennial legumes into corn silage systems. We decided to only focus on the most common legumes, alfalfa, red clover and white clover and we included annual ryegrass in our evaluation almost like a "control" since we have a long history of inter-seeding this species into corn often with success.  We conducted the study on Steve Stocking's farm.  The corn was planted on May 20th. 

Main effect treatments included:

1) Corn population - two populations of corn (a typical silage population at 33,000 plants per acre verses 27,000 ppa);

2) Herbicide timing glyphosate only (1X, once only at 2-leaf corn stage compared to 2X, once at 2-leaf stage and repeated at 4-leaf stage); and

3) Cover crop species -  a) Annual ryegrass seeded at 50 lbs/a; b) Alfalfa at 30 lbs plus Intermediate ryegrass at 5 lbs; and c) Clover - Red clover at 10 lbs and white clover 5 lbs plus Intermediate ryegrass at 30.  All cover crops were broadcast seeded (followed by light raking) on July 3 when corn was at the 4-leaf stage.

Research results and discussion:

2017 Carson Farm Strip Trial - Due to a severe weed infestation, the plots were unsuccessful in effectively establishing enough to continue the next year's phase.  The farmer decided not to continue the project with a reseeding.  

2017 Stocking Farm Field Demonstration - The Pursuit herbicide was only partially effective in weed control and the Kura clover was fairly sparse in germination and establishment.  Also, the farmer felt that the extra weeds significantly hurt his yield. By the end of August, there were sections of the field with some Kura clover in the under story; however, by the time the corn was harvested, there was very little visible clover.  The farmer decided not to continue this demonstration field the next year since it would have required another Clearflield hybrid and the same herbicide both of which he was disappointed in.  One of the challenges was that by being limited to the Clearfield line of corn hybrids, Steve was really limited in finding the best suited hybrid for his conditions.  The other challenge was the limited weed control  with only using the one herbicide product.   

2018 Stocking Establishment Trial -

Legume germination and early establishment was poor across all three seeding times.  It was very dry in June and July preventing the germination of legume seed and/or death of stressed seedlings.  Overall, the alfalfa germinated the best followed by red clover and white clover.  There was very little kura clover or subterranean clover that germinated regardless of planting time.  By June 20, the weeds in the "Corn Planting" time treatment strips were well in advance and competing heavily with any legume seedlings as well as competing with the corn plants.  By the end of the season, there were hardly any legumes present in this treatment. This was not totally surprising since we knew there was no herbicide options for this treatment.

On May 30 during the 2-leaf seeding and on June 20 when seeding the 4-leaf treatments, alfalfa had the most seedlings of all the legumes.   

Weed control   – As expected, there was extremely poor weed control with the CP treatment since no herbicide was applied at all.  A one-time application of glyphosate at the two-leaf corn stage provided about 50% to 70% control by the end of the season.  However, the 2X applications resulted in good to excellent season long control.  See Table 1.

Corn Yield – Due to limited time and labor, only the 1X and 2X glyphosate applications of the alfalfa plots of the 4 L seeding time treatments were evaluated for plant population and yield (Table 2).   The 2X plots had about 1.7 t/a greater yield compared to the 1x significant at the 10% level of probability.  Although yields were not collected for the CP and 2L treatments, corn plants in the CP plots were visabley shorter compared to the 4L plots and were likely to have had a significantly lower yield considering the level of weeds in those plots.

Summary for 2018 – Legume establishment was disappointing in this study most likely due to extremely dry conditions and a high corn population.  However, these findings suggest that glyphosate (a non-soil residual herbicide) applied at the 2 to 3 leaf stage followed by a second application at the 4 to 5 leaf stage could potentially be utilized to adequately control weeds allowing the interseeding of cover crops without the risk of herbicide residual injury nor impacting corn silage yields.   However, this need further investigation.

2019 Trial - The results are discussed by main effect treatments.

Corn population - Counts were made on July 3 when corn was at the 4-leaf stage.  Although the target for the high treatment was 33,000 ppa, we measured an average of 30,292 for this treatment (Table 3).  It was significantly higher than the low population which averaged 26,542 ppa.

Herbicide timing -  By July 23, ten days after the last herbicide treatment had been applied, we did find better weed control with the repeated (2X) treatment compared to the single application (1X) treatment (Table 3).  However, there was no significant interactions with the main treatment effects indicating the weed control differences were consistent regardless of corn population or cover crop.  Unfortunately, we were not able to evaluate the plots before harvest which occurred in early October.  When we made measurements on Oct. 22, most of the annual weeds had died off or died back due to previous frosts, so were unable to conduct weed ratings at that time.    

Cover crop germination and cover was better in 2019 compared to 2018.  By July 23 (10 days after seeding), annual ryegrass had germinated and had the best cover ratings compared to the alfalfa and clover treatments. On July 23, the alfalfa cover rating was not as high as the annual ryegrass but much better than the clover treatments.  This may have been somewhat due to germination times since there was only 10 days between seeding and when the rating was made.  At post-harvest on Oct. 22, the annual ryegrass clearly had the best cover.  The alfalfa treatment actually dropped in cover between July 23 and Oct 22.  This may have been due to the shading of the corn in August and September.  We observed this as well the year before.  The clover treatment was still low by October and not likely to do much more.  Percent cover was not effected by corn population nor herbicide timing and there were no significant cover crop by other main effect interactions.

Summary for 2019 –Glyphosate (a non-soil residual herbicide) applied at the 2 to 3 leaf stage followed by a second application at the 4 to 5 leaf stage did provide better weed control compared to a one time application at the 2 leaf stage.  However, this had no impact on the final percent cover in the fall.  Although alfalfa showed promise early in the season with adequate cover, it had poor cover by late October.  Lowering the corn population by 4,000 ppa did not make any difference in this study. Other systems need to be evaluated if interseeding of perennial legumes will be consistently successful.

Research conclusions:

We proposed to explore corn silage production systems that employ perennial living mulches to protect surface water and improve soil quality. Our overall goal is to increase the percent of in-season and post-harvest vegetative cover of corn silage fields in the Northeast.  For this project, our goal was to introduce and evaluate potential perennial legume cover crops and test their feasibility as a living mulch in corn silage.  It is too cost prohibitive for farmers to take a year out of production in order to establishment perennial legumes for living mulch.  An alternative approach is to inter-seed the cover crop into corn.  Our experience has been that inter-seeding success can be quite variable. It was our goal to test different cover crops and management practices that could enhance the success of inter-seeded legume cover crops.  

In our evaluation of different legumes, we found alfalfa to be the most successful in germination and seedling development when planted in corn at the 2-leaf or 4-leaf stage of maturity (Figure 1).  However, we found that it did not persist well by the time the corn was harvested most likely due to shade intolerance from the corn.  I observed that by August, when the corn was at its maximum height, the alfalfa became tall and thin (etiolated), thus, weakening it.  Recent research in Wisconsin has shown that a growth regulator applied to the alfalfa was important in assisting this crop to thrive when seeded with corn. Red and white clover was moderate in success in second year when there was adequate rainfall, but in the first year, they did poorly in dry conditions. Kura clover never germinated or developed well for us when inter-seeded in corn.

Figure 1. Alfalfa seedlings in mid-July

One concern with inter-seeding legumes is weed competition, yet, many residual herbicides used on corn cause severe injury or kill to the cover crops. The partner farmers were already using glyphosate resistant corn hybrids on their farm, so we decided to focus that herbicide since it has no residual effect. We found in our studies that glyphosate applied at the 2 to 3 leaf stage followed by a second application at the 4 to 5 leaf stage provided better weed control compared to a one time application at the 2 leaf stage.  In 2018, we also found a higher yield due to the better weed control but we were unable to measure yields in 2019 to test these treatments. However, we found that herbicide application timings had no impact on late season percent cover.  Also, we found that lowering the corn population by 4,000 ppa did not make any difference in cover crop development or percent cover.

Overall, we were disappointed in our attempts to inter-seed perennial legume cover crops for the purpose of a living mulch.  However, more research is needed to evaluate other practices that we did not look at such as different corn hybrids that may vary in late season completion and light patterns, timing of seeding, seeding rates, use of growth regulators, etc

Participation Summary
2 Farmers participating in research

Education & Outreach Activities and Participation Summary

3 Consultations
1 Curricula, factsheets or educational tools
3 On-farm demonstrations
1 Tours
1 Workshop field days

Participation Summary:

14 Farmers
12 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

August 4, 2018 - A Field Day sponsored by the White River Conservation District was held at Birch Meadow Farm (Steve Stocking) in Fairlee, VT to highlight various conversation practices including no-till corn, no-till alfalfa, and cover crops.  We also were able to show and discuss our Living Mulch Establishment trial.  There were approximately 14 farmers and four agriculture service providers that attended.

October 25, 2018 - a tour as part of a New England Ag Service Provider In-Service stopped by Birch Meadow farm where we showed and discussed the Living Mulch Establishment trial.  There were approximately 8 that attended.  A summary of the project results was handed out.

Stocking-study-summary is a report on two on-farm field trials evaluating methods of inter-seeding annual and perennial cover crops into field corn grown for silage.

Learning Outcomes

2 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

The cooperating farmers have learned the limitations of establishing cover crops as an under seeding in corn. 

Project Outcomes

1 New working collaboration
Project outcomes:

Since we felt we did not succeed to establish perennial legumes for the purpose of a living mulch when inter-seeded into corn, we did not and do not expect to see any adoption of the practices we attempted.  However, we did learn that timely applications of glyphosate could be used such that farmers interseeding annual cover crops without the risks of residual herbicides.  Since farmers in Vermont have not seen the development of weed resistance to glyphosate like has observed in the mid-West, we feel this practice could be viable for those farmers that want to inter-seed annual cover crops.

Assessment of Project Approach and Areas of Further Study:

There are many agronomic challenges to establishing perennial legumes into growing corn with the goal of having a strong stand at the end of the season.  We only looked a some of the variables of species and management that might have had an effect.  I think adding some additional treatments and more locations in order to repeat the study over different soils and conditions would have been helpful. 

We confirmed a few things we already new (such as kura clover is very difficult to establish - even in the best of conditions) and we learned a few new things about legume establishment when seeded in a growing corn crop.  I think the practice of a legume-based living mulch system has been shown to have merit based on years of research in Wisconsin and other states; however, there still needs to be work done on coming up with practical ways to consistently succeed in establishing these crops.

Information Products

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.