Environmental Constraints and Management Responses for Interseeding Cover Crops in Northeast Grain Rotations

Progress report for LNE20-404

Project Type: Research and Education
Funds awarded in 2020: $199,674.00
Projected End Date: 11/30/2023
Grant Recipients: Penn State University; Cornell University
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. John Wallace
Penn State University
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Project Information

Summary:

Problem and Justification. Integrating winter cover crops in annual cropping systems can provide important conservation and crop production benefits at field and watershed scales, yet recent surveys indicate that greater than 60% of grain crop acres in PA and NY remain fallow in winter. Farmers have considered post-harvest seeding cover crops a poor return on investment because of the limited growing season to establish cover crops following corn grain or soybean harvest. However, increasing interest in soil health has raised farmer awareness of alternative practices, including interseeding cover crops into corn earlier in the growing season. The recent development and commercial availability of high-clearance interseeder drills facilitates cover crop establishment early in the season (V5 corn growth stage) and applied research and extension programs within the Northeast have developed best management practices (BMPs) for drill-interseeding cover crops in no-till corn. Grower engagement and preproposal surveys suggest two primary challenges that prevent expansion of interseeding practices in the Northeast. First, farmers are unwilling to invest resources to interseed cover crops without assurance that conservation and production benefits of interseeded cover crops will be consistently realized. Second, the performance of interseeded cover crops is a function of context-dependent interactions between climate, soil and crop management practices. Our project will utilize participatory research and education programs to support the development of regionally-specific cover crop interseeding BMPs.

Solution and Approach. This project will engage PA and NY corn grain growers in educational activities that focus on current cover crop interseeding BMPs and conservation benefits to foster more widespread adoption of cover cropping. We will address technological barriers to adoption by engaging a distributed network of SWCDs and agricultural service providers within PA and NY that own interseeder grain-drills and operate either a no cost loan or fee-for-service program to facilitate and promote the integration of cover cropping for soil and water conservation. We will address environmental barriers to adoption associated with inconsistent performance by evaluating the performance of interseeding and post-harvest seeding strategies across distributed on-farm demonstration trials. This coordinated effort will assist in identification of environmental and management conditions where interseeding optimizes conservation benefits relative to post-harvest seeding. We will address management barriers to adoption using regionally-distributed on-station experiments that evaluate novel interseeding management practices. Experimental crop management practices will aim to increase resource availability in space and time to interseeded cover crops by manipulating corn population rates, varieties, row-spacing and interseeding timing.

Performance Target. Fifty agronomic farmers will implement a management practice that facilitates adoption or improves performance of interseeding cover crops in corn on 100 acres per farm. Changes in management practices will decrease soil erosion potential, decrease nitrate-N leaching, and increase weed suppression on 5,000 acres in the Northeast region.

Performance Target:

Fifty agronomic farmers will implement a management practice that facilitates adoption or improves performance of interseeding cover crops in corn on 100 acres per farm. Changes in management practices will decrease soil erosion potential, decrease nitrate-N leaching, and increase weed suppression on 5,000 acres in the Northeast region.

Introduction:

Two broad challenges prevent expansion of cover crop interseeding practices in the Northeast. First, farmers are unwilling to invest resources to interseed cover crops without first-hand experience that demonstrates conservation and production benefits of interseeded cover crops will be consistently realized. Second, the performance of interseeded cover crops is a function of context-dependent interactions between climate, soil and crop management practices. Our project will utilize participatory research and education programs to support the development of regionally-specific cover crop interseeding BMPs.

Research

Hypothesis:

We hypothesize that: (1) interseeded cover crop biomass production varies based on soil and climatic controls; (2) specific combinations of corn, cover crop and weed management practices increase cover crop biomass production and function; (3) management practices that increase temporal and spatial resources to interseeded cover crops will be positively correlated with cover crop biomass production; and (4) management practices that optimize performance of interseeded cover crops will vary based on environmental conditions.

Materials and methods:

Complementary on-farm and on-station research experiments will be conducted to address research hypotheses focusing on interactions between climate, soil, and management factors that influence cover crop interseeding performance. The overall research objective is to deepen understanding of the (1) environmental factors that constrain establishment of interseeded cover crops across a regional-scale and (2) management practices that improve establishment and performance of interseeded cover crops at field scales, including interseeding timing, corn hybrid selection, corn population planting rates, and cover crop species selection. Research outcomes will be used in educational activities to improve farmer understanding of interseeding BMPs.

Farmer Input. The design of on-farm and on-station experiments are in direct response to identified farmer constraints to adoption, which we have collected from input at previous workshops and conferences, as well as a pre-proposal survey of agricultural service providers and SWCDs working directly with farmers through interseeding programs. The assembled advisory committee will provide input on research objectives throughout the project.

On-farm research and experimental design. A distributed field experiment will be conducted across a climatic gradient, from southern PA to western NY, at farms participating in on-farm demonstration and educational activities. We anticipate conducting research trials at six locations across PA and NY in both the 2020-2021 and 2021-2022 growing season. A single factor experiment with three treatment levels will be imposed at each location (n = 6) and year (n = 2). Within each location and year, treatments will be imposed in grain corn production fields and replicated (n = 4) using different production fields as the experimental unit. This experimental design will produce 48 climate (location x year) by soil (field x year) observations to evaluate treatment differences. Treatments will include: (1) winter fallow; (2) post-harvest seeding of cereal rye at 60 lb ac-1 using the grower's preferred establishment method; and (3) drill-interseeding annual ryegrass at 25 lb ac-1 at the V3 corn growth stage. Plot size will be 12 corn rows wide (30 ft) and length will be determined by field size and constraints. Prior to implementation of field trials, the project team will consult with farmers to select (1) an appropriate herbicide program and corn population rate based on current BMPs, and (2) trial locations using soil maps to determine soil type variation within and among fields. Project team members and cooperators will assist in plot layout, cover crop seeding, and lead data collection efforts.

On-Station Research Experiment. On-station experiments will be conducted to identify specific combinations of management practices that increase biomass production and decrease spatial- and temporal- variability of interseeded cover crops by manipulating cash crop (corn hybrid, population rates, row spacing) and cover crop (establishment timing, species) interactions. We will replicate the field experiment across two growing seasons (2020-2021, 2021-2022) and three on-station locations, including Cornell's Musgrave Research Farm in Aurora NY and Penn State research farms in Rock Springs and Landisville PA. These stations span three USDA plant hardiness zones (6a, 6b, 7a) and encompass the range of climatic and soil conditions found in Northeast regions targeted for on-farm trials and educational activities.

A three-factor experiment with four replicates and arranged in a split-split plot design will be imposed at each location and year. Plot size of experimental units (split-split) will be 10 by 60 feet. Main plot treatments will include three corn management strategies representing increasing levels of light penetration into the canopy, or spatial resource partitioning: (1) a standard corn variety planted at 32,500 seeds ac-1 on 30” row spacing, (2) a flex-ear hybrid planted at 28,000 seeds ac-1 on 30” row spacing, and (3) a flex-ear hybrid planted at 32,500 seeds ac-1 on 60” row spacing. The first split plot will include three cover crop establishment strategies representing increasing levels of temporal resource partitioning, including (1) post-harvest seeding control, (2) drill-interseeding at the V5 growth stage, and (3) drill-interseeding at the V3 growth stage. The split-split plot will include two cover crop treatments, cereal rye at 60 lb ac-1 or annual ryegrass at 25 lb ac-1. Annual ryegrass and cereal rye are winter hardy species, have high N-scavenging and weed suppression potential, permit use of residual broadleaf herbicides at corn planting, and facilitate experimental contrasts between common interseeding and post-harvest seeding practices in a corn—soybean sequence. Experiments will be imposed following no-till soybean and nitrogen will be applied at planting using standard recommendations. The herbicide program will include a pre-plant burndown (glyphosate) with a broadleaf residual herbicide followed by a post-emergence glyphosate treatment just prior to interseeding.

On-Farm and On-Station Data Collection. Data will be collected at three growing season phases in both the on-farm and on-station experiments. Aboveground vegetation will be collected six weeks after interseeding to evaluate establishment success, just prior to grain harvest, and in late spring (April) prior to cover crop termination. At each sampling event, aboveground vegetation will be harvested in three representative 1.0 m2 quadrats per plot located between the middle two corn rows. Cover crops and weeds will be separated, dried, and weighed. Weeds will be separated by species or functional group.

The effect of corn competition on cover crop and weed dynamics will be measured using photosynthetically active radiation (PAR) with a line quantum sensor at each quadrat location six-weeks after interseeding at on-farm locations and every four weeks after interseeding at on-station locations. Soil samples will be collected at the time of interseeding to quantify soil inorganic N concentrations, providing an indicator of resource availability during the cover crop establishment phase. Soil samples will be processed and analyzed colorimetrically for ammonium (NH4+) and nitrate (NO3-) concentrations. As another indicator of corn competition, whole plot corn grain yield will be measured using farmer combine yield monitors or weigh wagons at the on-farm locations and the middle two rows of each plot will be measured using small plot combines at on-station locations.

To quantify nitrogen retention services, aboveground vegetation sub-samples collected prior to harvest and in spring will be ground and analyzed for C and N analysis using a departmental service. Risk of N-leaching will be quantified by collecting soil cores (2.5 cm diameter) in each quadrat in late spring, divided into depth increments of 0-20, 20-40 and 40-60, and analyzed colorimetrically for NO3- concentrations. Because soil erosion is directly related to living plant cover and biomass, which is spatially and temporally variable, we will use a cover crop sensor box (Noble Research Institute) to remotely sense cover crop quantity (cover, biomass) at a whole plot level just prior to harvest and at spring termination.

Treatment effects on cover crop, cash crop and weed responses, as well as N-cycling metrics, will be analyzed using linear mixed effects models to test hypotheses associated with on-farm and on-station experiments. In order to quantify the relative importance of climatic, soil, management and their interactions on interseeding performance, we will use a structural equation modeling (SEM) approach that includes management (PAR, corn yield, weed biomass, soil N), climate (cumulative growing degree days and precipitation) and soil (aggregate stability, soil organic matter) explanatory variables. Standard fertility tests, soil texture, field history, and weather data will be collected to generate soil and climate datasets.

Research results and discussion:

2020 - 2021 Coordinated On-station Field Experiments

To explore potential limiting factors to interseeded cover crop establishment, a field experiment was initiated in 2020 at RELARC, Pennsylvania Furnace, Centre County, PA and SEAREC, Manheim, Lancaster County, PA. The experiment was a split-split plot RCBD with four replications. Treatments were corn hybrid (determinate variety ZS9598 or a flex-ear hybrid LC0057) and standard versus wide row spacing (76 cm or 152 cm). Plots were split by cover crop interseeding timing (V3 or V6 corn growth stage) and cover crop species (cereal rye (Secale cereale L.) sown at 100 kg ha -1, annual ryegrass (Lolium perenne L. ssp. Multiflorum Lam.) at 28 kg ha -1, and medium red clover (Trifolium pratense L.) at 17 kg ha -1).

At SEAREC, cover crop biomass increased due to 152 cm corn spacing for all treatments except for cereal rye and medium red clover seeded at V6 in the flex ear corn. Cereal rye seeded at the V6 timing increased in biomass in the 152 cm determinate variety corn. Cover crop timing had no effect on cover crop biomass. Weed biomass was higher in 152 cm corn for all treatments except for cereal rye and medium red clover seeded at V6 in the determinate corn. We observed no differences in weed biomass between V3 and V6 interseeding timing with the exception of the V3 timing resulting in significantly higher weeds in cereal rye plots in 152 cm corn and determinate variety when compared to V6. At SEAREC, cover crop timing had no effect on corn grain yield, but planting corn in wide rows significantly reduced corn yield. The determinate variety yielded higher than the flex ear variety in the 76 cm corn, other treatments did not differ in grain yield. At RELARC, 152 cm corn spacing increased cover crop biomass in annual ryegrass and cereal rye plots and at both cover crop interseeding timing. The exception was cereal rye in the flex ear, v6 timing and annual ryegrass in the determinate variety, v6 timing where no difference in cover crop biomass was observed. No difference was observed in red clover biomass between 152 cm and 76 cm corn. Interseeding earlier at V3 increased both cereal rye and annual ryegrass biomass compared to the later interseeding timing. No differences were observed in weed biomass in annual ryegrass and cereal rye plots except for an increase in weed biomass in 152 cm corn in the V3 timing, determinate variety annual ryegrass. In medium red clover plots, 152 cm corn increased weed biomass at v6 timing in the flex ear variety, and at V3 timing in the determinate variety. At RELARC, 152 cm corn spacing yielded significantly less than standard spacing corn. Cover crop interseeding timing did not impact yields. A significant spacing by corn variety interaction was detected where lower yields were observed in flex-ear treatments at SEAREC in the 76 cm corn but not in the 152 cm corn.  

Light resource partitioning is a primary factor that determines interactions between corn, cover crops and weeds in an interseeded system. We measured photosynthetic active radiation (PAR; % transmission) at the soil surface for each corn variety by spacing combination at multiple time points between the V6 and VT to R2 growth stage of corn at each location. Treatment differences were similar among locations. Differences in PAR transmission became more apparent at sample timings after the V6 growth stage. Use of wide row spacing and determinate corn varieties resulted in the greatest level of PAR transmission, with wide row spacing and flex ear hybrids intermediate to narrow spacings.

2021 - 2022 Coordinated On-Station Field Experiments

Results from 2020 - 2021 field experiments indicated that weed control is likely a significant agronomic factor that limits the potential of wide-row interseeding, as well integration of cover crop mixtures in narrow- or wide- row corn. Consequently, rather than replicate the previous experiment, we initiated a graduate student-led (M.Sc. student, Tosh Mazzone) complementary field experiment  in the 2021 growing season and replicated at three locations (Landisville PA, Rock Springs PA, Aurora NY). The field experiment is on-going and focuses on evaluation of alternative herbicide management strategies for early-interseeding. Factors included herbicide application timing (PRE, POST), herbicide residual active ingredients, and cover crop species selection. Objectives are to define herbicide BMPs when interseeding cover crop mixtures that include grass, legume and brassica species. Complementary greenhouse experiments were conducted in 2020 - 2021 to assess the relative sensitivity of 12 cover crops species to 5 common corn herbicide programs. This work supports field based experiments while expanding inferences to a greater number of cover crop species. This work is intended to inform decision making that aims to integrate high-diversity mixtures in narrow- or wide- row corn, while maintaining weed control to meet crop protection goals and to maximize cover crop services.

2021-2022 Coordinated On-Farm Strip Trials

In 2021-2022, coordinated on-farm strip trials were conducted at locations in western NY (n = 5) and central PA (n = 2). A common cover crop mixture (annual ryegrass, medium red clover, forage radish) was interseeded across locations, allowing growers to evaluate performance under their management conditions relative to non-interseeded paired strips. An option of a third treatment, where farmers designed their own mixture was only adopted at one participating farm. Mid-season evaluations include estimates of cover crop establishment rates and PAR transmission at locations to determine relative differences in crop competitiveness. Late-fall and early spring cover crop biomass will be taken at each location and summarized in a trial report. We are currently, recruiting additional farms for the 2022-2023 growing season to participate in coordinated strip trials and anticipate expanding locations to more southern PA latitudes. Results will be incorporated into outreach programming, including management guides for the Northeast region. 

Participation Summary

Education

Educational approach:

In-field co-learning opportunities related to this project have been canceled in the 2021 and 2022 growing season due to university-based COVID restrictions on travel and in-person events.

Milestones

Milestone #1 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #1. 1,000 farmers (PA and NY) will learn about our project focusing on cover crop interseeding management practices and the performance target through Penn State and Cornell extension-outreach outlets, including the PSU Field Crop Newsletter and Cornell's What's Cropping Up newsletter, a weekly agricultural newspaper (Lancaster Farming) that is widely read by Amish and Mennonite communities, and through collaborating SWCD newsletters.

Proposed number of farmer beneficiaries who will participate:
1000
Proposed number of agriculture service provider beneficiaries who will participate:
250
Actual number of farmer beneficiaries who participated:
1000
Actual number of agriculture service provider beneficiaries who participated:
250
Proposed Completion Date:
May 15, 2020
Status:
Completed
Date Completed:
December 21, 2020
Accomplishments:

Due to pandemic restrictions, on-farm trials were delayed until the 2021-22 growing seasons. Consequently, we advertised the project in late 2020 in the Penn State Field Crop Newsletter and Cornell's What's Cropping Up Newsletter/Blog. The PSU Field Crop Newsletter subscription exceeds 10,000 readers. The published advertisement included a grower survey to generate feedback and recruit subscribers to a project specific-list serve.

Milestone #2 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #2. 200 farmers will sign up to an e-mail or written list-serve to receive notifications of educational events, outreach materials focused on interseeding best management practices, and on-station research findings that will be hosted on a PSU project website.

Proposed number of farmer beneficiaries who will participate:
200
Proposed number of agriculture service provider beneficiaries who will participate:
25
Actual number of farmer beneficiaries who participated:
40
Actual number of agriculture service provider beneficiaries who participated:
5
Proposed Completion Date:
October 15, 2020
Status:
Completed
Date Completed:
March 1, 2021
Accomplishments:

Currently, 45 growers have signed up to an email list serve. We will continue to solicit participation in the list serve in extension-outreach winter programing. 

Milestone #3 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #3. 6 farmers will agree to implement or assist in the implementation of on-farm research and demonstration trials to identify cover crop interseeding best management practices.

Proposed number of farmer beneficiaries who will participate:
6
Actual number of farmer beneficiaries who participated:
7
Actual number of agriculture service provider beneficiaries who participated:
3
Proposed Completion Date:
March 15, 2021
Status:
Completed
Date Completed:
March 1, 2021
Accomplishments:

A coordinated on-farm strip trial was initiated at seven farms in the 2021 growing season and will be completed in the spring of 2022. Farm locations included Niagara County, NY (n = 2), Genesee County, NY (n = 2), Ontario County, NY (n = 1), Cambria County, PA (n = 1), and Blair County, PA (n = 1). 

 

Milestone #4 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #4. 150 farmers complete and return an initial survey that documents cover crop management practices following corn production and the average number of acres receiving a cover crop.

Proposed number of farmer beneficiaries who will participate:
150
Actual number of farmer beneficiaries who participated:
37
Proposed Completion Date:
March 15, 2021
Status:
Incomplete
Accomplishments:

Initial surveys conducted in Fall of 2020 have been returned and survey analysis is ongoing.

Milestone #5 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #5. 100 farmers attend an off-season webinar or soil health workshop (Western NY Soil Health Alliance conference and PSU soil health workshop series) where they learn about management practices that increase interseeding performance and regional differences in cover crop performance and conservation benefits.

Proposed number of farmer beneficiaries who will participate:
100
Proposed number of agriculture service provider beneficiaries who will participate:
25
Proposed Completion Date:
March 15, 2022
Status:
In Progress
Accomplishments:

An invited webinar on interseeding was given on 7/29/20 as part of NY's Empire Farm Days Soil Health Series. There were 65 participants.

An invited webinar on wide- and narrow-row interseeding, and implications for weed management, was given on 1/22/21 as part of the virtual Practical Farmers of Iowa annual conference. There were 70 participants. Participants included both farmers and agricultural service providers.

A webinar on interseeding best management practices for Pennsylvania was given on 2/17/21 as a part of Penn State Extension's Making Cover Crops Pay webinar series. There were 65 participants. Participants included both farmers and agricultural service providers.

An invited webinar on wide-row interesting and solar corridor concepts was given on 3/4/21 as part of the Northeast Cover Crop Council annual conference that was conducted virtually. There were 50 participants. Participants included farmers, agricultural service providers and researchers.

Milestone #6 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #6. 6 farmers will agree to implement or assist in the implementation of on-farm research trials to identify cover crop interseeding best management practices.

Proposed number of farmer beneficiaries who will participate:
6
Proposed Completion Date:
March 15, 2022
Status:
In Progress
Accomplishments:

We anticipate expanding on-farm strip trials in the 2022 growing season to include 10 farms across a wider latitudinal gradient, including more southern locations in Pennsylvania.

Milestone #7 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #7. 200 farmers will attend one of six (PA and NY combined) on-farm field day workshops where they see and learn how corn, cover crop and herbicide management practices influence cover crop establishment success and conservation benefits.

Proposed number of farmer beneficiaries who will participate:
200
Proposed number of agriculture service provider beneficiaries who will participate:
25
Proposed Completion Date:
October 31, 2022
Status:
In Progress
Accomplishments:

On-farm field workshops and outreach events were canceled in the 2020 and 2021 growing seasons due to COVID restrictions. We anticipating meeting milestone goals by concentrating field workshop and outreach events to the 2022 growing season though the spring of 2023.

Milestone #8 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #8. 100 farmers acquire (hard copy or PDF download) a "Cover Crop Management Guide for the Northeast" that is published on the project website and compiles on-station and on-farm research findings.

Proposed number of farmer beneficiaries who will participate:
100
Proposed number of agriculture service provider beneficiaries who will participate:
25
Proposed Completion Date:
March 15, 2023
Status:
In Progress
Milestone #9 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #9. 50 farmers interseed cover crops on 100 acres in the 2022 crop year using management practices learned via project educational activities. Documentation of performance target will be based on a post evaluation survey conducted using the project e-mail and written list-serve.

Proposed number of farmer beneficiaries who will participate:
50
Proposed Completion Date:
April 15, 2023
Status:
In Progress
Milestone #10 (click to expand/collapse)
What beneficiaries do and learn:

Milestone #10. 20 farms are individually supported by project personnel in development of interseeding management plans and evaluation of production and conservation at a field scale.

Proposed number of farmer beneficiaries who will participate:
20
Proposed Completion Date:
April 15, 2023
Status:
In Progress

Performance Target Outcomes

Target #1

Target: number of farmers:
50
Target: change/adoption:

Farmers will implement a management practice that facilitates adoption or improves performance of interseeding cover crops in corn

Target: amount of production affected:

5000 acres

Target: quantified benefit(s):

Reduced soil erosion potential, decreased nitrate-N leaching, increased winter annual weed suppression

Additional Project Outcomes

Additional Outcomes:

Based on research objectives described in this proposal, a field experiment was completed at four locations (Landisville PA, Rock Springs PA - till, Rock Springs PA - no-till, Aurora NY) in the 2020 growing season. 

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.