Maximizing the effectiveness of cover crop rolling/crimping for improved weed suppression in no-till organic systems

Progress report for LNE23-473R

Project Type: Research Only
Funds awarded in 2023: $199,999.00
Projected End Date: 11/30/2026
Grant Recipient: Rodale Institute
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. Madhav Dhakal
Mississippi State University
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Project Information


Cover crops (CCs) are an integral part of the weed management package in rotational no-tillage-based organic crop production systems. We propose a novel research project to support farmers in the Northeast by improving CC rolling/crimping technology in rotational no-till systems. This 3-year project will address USDA-SARE’s vision: “Agriculture in the Northeast will be diversified and profitable, providing healthful products to customers (….)” by improving weed suppression with no additional fuel, labor, and cost, promoting two specialty crops to diversify mid-Atlantic agriculture, and promoting organic crops to provide healthful products to customers. The project is conceptualized and designed based on stakeholder inputs. High bounce-back of CC after rolling/crimping, delayed response to crimping, and unbearable weed pressure even with substantial CC biomass are the key problems this project intended to address. Thus, two-year novel research will be conducted in two USDA plant hardiness zones (5b and 6a) during 2023-2025 to investigate the effect of rolling/crimping patterns on CC termination, cash crop establishment, weed dynamics, and allelopathic effect with three cover crops [cereal rye (Secale cereale), hairy vetch (Vicia villosa), and crimson clover (Trifolium incarnatum)] in no-till organic sweetcorn and fiber-hemp. The experiment will be laid out in a split-plot arrangement with 9 treatments plus one no-CC control with four replications. Main plot will have three rolling/crimping patterns with respect to CC rows (parallel, perpendicular, and 30º angled) and subplots will be randomly allocated to three CC species. Cover crops will be terminated using a roller/crimper, and simultaneously no-till planted with cash crops. Cover crop biomass, density, bounced-back percentages, and residue percentage cover will be determined. Tensiometers will be installed15-cm below the soil surface in each plot to collect leached water samples and soil samples will be collected from 0-15 cm depth. Samples will be analyzed for three allelochemicals (p-Hydroxybenzoxazinone, cyanamide, and polyethylene glycol) abundant in the CCs by using reversed-phase high-performance liquid chromatography. Weed biomass and density will be measured twice in the summer and soil seedbank will be determined using the germination assay technique for two years. Hemp biomass, fiber yield, sweetcorn cob yield, and grain quality are the crop parameters to be quantified. To involve farmers in the project, two demonstration trials will be established in the third year of the project in both locations. Feedback and farmer’s evaluation will be recorded. The project will prioritize technology adoption by using step-by-step approaches such as farmer and key obstacles identification, workshops, and consulting services. The outreach plan will have field days, web article publications, social media posts, two webinars, two peer-reviewed publications, regional and international conferences, video production, educational materials production, newsletters publications, and face-to-face training. Technology that makes rolled/crimped surfaces smooth and suppressive to weeds would be appealing to growers.

Project Objective:

The goal of this project is to demonstrate the ability of cover crops in suppressing weeds with different rolling/crimping approaches and promote it for no-till organic production.

Three objectives were defined to achieve the goals:

Research Obj.1: Compare the effect of three different roller crimping patterns on weed suppression.

Research Obj. 2: Evaluate the interaction between rolling/crimping patterns and cover crop species by measuring the weed dynamics, sweetcorn (Zea mays) and fiber-hemp (Cannabis sativa) yield as high-value cash crops.

Outreach Obj.1: Establish demonstration sites in two USDA plant hardiness zones to educate growers on rolling/crimping techniques in the Northeast agroecosystems.


A survey conducted by Organic Farming Research Foundation in 2020 identified weed management in organic cropping systems as the topmost priority for future research (Snyder et al., 2022). Several studies demonstrated that weed control in organic agriculture remains a major and enduring challenge and a barrier to organic transition. While synthetic chemicals and intensive tillage are not options for organic no-till systems, thick cover crops mulch can be the most effective weed-suppressing tool. Studies have shown that up to 75% of weed suppression can be achieved with adequate cover crop biomass if properly rolled and crimped (Mirsky et al., 2013). Growers in the region are still struggling to achieve >75% ground cover after rolling/crimping (Lap Amon, personal communication). Additional concerns are the need for rolling/crimping twice before planting and high weed pressure even with substantial cover crop biomass. The necessity of proper rolling/crimping for efficient termination and weed suppression highlights the importance of understanding the factors that influence this process.

There is a dire need for immediate solutions that “satisfy sustainable agriculture goals in the Northeast”. The proposed cover crop-based approach will complement and enhance the existing roller/crimper technology for organic high-value crops rather than displacing it, which will allow research outcomes to be seamlessly introduced and adopted in existing organic systems. The enhanced utilization of rolling/crimping technology has great potential to reduce pesticide use and intensive tillage and ensure environmental benefits and crop resilience. The use of cover crops for organic no-till systems offers tremendous ecosystem services (Blanco-Canqui et al., 2015; Crézé et al., 2021) while providing healthful products to customers.

There are 4003 certified organic farms in 12 Northeast states with over 735,438 acres (USDA-NASS, 2020). Rodale Institute’s consulting team’s HubSpot database showed that we reached out to 517 farms in 2022 with ~3,000 acres certified organic whereas Northeast represented 187 farms (26% grain & 14% hemp) having 122,000 acres in production (including conventional) with ~30,000 acres in transition to organic. Out of 187 farms, 27 are transitioning to regenerative organic and have been practicing rotational no-till with roller/crimper. The average size of the farm is 25 acres, mostly producing soybean, corn, and vegetables. We saw 27 growers as early adopters and innovators of this novel approach in the Northeast and >160 farms will be early and late majority in the innovation adoption lifecycle (Rogers, 1962).

From non-replicated assessment, we discovered that the pattern of rolling/crimping has a significant impact on cover crop bounce-back and the early emergence of weeds. The fractional weed cover at the parallel rolling was 28% while <5% with the perpendicular pattern, two weeks after termination. Out of 425 visitors during the field day event (21 July 2022), approximately 50 growers had concerns about soil water exhaustion before cash crop planting and high bounce-back of cereal rye tillers. This indicates the need for better solutions for cover crop rolling/crimping. Thus, systematic research is needed to assess the weed dynamics, potential allelochemical retention, and crop vigor associated with the rolling/crimping patterns for an informed decision.



We hypothesize that pattern of cover crop rolling/crimping would affect surface mulch cover, weed emergence, weed seedbank, and crop productivity in no-till organic systems. Differences in cover crop desiccation duration among rolling/crimping patterns would affect surface soil moisture and the release and retention of allelochemicals into the soil. Differences in bounce-back percentages and weed emergence among three rolling/crimping patterns could impact in-season weed pressure and weed seedbank in the soil. The additional research questions include: Will crop stand establishment be affected by rolling/crimping patterns? Is the result cover crop-specific? What are the weed species mostly suppressed by the novel method?

Materials and methods:

The effect of cover crop rolling/crimping patterns on two high-value cash crops (sweetcorn and hemp) will be studied from 2023 to 2025 (2 years) through nesting research plots in two USDA plant hardiness zones (5b and 6a): Rodale Institute, Kutztown, PA (6a), and Rodale Institute-Pocono Organic Center, Long Pond, PA (5b). Both hemp and sweetcorn can be grown in these locations with relatively shorter growing degree days than common row crops like soybean and grain corn, which would provide a longer cover crop window for even continuous hemp or sweetcorn production. This will enhance adoption likelihood and promote specialty crop production in organic systems.

  1. Treatments: A total of 10 (9+1) treatments will be evaluated. Treatments include combination of three cover crop species (cereal rye, hairy vetch, and crimson clover) and three rolling/crimping patterns (parallel to the cover crop rows, perpendicular to the rows, and 30º angled with the rows) and no cover crop control. Cereal rye and hairy vetch are the major cover crops in the Northeast (Mirky et al., 2013), where farmer adoption of cover crop-based no-till grain crop systems has focused on these crops. Introducing hemp in the same system would be of interest to the growers including conventional farmers. Sweetcorn would provide enough time for cover crop establishment before a hard frost in the fall, which is especially critical for zone 5b. If performed well, angled rolling/crimping would address challenges associated with landscape positions.
  2. Methods: The experiment will be laid out in a split-plot arrangement (see attachment). Main plot will have three rolling/crimping patterns and subplots will be randomly allocated to three cover crop species and one control treatment with four replications (40 plots × 2 crops = 80 plots/site). The size of each plot is 20 ft × 40 ft. Two studies (hemp and corn) will cover ~3 acres in one location. Cover crops will be planted in the fall starting early September with hairy vetch and crimson clover at seeding rates of 25 and 15 lbs/A, respectively. Cereal rye will be planted in early October at a seeding rate of 160 lbs/A. In the spring, cover crops will be terminated using a 10 ft wide roller/crimper, and simultaneously no-till planted with yellow sweetcorn (Allure) and fiber-hemp (Santhica) @ 12 and 60 lbs/A, at 30” and 7.5” row spacings, respectively. Note that rolling and cash crop planting is in the same direction. Tractor will follow cover crop rows at parallel treatment. Perpendicular and angled patterns will be achieved by rolling/crimping at 90º and 30º of the cover crop rows, respectively. For no-cover treatment, weeds will be mowed before planting to avoid hairpinning. The 2023-2024 study will be repeated in 2024-2025 in both locations.


3. Data Collection:

Cover crop: The number of tillers/m2 for cereal rye and crimson clover will be determined a few days before termination using a 1-m2 quadrat. For hairy vetch, the number of upright flower buds/m2 will be determined because of its prostrate habit. Aboveground biomass will be sampled by using two 0.56 m2 quadrats from each plot and dried at a constant temperature of 55ºC for 72 hours to determine dry mass. Also, the pictures will be taken from three 1-m2 quadrats per plot using a camera to estimate standing green cover. Two days after rolling/crimping, bounced-back tillers (or buds) will be counted to estimate termination efficacy.

Allelochemicals: Following cover crop termination, one 1-ft long suction cup tensiometer will be installed 15 cm below the soil surface in each plot to collect leached water infiltrated through the residue and soil. Water samples will be collected after rainfall for three events. Samples will be stored at -20ºC before sending them to the University of Connecticut chemistry lab for analysis. A total of 480 water samples will be analyzed for three chemical compounds: p-Hydroxybenzoxazinone [2,4-Dihydroxy-2H-1,4-benzoxazin-3(4H)-one (C8H7NO4, MM=181.15)], abundant in cereal rye (Lee et al., 2010); cyanamide [(aminomethanenitrile, N≡C–NH2, MM=42.04)], abundant in hairy vetch (Geddes et al., 2015); and polyethylene glycol [poly(oxyethylene), C2nH4n+2On+1, MM=44.05n+18.02], a compound abundant in crimson clover and hairy vetch (White et al., 1989) using the reversed-phase high-performance liquid chromatography (HP-LC) technique (Wang et al., 2008).

Soils: Soil samples from 0-15 cm depth will be collected in fall 2023 for nutrient analysis, spring 2024, and 2025 after rolling/crimping for the allelochemical assay and soil moisture. Samples will be taken from five places in each plot. Samples will be composited across the block for nutrient analysis (n=16) in fall 2023. For the allelochemical test, all 160 samples will be analyzed for the chemicals discussed above using the HP-LC method.

Weeds: Weed samples will be collected from two, 0.56 m2 quadrats per plot centered on crop rows and between the rows, three weeks after planting. End-of-season density will be assessed before physiological maturity of the crop. Weeds will be separated into broadleaf, sedge, and grass, then dry to a constant weight at 55°C to determine dry matter, and ground to pass a 1-mm screen for total N analysis. Species richness will be estimated as the number of species kg-1 soil and diversity as the weighted average of species proportional abundances (Ryan et al., 2010). The emerged weed diversity will be compared to the soil seedbank germination assay data. Four soil cores of 10 cm diameter and 18 cm depth will be collected in each plot in April prior to field preparation and in September after the harvest. Soil will be spread over a flat plastic tray (25 × 50 cm) containing a 3 cm layer of vermiculite at the bottom. Trays will be watered daily. Weed seedlings will be identified after they emerge from the soil surface and allowed to grow until proper identification is made. Seedlings will be counted and removed weekly for six weeks. Then soil will be allowed to air dry, and vermiculite and soil will be mixed and packed back on the tray. The process will be repeated until viable seedbanks are exhausted. The seedbank data will be recorded at the species level.

Crops: Crop stand will be assessed by counting seedlings/m row length from 10 spots/plot. Hemp biomass will be determined before harvest from two 1-m2 quadrat areas. Cob yield will be determined by harvesting central two rows. Cob weight, length, cobs/plant, kernel rows/cob, and seed index will be determined for each treatment. Grain quality will be determined for total N and C.

4. Data Analysis and Presentation of Results: All statistical analyses will be performed in R version 3.6.1 (R Core Team, 2020). Weed data will be arcsine (√Y) transformed to satisfy the assumptions of normality and homoscedasticity. Analysis of variance (ANOVA) will test variance within crop yield, yield attributes, allelochemicals, weed density & biomass, seedbank density, and species richness & diversity at α=0.5. LSD will separate the means at α=0.5. Cover crops, rolling patterns, and the interaction between the factors will treat as fixed effects and replicate as random effect. Nonmetric multidimensional scaling (NMDS) ordination biplots will be used to determine degree of similarity between weed communities and second-order stochastic dominance to assess crop-weed risks (Nichols et al., 2020). At least two sets of results will be published in peer-reviewed journals. Results will be presented at ASA-CSSA-SSSA, WSSA, and regional conferences.

Research results and discussion:

We are at the beginning of this project.  Work completed to date includes:

Soils: Soil samples from 0-15 cm depth were collected in fall 2023 for nutrient analysis, and will be collected in spring 2024, and 2025 after rolling/crimping for the allelochemical assay and soil moisture. Samples were taken from five places in each plot. Samples were composited across the block for nutrient analysis (n=16) in fall 2023. For the allelochemical test, all 160 samples were analyzed for the chemicals discussed above using the HP-LC method. We have recently obtained laboratory results from Brookside Laboratories, Inc., a commercial soil testing lab and are in the process of analyzing these results.

Crops: In 2023-2024, sweetcorn and hemp will be planted in April/ May 2024. Crop stand will be assessed by counting seedlings/m row length from 10 spots/plot. Hemp biomass will be determined before harvest from two 1- m2 quadrat areas. Cob yield will be determined by harvesting central two rows. Cob weight, length, cobs/plant, kernel rows/cob, and seed index will be determined for each treatment. Grain quality will be determined for total N and C.

Figure 1. Experimental layout.Experimental Design

Figure 2. Plots showing different cover crops in the field (Rodale Institute-Pocono Organic Center, Long Pond, PA site).Cover Crops at Pocono site

We also conducted a survey among growers during the 2023 Annual Field Day of Rodale Institute, which was attended by more than 450 participants. We asked questions like, practice of minimum or no-tillage with cover crops, use of roller/crimp for termination of cover crops, (if so) motivation for using roller crimping, etc. We are analyzing the survey data, which will be included in the next annual report.

Research conclusions:


Participation Summary
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.