Progress report for LS22-374
Project Information
Sometimes looking to the past for answers is meaningful. An ancient cropping practice called “intercropping,” or companion crop production, created a mutually beneficial ecosystem and functionally diverse plant community to increase individual plant production. This approach entailed a multi-layered agroecosystem where different crops filled different functional niches. Two major benefits of returning to this technique would be lower input costs and better crop protection from pests and diseases. While American Indians used "three sister crops," including squash, corn, and beans for companion cropping, the underlying principles can be utilized for improving the sustainability of larger and commercial farming operations with positive results for producers. We propose cover crop inter-seeding into corn (one of the most resource-intensive crops) to enhance utilization of unused functional niches in corn production systems, improve soil-plant interactions, reduce resource inputs, and improve cropping system productivity. Our systematic approach includes Social Science research that will engage growers from diverse communities (certified organic, small diverse, African American, American Indian, other underserved, and conventional) to assess potential risks/benefits of cover crop inter-seeding and barriers to acceptance. Our experiments will compare four cover crops inter-seeded with corn at three seeding rates (standard, low and high) under two tillage systems (tilled or no-tilled). The experiments adopt the basic principles of ‘companion cropping’, where success is based on choosing the right combinations of nitrogen-fixing legumes, rapidly establishing land-covers, and crops that occupy different functional niches aboveground and belowground. Our agronomist will evaluate cover crops and their management practices (seeding rate and tillage type) for their potential for bio-drilling, soil compaction alleviation, and weed suppression. Our soil scientist will identify cover crops and their management practices that optimize microbial activity and enhance soil health. Our entomologist will quantify natural pest control benefits conferred by inter-seeded cover crops aboveground and belowground. Our economist will conduct a cost-benefit analysis based on monetary benefits, management costs, and potential disadvantages of inter-seeding. We will work with farmers to conduct on-farm trials based on their preferred treatments and assessments of on-station research. Project key personnel will work with a team of collaborators including extension agents, NRCS, nonprofit, commodity board, and 1890 university personnel, point-persons for American Indians and small, diversified farmers to ensure outreach to diverse communities and effective farmer engagement. Results will be disseminated to producers and stakeholders through a training workshop, field days, presentations at regional farming conferences and producer meetings, and print/online media. By optimizing management and removing technical barriers to adoption of cover cropping, farmers will benefit from: reducing compaction; building healthier soils; reducing inputs for weed, fertility, and pest management; strengthening resilience to climate extremes; and stabilizing their economic viability. Reducing resource inputs will help protect natural resources; increasing crop, insect, and microbial diversity in the system will promote climate/weather-related risk management strategies and resilient agriculture; and including woman- and family-farmers as cooperators will help strengthen the family farm system of agriculture, the backbone of rural communities. Finally, our social scientist will assess how these outcomes improve the community’s quality of life.
- Engage growers from diverse communities to assess potential risks/benefits of cover crop inter-seeding and barriers to acceptance and determine the impact of project results in addressing these barriers and improving the community quality of life.
- Evaluate different cover crops (white clover, buck wheat, pigeon pea, and their mixture) inter-seeded with corn at multiple seeding rates and under conventionally tilled or no-tilled conditions to identify cover crops and their management practices that alleviate soil compaction, suppress weed infestation, and enhance microbial communities that improve nutrient availability and soil health.
- Quantify natural pest control benefits conferred by inter-seeded cover crops aboveground and belowground.
- Evaluate economic consequences of inter-seeding based on monetary benefits, and management costs.
- Develop a collaborative outreach program to catalyze the integration of a regionally-specific inter-seeding system.
Rationale for selection of cover crop species
Legume-based cover crops, when inter-seeded into organic systems, can lead to economic and environmental efficiency because of nutrient supply and control of soil erosion and nutrient leaching (Sanders et al., 2017). White clover may be a good option because it can be as effective as herbicides to control weeds (Hartwig and Ammon, 2002) and demonstrates shade tolerance (NRCS, 2011). White clover also encourages the association between mycorrhizal fungi and corn plants to assist in nutrient supply from soils with high phosphorous fixation capabilities (Deguchi et al., 2007). Buckwheat is another cover crop that has been shown to work well as an inter-seeded cover crop with corn (Loran Steinlage- row crop farmer, Presentation at the Conference on Building Soil Health: Principles, Practices and Profitability, Clemson, SC, 10/28/2019). Its benefits include rapid establishment and land cover, strong weed suppression, phosphorous scavenging, and ability to thrive in low fertility soils and attract beneficial insects (Clark, 2012). It produces abundant fine roots, which makes soil friable (Clark, 2012), which in turn makes this species a good choice for compacted soils in the Southeast. Another species, pigeon pea produces a deep root system with a strong taproot. It is moderately shade tolerant (Aniela, 2018) and well-suited for intercropping as it draws water from deeper soil profiles than most legumes, so will not interfere with the water uptake of other crops and grasses (Sheahan, 2012). This crop has been valued for its bio-drilling ability in many other parts of the world (Valenzuela, 2011). However, its potential for compaction alleviation when used as an inter-seeded cover crop has never been tested in the U.S. Testing a mixture of the three species (white clover, buck wheat, and pigeon pea) will allow us to evaluate any complimentary interactions among these functionally distinct species. The same cover crops were tested in our preliminary research as well (results given under “preliminary research” in the “Problem, Rationale and Significance” section).
Cooperators
Research
MATERIALS AND METHODS
Objective-1:
To achieve objective 1, the survey launched in year 1 to gather grower perceptions was continued to collect data and a second round of in-depth interviews were conducted with the cooperating farmers to gather their perspective on the survey findings. Together these results have helped outline the next steps for the upcoming year.
Objective-2
To test objective 2 (best management practices for interseeding), a field trial was conducted at Clemson University Student Organic Farm in Clemson, SC in 2023. In 2022, the field trial was conducted at Clemson’s Pee Dee Research and Education Center (PDREC) certified organic farm (Florence, SC). In both locations, four different cover crop treatments: white clover, buck what, pigeon pea, and their mixture were compared against two control treatments: Control-1: No cover crops, but received fertilizer; Control-2: No cover crops, no fertilizer. The six cover crop treatments (three different species, their mixture, and two controls) were tested under no-till and conventional till conditions. In Florence, the whole field was initially disked uniformly; before corn planting, conventional till treatment was disked twice while reduced till did not receive any further tillage. At Clemson, the whole field was initially run with ripper plow, then disked uniformly after two weeks; Conventional till treatment was disked twice while reduced till was cultivated using a rolling basket cultivator two weeks after the initial disking. Further, at Clemson, a day before corn planting, the entire area was leveled using the rolling basket cultivator. Details of crop husbandry in both locations are given in Table 1. Though we targeted to interseed cover crops at the V4 corn growth stage, due to labor shortage and/or unfavorable weather conditions, we accomplished it between V9 and V10 corn growth stages (at 65 DAP) at Florence (2022) and between V8 and V9 (at 55 DAP) at Clemson in 2023. We followed a manual broadcast interseeding approach using a precision garden seeder (Model-1001B, Earthway products Inc, Bristol, IN) in both locations. Cover crop row spacing was 9 inches in Florence and 7.5 inches in Clemson. Cover crops were sown at standard, low (1.5 times less than standard), and high (1.5 times greater than standard) seeding rates as given in Table 2.
Table 1. Crop husbandry in study locations
|
Parameters |
Florence (2022) |
Clemson (2023) |
|
Plot size |
20 feet x 20 feet |
20 feet x 18 feet |
|
Corn variety |
Little Mill H117 SC |
Albert Lea Organic Viking/Blue River Corn, O82-14GS-P |
|
Corn planting date |
26 April 2022 |
12 May 2023 |
|
Corn row spacing |
30 inches |
30 inches |
|
Corn plant population |
30,000 plants/acre |
36,000 plants/acre |
|
Fertilizer materials |
Chicken litter |
Nature Safe 10-2-8 fertilizer composed of natural feather meal, meat and bone meal, blood meal, and sulfate of potash. |
|
Fertilizer application rate (as per soil test) |
140-80-160 lbs/acre N-P-K |
120-0-40 lbs/acre N-P-K |
|
Irrigation |
~ 0.10 inch/hour/per acre applied almost daily through drip irrigation from V4 stage to physiological maturity |
Rainfed |
Table 2. Cover crop seeding rates (see attached)
Weeds were managed in the ‘control plots’ through hand-weeding at Clemson in 2023. Plots were maintained following the National Organic Program guidelines (NOP Final Rule, 2000; https://www.ams.usda.gov/rules-regulations/establishing-national-organic-program) under the supervision of trained farm crew. Plots were arranged in a split-plot randomized complete block design with a three-factor factorial treatment design (tillage, cover crops, and seeding rates as the three factors). There were two replications for each tillage-by-cover crop treatment-by-seeding rate treatment combination.
Weed biomass was measured to determine the ability of cover crops to suppress weeds. Weed biomass was collected from a randomly placed quadrant frame of known area (0.25 m2 at Florence and 0.133 m2 at Clemson) from each plot. Measurements were made at 71 DAP (V9-V10) and 105 DAP (R5-R6) at Florence and 91 DAP (R4) at Clemson. Cover crop biomass was also measured at 90 DAP (R4) at Clemson using the quadrat method.
Corn performance was measured aboveground and belowground. Aboveground corn performance was measured using plant height, biomass, and grain yield. Corn plant height was measured at physiological maturity (119 DAP at Florence and 114 DAP at Clemson). Corn biomass was hand harvested from 1-m row length at physiological maturity from each plot to determine dry weight. Each plot was combine-harvested at harvest maturity (136 DAP at Florence and 144 DAP at Clemson) to measure grain yield.
To measure vertical root penetration and other root traits of corn, soil cores were taken from a 1-m depth using the gas-powered soil core sampler at corn physiological maturity. Vertical root penetration was assessed using the core-break method (van Noordwijk et al., 2000) at Florence. The 1-m soil cores were cut into 10-cm long segments. The number of roots protruding from the bottom cut-face of each segment was counted and recorded to estimate vertical root penetration. After counting, roots were separated from the soil, washed and cleaned. Cleaned roots were scanned, and the images generated were analyzed using the WinRhizo software to estimate root traits such as length, surface area, volume, and diameter. At Clemson, root samples were collected using the shovelomics method. Root samples were collected from soil profile occupying a volume of 755.2 in3 (8 x 8 x 11.8 in LxBxH) at corn’s physiological maturity (132 DAP). Roots were separated, washed, and cleaned, and scored using a shovlelomics score board to estimate traits like number of whorl of brace roots (BR) and crown roots (CR), number of BR and CR per whorl, angle of BR and CR, lateral root length per whorl and lateral root density per whorl. Afterward, roots were scanned, and the images generated were analyzed using the WinRhizo software to estimate root traits such as length, surface area, volume, and diameter.
To estimate soil compaction, we measured bulk density and penetration resistance. To measure bulk density, soil cores were taken from 20-cm depth using a gas-powered soil core sampler (AMS, Inc., American Falls, ID) at a corn row and a cover-crop row in each plot. Soil cores were collected at 70 DAP (V9-V10) and 104 DAP (R5-R6) at Florence and at 67 DAP (R1-R2) and 116 DAP (physiological maturity) at Clemson. Bulk density was calculated as the ratio between soil dry weight and soil volume. Soil penetration resistance was measured using a Dickey-John Soil Compaction Tester at a corn row and a cover-crop row in each plot. Penetration resistance was measured at 67 DAP (V10-Vt) and 116 DAP (physiological maturity) at Florence and at 61 DAP (R1-R2) and 116 DAP (physiological maturity) at Clemson. Volumetric soil water content was measured using a Hydrosense II CS658 soil moisture probe at 77 DAP (V10-Vt), 99 DAP (R4-R5), and 115 DAP (physiological maturity) at Florence and at 59 DAP (V9-Vt), 87 DAP (R3-R4), and 115 DAP (physiological maturity) at Clemson.
Soil cores (0-15 cm) were randomly collected with soil corer (5 cm diameter) from replicated research plots at corn’s physiological maturity. Collected soil cores were sieved (2 mm) and stored at 4ºC until use. In the laboratory, soils were analyzed for water content by drying the soils at 60ºC until a constant weight was reached. Nitrogen concentrations (NO3- + NH4+) were determined after extracting the soils with 1 M KCl for 1 hour followed by filtration and colorimetric analyses. Organic nitrogen mineralization potentials were estimated anaerobically incubating soils in dark at room temperature for 7 days, followed by quantifying the changes in NH4+ concentrations. Microbial respiration was estimated by incubating soil samples in dark at room temperature for 24 hours. The CO2 production was quantified and used to calculate the respiration rates. Activities of soil enzymes associated with carbon and nitrogen cycling were measured with fluorescence methods. Active carbon concentrations and soil pH were also analyzed.
Objective 3: Quantifying pest control benefits of inter-seeded cover crops
Co-PI Blubaugh and her team measured pests and beneficial arthropods to monitor any risks of increased pest susceptibility and quantify natural pest control services that result from improved soil structure, microclimate, and plant diversity provided by the inter-seeded system. All measurements were made as part of the field trials at Clemson in 2023.
Objective-4: Economics of inter-seeding
Partial Budget analysis:
To assess the cost-effectiveness of using cover crops and reduced tillage on organic corn production, we conducted a partial budget analysis. The partial budget analysis compares details contributing to added or reduced costs and returns between treatments. In our current study, the added expenses of using different cover crops were considered adverse effects, whereas the added revenues from increasing yield were considered the positive effects. The results of the partial budget analysis also show whether the increased revenues from additional grain yield can offset the additional costs associated with cover crops.
The tillage costs were obtained from the reports published by the University of Minnesota Extension (Upper Midwest Tillage Guide). The costs for cover crops were obtained from the field researchers and calculated based on the seed rate used. All other costs that were kept constant were estimated based on the South Carolina irrigated and non-irrigated corn production enterprise budget published by Clemson University Extension Service. The price for the grain yield came from the NASS, USDA for each marketing year of 2022 and 2023, respectively.
Gross revenue per treatment was computed by multiplying the grain yield per treatment by the price for the respective marketing year. The net return or profit is calculated by subtracting the ‘total costs’ from the ‘total or gross revenue’.
Table 3 represents the costs of key materials used in land preparation in the trials conducted at Florence in 2022 and at Clemson in 2023. The total costs of the same treatment at the two locations differed due to the type of irrigation received. Florence received irrigation, while Clemson was rainfed. Hence, there was a difference in the calculation of total costs for each treatment.
Table 4 focuses on the estimated costs associated with different seeding rates (high, low, and standard) for various cover crop species, including buckwheat, pigeonpea, white clover, and a mix of species. It is evident that pigeon pea is the most expensive across all seeding rates, whereas white clover is the least expensive.
Table 3. Estimated materials costs used for different cover crops inter-seeding under different tillage systems in 2022 and 2023.
|
2022 ($/acre) |
2023 ($/acre) |
||
|
Seeds |
$105 |
Seeds |
$126 |
|
Irrigation labor, energy |
$54 |
||
|
Lube, filters |
$3.51 |
Lube, filters |
$4 |
|
Fuel |
$23.40 |
Fuel |
$23.40 |
|
Fertilizer costs |
$393.50 |
Fertilizer costs |
270.72 |
|
Operating costs |
|||
|
Tillage costs |
$108.95 |
Tillage costs |
$108.95 |
|
Pre-harvestor |
$20.75 |
Pre-harvestor |
$20.75 |
|
Harvestor |
$29.46 |
Harvestor |
$29.46 |
|
Irrigation system |
$287.01 |
||
|
Custom hire |
$83.50 |
Custom hire |
$53.75 |
|
Machine labor |
$6.08 |
Machine labor |
$6.08 |
|
Total costs |
$1115.16 |
Total costs |
$643.11 |
Table 4. Estimated costs for cover crops with different seeding rates.
|
Cover crop Cost |
Seeding rate |
||
|
High |
Low |
Standard |
|
|
Buckwheat |
$247.72 |
$110.10 |
$165.15 |
|
PigeonPea |
$482.62 |
$215.32 |
$321.75 |
|
White clover |
$154.50 |
$67.05 |
$102.03 |
|
Mix |
$295.93 |
$131.68 |
$196.48 |
Objective-5
As part of objective-5 (outreach efforts), we conducted presentations and made publications.
A producer meeting was conducted involving PI Narayanan, her Ph.D. student, and the farmer cooperators. In this meeting, the Ph.D. student presented updates about the on-station trials. Plans for the on-farm trials were discussed. Additionally, PI Narayanan also had multiple one-on-one meetings with the project team members including the farmer cooperators.
The project team had an annual meeting on March 21, 2024. The project team involving collaborators, farmer cooperators, and advisory board members were updated about the project progress by presentations by the PI, Co-PIs, and graduate students. Project team also discussed plans for the coming season.
Objective-1:
Updates of survey findings: Overall, 59 farmers began the survey. In year one, 37 farmers completed the survey. In year two, an additional 7 farmers completed the survey, bringing it to a total of 44 completed surveys.
Of the 44 farmers, they were on average 47 years old (M=47.18, SD=13.19), with a decent split in gender identities with 22 identifying as male and 20 as female. No one identified as transgender. Majority of the growers indicated having completed a four-year degree or more (n=32). A total of 36 farmers identified as being White or Caucasian, 5 as Black or African American, 2 indicated being Hispanic or Latina/Latino, and 1 as Asian Indian. Political ideology, measured on a 5-point scale (1= “very conservative” to 5= “very liberal”), indicated a range of ideologies (M=3.11, SD=1.54). There were 10 who identified as either leaning, weak, or strong Democrat, 10 as independents, and 17 as either leaning, weak, or strong Republican.
With respect to their news media diets (1= “none at all” to 5= “a great deal”), growers mostly indicated not using traditional media outlets as much as social media outlets. Among traditional news, sources like Fox News, Brietbart, and One American News (M=1.38, SD=0.73) and sources like MSNBC, CNN, and Huff Post (M=1.47, SD=0.83) appeared to be the least used, followed by sources like the The New York Times and The Washington Post (M=1.93, SD=1.11) and sources like ABC News, CBS News, and NBC News (M=2.02, SD=1.14). Social media sources such as Facebook and Twitter ranked somewhat higher in use (M=2.45, SD=1.27).
Growers mentioned on a 5-point scale (1= “not at all important” to 5= “extremely important”) that science was somewhat important to their daily life (M=3.74, SD=1.10). Growers also indicated on a 5-points scale (1= “very distant” to 5= “very close”) that they felt somewhat close to science in general (M=3.78, SD=1.03) and to agricultural science in specific (M=3.91, SD=1.05).
There were 23 farmers who mentioned practicing conventional farming, 7 who identified as being certified organic, and 25 indicated being uncertified, but using organic practices. There were 27 farmers who practiced reduced till farming (i.e., less intensity, shallower depth, and less area disturbed, either in the bed, field or across the farm) and 18 no-till farming (i.e., zero tillage or direct drilling).
A total of 32 growers indicated using cover crops, of which 13 started using them less than 5 years ago and 19 have been using them for over 5 years. While two mentioned not using them and having no intention of using them in the future, 11 indicated intending to do so in the future, and 6 mentioned that they were curious about using cover crops but were concerned about risks to crop productivity. Thirty-one planted their cover crops on the land they owned and 8 on the land they lease. Thirty-three use legumes (such as alfalfa or clover) as their cover crops, 34 use grasses (such as ryegrass or barley), 23 use brassicas (such as radishes or turnips), 4 uses non-legume broadleaves (such as spinach or flax), and 30 use multi-species mixes. As for the sources the growers used to get information about cover crops and/or inter-seeding, several mentioned using university outreach (n=33), other growers (n=29), NRCS (n=25), and magazines (n=23), and some mentioned television programs (n=6) and radio programs (n=3).
On a 5-point scale (1= “strongly disagree” to 5= “strongly agree”), most growers indicated that the benefits of cover crops outweigh their risks (M=4.36, SD=0.85). However, the growers who were using cover crops (M=4.66) felt were more likely to agree with this sentiment (t=-2.93, p=0.008) than those who were not (M=3.89).
Among a list of benefits, on a 5-point scale (1= “not at all important” to 5= “extremely important”), growers rated improved soil health (M=4.65, SD=0.56) as the most important benefit from cover crops followed by: increased soil organic matter (M=4.50, SD=0.68); reduced soil compaction and improved field trafficability (M=4.48, SD=0.80); improved weed control, beneficial insects, disease suppression of weeds, pathogens, and insect pests (M=4.44, SD=0.74); reduced soil erosion (M=4.40, SD=0.92); increased biodiversity (M=4.29, SD=0.80); recycling nutrients (M=4.27, SD=1.01); attracting pollinators and other beneficial insects (M=4.19, SD=1.02); increased water filtration (M=4.15, SD=0.95); decreased input costs (M=4.12, SD=1.04); increased profitability (M=4.00, SD=1.03); wildlife habitat and landscape aesthetics (M=3.79, SD=1.15); increased yields on cash crops (M=3.77, SD=1.26); climate adaptability (M=3.75, SD=1.08); and, finally carbon storage (M=3.67, SD=1.23). See Figure 1 for an overall comparison of the perceived benefits.
The benefits related to soil i.e., improved soil health, increased soil organic matter, and reduced soil compaction and improved field trafficability were among the top perceived benefits for cover crops. However, there was one benefit that was perceived to be more important than others among growers using cover crops. Growers who were using cover crops (t=-2.84, p=0.009) were significantly more likely to rate soil health from cover crops as being more important (M=4.83) than those who did not use cover crops (M=4.34).
Among a list of risks, on a 5-point scale (1= “not at all important” to 5= “extremely important”), growers rated the most important risks as choosing the correct cover crop most compatible with particular crops (M=3.87, SD=1.19) followed by: the additional costs for seed, planting, management, termination etc. (M=3.49, SD=1.27); where chemicals produced from certain cover crops interfere with crop growth of other plants (M=3.36, SD=1.29); cover crops becoming weeds in cash crops (M=3.32, SD=1.35); the lack of information or recommendations regarding cover crop selection and management (M=3.30, SD=1.30); the depletion of soil moisture effects depending on weather or management (M=3.26, SD=1.19); unavailability of cover crop seeds (M=3.26, SD=1.37); the increase in insect pests (M=3.23, SD=1.34); the insufficient economic returns (M=3.23, SD=1.42); the yield reduction of cash crops (M=3.21, SD=1.27); the increase in labor needs (M=3.13, SD=1.36); the interference with cash crop operations (M=3.09. SD=1.28); diseases risks (M=3.06, SD=1.24) and the difficulty incorporating cover crops with tillage (M=2.74, SD=1.42). See Figure 2 for an overall comparison.
The perceived risk that was rated the most important was about choosing the correct cover crop most compatible with particular crops, and this was perceived a higher risk (t=2.51, p=0.02) among those not currently using cover crops (M=4.33) compared to those who were using cover crops (M=3.59).
There were only 16 growers who indicated currently or in the past practicing cover crop inter-seeding and only 8 who indicated currently or in the past having used cover crop inter-seeding into corn. Fourteen participants indicated using broadcasting seeding method and 5 mentioned ariel seeding method for inter-seeding. Among those who indicated not using cover crop inter-seeding, 15 indicated it was because they did not feel confident about timing of crop and cover crop sequences, 11 noted it was because of lack of equipment, 9 indicated it was due to lack of financial resources and lack of labor, 8 that it was lack of guidance from extension personnel, and 3 people mentioned not seeing any advantages and increased risk with non-irrigated situations, lack of general information available for highly-diversified small farm growers, and that they were going to try this year.
With respect to things that would improve their quality of life (1= “not a lot” to 5= “a great deal”), growers felt that improved stewardship to their land (M=4.00, SD=1.05), ease of management (M=3.76, SD=1.08), increased resilience to weather extremes (M=3.76, SD=1.10), ease of decision-making (M=3.48, SD=1.13), cover crops (M=3.46, SD=1.21), and cover crop inter-seeding into corn (M=1.91, SD=1.24) all contributed at different levels. As of now, growers rated that cover crop inter-seeding into corn to be the least important to improving their quality of life in comparison to cover crops in general (t=7.51, p<0.001), ease of decision-making (t=8.00, p<0.001), increased resilience to weather extremes (t=8.58, p<0.001), ease of management (t=8.50, p<0.001), and improved stewardship to their land (t=9.42, p<0.001). There were no significant differences among those who were current users and those who were not with respect to how much cover crops in general (t=-1.21, p=0.24) or cover crop inter-seeing (t=1.30, p=0.204) contributed to their quality of life.
Growers were asked on a 5-point scale (1= “not knowledgeable at all” to 5= “extremely knowledgeable”) about their perceived knowledge, and there was a significant difference in this regard to cover crops in general and cover crop inter-seeding into corn (t=7.74, p<0.001). Relatively, growers indicated feeling more somewhat more knowledgeable about cover crops in general (M=3.09, SD=1.11) than about cover crop inter-seeding into corn (M=1.98, SD=1.18).
On a 5-point scale (1= “strongly disagree” to 5= “strongly agree”), growers indicated being neutral to somewhat supportive of using cover crop inter-seeding into corn (M=3.54, SD=0.98), most weren’t seeing farmers like them using cover crop inter-seeding into corn (M=2.37, SD=1.10), indicated that farmers like them considered it not quite valuable to inter-plant cover crops into strands of corn (M=2.74, SD=0.98), and they indicated feeling too confident in being able to use cover crop inter-seeding into corn (M=2.96, SD=1.09).
Interviews discussing survey results: The survey findings gathered in year 1 provided insights on grower perceptions with respect to cover crops and cover crop inter-seeding into corn. These findings were shared with the four co-operating farmers (Farmer 1 (S), Farmer 2 (R), Farmer 3 (W), and Farmer 4(E)), who then provided helpful insights into why certain benefits or risks were appraised as such. They also helped inform next steps for objective 1.
In response to why soil health-related benefits in the survey were considered the most important benefit to cover crops, the cooperating farmers provided a few potential reasons. As Farmer 1 mentioned, taking care of soil has always been important to growers where even the education materials they received and consumed all often pointed to the value of healthy soil and ways to protect it. So, if cover crops could contribute positively to soil health, then they would be considered a valuable benefit for most growers. Farmer 1 also mentioned how having healthy soil can be beneficial for small-scale and large-scale farmers. Farmer 2 mentioned how several other benefits of improving yields or reducing erosion all connect back to having good/healthy soil. Farmer 2 also mentioned how the benefit of having healthy soil is something a grower can notice and measure more directly compared to some of the other benefits listed. Farmer 4 also agreed with this notion, and mentioned how soil health could be noticeable for farmers if they saw an increase of red worms in their field and how soil samples could also be sent to assess for the amount of organic content in it – all measurable impacts. In other words, improving soil health is a concrete and tangible benefit a grower might be able to assess themselves compared to other benefits which may be considered relatively more abstract or hard to measure by growers.
The least important benefits in the survey with respect to cover crops pertained to climate adaptability, carbon storage, increased yields of cash crops, and aiding wildlife landscape aesthetic. With respect to the benefits of climate adaptability and carbon storage, a couple of Farmers 1 and 2 mentioned how these can seem abstract for growers. As they mentioned, improvements in soil health can be something a grower can see and assess for themselves, but knowing whether cover crops are contributing to climate adaptability or carbon storage can be relatively abstract and not tangible. Farmer 3 mentioned that although having carbon in the soil can be help with the health of the soil, benefits related to the climate could potentially be priming political ideologies, which might be making it less appealing benefit for growers. Farmer 4 also mentioned that if farmers were able to get carbon credits that translated to financial incentives how that could also motivate growers to adopt cover crop inter-seeding. As Farmer 4 noted, some growers might need help connecting the dots in showing how better soil can mean better organic matter in soil, better yields, better for the environment, etc.
The cooperating farmers also mentioned how it is reasonable and understandable why growers might feel anxious about making sure they plant the right cover crop. One cooperating farmer mentioned how their perceived lack of knowledge and lack of confidence in working with cover crops made them anxious about the process. As a way to ease into the process, Farmer 1 recommended having the growers start small with only testing it in a small section of their farm to test the benefits of cover crop inter-seeding. Farmer 2 explained how growers had to study their farms and their crops to have a plan for what crops would work well as cover crops for their farm and figure out their planting system. Farmer 3 also reported the importance of educating growers of cover crops and their benefits to be a key component to drive adoption. Farmer 4 also mentioned the importance of educating growers in not only what cover crops to use, but also inform them of the best times for when they should be planted and harvested so they don’t end up with either lack of germination, stunted growths, or becoming too quick to seed. Farmer 2 also mentioned how some farmers (and some people in general) do not like change and so it might not be possible to convince everyone to make a change. To convince people to change and given the amount of resources a grower would have to endure to practice cover crops, it would require making the case for why it will be worth it. Farmer 4 mentioned how the point of short-term investment leading to long-term benefits is key to cover crop communication and potential adoption. In other words, it will be important to convince the growers of how the benefits of cover crop inter-seeding outweigh the risks of implementing this practice, and overall contribute to improving their quality of life. However, every farmer might have their own vision for what it might mean to have a better quality of life, which makes it challenging. For example, for Farmer 4, having a beautiful field throughout the year, giving him reasons to be on farm often, and having wildlife are some rewarding benefits he feels he receives from cover crops.
Data from years 1 and 2 show the importance of conveying the perceived concrete/tangible benefits to soil health and equipping growers with the knowledge and/or resources to receive information on the type of cover crops to use and when/how to plant and harvest them are key messages to convey to help with the adoption of cover crops. Data also showed that while some growers can see the interconnectedness of soil health with climate and other listed benefits (of yield, of profitability, costs, etc.), it is not always clear to everyone or is the most convincing in understanding how cover crop inter-seeding could contribute to improving their quality of life.
Objective-2
Cover crop biomass
At all seeding rates and under both tillage treatments, buckwheat had higher biomass than other cover crops (Figure 3). Buckwheat grew vigorously compared to the other two cover crops. White clover generally had lower biomass than other cover crops at all seeding rates and under both tillage treatments.
Corn biomass
Corn biomass was not reduced by interseeded cover crops under conventional or reduced tillage treatments at both locations (Florence and Clemson) (Figure 4).
Corn grain yield
Interseeding appeared to have a positive impact on corn grain yield; e.g., corn yield was numerically higher when buckwheat was interseeded at standard seeding rates under conventional and reduced tillage in 2022.
In 2023, the corn yield improvement was statistically significant when buckwheat was interseeded at high seeding rates, compared to control-2 (No cover crops, no fertilizer).
Weed biomass
In 2022, when weeds were not controlled in the control plots, weed biomass was numerically less under buckwheat and white clover at high seeding rate under conventional tillage conditions.
In 2023, control plots were maintained as weed-free; still, specific interseeding treatments, e.g., buckwheat and pigeon pea at low and high seeding rates, achieved the same level of weed suppression as compared to control plots under conventional and reduced tillage conditions. (Figure 6).
Volumetric water content
In 2022 and 2023, volumetric water content in the upper 20-cm soil profile was not reduced by interseeded cover crops at any seeding rates, compared to both control treatments (no cover crop and/or fertilizer) under both tillage treatments (Figure 7). This does not support the possibility of interseeded cover crops reducing the available soil water to the cash crops. In 2023, under conventional tillage conditions, volumetric water content was significantly higher in plots with interseeded pigeonpea (indicating water saving) at low seeding rate than that under control 2 (no-cover crop, no-fertilizer).
Bulk density, penetration resistance, and root traits
Interseeded cover crops had no effects on bulk density and penetration resistance. Corn root traits are currently under analysis.
Soil physical, chemical, and biological properties
In 2023, soil samples were collected before corn planting and at corn’s physiological maturity. These were analyzed for physical, chemical and biological properties to investigate the effects of interseeded cover crops at different seeding rates and tillage conditions to soil health. These properties are pivotal in defining the foundational role of soil within ecosystems. Understanding these soil properties is essential for managing ecosystems sustainably, optimizing plant growth, and preserving biodiversity. Physical properties include bulk density, penetration resistance, aggregates and water-holding capacity while chemical properties deal with the amount of inorganic nitrogen, phosphorus and active carbon, electrical conductivity and pH. Enzyme activities, nitrogen and carbon mineralization, microbial biomass, and microbial gene abundance were measured to determine biological properties.
Biological Properties
Carbon cycling enzyme activity
β-glucosidase enzyme activity
β-glucosidase (BG) plays a pivotal role in soil organic matter and plant residue degradation. It stands out as one of the most frequently documented immobilized enzymes, often cited in literature as an indicator of management impacts. Increasing BG activity, typically correlated with higher soil microbial biomass, signifies a soil's capacity to decompose plant residues and enhance nutrient accessibility for subsequent crops. In 2023, pigeonpea at high seeding rate showed significantly higher β-glucosidase activity compared to both controls and background soil under conventional tillage condition (Figure 8). The rest of the treatments were statistically comparable to either controls or background.
Nitrogen cycling enzyme activity
Leucine aminopeptidase and asparaginase enzymes play complementary roles in nitrogen cycling in soil by facilitating the breakdown of organic nitrogen compounds and releasing nitrogen in forms accessible to plants and microorganisms. Their activities contribute to nitrogen mineralization, microbial growth, soil fertility, and ecosystem functioning. Elevated enzyme activities serve as indicators of soil health and ecosystem functioning. In 2023, compared to background soil, leucine amino peptidase and asparaginase activities under both tillage conditions were higher across all treatments including controls (Figure 9). Under conventional tillage condition, mixture at low seeding rates had statistically higher asparaginase activity compared to control-1 and background.
Potentially mineralizable nitrogen
Potentially mineralizable nitrogen (PMN) refers to the pool of organic nitrogen compounds present in soil that has the potential to be mineralized or converted into inorganic forms such as ammonium (NH4+) and nitrate (NO3-), by soil microorganisms through decomposition processes. High PMN in soil signifies improved soil fertility and enhanced nutrient availability. In 2023, potentially mineralizable nitrogen was statistically similar in background soil and across all treatments and controls (Figure 10). This could be an indication that the soil where the experiment was conducted contained organic matter which remains relatively stable throughout the growing season, or soil microbial populations and activity levels relatively constant over time.
Soil chemical properties
Inorganic nitrogen, electrical conductivity and pH
Inorganic nitrogen represents the amount of available nitrogen in the soil in the form of nitrate and ammonium. Soil electrical conductivity or EC is the measure of the soil’s ability to conduct electricity, and is highly affected by the concentration of soluble salts in the soil. The measure of the acidity and alkalinity of soil is pH. It is one of the most important soil properties because it affects many soils chemical properties affecting nutrient availability to plants. In 2023, compared to background, inorganic nitrogen and EC were significantly reduced in all treatments under both tillage conditions (Figure 11). Inorganic nitrogen was significantly reduced uniformly compared to background which could be an indication that cover crops do not compete with corn for inorganic nitrogen. Evident by uniform soil inorganic nitrogen content across plots and treatments. EC and inorganic nitrogen content were related. EC is affected by the concentration of soluble salts (inorganic nitrogen) in the soil. When corn absorbed inorganic nitrogen, EC also eventually declined. pH, on the other hand, was increased across all treatments compared to background.
Conclusions based on the two-year field trials
Interseeded cover crops did not reduce corn biomass, grain yield, soil water content and nitrogen use efficiency in the organic corn production system under conventional or reduced tillage conditions in both years. Interseeding appeared to have a positive impact on corn grain yield; e.g., corn yield was increased when buckwheat was interseeded. Our results did not support the possibility of interseeded cover crops reducing the available soil water to the cash crops. Further, in 2023, interseeded pigeonpea appeared to result in more moisture retention in soil. Buckwheat and pigeon pea appeared to have a weed-suppression effect as well. Interseeded cover crops did not reduce enzyme activities for both nitrogen and carbon cycling. No competition for inorganic nitrogen between cover crops and corn was observed. The results from our study indicate a positive impact of cover crop interseeding on corn performance, soil moisture retention, and weed suppression. The results will be verified in the 2024 season.
Objective-3
In 2023, we found fewer herbivore pests, and only half as much corn earworm damage to corn ears in inter-seeded plots that had living ground cover, relative to control plots (Figure 12). Beneficial predatory insects tended to be more abundant in inter-seeded plots but were not significantly different from controls.
Objective-4
Cost and revenue results:
Figures 12 and 13 illustrate the revenue and net returns from corn grain yield with interseeded cover crops under conventional and reduced tillage conditions for the years 2022 and 2023 respectively. The green bar in the figures represents net returns, while the orange bar represents the revenue generated. These bar graphs are set to compare the economic outcomes across multiple cover crop treatments with different seeding rates and 2 control groups with no cover crops. Ctl1 in the figures represents the control treatment 1 with no cover crops but received fertilizers, whereas Ctl2 stands for the control treatment 2 with no cover crops or fertilizers.
In 2022, all categories under both tillage systems appeared to generate positive revenue. However, net returns vary significantly. Some categories, especially under reduced tillage, show negative net returns, meaning that the costs associated with those particular seeding rates and cover crops might have exceeded the revenue generated from the yield. In 2023, the net returns are much more favorable, with fewer categories showing losses. This could be due to increased yield efficiency, and reduced costs due to no irrigation.
Conventional tillage shows a consistent pattern of revenue exceeding net returns, but in 2023, the gap between revenue and net returns narrows compared to 2022, indicating better profitability.
Partial budget analysis results:
In this study, the added costs of using cover crop interseeding were associated with different seeding rates and fertilizer costs. The comparable treatment (Ctl2) has no cover crops and no fertilizers. The net return for each cover crop treatment relative to no cover crops and fertilizers is presented as the difference between the total positive and negative effects of using cover crops.
The data in Tables 5 and 6 represent the results of partial budget analysis results for field trails conducted in Florence, SC and Clemson, SC, respectively. The total negative effects incurred with using cover crop treatments were defined as the added cost plus reduced returns, whereas the total positive effects were calculated as the reduced costs plus the added returns, respectively. The total effects were the differences between the total positive and negative effects. The total effects of most treatments were negative when compared to the control, implying that these treatments were less profitable compared to the control. The few treatments that did have positive effects, under reduced tillage are worth noting for potentially beneficial economic outcomes.
Objective-5
The project team made multiple presentations and publications.
Presentations in field days and relevant meetings:
- Cover crop interseeding in organic production system. Southern Agronomy Society of America Annual Meeting (Feb 3-5, 2024)
- Co-optimizing diversity and prosperity in agroecosystems (Invited department seminar). University of Illinois Urbana-Champaign, Natural Resources and Environmental Sciences: (3/2024)
- Multi-trophic consequences of biodiversity in agroecosystems (Invited seminar). The Land Institute, Salina, KS (2/2024)
- Cover crop interseeding in organic corn production. SARE-YES Poster.
- Participated in 2023 PREC and PDREC field days
Publications:
- St Aime R., Bridges W.C., Jr., Narayanan S. 2023. Interseeded cover crops did not reduce the performance of silage corn in the sandy loam soils of South Carolina. Agrosystems Geosciences and Environment. 6:e20364.
- Holmes, K. D., & Blubaugh, C. K. 2023. A Guide to 23 Global Syntheses of Plant Diversity Effects: Unpacking Consensus and Incongruence across Trophic Levels. The Quarterly Review of Biology, 98, 121-148. https://doi.org/10.1086/726687
- Blubaugh, C.K., Huss, C.P. Lindell, H.C, and Basinger, N.T. Cover crops dismantle ant/aphid mutualisms to strengthen herbivore suppression. (In review at Ecological Applications)
Co-PI Idassi interacted with underserved farmers in multiple meetings, workshops, and conferences. He conveyed the project results in these venues. Our project was covered by the Clemson News Media, which was reprinted by multiple news magazines/newspapers. This facilitated outreach to public. The project team members were in frequent communication with farmers, educators, and stakeholders which also helped to disseminate the project results and expected outcomes and provide consultations.
Education
The project includes involvement of graduate students for the implementation of the project. The PI, Co-PIs, collaborators, and/or the farmer cooperators are working with the students and training them in interdisciplinary research, cover crop culture, and data collection, analysis, and interpretation. The project involved the participation of >10 undergraduate students through Clemson University Professional Internship and Co-op (UPIC) program, a high school student through the SARE YES program, and 5 high school students through ‘Directed Research’ summer course (Summer Program for Research Interns). We anticipate that these trainings of graduate, undergraduate, and high-school students will help grow new ‘sustainable agriculture’ professionals. The SARE YES grant that the PI received in 2023 enhanced the educational impacts of this project. PI worked with Clemson University MANRRS (Minorities in Agriculture, Natural Resources and Related Sciences), and recruited an underrepresented minority (URM) student to this project through the YES grant. The team submitted a poster to SARE based on their YES project.
PI Narayanan teaches multiple courses related to crop science and agronomy (e.g., Principles of Field Crop Production, Major World Crops, and Crop Physiology). Co-PI Tallapragada teaches courses related with social science research methods and societal, ethical, and diversity issues (Survey Design, Research Methods, and Diversity and Public Relations). The knowledge gained from the proposed project were integrated to the curriculum of these courses. Thus, the project has contributed to enhancing the institutional educational capacity related with sustainable agriculture.
Educational & Outreach Activities
Participation Summary:
The project team made multiple presentations and publications.
Presentations in field days and relevant meetings:
- Cover crop interseeding in organic production system. Southern Agronomy Society of America Annual Meeting (Feb 3-5, 2024)
- Co-optimizing diversity and prosperity in agroecosystems (Invited department seminar). University of Illinois Urbana-Champaign, Natural Resources and Environmental Sciences: (3/2024)
- Multi-trophic consequences of biodiversity in agroecosystems (Invited seminar). The Land Institute, Salina, KS (2/2024)
- Cover crop interseeding in organic corn production. SARE-YES Poster.
- Participated in 2023 PREC and PDREC field days
Publications:
- St Aime R., Bridges W.C., Jr., Narayanan S. 2023. Interseeded cover crops did not reduce the performance of silage corn in the sandy loam soils of South Carolina. Agrosystems Geosciences and Environment. 6:e20364.
- Holmes, K. D., & Blubaugh, C. K. 2023. A Guide to 23 Global Syntheses of Plant Diversity Effects: Unpacking Consensus and Incongruence across Trophic Levels. The Quarterly Review of Biology, 98, 121-148. https://doi.org/10.1086/726687
- Blubaugh, C.K., Huss, C.P. Lindell, H.C, and Basinger, N.T. Cover crops dismantle ant/aphid mutualisms to strengthen herbivore suppression. (In review at Ecological Applications)
Co-PI Idassi interacted with underserved farmers in multiple meetings, workshops, and conferences. He conveyed the project results in these venues. Our project was covered by the Clemson News Media, which was reprinted by multiple news magazines/newspapers. This facilitated outreach to public. The project team members were in frequent communication with farmers, educators, and stakeholders which also helped to disseminate the project results and expected outcomes and provide consultations.
The project includes involvement of graduate students for the implementation of the project. The PI, Co-PIs, collaborators, and/or the farmer cooperators are working with the students and training them in interdisciplinary research, cover crop culture, and data collection, analysis, and interpretation. The project involved the participation of >10 undergraduate students through Clemson University Professional Internship and Co-op (UPIC) program, a high school student through the SARE YES program, and 5 high school students through ‘Directed Research’ summer course (Summer Program for Research Interns). We anticipate that these trainings of graduate, undergraduate, and high-school students will help grow new ‘sustainable agriculture’ professionals. The SARE YES grant that the PI received in 2023 enhanced the educational impacts of this project. PI worked with Clemson University MANRRS (Minorities in Agriculture, Natural Resources and Related Sciences), and recruited an underrepresented minority (URM) student to this project through the YES grant. The team submitted a poster to SARE based on their YES project.
PI Narayanan teaches multiple courses related to crop science and agronomy (e.g., Principles of Field Crop Production, Major World Crops, and Crop Physiology). Co-PI Tallapragada teaches courses related with social science research methods and societal, ethical, and diversity issues (Survey Design, Research Methods, and Diversity and Public Relations). The knowledge gained from the proposed project were integrated to the curriculum of these courses. Thus, the project has contributed to enhancing the institutional educational capacity related with sustainable agriculture.
Learning Outcomes
Sustainability
Cover cropping
Project Outcomes
Organic corn production in the U.S. increased more than 50% between 2016 and 2019 (USDA NASS, 2020). However, soils on which corn is grown are erosive and, therefore, susceptible to land degradation (Thaler, 2021). Cover crop inter-seeding into standing corn crops helps address this issue. Inter-seeded cover crops can provide numerous benefits such as increased nutrient supply to the row crop (Teasdale et al., 2007; Deguchi et al., 2012; Finney et al., 2016; Thapa et al., 2018; Perrone et al., 2020), increased nutrient use efficiency (Ochsner et al., 2010), increased species richness and function of the soil microbes (Nakamoto and Tsukamoto, 2006; Deguchi et al., 2007; Dabney et al., 2010) and macrofauna (Pelosi et al., 2009), improved soil structure/stability (Hall et al., 1984; Snapp et al., 2005), reduced soil compaction (Raper et al., 2000), and suppressed weed emergence (Thelen et al., 2004; Brooker et al., 2020). Soil health benefits conferred by inter-seeded cover crops also support water storage, organic matter decomposition, and nutrient cycling, which can reduce agricultural inputs and buffer crops from anticipated climate extremes (Kaye and Quemada 2017). According to the Organic Farming Research Foundation survey among farmers (NORA, 2016), 42% of respondents in the South demanded more research to identify cultural practices to improve soil health that would improve the resilience of production systems to extreme weather. Because reducing weed pressure on crops without affecting soil health through intense and frequent tillage and cultivation practices is a major challenge in organic row crop production, inter-seeded cover crops that suppress weeds and improve soil health would be an innovative approach to improve the economic, environmental, and social well-being of southern producers. The proposed project will optimize an inter-seeded cover crop system for belowground complementarity between cover crop and cash crop, ecosystem services, and overall system profitability. The project will deliver a toolkit of reduced tillage and cover crop management practices that stabilize production and profitability for farmers in a changing climate.