Effects of Using a Native Legume as a Cover Crop in Small Scale Vegetable Production

Progress report for FS22-345

Project Type: Farmer/Rancher
Funds awarded in 2022: $15,000.00
Projected End Date: 03/31/2024
Grant Recipient: NANIH Farm and Garden, Inc.
Region: Southern
State: Virginia
Principal Investigator:
Patrick Johnson
NANIH Farm and Garden, Inc.
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Project Information


Cover crops also known as green manuring is one of the lynchpins of an ecologically based farming system. Some of the benefits of cover cropping include:

  • Increasing earthworms and beneficial microorganisms
  • Increase plant available Nitrogen
  • Increase organic matter content
  • Preventing erosion
  • Mining of minerals
  • Providing habitat for beneficial insects and organisms
  • Improving soil structure
  • Increased water holding capacity
  • Reduced weed populations
  • Reduced pest populations

Using native cover crops has the potential to increase the number and diversity of beneficial insect thus increase the overall number of species present on a site (Tallemy, 2018). Native cover crops are easier to establish than there non-native counter parts and promote the presence of less pests and diseases and compete less  with the main crop for soil resources like moisture (Danne, Thomson, Sharley, Penfold, and Hoffmann, 2010). This project will also demonstrate how low income, socially disadvantaged farmers can successful harvest wild plants and use them as cover crops thus eliminating or greatly reducing the cost of the cover crop. Growing native plants as cover crops have the following potential benefits:

  • Reduced establishment costs;
  • Reduced loss of topsoil;
  • Nutrient mining;
  • Attracting beneficial organisms;
  • Reduced soil erosion;
  • Feeding microorganisms;
  • And, Adding soil biomass (Koperek, 2018)
Project Objectives:

This project will be carried out in two phases. Phases I involves observation of wild Chamaecrista fasciculata (partridge pea) and an initial determination of seeding rates for coastal plain soils. The principle investigator for this project is a permaculturist. Permaculture design is based on the careful observation of patterns found in nature. It is the goal of this first phase of research to characterize and document the wild growth habits of Partridge pea. In phase I we will use the visual reconnaissance method to identify wild patches of partridge pea growing at the Airport Food Forest Farm. By carefully documenting the life cycle and seasonal growth patterns of wild partridge pea we will create a blueprint for those wishing to use a wild plant or plants as a cover crop.

The sampling procedure will be as follows:

The site will be divided into three plots of the following sizes 50’ x 100’; 50’ x 180’; and 50’ x 180’.

A hand drawn map will be made of each plot. We will use a compass to draw a line along the long axis of the map. A line will also be drawn along the short axis of the map roughly perpendicular to the long axis. We walk along these lines to visually identify populations of partridge pea. Each wild plot of partridge pea will be flagged. We will note the following items: Size of stand, members of plant community, stage of plant development, soil moisture level, soil ph., light conditions (estimate); beneficial insect and animals, growth habits (date of first emergence, date of first flowering, date of pod formation, plants physical characteristics).  A summary of the collected date will be submitted in the final report.

The second part of year one is an initial varietal trail to determine the proper seed rate. For our experiment we will use seeding rates of 10, 15, 20, 25, 30 lbs/ac for each available commercial variety. The varietal trial will be held at Dayspring Farm (DSF). The plot size will be at least 1/10 or 4000 ft2.  Each variety of partridge pea will be planted at 5 different seeding rates with no control. A total of 20 plot will be used averaging 200 ft.2.  


An initial assessment of partridge pea varieties will be conducted in the spring of 2021 to help determine spacing for maximum potential of the cover crop. Varieties used for test plots will depend on the availability of seeds. Potential varieties for trails are Comanche (cultivar); Shelly (cultivar); Lark Selection or Non-specific variety (NSV).  Half of the seeds at each site will be inoculated with cowpea inoculant to determine if this makes a difference in nitrogen fixation rates.  We will use seeding rates of 10, 15, 20, 25, 30 lbs/ac for each available commercial variety Plots will be assessed monthly for ground cover, height and biomass. A 15in x 15in section of each plot will be randomly selected. Measurements will be taken weekly after the first month of growth from the randomly selected site. Coverage is measured by assigning a visual score from 1-10 (1 least covered to 10 most covered). Height is measured and recorded. The same sample will be cut to 1 inch, the sample bagged, the bagged material dried, and weighed to determine above ground biomass in tons per acre. When testing for nitrogen we propose to use the following procedures: We will be drying cover crop samples to estimate biomass. We will send the dried samples to a lab get N per acre. b to determine total N analysis. We will multiply the biomass per acre by the %/N/100 to get lb N per acre.

Phase II

In phase I we endeavored to learn the natural growth habits of partridge pea and the best potential variety and seeding rate to use in a commercial vegetable farming cover crop rotation. After learning the best performing variety, we will compare the top performing variety to the native variety found at the Airport Food Forest Urban Farm (AFF). If enough seed is not collected from the AFF or if special procedures such as scarification is needed for germination of the native seed collected at the AFF, then both sites  AFF and DSF will only use the top performing varity of partridge pea for the phase II experiment. We will compare the perform of partridge pea at both sites to a commonly use cover crop plant, “Iron and Clay” southern peas (Vigna unguiculata). This cover crop exhibit some of the characteristics of partridge peas. Site 1 is AFF. Site 2 is Dayspring Farm (DSF). In Phase II we will use two economic factors, seed cost and differential impacts on production of the brassica crop to determine the economic viability of partridge verses a tradition covercrop--iron and clay cowpeas.  AFF will plant native variety and or top performing variety in a 400 ft2 plot.  DSF will plant the naitve variety and top perform variety from the field trial in a 400 ft2 plot. Both site will plant iron and clay cowpea at the equalivency rate in a 400 ft2 plot. We will again measure cover crops biomass, height, and ground cover for the partridge peas and the iron and clay cowpea. Pre and post soil tests will be taken from both sites at planting and 7 days after termination of crop and incorporation of biomass. The same varieties brassicas will be planted at both sites after termination. Weeding and water schedule will be the same (unless variation is justified). Performance of each cover crop will be based on crop yield performance of the brassicas.

Summery of Experiment

  • We are looking at beginning the partridge pea variety trail in May of 2022.
  • For the phase II study we are proposing to compare all the following at both sites:
  • Best variety #1 at best seeding rate (based on Phase I variety trial at Dayspring Farm).
  • Best variety #2 at best seeding rate.
  • Native partridge pea from AFF at comparable seeding rate.
  • Southern pea at 50 (drilled) or 80 (broadcast and raked) lbs./ac
  • We test for nitrogen by multiplying the biomass per acre by the %/N/100 to get lb N per acre.
  • We will follow all cover crop with the same varitey of brassicas and compare each performance in terms of yield (weight per plot).
  • Economic comparison points: Cost of seeds and yield of brassica crop.


Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Leonard Githinji (Researcher)


Materials and methods:


The area of the plot 4300 Sq Ft. was divided into seven evenly divided beds approximately 6.25 wide x 2 feet wide. Each section of the bed was assigned a number correlating to the letters on the north end of the plot (exam A-1, A-2 etc..). Each section was further divided into 43 sections each measuring 2 long. A number was assigned a number written on paper and placed in a bag. The number were randomly selected from the bag. Once selected,  the section was identified in the field and a sample was taken from the corresponding section of field. Sample were taken from the section using a wood 2 X 2 quadrat. The quadrat was slide in the cover crop at ground level. The plant material within the quadrat was cut at ground level and placed in a clean plastic bucket. The bucket was weighed in pounds.

Dry Weigh Sample

After all the subsamples were collected the were combined into one sample for dry weigh analysis. The subsample was mixed together on a clean tarp. A process of clipping and chopping was used to make toe sample size smaller. The large biomass pile was then split into four evenly size piles. Two diagonal pieces for the four were discarded. The remaining diagonal pile were mixed together and the process was repeat until the pile was small enough to fill a gallon sized bag.

Size of Area: 50 Ft. X 86 Ft. = 4300 Sq. Ft.

Planting: the field was divided in half the rows planted 1 ft. apart and the other half planted 6 inches apart.

The seeding was done with a Jang seeder with spinach seeding rate. The front section of the plot  was marked for the 4 varieties selected for trail: Cherokee National Forest; 1) Non-Select; 2) Cherokee National Forest; 3) Comanche; and 4) Lark. The seeds of all varieties were cold stratified for 30 days before planting. Cold stratification achieved poor germination results in all varieties except Cherokee National Forest. Seven days after planting Cherokee variety began sprouting. Eleven days after planting growth noticed in all varieties except Lark. Poor germination was noted in all varieties except Cherokee National Forest. The decision was made to replant all varieties except Cherokee Nation Forest. Replanted seeds were treated the same as earlier planting except were subjected to seed coat scratched with sandpaper. The addition treatment did not result in increased germination in planted varieties. Only Cherokee National Forest achieved measurable results for the second year trail.

Research results and discussion:

Observational Summary

Outcome of first year (2022) trials with ‘Cherokee National Forest’ partridge pea

The partridge pea cover crop accumulated a little over two tons per acre aboveground dry weight

biomass at 85 days after planting, and 2.5 tons at 105 DAP (Table 1). This represents growth

rates of about 53 lb/ac-day during the first 85 days and suggests a somewhat slower rate of

accrual (34 lb/ac-day) during the 20 day additional growth period from early to late flowering

stages (85 – 105 days).


The 85-day samples for the 6 inch row spacing gave a higher mean biomass than the 12 inch row

spacing, while there was no difference for the 105 day sampling date (Table 1). This suggests

that the narrow-row spacing may hasten canopy closure and that the crop later “fills in” the wide

spacing so that biomass and canopy closure for the two spacings are similar.

Sample #1 taken on 8-24-22.

Dry weight: 117 grams


Wet Weight with Bucket or Tarp Weight (lbs.)

Wet Weight Minus Bucket or Tarp Weight (lbs.)

















Sample # 2 taken on 9-13-22.

Dry weight____135 grams____


Wet Weight with Bucket or Tarp Weight (lbs.)

Wet Weight Minus Bucket or Tarp Weight (lbs.)

















Table 1. Aboveground dry weight biomass (lb/ac) of ‘Cherokee National Forest’ Partridge Pea at

Dayspring Farm in 2022. Means and standard error of the mean (SEM) of five replicate samples;

and means for 2-3 samples at each row spacing.

Sampling date Mean, lb/ac SEM Mean 6” spacing Mean 12” spacing

Aug 24 (85 DAP) 4,489 1,150 5,092 3,584

Sep 13 (105 DAP) 5,173 1,271 5,173 5,173


These statements are made with low confidence because of the high variability in the individual

samples (SEM is about 25% of the means). Yet, these data suggest that partridge pea may be a

valuable summer cover crop, either alone or in combination with a summer grass such as pearl

millet or foxtail millet. Benefits include:

 Sufficient canopy cover to suppress weeds.

 Sufficient residue to protect the soil surface after a non-tillage cover crop termination

(mowing, roller-crimping, or frost-kill).

 Good performance in a coastal plain sandy soil in the Ultisol order and in a rainy, warm-

temperate climate – a challenging soil-climate combination that most Southern region

farmers face.

 Generation of at least two tons per acre of legume biomass to feed soil life.

 Assuming a N content of 2.5%, the partridge pea biomass accrued at least 100 lb N/ac. If

the soil profile is low in soluble N, most of the crop N represents fixation of atmospheric

N for building soil organic matter and providing N to subsequent crops.

 A summer cover crop that can follow a short-season spring vegetable such as spinach,

lettuce, arugula, or scallions, and precede a fall crop such as cabbage or other head

brassicas, late beets or carrots, fall greens, or garlic.

Participation Summary
2 Farmers participating in research

Educational & Outreach Activities

3 Consultations
1 Curricula, factsheets or educational tools
1 On-farm demonstrations
5 Webinars / talks / presentations
2 Workshop field days
2 Other educational activities: N/A

Participation Summary:

310 Farmers participated
412 Ag professionals participated
Education/outreach description:



Number of People Reached


Field Day with VSU



VSU Urban Agriculture Class



BUGS Conference






Virginia Biological Farming Conference

55 directly, 200 indirectly


Total Reached



Learning Outcomes

29 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key changes:
  • Many of the farmers that I talked were unaware of the potential to use native plants as cover crops are were quite intrigued.

  • Farmers learn about the importance of leaving or creating habbit for benefical insect populations.

Project Outcomes

10 Farmers changed or adopted a practice
1 New working collaboration
Project outcomes:

Farmers that I have engaged in direct conversation have been surprised that plants that considered to be weeds could be of benefit to them. This new way of looking at native plants will undoubtedly lead to a reduction in herbicide use which will save farmers money. Also the use of native plants as cover crops has the potential to save farmers money.

Information Products

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