Proposal: Companion Planting (Intercropping) Corn, Beans, and Squash in Wisconsin Market Farms

While monocrops are considered the norm for small- and large-scale modern farming, intercropping, or the planting of more than one crop in a single field (also called polycropping or polyculture), has been used in the Americas and around the world since the beginning of agriculture. In this study, we will examine the effects of intercropping on the yield, performance, and input requirements of corn, beans, and squash—the “three sisters,” a polycrop system that has been planted together across the Americas for thousands of years. Up to ten market farmers and other growers will grow these plants in two ways: monocropped and intercropped for a side-by-side comparison. Other than the growing method, variables will be held constant within each location: moisture, sunlight, compost, soil, plant varieties, and mulch. Throughout the growing season and at harvest, participants will collect data on crop growth, plant health, labor inputs, plant yield, biomass production, soil nutrients, and more. This will allow us to help small-scale growers maximize their crop production, acreage, resources, and labor by providing evidence-based analysis of the benefits (reduced fertilizer input, efficient use of space, less weeding, moisture retention, etc.) and disadvantages (less familiar method, soil depletion, etc.) of intercropping.

Project Objectives

  1. Evaluate the different intercropping methods used for corn, beans, and squash to identify which is/are best adapted to northern climates.
  2. Evaluate effectiveness of each method through side-by-side field trials in ten locations.
  3. Share results through website, social media, conference presentations, and articles submitted to trade
    and hobbyist publications.


Nov. 2018–Mar. 2019
Recruit two outstanding participants from local farmers’ markets, listings of organic
farmers, and listservs.

Apr. 2019
Procure seeds, fertilizer, straw, trellises, and other equipment (project coordinator).
Prepare beds.

Begin of May 2019
Plant out plots in ten locations (see descriptions and attached diagrams for details).

May–Sep. 2019
Water, weed, and care for crops with photos and short updates recorded every two weeks submitted to project coordinator by participants.

Sep. 2019
Harvest all plots and measure yield, gather final labor data, pay participants.

Oct.–Dec. 2019
Analyze data, prepare and publish detailed report, write and submit articles, prepare and deliver

Materials and Methods

Each participant will prepare two 150 ft² plots near one another and in full sun. The project coordinator will collect soil samples and help each participant with plant out to ensure uniformity across participants. The plots will be planted as follows (see also diagram):

Corn: 60 ft², eleven 12-in mounds at 3-ft spacing, each with 2 qt mixed-in compost and five seeds, thinned to three plants.
Beans: 30 ft², eleven 12-in mounds at 1.5-ft spacing, each with 2 qt mixed-in compost, one bamboo trellis, and three seeds, thinned to two plants—planted two weeks after corn.
Squash: 60 ft², three 18-in mounds at 7-ft spacing, each with 2 qt mixed-in compost and two seeds, thinned to one plant—planted two weeks after corn.

Corn and Beans: eleven 18-in mounds at 4-ft spacing, each with 4 qt mixed-in compost and five corn seeds thinned to three plants; followed in two weeks by three bean seeds thinned to two plants.
Squash: three 18-in mounds between corn and bean mounds, each with 2 qt mixed-in compost and two seeds thinned to one plant—planted two weeks after corn.

Both plots will be watered in and mulched with two square straw bales after initial planting.

Throughout the season, participants will weed, water, and record observations (hours, tasks complete, plant performance data, photographs) using a provided forms. As the crops mature, each participant will harvest ripe vegetables and weigh them, keeping a running total of yield per plant segregated by growing method.

At season’s end, the project coordinator will return to pay participants, weigh the segregated dried biomass, and collect forms and soil samples. We will evaluate marketable yield vs. cost and labor, the land equivalent ratio (LER) of the study’s plots, andother performance statistics.


Apr.–Sep. 2018
The project, its goals, and its methods will be shared online through the Low Technology Institute’s website (, Facebook page (, Twitter account (, and Instagram profile ( Monthly updates sharing the data will be shared through these channels. Participants will be asked to share through their farm and/or personal websites and social media accounts, as they feel comfortable.

Sep.–Nov. 2018
A detailed report will be made publicly available through the above-mentioned channels. A short video and podcast episode summarizing the study and its findings will be produced and shared online. Short summary articles will be prepared for and submitted to publications such as the following:

Organic Growers’ Publications
Acres USA (
Organic Farming (
Growing for Market (
Greenhorns (

Wide-Audience Publications
Mother Earth News (

General Agricultural Publications
Modern Farmer (
Farm World (
Farm Journal (

The sample size of this study may not be robust enough for an academic article, but the data will be freely available for any researcher to use in further research. Presentations of the study and results may be made at local or regional meetings for market gardeners or other small-scale growers. In addition, a short, one-page graphical summary (similar to a social media “infographic”) of the study and its results will be shared online.

All disseminated information will be targeted at three audiences: market gardeners, small- to moderate-scale growers, and large-scale personal gardeners.

Previous Research

Because intercropping—specifically that of corn, beans, and squash—has been used for thousands of years, it occurs frequently in social science and horticulture literature. The former report on the use of intercropping in past and present indigenous societies in Asia, Africa, and the Americas; these are myriad and will not be covered here (but will carry an expanded version of this research review). Horticultural researchers have conducted intercropping experiments, largely in two categories: small-scale growing (usually in tropical environments) and polycropping in industrial agriculture.

A search of the National Sustainable Agricultural Information Service, SARE’s reports, academic article databases, and Google Scholar yielded information related to this study. Each resource was searched for keywords such as “intercropping,” “polycrop,” “polyculture,” “companion planting,” “three sisters,” “corn, beans, and squash,” and variants of these terms.

Many studies speak to the reasons for intercropping: increased nitrogen availability with legumes; greater use of space (growing horizontally and vertically), soil moisture retention, weed reduction through allelopathy and shading, diversity of plants making production of at least one more likely, and disease and pest reduction—all together these contribute to a symbiosis that creates greater yield (citations in online version).

The most similar study took place over three years in Costa Rica (Risch and Hansen 1982). They planted six configurations: corn; beans; squash; corn and squash; corn and beans; and corn, beans, and squash. They measured biomass, soil fertility, yield, and plant performance, finding that corn and beans grew well when mixed but squash growth was stunted. Corn and squash had lower yields in mixture, but beans produced equally well in mono- or polycrop. This study, however, took place in a tropical environment with corn and bean varieties not adapted to our northern climate. A recent similar study looked closely at the effects of soil nutrients, suggesting greater biomass with intercropping across a variety of soil nutrient levels due to root complementarity (Zhang et al., 2014). The methodology of these studies, as well as the summary information in Mt. Pleasant (2006), heavily influenced our project design.

SARE has supported many studies with the broad search terms listed above, which again fall into indigenous and industrial foci. A few studies worked to revive native agriculture practices but did not provide data directly relevant to polyculture itself (such as LNC08-30; LNC04-248, to encourage adoption of three-sisters system in Minnesota; and FNC13-919, to encourage traditional foodways as part of a wider food-security effort). Many other studies focused on polycultures and related topics in industrial contexts only tangentially related to this study (e.g., GNC06-064, FNC13-907, GW11-005, LNE10-295, OS16-093, and GW08-016). The most similar SARE-supported study (FNE02-434) grew three sisters polycrop in Vermont, focusing on indigenous practices as well as soil nutrition additions and their effects with mixed results; this grower had no “control” beds, as in our study, but we are taking the grower’s advice to mulch the beds with straw.

Mt. Pleasant, Jane. 2006. “The Science behind the Three Sisters Mound System.” In Histories of Maize: Multidisciplinary Approaches to the Prehistory, Linguistic, Biogeography, Domestication, and Evolution of Maize, edited by John E. Staller, Robert H. Tykot, and Bruce F. Benz, 529–37. Walnut Creek, CA: Left Coast Press.

Risch, Stephen J. and Michael K. Hansen. 1982. “Plant Growth, Flowering Phenologies, and Yields of Corn, Beans and Squash Grown in Pure Stands and Mixtures in Costa Rica.” Journal of Applied Ecology 19, no. 3 (December): 901–16.

Zhang, Chaochun, Johannes A. Postma, Larry M. York, and Jonathan P. Lynch. 2014. “Root foraging elicits niche complementarity-dependent yield advantage in the ancient ‘three sisters’ (maize/bean/squash) polyculture.” Annals of Botany 114, no. 8 (October): 1719–33.

Benefits and Impacts

This study will evaluate the effectiveness of intercropping corn, beans, and squash in small-scale operations by measuring labor, soil nutrients, plant performance, and yield. Accordingly, it will result in “improved income or profitability” by giving market gardeners the information needed to maximize the yield return on labor and/or assets. Similarly the study will “improve crop production and/or production efficiency” by identifying whether monocropping or polycropping produces the highest yield with the lowest labor in a northern climate.

Labor will be measured in hours worked per plot throughout the growing season. To encourage careful documentation, participants will be paid according to hours recorded. Each fortnight, participants will note basic information on a form: time worked per plot, type of work performed (weeding, watering, harvesting, etc.), plant performance (height of corn, health of foliage, presence of pests), and pictures. Weather data will be drawn from nearby weather stations.

Soil nutrients will be measured at the begin and end of the study at each test location. Samples will be collected and combined from six locations in each monocrop and polycrop plot, producing one “before” and one “after” sample per plot. These samples will be sent to the University of Wisconsin Soil and Forage Lab for testing. Soil texture and morphology will be recorded on site at the time of planting.

Plant performance will be measured qualitatively and quantitatively. Participants will report the size and vigor of plant growth as well as pests or deficiencies throughout the season. They will note when tassels and flowers first appear and the first ripe produce is available from each type of plant per plot. At the end of the season, total biomass (dry weight) per plant type per plot will be measured.

Total yield from each type of plant per plot will be measured by weighing.

Contribution to Sustainable Agriculture

Any study that seeks to maximize the yield of a plant when compared to its inputs has implications for questions of sustainability. The most efficient method for producing a higher yield uses less resources and reduces the agricultural footprint on the environment. These methods of growing corn, beans, and squash all involve mulching and amending the local soil, creating a better growing environment and increasing soil health. And of course, any method that can reduce the labor of growing a crop will make farmers’ lives easier and bottom lines more healthy.

By comparing these different growing methods, farmers in the north-central region (and beyond) will have baseline data about a polycropping group of popular market vegetables. If, for example, the intercropped corn, beans, and squash return comparable yields to monocropped equivalents but less weeding and water are needed, market farmers can try this method without risking a year’s crop to experimentation.

Additionally, by recording and publishing our methods and results, others can attempt to replicate the experiment or build off of it in a larger study. Finally, this study will add to a body of data for polycropping, which is largely focused in tropical and southern climates.


Personnel – $7,600

Study Participants: $20/hr × 25 hr/participant × 10 participants = $5,000

The ten participants will carry out the day-to-day monitoring and work associated with the study. In addition to assisting with the planting of the two plots on each of their properties, the participants will be responsible for weeding, watering, and maintaining the plants, which may include monitoring for pests and disease. Every two weeks the participants will take a photo of each plot and make a few notes about their observations as well as log their time, which they will share with the project coordinator. Participants will weigh any yields collected through the growing season.
At the end of the season, the participants will help with the final harvest and measuring of biomass.

Study Organizer: $20/hr × ((5 hr/location × 10 locations) + 80 hr organizing and analyzing) = $2,600

The organizer will spend lead-up time recruiting farmers to participate in the study. This will primarily be done through face-to-face solicitation at farmers’ markets and through contacting farmers by email and Fair Share (a local growers organization). Just before the planting starts, the coordinator will gather the materials: seeds, compost, mulch, poles and then transport the materials to each participant’s farm.

The organizer will assist each participant with their planting to insure that each plot is created in a uniform way. Throughout the study period, the organizer will be in contact with participants through email and will compile the notes and photos into a small database. As the season ends, the organizer will again visit each participant to assist with the harvest and weighing of the biomass, as well as getting the final labor totals and paying the participants.

After all data have been gathered, the organizer will perform basic statistical analyses to determine various measures such as overall yield, yield versus cost, and yield versus labor, as well as create a narrative description of the results. All of this information and a description of the study will be prepared for trade publication and general audiences. The organizer will submit these articles (as discussed elsewhere) as well as provide all data online with open access.

Materials and Supplies – $610

Purple Cow Activated Organic Compost: (2 bags/plot × 20 plots × $10/bag) = $400

This is the quoted price for the recommended application rate, as determined in a recent discussion with a Purple Cow sales representative. By using one type of compost, it reduces the variability of using participant-generated compost across ten different grow operations. The compost will be top dressed and dug in at planting.

Straw: 2 small bales/plot × 20 plots × $4/bale = $160

The straw will be procured from sources suggested by participants and/or a local source known to the project organizer. It will be used to mulch the crops at planting.

Seeds: 1000 corn seeds at $25 + 700 bean seeds at $15 + 100 squash seeds at $10 = $50

We will be growing one variety each of corn, beans, and squash. The types will be determined by a vote among participants. The corn may likely be a dry variety (e.g., popcorn or milling corn). The beans will likely be a dry pole variety. The squash will be a winter variety. The seeds will be bought from a certified organic provider.
{We will discuss this, and if we have a strong preference for sweet corn and green beans, we can do that, but your labor will go up, as you have to harvest them over a longer period and weigh them at each harvest.}

Travel – $981

Mileage: 10 sites × 2 visits each × estimated 90 mi/visit × 54.5¢/mi = $981

This represents two trips to each of the ten participants for the project organizer to help plant out at the begin of the season and measure yields and biomass at the end. This estimate is based on a similar study completed in 2018.

Other Direct Costs – $443

University of Wisconsin Soil and Forage Lab: 20 soil samples × $23/sample × 10 percent discount + $20 shipping: $434

To compare soil nutrient levels before and after the growing season, samples will be collected and submitted to the lab for analysis. The monocrop plots will be sampled at 4 in (10 cm) below surface at six locations (two samples in each of the three plant’s growing area); the sample will be mixed. The polycrop plot will also be sampled in six locations and mixed. Samples will be collected before planting and after the last harvest.

Printing Costs: 15 pages printed/participant × 10 participants × 6¢/page = $9

Participants will receive forms to fill out for every other week to record growth, labor, and other observations.

Equipment (covered at 50 percent) – $55

Bean Poles: 11 poles per participant × 10 participants × $1/pole × 50 percent= $55

The monocrop pole beans will need a corn-like trellis to grow up. This will keep variability out of the study: if we used a different trellis system the beans might produce more or less due to their growing configuration, thus a corn-like pole of bamboo will be used.

Total Budget: $9,689

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