Research Project No. 2 — Comparing Potato-Growing Methods

The institute is partnering with a group of independent market farmers to test potato-growing methods. We will be sharing the progress and results of this study on our digital platforms and providing logistical support to this citizen-science effort. Funding for the project has been provided by the USDA’s Sustainable Agriculture Research & Education organization.

Abstract

PototoFlowerPotatoes are one of the most productive plants per area. They grow in poor soils and provide complete nutrition. Ancient and modern growers have devised strategies to maximize yield and simplify the growing process. Unfortunately these methods have not been subject to comparative study to separate the serious from the gimmicky.

This study will evaluate the relative performance of five nonmechanized, potato-growing methods: trenching (control), newspaper mulch, potato tower, container bag, and straw mulch. Each of the ten participants will cultivate potatoes holding all other variables equal: fertilizer, mulch, water, sun, plot size, and type and amount of seed potatoes. Data, segregated by method and collected throughout the season, will include local soil conditions, location-specific weather, labor, materials costs, weeding, and yield.

The outcomes of this study will support sustainable agricultural practices for market-scale growers. By identifying high-yielding methods, we reduce the amount of inputs (water, fertilizer, labor, materials) needed to grow a larger crop each year and increase profits over less-productive methods. By tracking the labor needed as well as yield, we can reduce the sometimes back-breaking labor of harvesting and cleaning potatoes. Finally, this information will be of interest to anybody who grows potatoes, not just market gardeners.

PotatoDiagram

Objectives

  1. Identify five different garden potato-growing methods and recruit ten study participants.
  2. Evaluate effectiveness of each method through side-by-side field trials in ten different locations.
  3. Share results through website, social media, and articles submitted to trade publications.

Previous Studies

Most research on potatoes is focused on pest and disease prevention, maximizing yield versus resource use, and breeding, all in industrial contexts. Nevertheless, a search of the National Sustainable Agricultural Information Service, the American Journal of Potato Research, and the academic articles available on the University of Wisconsin–Madison and Washington University in St. Louis library databases, as well as industry publications (Spudman, Potato Country, and Potato Review) and Google Scholar did yield information related to this study. Each resource was searched for keywords such as “small-scale potato,” “container potato,” “garden potato,” “potato mulch,” “potato tires,” “potato growing methods,” “potato tower,” and “potato comparison.” It should be stressed, however, that the study proposed in this application has no direct antecedent in the academic or industry literature as far as could be found in this review.

Although for industrial applications, a few studies did have information that can be applicable to our research design. In a side-by-side mulch comparison, straw mulch has been noted to increase potato size and yield as compared to manual weeding (Genger et al. 2017). Another study showed that in a side-by-side comparison of drip irrigation, above-ground drip irrigation was more beneficial in terms of water use and cost than below-ground drip irrigation (Ondera et al. 2005). Presprouted tubers were shown to give higher yields than nonsprouted tubers when the growing season was short but the same treatment resulted in a smaller yield with a longer growing season in another small study (Hagman 2012). A comparison between conventional and organic growing methods indicated that organic methods produced a lower yield but higher quality tuber in a Polish study (Flis et al. 2012). Another comparative study examined the effects of three irrigation amounts on industrial potato yields, suggesting that lower irrigation rates may be possible in some contexts (Erdem et al. 2006).

SARE has previously supported fifty-eight studies with “potato” in the title. A few of these projects did have side-by-side comparisons of various potato-growing variables, but these compared a single variable (e.g., management practice, insecticide, cover crop) to a control and none of them discussed the small-scale market-gardener-friendly growing methods tested in this proposal. The closest studies compared three no-till methods to one another (FNE10-687), the effects of paper-mill-waste mulch on potatoes (FNE96-127), and fertilization methods (FNE14-792).

I should note that Mother Earth News did have the most extensive information about the five different growing methods but had no side-by-side comparisons. A Google search returned many articles describing various growing methods but similarly no side-by-side comparisons could be found. Solicitations of potato-grower forums and the Kenosha Potato Project staff for any known studies of this type returned no positive responses.

References Cited:

Erdem, Tolga, Yesim Erdem, Halim Orta, and Hakan Okursoy. 2006. “Water-yield relationships of potato under different irrigation methods and regimens.” Scientia Agricola 63(3): 226–31. http://dx.doi.org/10.1590/S0103-90162006000300003

Flis, Bogdan, Ewa Zimnoch-Guzowska, and Dariusz Mankowski. 2012. “Correlations among Yield, Taste, Tuber Characteristics and Mineral Contents of Potato Cultivars Grown at Different Growing Conditions.” Journal of Agriculture Science 4(7): 197–207. http://dx.doi.org/10.5539/jas.v4n7p197

Genger, Ruth K., Douglas I. Rouse, and Amy O. Charkowski. 2017. “Straw mulch increases potato yield and suppresses weeds in an organic production system.” Biological Agriculture & Horticulture 1–17. https://doi.org/10.1080/01448765.2017.1371077

Hagman, Jannie. 2012. “Different pre-sprouting methods for early tuber harvest in potato (Solanum tuberosum L.).” Acta Agriculturae Scandinavica 62: 125–31. http://www.tandfonline.com/doi/abs/10.1080/09064710.2011.583935

Ondera, Sermet, Mehmet Emin Caliskanb, Derya Ondera, Sevgi Caliskanb. 2005. “Different irrigation methods and water stress effects on potato yield and yield components.” Agricultural Water Management 73(1): 73–86. https://doi.org/10.1016/j.agwat.2004.09.023

Environmental, Economic, and/or Social Benefits

This study will evaluate the effectiveness of five potato-growing methods by measuring labor, cost of inputs, 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 the highest yielding among the tested methods for improving crop production efficiency.

Labor will be measured in hours worked per method throughout the growing season. To encourage careful documentation, participants will be paid according to hours recorded. Input costs will be simply computed by the cost of materials: compost, seed potatoes, mulch, and containers (if any). As all variables are kept consistent except growing method, the difference in yield (as measured by seed weight versus produced weight) can be computed as compared to the control plots. In addition, photos and impressions of the participants will be recorded every two weeks and may lead to further, unexpected insights.

Contributions 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 potatoes 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 and/or expenses 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 how much return on investment they may get for each growing method. If, for example, the most expensive growing method (“potato towers”) is the most productive method, but the cheapest (“trench and hill”) or least labor intensive (“straw mulch”) growing methods are only marginally less productive, a farmer can choose to save the money and still be confident in his or her choice. Additionally, by recording and publishing our methods and results, others can attempt to replicate the experiment or build off of it in a larger-scale study.

Timeline

Nov. 2017–Mar. 2018 – Recruit 4 outstanding participants from local farmers’ markets

Apr. 2018 – Procure seed potatoes, fertilizer, straw, bags, newspaper, and tower segments

May 2018 – Install plots in ten locations. Each location will receive five, 8-×-8-ft plots: “control” (potatoes planted in a composted trench, hilled and mulched with straw after emergence), “straw mulch” (potatoes planted on composted ground, covered in straw mulch), “newspaper mulch” (same as “straw mulch” with two layers of newspaper below the straw to suppress weeds), “container” (potatoes grown in 55-lb woven grain bags with mixture of soil, compost, and straw, with more added as plant emerges), and “tower” (potatoes grown in a 2-×-2-ft wooden set of frames that stack and are filled with soil, compost, and straw as the plant grows). See attached diagram for details.

May–Sep. 2018 – Water, weed, and care for crops with photos and short updates recored every two weeks

Sep. 2018 – Harvest all plots and measure yield, gather final labor data, pay participants

Oct.–Dec. 2018 – Analyze data, prepare and publish detailed report, write and submit articles

Dissemination of Results

Apr.–Sep. 2018 – The project, its goals, and its methods will be shared online through the Low Technology Institute’s website (https://lowtechinstitute.org/), Facebook page (https://www.facebook.com/lowtechinstitute/), Twitter account (https://twitter.com/Low_Techno), and Instagram profile (https://www.instagram.com/lowtechinstitute/). 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 (https://www.acresusa.com/)
Organic Farming (https://www.soilassociation.org/)
Growing for Market (https://www.growingformarket.com/)
Greenhorns (http://www.thegreenhorns.net/)

Wide-Audience Publications
Mother Earth News (https://www.motherearthnews.com/)
Organic Life (https://www.rodalesorganiclife.com/)

General Agricultural Publications
Modern Farmer (https://modernfarmer.com/)
Farm World (http://www.farmworldonline.com/)
Farm Journal (https://www.agweb.com/farmjournal/)

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 “meme”) 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 potato growers, and large-scale personal gardeners.

Budget Explanation

Personnel
Study Participants: $20/hr × 5 hr/plot × 5 plots/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 five plots on each of their properties, the participants will be responsible for weeding, watering, and maintaining the plants, which may include monitoring for Colorado Potato Beetle. 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.

Each of the plots requires different maintenance. The control plot requires initial trenching, composting, and planting. Once the plants have emerged they must be hilled and mulched with straw. The straw mulch plot requires composting and planting the tubers before being covered with straw mulch. The newspaper mulch plot is similar but also requires the layering of newspaper on the spaces between the rows before the application of straw. The container bags must be filled with a mix of topsoil, compost, and straw. As the plants grow, more of this mix must be made and added to the bags. The towers are similar to the containers, but on a larger scale: as the plants grow, new tower levels are added and filled with the topsoil-compost-straw mixture.

At the end of the season, the participants will help with the harvest and measuring of yield.

Study Organizer: $20/hr × ((1 hr/plot × 50 plots) + 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 found in online listings of market participants. Just before the planting starts, the coordinator will gather the materials: seed potatoes, mulch, bags, containers, and compost 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 potatoes, 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
Purple Cow Activated Organic Compost: (3 bags/plot × 50 plots × $7.86/bag) + $150 delivery = $1,329
This is the negotiated 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.

Straw: 2 small bales/plot × 50 plots × $3/bale = $300
The straw will be procured from sources suggested by participants and/or a local source known to the project organizer.

Seed Potatoes: 21 seed potatoes/plot × 50 plots ÷ ca. 500 potatoes/bag ×$129/bag = $258
We will be growing Kennebec potatoes as this is the potato with which most participants have experience and prefer to grow (based on responses from participants). This variety has the added benefit of being a commonly grown potato and therefore the study can be easily replicated. We will use certified seed potatoes from a common source (Paradigm Gardens in Madison is the likely source and provided the above price quote) to reduce variability among plots and participants.

Travel
Mileage: 10 sites × 2 visits each × estimated 30 mi/visit × 53.5¢/mi = $321
This represents two trips to each of the ten participants for the project organizer to help plant and harvest the potatoes.

Other Direct Costs (covered at 50 percent)
Grain Bags: 20 bags/bed × 10 plots × $0 (free from local breweries) × 50 percent = $0
Grain bags of woven polypropylene fabric will be used for the containers used to grow potatoes. This bag type will allow extra water to weep from the container instead of remaining soggy. The organizer recently obtained 500 of these bags for free from the Wisconsin Brewing Company and has secured a promise of 200 more bags to be donated for free to the project.

Newspaper: 2 lb/bed × 10 plots × $0 (free from local source) × 50 percent = $0
Twenty pounds of newspaper (plain newsprint, not magazine glossy) will be gathered to mulch under straw for one of the beds. This will either come from a local newspaper or the project organizer’s own newspaper pile.

Tower Frames: 5 frames/bed × 5 beds × 10 plots × $16 materials & labor × 50 percent = $2,000
The tower frames will be made of untreated pine wood screwed to interlocking corner posts.

Total Budget: $11,808


13 thoughts on “Research Project No. 2 — Comparing Potato-Growing Methods

  1. I am looking forward to your findings as I am about to plant my potatoes out this morning on perhaps our last frosty morning here in South Australia

    Like

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