Investigating the Impact of Plant Spacing on Yields of Sweet Potato Produced in Organic Systems

Project Overview

Project Type: Graduate Student
Funds awarded in 2017: $16,443.00
Projected End Date: 08/31/2019
Grant Recipient: Tennessee State University
Region: Southern
State: Tennessee
Graduate Student:
Major Professor:
Dilip Nandwani
Tennessee State University


  • Vegetables: sweet potatoes


  • Crop Production: varieties and cultivars
  • Education and Training: extension
  • Pest Management: mulches - general
  • Production Systems: organic agriculture
  • Soil Management: composting

    Proposal abstract:

    Currently, sweetpotato production is perceived to be on the decline in Tennessee. Although sweetpotato is grown in warm climatic areas, not much research has been done on the effect of plant spacing on the yield performance. Growers desire more information on sweetpotato yields in organic cropping systems and likewise its market value to determine its profitability. Employing organic farming techniques would be profitable to the environment, farmers, consumers and communities as it is safe, ecofriendly, increases soil fertility, minimizes pesticide use and is sustainable. Two variety trials will be carried out in summer of 2017-2018 on the certified organic research farm at Tennessee State University, Nashville, Tennessee. The effects of 8”, 14” and 18” row plant spacing on the yield performance of cv. Beauregard, Centennial and Covington will be measured and compared. A randomized complete block design with two treatments and three replications will be implemented using 36” wide beds with 48” spacing between rows. Growing practices and materials will be strictly adhered to as per the national organic standard board (NOSB) regulations throughout the growing season. Data will be collected on the root number, sizes and yields of sweetpotato in each treatment. Results from this study will provide more insight into the responses of field-grown sweetpotato to difference in plant spacing. Findings will be shared with farmers, researchers and stakeholders during small farm expo, field day and presented in American Society for Horticultural Science conference.

    Project objectives from proposal:

    1. Access the effect of three plant spacing patterns (8”, 14” and 18” in-row) on yield, number and sizes of three sweetpotato varieties grown in an organic management system. The outcome will provide information to growers and stakeholders alike on the effect of plant density population using various spacing on yield and size of sweetpotato grown organically and the better performing varieties among the selected commercial varieties for the project. The result of this study would contribute to existing knowledge of sweetpotato organic growers on best cultivation practices to maximize profit and achieve better returns on their investment.

    2. To disseminate information of project findings with researchers, Tennessee's small and minority growers through TSU's Cooperative Extension Agents, Small Farm Expo, field demonstrations, fact sheets, and social media videos. The number of growers/producers that gain knowledge about science-based tools through outreach and education programs will be monitored and surveyed. We expect 400 small farm attendees at the annual farm Expo event held at Tennessee State University in the summer and at least 100 individuals will gain knowledge as a result of this project. Additional events include regular farm visits and field days.

    According to National Organic Standards Board (NOSB, 2015), the 2015 crops subcommittee research priorities 'include the exploration of crop rotations, sanitation practices, plant spacing and other factors that influence disease as well as exploration of organic whole farm systems to meet the need for diverse ecological systems, food safety and sustainable organic farming systems”. Organic sweetpotato growers also frequently ask on extension outreach what the most ideal plant spacing is to achieve excellent yields and greater return investments. Therefore, research exploring plant spacing as a factor that influences organic whole farm systems is needed.

    Sustainability trends have motivated a new interest in producing healthy organic crops as decreasing availability of pesticide-free, quality vegetables becomes one of the great concerns in today's agricultural production environment. Information on production recommendations for the organic sweetpotato market is scarce. An organic survey report by the United States Department of Agriculture representatives, Tom and Joseph (2014) outlined the current acreage for organic sweetpotato production in Tennessee to be 8 acres with a total number of 7 farms. Therefore certified organic sweetpotato production in Tennessee, may be well below current demand.

    The results of trials would provide insight to the most ideal plant spacing for more profitable marketable yields, root number and morphology (length, weight and diameter) for organic growers. The study would also assist in evaluating the adaptability of the varieties to climatic conditions of Tennessee area of south-eastern United States and other locations across the United States with similar warm long growing seasons. The information would also be beneficial to sweetpotato growers transitioning into organic production.

    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.