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


    The goal of this research project was to investigate the impact of plant spacing on yield performance of sweetpotato varieties in an organic management system in Tennessee and to share our findings with farmers, researchers and stakeholders. The sweetpotato crop is increasing in popularity. Partly due to its nutritional value, wide range of flesh-color types being introduced from all over the world, low cost of production, ability to grow well on marginal lands with little amounts of water and its sweet taste. The sweetpotato fresh markets and processing industries are enlarging as a result of the development of new and improved value-added products. Sweetpotato production in Tennessee, however, is believed to have declined since 1980 and currently certified organic sweetpotato production is below consumer demand. A preliminary trial was conducted in the fall of 2017 on the certified organic research farm at Tennessee State University, Nashville, Tennessee. The effect of 12” in row plant to plant spacing on the yield performance of cv. Beauregard, Centennial and Covington was measured. A randomized block design was implemented using 36” wide beds with 72” spacing between rows and cultivars. Cultivars were grown with strict adherence to the rules of the national organic standards board (NOSB). Data was collected on the sizes and yields of sweetpotato. Marketable yields were highest in the Covington followed by the Beauregard and Centennial varieties respectively. Of the three varieties, Covington also had the highest U.S. no 1 and least number of U.S. no 2, Meanwhile jumbo-sized roots were observed only in Beauregard cultivar. In the summer of 2018 the effects of 8”, 12”, 14”, 18” and 24” row plant spacing on the yield performance of cv. Beauregard, Evangeline and Covington was measured and compared. An increase in sweetpotato yields was observed with increased plant spacing. The effect of plant spacing on yields was highly significant (p<0.001). The highest marketable yield overall was observed in the Beauregard (35, 719 lbs/acre) cultivar with a 24” plant spacing. The findings from this study contribute to and help fill in existing knowledge gaps on how yield production of various sweetpotato cultivars in sustainable farming systems are affected by differences in plant spacing. Information gathered was shared with farmers, researchers and stakeholders during small farm expo, field day and conference presentation.

    Project objectives:

    1. Determine the impact of the plant spacing pattern on yield and sizes of three sweetpotato varieties grown in an organic management system.
    2. Access the effect of five plant spacing patterns (5”, 8”, 12”, 18” and 24” in-row) on yield and sizes of three sweetpotato varieties grown in an organic management system.
    3. 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.
    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.