<b>A multifaceted approach to weed management in organic sweetpotato systems</b>
Creators: name: Cooper, Emmanuel Gonfatee
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 300804
subject: Horticultural crop protection (incl. pests, diseases and weeds)
classificationCode: 300801
subject: Field organic and low chemical input horticulture

description: Sweetpotato (<i>Ipomoea batatas</i> L.) is a staple crop that provides nutritional benefits to humans globally, but it is subjected to yield loss when competing with weeds, especially during the early stage of establishment. Despite increased organic sweetpotato production in the United States, growers face challenges with limited weed management options and often resort to time-consuming and costly cultivation and hand-weeding. To address this challenge, experiments were developed to determine (1) the effect of sweetpotato cultivar on the critical weed-free period, (2) the effects of in-row plant spacing and cultivar selection on weed suppression and sweetpotato yield, and (3) the impact of buckwheat and silage tarps for row-middle weed control. 1) In 2022, field research was conducted at the Samuel G. Meigs Horticulture Research Farm (Meigs), Lafayette, IN, and at the Southwest Purdue Agricultural Center (SWPAC), Vincennes, IN to estimate the critical weed-free period for ‘Covington’, ‘Murasaki’, and ‘Monaco’ in the Midwest. The experiment was a split-plot design, with weed-free interval treatments as the main plot factor and cultivar as the subplot factor. Weeds were removed by hand and allowed to establish and compete with the crop beginning at 0, 14, 21, 28, 35, or 42 days after transplanting (DAP). As weed-free interval increased from 0 to 42 DAP, predicted total yield increased from 19 kg ha<sup>-1</sup> to 20,540 kg ha<sup>-1 </sup>for Covington, 3 kg ha<sup>-1</sup> to 11,407 kg ha<sup>-1</sup> for Monaco, and 125 kg ha<sup>-1 </sup>to 13,460 kg ha<sup>-1 </sup>for Murasaki at the Lafayette location. A threshold of ≤10% total yield reduction was achieved by maintaining sweetpotatoes weed-free 24 DAP for Covington, 20 DAP for Murasaki, and 33 DAP for Monaco. 2) In 2022 and 2023, studies were conducted at Meigs, Lafayette, IN and SWPAC, Vincennes, IN to evaluate in-row plant spacing and cultivars for weed control and sweetpotato yield. The experiment was a split-split plot design, with in-row spacings of 20, 30, and 40 cm as the main plot factor, weeding frequency (‘critical weed-free period’ and ‘weed free’) as the subplot factor, and sweetpotato cultivar (‘Covington’ and ‘Monaco’) as the sub-subplot factor. However, in 2022, we evaluated only in-row spacing and weeding frequency because of poor establishment of Monaco. In-row spacing had no significant effect on weed densities at 4, 5, and 6 WAP. As in-row spacing increased from 20 to 40 cm, total sweetpotato yield pooled across both locations in 2023 decreased from 30,223 to 21,209 kg ha<sup>-1</sup> for Covington and 24,370 to 20,848 kg ha<sup>-1</sup> for Monaco, however, jumbo yield increased for both cultivars. Findings from this study suggest that an in-row spacing of 20 cm may provide greater yield than the standard spacing, 30 cm, for both Monaco and Covington cultivars and could reduce weed interference through more rapid sweetpotato canopy closure. 3) The experiment was a randomized complete block design, with three row-middle treatments [tarp, buckwheat, and cultivation] and four replicates. Row-middle treatments were established immediately after transplanting ‘Covington’ slips 30 cm apart into raised bed plots consisting of a single row 6 m long and 2 m apart on-center. Buckwheat was planted three weeks after transplanting (WAP) at a rate of 108 kg ha<sup>-1</sup> in row-middle. Row-middles for the tarp treatment were covered for the entire growing season. Weed density at 6 WAP was 184 plants m<sup>-2</sup> for the buckwheat, and 162 plants m<sup>-2</sup> for the cultivation treatments. Total yield was 11,050 kg ha<sup>-1</sup> for the buckwheat, 19,790 kg ha<sup>-1</sup> for the cultivation, and 17,810 kg ha<sup>-1</sup> for the tarping treatments. Tarping effectively suppressed weeds and produced sweetpotato yields comparable to cultivation indicating potential for organic growers. Buckwheat yields were lower than those from tarping and cultivation.