The Impact of Weeding Regime, Planting Density, and Growth Habits on Watermelon Yield in an Organic System

Abstract

<jats:p>The southeastern United States produces 50% of U.S. conventional watermelon (<jats:italic>Citrullus lanatus</jats:italic>) but only 7% of U.S. organic watermelon. Weeds are a major threat to watermelon yield in the southeastern United States, and organic weed control is estimated to cost 20-times more than conventional herbicide programs. The objectives of this study were to determine the optimal weed control regime to reduce hand-weeding costs while maintaining yield and to compare the weed suppression of two watermelon types with differing growth habits in an organic system. In 2014 and 2015, watermelon plots were randomly assigned to the following treatments in a factorial arrangement: vine or compact growth habit; 1.0- or 0.5-m in-row spacing; and weekly weed control (kept weed-free by hoeing and hand-pulling weeds) for 0, 4, or 8 weeks after transplanting (WAT). At the time of the watermelon harvest, not weeding resulted in average total weed densities of 86.6 and 87.0 weeds/m<jats:sup>2</jats:sup>, and weeding for 4 WAT resulted in average total weed densities of 26.4 and 7.0 weeds/m<jats:sup>2</jats:sup> in 2014 and 2015, respectively. Nonetheless, weeding for 4 WAT resulted in watermelon yields and fruit counts comparable to those of weeding for 8 WAT during both years. This partial-season weeding regime resulted in 67% and 63% weeding cost reductions for vine and compact plants, respectively, in 2014, and a 43% reduction for both growth habit types in 2015. In 2015, a separate experiment that evaluated weeding regimes that lasted 0, 1, 2, 3, 4, and 8 WAT found that yields resulting from weeding for 3 WAT were greater than those resulting from weeding for 2 WAT. However, the yields did not differ when weeding was performed for 4 WAT and 8 WAT.</jats:p>

Impact of the Different Vegetation Spaces on the Yield Components of Seedless Watermelon

“…Plant density is a factor determining the degree of competition between plants ( López-Elías et al, 2011, Stone et al, 2019. Watermelon yield, fruit weight, and number can be adjusted by inrow spacing (Motsenbocker & Arancibia, 2002;Ramos et al, 2009;López-Elías et al, 2011;Sabo et al, 2013;Oga & Umekwe, 2016;De Paula et al, 2020).…”

“…Watermelon yield, fruit weight, and number can be adjusted by inrow spacing (Motsenbocker & Arancibia, 2002;Ramos et al, 2009;López-Elías et al, 2011;Sabo et al, 2013;Oga & Umekwe, 2016;De Paula et al, 2020). If a grower bases the decision on inrow spacing only on maximizing yield, then narrower spacing appears to be optimal (Roberts & Duthie, 1995;Motsenbocker & Arancibia, 2002;Ramos et al, 2009;Campagnol et al, 2012;Stone et al, 2019). Different spacing did not affect the fruit quality (Ramos et al, 2009) although it was found that lower plant spacing provided higher total soluble sugars to the fruits (De Paula et al, 2020).…”