Interaction of common purslane (Portulaca oleracea) and Palmer amaranth (Amaranthus palmeri) with sweet potato (Ipomoea batatas) genotypes

Abstract

Greenhouse replacement series studies were conducted to determine the relative competitiveness of NC10-275 (unreleased, drought tolerant; upright, bushy, and vining growth with large leaves) and Covington (the most commonly grown genotype in North Carolina; vining growth with smaller leaves) sweet potato genotypes with weeds. Sweet potato genotypes were grown with Palmer amaranth (tall growing) or common purslane (low growing) at five planting (sweet potato to weed) proportions of 100:0, 75:25, 50:50, 25:75, and 0:100 at a density of four plants per pot. Reduction in common purslane shoot dry biomass was greater when growing with NC10-275 than when growing with Covington or alone. When growing with common purslane, shoot dry and root fresh biomass of Covington was 18% and 26% lower, respectively, than NC10-275. Relative yield (shoot dry biomass) and aggressivity index (AI) of common purslane was lower than both sweet potato genotypes. Palmer amaranth shoot dry biomass was similar when growing alone or with Covington, whereas it was reduced by 10% when growing with NC10-275 than alone. Palmer amaranth competition reduced shoot dry biomass and root fresh biomass of Covington by 23% and 42%, respectively, relative to NC10-275. Relative yield and AI of Palmer amaranth was greater than Covington but lower than NC10-275. This research indicates that sweet potato genotypes differ in their ability to compete with weeds. Both sweet potato genotypes were more competitive than common purslane, and the following species hierarchy exists: NC10-275 > Covington > common purslane. In contrast, NC10-275 was more competitive than Covington with Palmer amaranth, and the following species hierarchy exists: NC10-275 ≥ Palmer amaranth > Covington.