Season-Long Interference of Yellow Nutsedge (Cyperus esculentus) with Direct-Seeded and Transplanted Watermelon (Citrullus lanatus)

Field studies were conducted in the spring of 1997 and 1998 to quantify the effect of season-long yellow nutsedge interference on watermelon yield. The competitive ability of watermelon with yellow nutsedge was compared in two establishment methods (watermelon transplanted and direct seeded). Critical yellow nutsedge densities and the biological threshold (BT) were used to characterize the competitive ability of watermelon. The critical density in both direct-seeded and transplanted watermelons was 2 yellow nutsedge$\text{plants}/{\rm m}^{2}$. The BT of yellow nutsedge in seeded watermelons was 37 yellow nutsedge$\text{plants}/{\rm m}^{2}$, whereas the BT in transplanted watermelons was 25$\text{plants}/{\rm m}^{2}$. Transplanting watermelons did not improve their competitive ability with yellow nutsedge. Percent yield loss was similar for both establishment methods at the respective yellow nutsedge densities. Over 40% yield loss was incurred with 12 yellow nutsedge$\text{plants}/{\rm m}^{2}$for both establishment methods. Furthermore, it was concluded that watermelons are poor competitors with yellow nutsedge.