Effect of pre-emergent herbicides applied by drip irrigation in the transplanted onion crop

Abstract

Herbigation has several advantages, such as the reduction of drift, the operator’s exposure to the product, and the reduction of costs associated with weed management. This work was carried out in the Department of Caaguazú, Paraguay, during the period from March to October 2018, to evaluate the efficacy of different doses of pre-emergent herbicides applied via irrigation water in the transplanted onion crop. The experimental design used was the randomized complete blocks with arrangement in divided plots (5>5), where the main plot consisted of the herbicides (Flumioxazin, Oxyfluorfen, Pendimethalin, Trifluralin and S-metolachlor) and the subplots of the doses of Flumioxazin (0, 15, 25, 35 and 45 g a.i. ha-1), Oxyfluorfen (0, 240, 312, 384 and 456 g a.i. ha-1); Pendimethalin (0, 800, 1,000, 1,200 and 1,400 g a.i. ha-1); Trifluralin (0, 576, 768, 960 and 1,152 g a.i. ha-1) and S-metolachlor (0, 480, 960, 1,440 and 1,920 g a.i.ha-1) with four repetitions. The weeds with the highest relative importance were: Digitaria horizontalis, Richardia brasiliensis, Galinsoga parviflora, Bidens pilosa, Amaranthus spinosus and Portulaca oleracea. Herbicides in the studied doses applied through irrigation water were effective on sensitive species and did not cause symptoms of phytotoxicity on onion crops until 21 DAA. The evaluated doses of Oxyfluorfen, Pendimethalin, Trifluralin and S-metolachlor did not affect the bulb yield in the transplanted onion crop.