Fitotoxic effects of trifluralin to hybrid maize (zea mays l) and their persistance

The objective of the study was to analyze the susceptibility of three different types of hybrid maize to carryover potential of trifluralin using the bioassay, and persistence of trifluralin. Herbicide toxicity was analyzed by determining the inhibition of root and shoot length and fresh weight. In addition, using the bioassay trifluralin persistence in the leached chernozen soil type was studied applying two doses. Herbicide degradation was monitored over a period of one year following application during the two trial years. The hybrids tested showed a significant susceptibility to herbicide tested. The doses analyzed inhibited root length and fresh weight. Regression analysis was used to determine I50 values for the parameters tested thus proving fresh root weight reduction to be the most susceptible and accurately computed parameter. Hybrid ZPSC 633 was the most susceptible (with regard to the parameters tested). Higher herbicide doses provoked slower degradation of trifluralin, as confirmed by calculated DT-50 values. Trifluralin residues (applied at the rate of 960 g a.i.7ha) provoked no damage to ground parts. Root length and fresh weight inhibition was about 10% in the case of the most susceptible hybrid. However trifluralin (applied at the rate of 1920 g a.i./ha) residues one year following application provoked damage to ground parts (up to 20% in the case of the most susceptible hybrid), whereas root length and fresh weight inhibition was approx. 30%.