Herbicide selectivity to corn (Zea mays L.) hybrids

Four experiments in pots, in greenhouse, were performed with the corn hybrids IAC 7777, C-72 and IAC 1227, in clay and loamy soils, to stud' the selectivity of single mixed applied herbicides. In each experiment two he rb ic id es and their misture were applied in pre-emergence, as follows: I) atrazine at 2,40 kg a.i./ha, pendimethalin at 1,75 kg and atrazine at 2,00 kg plus pendimethalin at 1,25 kg; II) atrazine at 2,40 kg, metola chlor at 3,24 kg and atrazine at 2,00 kg plus metolachlor at 2,52 kg; III) cianazine at 2,25 kg, pendimethalin at 1,50 and cianazine at 1,75 kg plus pendimenthalin at 1,00 kg; IV) atrazine at 2,40 kg, alachlor at 2,40 kg and atrazine at 1,60 kg plus alachlor at 1,68 kg. Each experiment had a check treatment. Dry matter weight and lenght of roots and shoots in four growth stages, in periods of 36, 49, 27 and 37 days, respectively, for experiments I, II, III and IV, were measured. There were two replications for each sampling time, each treatment and each hybrid in a completely randomized block design. Pendimethalin and cianazine, single or mixed with other herbicides, did not cause any injuries on the corn growth. In the three experiments in which atrazine was appl ied it showed stimulant effects on growth in several sampligs, increasing dry matter weight. Metolachlor and alachlor caused fitotoxic effects on roots and shoots, in the first samplings, with reduction of shoot and root weight and lenght. The hybrid IAC 7777 showed the most vigorous growth, followed by C-72, both significantly higher than IAC 1227, which was also the less tolerant to the herbicides used. The corn plants showed better growth in the loamy soil due to its higher fertility level and texture.

herbicides; selectivity; Zea mays L.; hybrids