Fitotoxic effects of trifluralin to hybrid maize (Zea mays L.) and their persistance

Abstract

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%.

U radu je ispitivana osetljivost tri različita hibrida kukuruza na trifluralin, metodom biotesta. Utvrđivana je inhibicija dužine i sveže mase korena i izdanka, kao pokazatelj fitotoksičnosti herbicida. Takođe ispitivana je metodom biotesta, perzistentnost trifluralina u zemljištu tipa degradirani černozem, pri čemu je herbicid primenjen u dve količine. Degradacija herbicida praćena je od primene, pa do godinu dana nakon toga tokom dve uzastopne godine. Ispitivani hibridi ispoljili su značajnu osetljivost, pri čemu je inhibicija dužine i sveže mase korena bila mnogo izraženija za sve ispitivane koncentracije. Regresionom analizom utvrđene su I50 vrednosti za sve merene parametre, koje su potvrdile da je redukcija sveže mase korena najosetljiviji i najprecizniji mereni parametar. Najveću osetljivost ispoljio je hibrid ZPSC 633 (u odnosu na sve merene parametre). Ispitivanja perzistentnosti pokazala su da veća količina primene herbicida uslovljava nešto sporiju degradaciju, a što je potvrđeno izračunatim DT-50 vrednostima. Ostaci trifluralina godinu dana nakon primene 960 g a.m./ha nisu izazvali oštećenja nadzemnog dela, a inhibicija dužine i sveže mase korena bila je oko 10% za najosetljiviji hibrid. Ostaci trifluralina primenjenog u količini od 1.920 g a.m.7ha (godinu dana nakon aplikacije) bili su srazmerno veći, tako da su konstatovana i oštećenja nadzemnog dela (do 20% za najosetljiviji hibrid), dok je inhibicija dužine i sveže mase korena bila oko 30%.