Phytotoxic effect of imazethapyr to hybrid maize (Zea mays L.) and its persistence

Abstract

The objective of the study was to analyze the suspectibility of three different types of hybrid maize to carryover potential of imazethapyr. Herbicide toxicity was analyzed using the bioassay, by determining the inhibition of root and shoot lenght and fresh weight. In addition, using the bioassay imazethapyr persistence in the leached chernozem soil type was studied. The aim was to determine the residues of imazethapyr based on the most sensitive parameter tested with regard to rate and time of application. Herbicide degradation was monitored over a period of one year following application during two trial years. The hybrids tested showed a significant susceptibility to herbicide tested. The doses analyzed inhibited root lenght and fresh weight to a greater extent. Regression analysis was used to determine I50 values for the parameter tested, thus proving root fresh weight reduction to be the most susceptible and accuretly computed parameter. Hybrid ZPTC 125 was the most susceptible (with regard to the parameters tested) Higher herbicide doses and post-em treatment provoked slower degradation of imazethapyr as confirmed by calculated DT-50 values. Imazethapyr residues (applied at the rate of 80 and 120 g a.i./ha pre-emergence) provoked no damage to ground parts (in both trial years). Shoot growth and fresh weight were reduced by 10 % in the post-emergence treatment (which was more prominent in the first trial year). Root lenght and fresh weight inhibition was more prominent, especially with the application of higher doses even in post-emergence treatments (for the most susceptible hybrid a little bit less than 20 % and aprox. 30 % in the first and second trial year, respectively).

U radu je ispitivana osetljivost tri hibrida kukuruza na imazetapir. Metodom biotesta utvrđivana je inhibicija dužine i sveže mase korena i izdanka, kao pokazatelj fitotoksičnosti herbicida. Osim navedenog, biotest metodom je praćena i degradacija imazetapira u zemljištu tipa degradirani černozem, da bi se, na osnovu prethodno određenog najosetljivijeg merenog paramétra utvrdio nivo ostataka godinu dana nakon primene, a u zavisnosti od količine i vremena primene. Ova ispitivanja vršena su 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 I5o vrednosti za sve merene parametre, koje su potvrdile da je redukcija sveže mase korena najosetljiviji i najprecizniji mereni parametar. Najveću osetljivost ispoljio je hibrid ZPTC 125. Ispitivanja perzistentnosti pokazala su da veća količina i kasnije vreme primene herbicida uslovljavaju nešto sporiju degradaciju, a što je potvrđeno izračunatim DT-50 vrednostima. Godinu dana nakon primene ostaci imazetapira (primenjenog u količini od 80 i 120 g a.m./ha, nisu izazvali oštećenja nadzemnog dela (u obe godine ispitivanja). U post-em tretmanu redukcije rasta i sveže mase izdanka bile su do 10% (i izraženije u prvoj godini). Inhibicije dužine i sveže mase korena bile su izraženije, i uvek veće pri većoj količini primene i u post-em tretmanu, tako da su za najosetljiviji hibrid iznosile nešto manje od 20 % u prvoj, odnosno približno 30 % u drugoj godini ispitivanja.