Response of tomato to simulated soil residues of imazamox

Abstract

Imazamox is a selective imidazolinone herbicide applied post-emergence. As imidazolinone herbicides are characterized by extended persistance in various media, there are numerous evidences of their eff ects on the next susceptible crops in crop rotation schemes. A laboratory bioassay was conducted to investigate the sensitivity of tomato to the residual activity of imazamox in a sand soil (pH 7.63, humus 0.91%, sand 91.44%, silt 1.32% and clay 7.24%). The eff ect of three diff erent levels of soil moisture (20, 50 and 70% fi eld water capacity – FWC) was also examined. Imazamox was applied at diff erent rates from 6.25 to 800 μg a.i./kg soil. The parameters measured 21 days after treatment were shoots and roots fresh weight and root length as well as the content of water soluble proteins. The content of soluble proteins was determined by Bradford’s method (1976). Imazamox caused a growth delay and lower protein content at all levels of soil moisture, and the degree of change depended on the application rate. In plants grown in soil with 20% FWC, root fresh weight showed the highest inhibition, root length showed less sensitivity and there was no statistically signifi cant reduction in shoot fresh weight. In soil containing 50% FWC, concentrations ≥100 μg a.i./kg soil caused a signifi cant reduction in root fresh weight and root lenght, while only the two highest concentrations caused a signifi cant reduction in shoot fresh weight. Root lenght was the most sensitive parameter in soil of 70% FWC, while shoot fresh weight was the least sensitive parameter. Soluble protein contents were lower in all trial variants, but the changes did not depend on herbicide concentration.