Persistence of Imazapyr herbicide in the soil and its phytotoxic effect on winter and summer crops

Abstract

Imazapyr is a broad-spectrum herbicide of the imidazolinone chemical family that in Argentina is used on imidazolinone-tolerant corn and sunflower (Clearfield). Determining the persistence of imazapyr is important since its level of activity in the soil is high. The objective of this study was to determine the phytotoxic persistence of two rates of imazapyr applied on Clearfield sunflower through of its phytotoxic effect on winter and summer crops. The experiment was performed in a clay loam soil of Balcarce (Buenos Aires Province) by mean of a randomized complete block design with four replications. Treatments included 80 and 160 g of imazapyr of active ingredient (a.i.)/ha and a non-treated control. Soil samples were collected every month after the sunflower harvest (March 2003). At the end of the sampling period, a bioassay in a growth chamber was performed with corn wheat, canola and non tolerant sunflower and corn. Concurrently, non-imidazolinone tolerant corn and sunflower as well as potato were seeded in the field and their yield was measured. Results were analyzed by variance analysis (p = 0.5). Duration of phytotoxic persistence determined with the bioassay could be aligned as follows: wheat > canola > sunflower = corn. In the field, none of the crops showed negative effects indicating absence of residual effect in the crops.

Keywords

• imidazolinone
• bioassay
• residual effect
• Clearfield