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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #304274
Title: Adsorption and transport of imazapyr through intact soils columns taken from two soils under two tillage systems

Author
item PORFIRI, CAROLINA - National Institute Of Agricultural Technology(INTA)
item MONTOYA, JORGELINA - National Institute Of Agricultural Technology(INTA)
item Koskinen, William
item AZCARATE, PAMELA MARIELA - National Institute Of Agricultural Technology(INTA)

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2015
Publication Date: 8/1/2015
Citation: Porfiri, C., Montoya, J.C., Koskinen, W.C., Azcarate, P. 2015. Adsorption and transport of imazapyr through intact soils columns taken from two soils under two tillage systems. Geoderma. 251-252:1-9.

Interpretive Summary: Imazapyr is a imidazolinone herbicide used to control a wide spectrum of weed species. It's use has increased since the creation of a new type of nontransgenic imidazolinone resistant sunflower. This herbicide is considered to be mobile in soil with a potential for offsite transport. Adsorption and transport of imazapyr were evaluated in two soils with different physical-chemical properties, subject to long-term conventional tillage and no tillage systems using the batch equilibrium method. The adsorption coefficient values were relatively low and were positively correlated with clay content of the soils. Imazapyr desorbed less from no-tillage soils as compared to conventional tillage soils. Desorption was hysteretic in all soils, that is once bound to soil, the herbicide did not readily desorb. Desorption data indicate that using sorption data to describe offsite movement in soil would overpredict offsite movement. Soil column experiments showed that the magnitude of the sorption processes was not enough to significantly affect the migration of the herbicide. These data will facilitate regulators' determination of potential offsite movement of these chemicals. Also, if imidazolinone herbicides become widely used due the developed of a new type imidazolinone-tolerant crop, precautions must be taken to minimize potential offsite transport.

Technical Abstract: Imazapyr (2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-3- pyridinecarboxylic acid) is an imidazolinone herbicide used to control a wide spectrum of weed species. It's use has increased since the creation of a new type of nontransgenic imidazolinone resistant sunflower. This herbicide is considered to be mobile in soil with a potential for offsite transport.Adsorption and transport of imazapyr were evaluated in two soils with different physical-chemical properties, subject to long-term conventional tillage and no tillage systems using the batch equilibrium method. Displacement experiments through intact soil cores were done using imazapyr as reactive solute and bromide as nonreactive solute. Equilibrium and nonequilibrium transport models (CXTFIT 2.1) were employed to describe the breakthrough curves. The adsorption coefficient values ranged from 0 to 1.1 L kg-1 and were positively correlated with clay content. Imazapyr desorption for no-tillage soils was slightly higher than for conventional tillage soils. Transport models showed that physical nonequilibrium had only a minor impact on bromide migration and can be assumed to be negligible in the studied soils. No-tillage soil columns were characterized by timedependent adsorption kinetics, whereas soils under conventional tillage were governed predominantly by instantaneous adsorption processes. Breakthrough curves of bromide and imazapyr occurred almost simultaneously. The relative concentrations peaks of both compounds appeared before one pore volume. The magnitude of the retardation processes was not enough to significantly affect the migration of the herbicide. If imidazolinone herbicides become widely used due the developed of a new type imidazolinone-tolerant crop, precautions must be taken to minimize potential offsite transport.