Sorption-desorption of rimsulfuron, nicosulfuron, and metabolites in soils from Argentina and the USA

Authors: AZCARATE, MARIELA - Instituto Nacional De Tecnologia Agropecuaria; Schneider, Sharon; MONTOYA, JORGELINA - Instituto Nacional De Tecnologia Agropecuaria; Koskinen, William

Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2018
Publication Date: 11/29/2018
Citation: Azcarate, M.P., Papiernik, S.K., Montoya, J.C., Koskinen, W.C. 2018. Sorption-desorption of rimsulfuron, nicosulfuron, and metabolites in soils from Argentina and the USA. Agricultural and Environmental Letters. 3:180048. https://doi.org/10.2134/ael2018.09.0048.
DOI: https://doi.org/10.2134/ael2018.09.0048

Interpretive Summary: Sulfonylurea herbicides are used throughout the world to control a large variety of weeds in crops including wheat, rice, corn, and soybean, and potato. To better understand how these compounds behave after their application to soil, we performed sorption-desorption studies to measure how these chemicals partition between soil and water. These tests are an indicator of the potential availability of the herbicide compounds to be taken up by plants or contaminate water resources. We tested rimsulfuron and its metabolites IN-E9260, IN-70941, and IN-70942; and nicosulfuron and its metabolites IN-HYY2 and IN-GDC42. Soils were collected from two depths in the upper slope, backslope, and lower slope of landforms in La Pampa, Argentina and Minnesota, USA. The results demonstrate that quantitative data like the values presented here are required for accurate prediction of herbicide fate in soils because: (1) The Kd determined for the sulfonylurea parent compound does not necessarily represent the Kd for similarly-structured metabolites; (2) Results from one geographical region cannot be reliably generalized to another region; (3) The Kd value determined for surface soils cannot be reliably extrapolated to nearby soils; and (4) Sorption values alone do not characterize herbicide availability for leaching or plant uptake. Scientists, extension specialists, and risk assessors can use this information to more accurately predict the beneficial (weed control) and detrimental (crop damage, water contamination) effects of the use of these herbicides.

Technical Abstract: Sulfonylurea herbicides provide broad-spectrum weed control in a variety of crops. To better understand the potential mobility and persistence of these compounds and their metabolites in soil, sorption-desorption studies were conducted using 14C-labeled compounds: rimsulfuron and its metabolites IN-E9260, IN-70941, and IN-70942; nicosulfuron and its metabolites IN-HYY2 and IN-GDC42. Soils were collected from two depths in the upper slope, backslope, and lower slope of landforms in La Pampa, Argentina and Minnesota, USA. Soil-water partition coefficients (Kd) ranged from 0 to 21 mL/g, and were usually =2 mL/g. Metabolite Kd values differed from the parent compound Kd by up to an order of magnitude. For all compounds, desorption was hysteretic. For most compounds tested, Kd values were greater in the USA soils, which were higher in organic carbon and pH than the Argentina soils. At both sites, Kd values were lowest in the upper slope and highest in the lower slope.