Oxadiazon Dissipation in Water and Topsoil in Flooded and Dry-Seeded Rice Fields

Aldo Ferrero,Serenella Piano,Francesco Vidotto,Silvia Fogliatto,Marco Milan,Michéle Negre

doi:10.3390/agronomy9090557

Abstract

The aim of the present study was to assess the behavior of oxadiazon in topsoil and waters of paddy fields cultivated according to the two rice seeding systems: conventional water seeding (CON) and dry seeding (DRY). The study was carried out from 2012 to 2013 in Vercelli, north-west of Italy, the most important rice growing area of Europe. Variations in oxadiazon concentrations were studied over time in topsoil, paddy water, inlet water and outlet water. Over the two years, the estimated oxadiazon topsoil half-life was 3.27 days, without significant differences between systems and years. Oxadiazon dissipation in the paddy water was rapid during the first week, but less pronounced late in the season. Residues of oxadiazon were frequently detected in inlet waters. Transfer of oxadiazon residues in outlet waters occurred over all the growing seasons, with important peaks in the first weeks after the treatment. A possible way to reduce the transfer of oxadiazon to water bodies could be increasing the residence time of the herbicide in the paddy fields during the first 7–10 days after spraying, avoiding the release of water from them.

Highlights

Oxadiazon (5-terbuthyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-(3H)-one, is a herbicide widely used to control annual broad leaved weeds and grasses in fruit trees, turf, rice, soybean, sunflower, cotton, some flower species and ornamental plants
The presence of this herbicide in surface and ground waters is mentioned in different reports made by environmental authorities, as well as by several monitoring studies conducted in many countries of the world [9,10,11,12,13,14,15,16]
During 2012 in the soil samples collected the day before the treatment, oxadiazon residues were found at concentrations ranging from 23.44 μg/kg to 37.71 μg/kg

Summary

Introduction

Oxadiazon (5-terbuthyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-(3H)-one, is a herbicide widely used to control annual broad leaved weeds and grasses in fruit trees, turf, rice, soybean, sunflower, cotton, some flower species and ornamental plants. The risk of water contamination by Plant Protection Products (PPPs) is generally higher for surface water than for groundwater due to the interconnections between flooding waters and the network of ditches, channels and rivers that permeate rice areas [7,8]. Despite its old introduction into the market, oxadiazon is still an herbicide largely applied in direct-seeded rice, mainly to control Heteranthera spp The presence of this herbicide in surface and ground waters is mentioned in different reports made by environmental authorities, as well as by several monitoring studies conducted in many countries of the world [9,10,11,12,13,14,15,16].

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Conclusion