Understanding the Opportunities to Mitigate Carryover of Imidazolinone Herbicides in Lowland Rice

Vinicios Rafael Gehrke,Luis Antonio De Avila,Marcus Vinicius Fipke,Edinalvo Rabaioli Camargo

doi:10.3390/agriculture11040299

Abstract

(1) Background: The Clearfield™ system (CL) is currently the primary tool for selective weedy-rice management in irrigated rice. However, herbicide persistence in the soil may cause damage to successive crops. Thus, it is necessary to understand agricultural practices that can favor the dissipation of these herbicides. The objective of this study was to analyze the factors that affect the persistence of imidazolinones and to use this information to provide management strategies to mitigate carryover in lowland rice. (2) Methods: A literature review was performed, and the publications were selected using the soil half-life parameter. The data were summarized according to the biotic conditions, soil parameters, and environmental variables. (3) Results: Imidazolinone dissipation in soil occurs primarily through biodegradation. The herbicide biodegradation rate depends on environmental conditions such as temperature and bioavailability of the herbicide in the soil. Herbicide bioavailability is affected by soil conditions, with higher bioavailability in soil with higher pH, less clayey texture, moderate organic matter content, and higher soil moisture levels. Therefore, environmental conditions that favor biological activity, especially high temperatures, reduce the herbicide half-life in the soil. Strategies to mitigate carryover should focus on improving herbicide availability and enhancing biological activity in the soil, especially in the rice off-season, when low temperatures limit herbicide biodegradation. Cover and rotational crops, such as ryegrass and soybean, are recommended, with the potential to mitigate soil residues. (4) Conclusions: The establishment of crops other than rice would automatically enhance degradation rates as soil amendment practices such as pH correction and drainage practices would favor soil availability and biological activity.

Highlights

To meet food demand, global agriculture is inextricably linked to pesticide use due to its practical and affordable nature and its importance in increasing food security
Strategies to mitigate carryover should focus on improving herbicide availability and enhancing biological activity in the soil, especially in the rice off-season, when low temperatures limit herbicide biodegradation
The pesticide fate in the environment could result in various adverse effects, including damage to non-target organisms, groundwater contamination, and persistence in the water, air, plants, animals, and soil [1]

Summary

Introduction

Global agriculture is inextricably linked to pesticide use due to its practical and affordable nature and its importance in increasing food security. The imidazolinone herbicides (imazapyr, imazapic, imazethapyr, imazamox, and imazaquin) are, in general, soil-persistent herbicides and can carryover, affecting rotational crops. These compounds act by inhibiting the acetolactate synthase (ALS) enzyme, vital in the biosynthesis of branched-chain amino acids [2]. These herbicides are characterized by a slow degradation rate in the soil and specific selectivity [3,4]. Imazethapyr and imazapic were indicated for certain crops such as beans and soybean in highland cultivation systems where sufficient degradation occurs during the growing season so that damage is not observed in subsequent crops [5,6,7]

Objectives

Methods

Results