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

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.

Imidazolinone herbicide dissipation in rice fields as affected by intermittent and continuous irrigation

“…Dissipation is the process of losing the herbicide from the applied site to the environment involving: 1) volatilization, 2) drift, 3) runoff, 4) leaching, 5) degradation, 6) plant metabolization, and others (Farha et al, 2016;Jin et al, 2013). For IMI, the primary process responsible for dissipation is microbial degradation (Gehrke et al, 2021). Microorganisms use the herbicide molecules to modify them into simpler compounds that can be used in their metabolism (Singh, Singh 2016).…”

“…The CL rice system is the most successful weedy rice control tool up to date (Avila et al, 2021a). In rice, with the use of IMI herbicide in CL rice system, farmers have the option of using only one herbicide to control weedy rice (Oryza sativa L.), Echinochloa spp., Cyperus spp., Aeschynomene spp., Luziola peruviana J., Urochloa plantaginea L., and other weeds (Avila et al, 2021b;Gehrke et al, 2021). In Brazilian CL system, one of the options is the commercial mixture of imazapyr + imazapic (Kifix™), which has residual soil activity that improves weed control after application and helps to prevent reinfestation (Avila et al, 2021a).…”

“…In Brazil, Rio Grande do Sul (RS) State, the top rice producer contributing with 70% of the rice in the country ( Sociedade Sul-Brasileira de Arroz Irrigado, 2018), approximately 85% of the area is cultivated with imidazoline-resistant cultivars (Avila et al, 2021b;Instituto Rio Grandense do Arroz, 2019). Although the imidazolinone herbicides (IMI) used in the CL system are highly selective and efficient, these herbicides have high persistence in the soil and can cause crop injury by carryover, affecting the rotational crop or non-CL rice cultivars (Gehrke et al, 2021).…”

“…Therefore, several factors may affect IMI sorption, including soil pH. In low soil pH, these molecules interact strongly with soil particles, slowing the dissipation processes (Gehrke et al, 2021;Su et al, 2019). This fact is due to the amphoteric behavior of IMI, which allows these herbicides to act as weak acids or bases, depending on the pH of the environment in which they are present (Gianelli et al, 2014).…”

The ameliorative effect of protein hydrolysate on the imazamox-damaged young wheat plants

“…The herbicide biodegradation rate depends on environmental conditions and the bioavailability of the herbicide in the soil. The bioavailability of the herbicide is affected by soil conditions, where with a higher bioavailability in soil with less clay texture, higher pH, higher soil moisture and a moderate organic content (Gehrke et al, 2021). However, their residual amounts may have on subsequent sensitive crops in the crop rotation (Liu et al, 2016).…”