Agronomic Practices for Mitigating Clomazone Mobility: Medium-Term Effects in Rice Agroecosystems

Clomazone is a widely used herbicide in rice cultivation, known for its high toxicity to aquatic organisms and its potential to contaminate water bodies. This study investigates the medium-term effects (after four and five years) of rice management practices on the environmental fate of Clomazone under semi-arid Mediterranean conditions. The practices investigated are tillage systems, irrigation methods, and compost application. A field experiment was conducted to compare the following treatments: sprinkler irrigation combined with no tillage (S-NT), sprinkler irrigation combined with conventional tillage (S-T), flooding irrigation with conventional tillage (F-T), and each of the above with a single compost amendment (S-NTC, S-TC, and F-TC, respectively). Compost application consistently enhanced the soil’s capacity to adsorb Clomazone, regardless of the irrigation or tillage regime. However, the use of sprinkler irrigation was shown to increase Clomazone persistence, regardless of the tillage method (S-NT and S-T), which may in turn elevate the risk of groundwater contamination. Compost addition significantly reduced Clomazone leaching losses, particularly under sprinkler systems; leaching decreased from 47% to 27% in S-NT and from 48% to 36% in S-T after five years. These findings highlight that the application of compost, particularly when combined with sprinkler irrigation, could be a sustainable agricultural approach to significantly reducing the environmental risks associated with Clomazone in rice cultivation, at least in the medium term.