Bound 14C-metsulfuron-methyl residue in soils.

Area of Science:

• Environmental Chemistry
• Soil Science
• Agrochemicals

Background:

• Metsulfuron-methyl is a widely used herbicide.
• Understanding the fate of herbicides in soil is crucial for environmental safety and agricultural practices.
• Bound residues (BR) of herbicides can persist in soil and potentially affect crop growth.

Purpose of the Study:

• To investigate the factors affecting the formation of bound residues (BR) of 14C-metsulfuron-methyl in different soil types.
• To identify the main components of 14C-metsulfuron-methyl derived BR.
• To assess the contribution of BR to the phytotoxic effects on subsequent crops.

Main Methods:

• Incubation of 14C-metsulfuron-methyl in seven different soil types.
• Analysis of soil properties including pH, clay content, organic matter (OM), and cation exchange capacity (CEC).
• Identification of BR components using liquid chromatography-mass spectrometry (LC-MS) and isotope tracing.

Main Results:

• Soil pH was the dominant factor negatively correlated with 14C-BR formation, while clay content showed a positive correlation initially.
• The maximum 14C-BR content ranged from 19.3% to 52.6% of the applied amount across the soils.
• Key components of 14C-BR included 14C-[2-amino-4-hydroxyl-6-methyl-1, 3, 5]-triazine, 14C-[2-amino-4-methoxy-6-methyl-1, 3, 5]-triazine, and the parent 14C-metsulfuron-methyl.

Conclusions:

• Soil pH is the most critical factor governing the formation of metsulfuron-methyl bound residues.
• The presence of the parent metsulfuron-methyl compound within the bound residues can explain observed phytotoxicity in rotational crops.
• Further research into the long-term environmental impact and degradation pathways of metsulfuron-methyl is warranted.