Herbicide toxicity to Nitrospirillum amazonense: assessing bacterial survival and microbial functionality

Area of Science:

• Agricultural Science
• Microbiology
• Environmental Science

Background:

• Herbicides can harm beneficial soil bacteria crucial for plant growth.
• Nitrospirillum amazonense enhances sugarcane growth via biological nitrogen fixation (BNF) and indole-3-acetic acid (IAA) production.
• Understanding herbicide impacts on N. amazonense is vital for sustainable sugarcane farming.

Purpose of the Study:

• To assess the in vitro effects of nine pre-emergent herbicides on N. amazonense survival and function.
• To identify herbicides compatible with N. amazonense for integrated weed management in sugarcane.

Main Methods:

• Four in vitro assays were conducted.
• The study evaluated the impact of nine specific pre-emergent herbicides.
• Bacterial survival, growth, indole-3-acetic acid (IAA) production, and biological nitrogen fixation (BNF) were measured.

Main Results:

• Herbicides showed varied effects on N. amazonense.
• Indaziflam, metribuzin, S-metolachlor, and sulfentrazone had no negative impact; some even enhanced growth, IAA, or BNF.
• Isoxaflutole was growth-promoting at low doses but toxic at high doses; clomazone and imazapic reduced growth but boosted IAA and BNF; flumioxazin and tebuthiuron increased growth and BNF but decreased IAA.

Conclusions:

• Herbicides induce specific modulations in N. amazonense, affecting survival and plant growth promotion mechanisms.
• Herbicide selection is critical for integrated management systems.
• Compatible herbicides can be strategically combined to maintain weed control and microbial benefits, advancing sustainable sugarcane production.