Delivering metribuzin from biodegradable nanocarriers: Assessing herbicidal effects for soybean plant protection and weed control

Several studies have reported improved weed control and targeted delivery of herbicides by nanocarriers. However, the effects on crops and non-target organisms need to be considered. Here, we investigate the crop and soil health treated with metribuzin in conventional and biodegradable nanoformulations (poly-ε-caprolactone - PCL and lignin-PCL) (both at 480 g a.i. ha-1). Weed control of Amaranthus retroflexus by the nanoformulations was also evaluated as a measurement of target delivery. Soybean plants did not show any differences in photosynthetic parameters and a slight oxidative stress with nanoherbicide treatment, with biomass reduction occurred at 60 days after application. The root accumulated metribuzin formulations and translocated to the aerial part for both plant species. The polymeric nanomaterials in the soil mitigated alterations in the bacterial community. Metribuzin formulations, mainly nanoformulations even at low dose (48 g a.i. ha-1) caused severe photosynthetic damage in the weed species, with reduction of chlorophyll content (up to 2.35 time) and electron flow (up to 9.22 times), leading to eventual mortality. MTZ nanoformulations presented a greater efficacy (even in 10-fold less dose) for weed control compared to conventional formulation. These findings suggest that MTZ nanoformulations improve weed control and attenuate the negative effects on crop and soil health, offering an important nano-enabled strategy for sustainable weed management.