A novel engineered nanoherbicide: improving performance, efficiency and sustainability of herbicide bentazon

A new nanoherbicide using bentazon (Btz), a widely used post-emergence herbicide, was developed in the present work, to considerably reduce the required dosages without compromising its efficacy. Biocompatible and biodegradable nanoparticles (i.e. amorphous calcium phosphate, ACP) have been engineered to act as a carrier for the sustained delivery of the herbicide. The resulting nanocomposite (Btz-ACP) was characterized through complementary techniques, such as PXRD, FTIR, TEM, and elemental analysis, confirming the successful loading of Btz onto ACP nanoparticles and the subsequent pH-responsive release of the herbicide in aqueous media. Release kinetic constants of 0.11 h-1 and 0.2 h-1 were found at pH 7 and pH 4.5, respectively. We also found that the retention of Btz-ACP was increased in inert soils in comparison to the free herbicide, indicating its potential to mitigate groundwater contamination. This new nanoherbicide allows a significant reduction of herbicide dosage by up to 60% compared to the commercial product at the recommended dosage (1 kg ha-1) to efficiently control the growth of Sinapis alba (white mustard). Notably, the most diluted Btz-ACP formulation (0.4 kg ha-1) exhibited the highest weed control at 10 days post treatment (96.3 +/- 8.8% mortality), outperforming all other tested treatments: commercial formulations (77.4 +/- 24.5% of mortality at the recommended dose and 74.5 +/- 20.1% at the reduced dose of 0.7 kg ha-1) but also higher doses of Btz-ACP (0.6 kg ha-1) (78.1 +/- 18.9% of mortality) with an inverse concentration-efficiency relationship. This may be due to the reduction of nanoparticle aggregation at low dosages, thus favoring nanoparticle penetration through the leaves. Interestingly, despite the huge reduction of dosage, the herbicidal effect is still visible after 28 days post-treatment, avoiding the regrowth of the target plant. The results demonstrate that this new nanomaterial offers a very promising approach to sustainable agriculture with reduced environmental impact.