Yashwanth Arcot

The limited water solubility and environmental instability of natural pesticidal compounds impede their broader agricultural use. This study reports an amphiphile-assisted nanoprecipitation method to imbibe azadirachtin-rich neem seed extract (NSE) within a glycine carrier matrix, yielding a stable nanocomposite biopesticide. The formulation, prepared using polyoxyethylene sorbitan monooleate as a stabilizer and glycine as the matrix former, followed by lyophilization, exhibited a hydrodynamic diameter of ∼8 nm when redispersed in water. This glycine nanopesticide (GNP) significantly improved the photostability of azadirachtin under UV-AB irradiation (2000 μW/cm²); spectrophotometric analysis revealed a 27.7% reduction in photodegradation over a 4 day period compared to unformulated NSE powder demonstrated dialysis-based in vitro release assay showed sustained release, with 68.2 ± 2.1% released over 7 days, fitting an exponential model with a time constant of 37.6 h. Contact bioassays against Spodoptera frugiperda larvae revealed enhanced larvicidal potency. LC₅₀ values showed a 1.5- to 6.6-fold improvement compared to unformulated NSE over 11 days. On day 7, GNP had an LC₅₀ of 0.13 mg/mL, compared to 0.86 mg/mL for NSE powder. The nanoformulation also improved wettability on tomato leaves, reducing the contact angle from 99.0° ± 1.6° (DI water) to ∼60° at a concentration of 100 mg/mL GNP. This approach offers a practical method for improving the stability, delivery, and efficacy of hydrophobic biopesticides.

Recently, increasing frequency and severity of drought events have resulted in significant crop yield reductions worldwide, indicating the critical need for innovative agricultural water management strategies to enhance water use efficiency. Addressing this challenge, we present a novel approach involving the strategic placement of highly hydrophobic sand layers below the subrhizosphere. This method utilizes silica sand modified via a facile, single-step surface treatment, yielding a material with strong hydrophobicity, characterized by a static water contact angle of 133.0 ± 1.0°. Importantly, the modified sand demonstrated stability and retained its hydrophobic properties under simulated adverse agricultural conditions. Systematic investigations of the hydraulic properties revealed that the incorporation of these hydrophobic sand layers substantially controlled the vertical infiltration flux of irrigation water. Specifically, a hydrophobic sand layer with an areal density of 796.5 mg/cm² extended the water infiltration time by a factor of approximately 5.5 relative to control soil columns, even following 14 days of sustained irrigation. This engineered impedance promotes saturation within the rhizosphere, thereby potentially enhancing the efficiency of root water uptake. Furthermore, experimental observations indicated a positive correlation between the presence of the hydrophobized subsoil layer and the retention of organic matter within the overlying soil matrix, suggesting ancillary benefits for long-term soil fertility maintenance. Consequently, deploying subrhizosphere hydrophobization using organosilanes as a preplanting soil conditioning treatment presents a potentially more applicable strategy for improving water conservation and soil health, particularly in water-scarce agricultural regions.