Precision agrochemical delivery with nanoscale biopolymers

Maintaining global food security is one of the most significant challenges currently facing our society, exacerbated by the growing population, stagnating crop yields, and climate change. Low efficiencies in agrochemical delivery and utilization by plants (averaging 10−20%) further complicate these issues. As such, it is crucial to develop low-cost, high-efficiency, and sustainable agricultural fortification strategies. One such strategy is enhanced efficiency fertilizers or pesticides, which increase precision and reduce losses via runoff, leaching, degradation, and volatilization. Polysaccharides represent an ideal delivery platform due to their biodegradability, biocompatibility, and abundance. However, hydrophilicity renders native polysaccharides ineffective at controlling the release of water-soluble agrochemicals. To overcome this limitation, we used a solvent-free, vapor-phase modification strategy to generate hydrophobic shells on the surface of nanofibrillated cellulose (CNF) prills and evaluated the effects of these tunable diffusion barriers on fertilizer and pesticide release behavior. Hydrophobic shells of different thicknesses were created on CNF prills by esterification with acyl chlorides of varying alkyl chain lengths. Fertilizer release rates were largely invariable to pH and NPK loading but were tunable over 3 orders of magnitude by varying the alkyl chain length and the degree of substitution (i.e., shell thickness). Similar tunability exists for pesticides. This work demonstrates the potential of controlled surface modification to generate a mineralizable and tunable agrochemical release platform from naturally sourced and sustainable feedstocks