Utilization of biochar as a carrier for the integrated controlled release of fertilizers and pesticides: Synergistically reducing application rates and enhancing efficiency

This study has developed a biochar-based composite (BPF+SO+AP) to address the dual challenges of low phosphorus fertilizer utilization and rapid pesticide degradation in agriculture. Cotton straw, bentonite, and KH₂PO₄ were co-pyrolyzed to synthesize a porous biochar phosphorus fertilizer (BPF), followed by encapsulation the neonicotinoid pesticide acetamiprid (AP) using starch oxide (SO). Phosphorus was immobilized within the biochar matrix through complexation, enabling slow nutrient release, while the adhesive properties of starch oxide effectively entrapped AP within the biochar, enhancing pesticide retention. In performance tests, the composite demonstrated superior slow-release behavior, reducing phosphorus leaching by 89.9 % and AP loss by 31.9 % compared to conventional applications. Additionally, it enhanced cotton seedling growth by 20.2–29.4 % and protected cotton from aphid infestation for at least 45 days. The system also protected AP from UV-induced degradation, extending its field durability by 68.3 % under 72-hour UV exposure, attributed to biochar’s light-absorbing properties and shielding effects from bentonite and SO. By enabling synergistic reductions in fertilizer and pesticide application rates, this system mitigates environmental risks such as eutrophication and non-target organism toxicity. The work provides a cost-effective, sustainable strategy for precision agrochemical delivery, leveraging agricultural waste (cotton straw) and biodegradable materials (starch), with significant potential for scalable implementation in eco-friendly farming practices. • Novel cotton-straw biochar composite (BPF+SO+AP) with bentonite, KH₂PO₄, and starch oxide-encapsulated acetamiprid. • 1:1 starch oxide/biochar ratio enables dual slow-release of phosphorus and acetamiprid, boosting efficiency. • pH-responsive release, salt resistance, and 68% lower acetamiprid UV degradation ensure environmental stability. • Enhances cotton growth with 45-day aphid control while reducing pesticide application frequency. • Cuts fertilizer/pesticide inputs and soil/water pollution, advancing sustainable agriculture practices.