Abstract
Addressing the issues of slow decomposition and low nutrient release efficiency associated with traditional straw returning, this study innovatively applied ultrasound-assisted centrifugal separation technology to prepare submicron/nano-straw particles and systematically conducted a multi-scale investigation from microscopic to macroscopic levels. The core finding reveals that when the particle size reaches the 1 μm threshold, ultrasonic cavitation vigorously disrupts the straw structure, leading to efficient lignin removal (77.45 %) and a significant reduction in cellulose crystallinity, thereby fundamentally enhancing the degradation rate. Concurrently, the cavitation effect optimizes elemental ratios (e.g., C, N, and K elemental proportions increasing by 1.05 to 8.50 times) and exposes active functional groups such as C-N and N-H bonds, effectively overcoming the bottleneck in nutrient release. Furthermore, cavitation increases the abundance of hydrophilic groups on the straw surface, enhancing its water-holding capacity by 13.84-18.52 %. Soil columns experiment and pot trials confirmed that the nano-straw prepared by this technology substantially reduces nutrient loss, significantly increases soil available potassium content, ultimately synergistically increasing rice yield by 25.27 %. In summary, by simultaneously optimizing the straw's degradability, fast-acting nutrient release capacity, and water retention, ultrasonic technology solves the core challenges of traditional straw returning and provides a novel strategy for developing new fast-acting straw fertilizers.