Composting and grinding pretreatment enhances nutrient release and seedling quality in straw-based substrate of binderless boards by modifying lignocellulosic properties

In China, the reliance on topsoil for seedling cultivation has led to severe arable layer degradation. To address this, we developed straw-based binderless substrate boards from wheat and corn straw, integrating composting and mechanical processing as innovative pretreatments. This study evaluates how these treatments enhance nutrient release and seedling growth by modifying lignocellulosic properties. Composting reduced hemicellulose content (corn straw: 28.4 % to 21.1 %) and increased lignin accumulation, while grinding disintegrated straw surfaces, exposing fibers and improving substrate structure. Thermogravimetric and FTIR analyses confirmed hemicellulose degradation and lignin stabilization. Grinded substrates exhibited superior bulk density (0.20 g/cm³), ammonium nitrogen (74.6 mg/kg), and available potassium (1410.0 mg/kg), with grinded wheat straw (GWS) achieving the highest seedling emergence (105.0 plants/100 cm²) and fresh weight (10.7 g/100 plants). These results highlight that composting combined with grinding optimizes lignocellulosic breakdown, enhances nutrient availability, and improves seedling performance. This approach offers a sustainable alternative to topsoil use, balancing agricultural waste valorization with ecological conservation.