Assessment of biochar quality and agronomic efficiency produced from rice-husk and saw-dust at different temperature regimes

Declining soil fertility and the limited use of sustainable soil organic amendments has resulted in reduced crop productivity in Nepal. This study assessed biochar produced from rice husk and sawdust at three different pyrolysis temperatures (200°C, 400°C, and 600°C), characterized their properties and applied them as soil amendments to test their agronomic effect on kidney bean production. The highest biochar yields were achieved at lower pyrolysis temperatures (200°C) for both rice husk (40%) and sawdust (38.4%). Ash content was significantly higher in rice husk (33.6%) compared to sawdust biochar (5.8%) across all temperatures. Sawdust biochar had higher volatile matter (91%) than in rice husk biochar (61.5%). The fixed carbon content was greater at 200°C and 400°C for both rice husk and sawdust biochar. FT-IR result showed significant loss of aromatic groups with increasing temperature. Biochar from all three temperatures was then used in a pot experiment to grow kidney beans and assess their agronomic effects. Seven treatments were used: control (CK), rice husk biochar at 200°C (RH200), 400°C (RH400), and 600°C (RH600), sawdust at 200°C (SD200), 400°C (SD400), and 600°C (SD600) following a completely randomized design with 3 replications per treatment. Cattle manure was applied uniformly (25 t ha-1) across all treatments, including the control. Over 50 days, SD400 resulted in the tallest plants, SD600 produced the thickest stem and RH600 had the highest number of leaves. Biochar applications showed significantly higher fruit weight and counts, which was on average 24 % higher than the control, with no significant differences between rice husk and saw dust biochar at three different temperatures. The study suggests that high quality biochar can be produced from both rice husk and saw dust and its application boost legume yields, which is crucial for enhancing country’s nutritional and food security.