Evaluation of biochars derived from rice husk, wood chip, and cow manure: effects on soil properties and lettuce growth

This study evaluated the effects of biochars derived from different feedstocks on soil properties and the growth of lettuce (Lactuca sativa).Biochars produced from rice husk (RH), wood chips (WD), and cow manure (CM) were applied to soil at rates of 100, 200, 400, and 800 kg 10 a -1 .Across the biochar treatments, soil organic matter and cation exchange capacity generally increased compared with the control.In particular, the CM biochar produced the most pronounced increases in available phosphorus and pH, but it also elevated electrical conductivity (EC), indicating a potential risk of growth inhibition at higher application rates.In contrast, the RH biochar tended to slightly reduce EC as the application rate increased.The WD biochar showed the greatest growth response at the lowest application rate (100 kg 10 a -1 ), where the mean fresh weight of lettuce reached 80.4 g per plant.Regarding soil biological activity, soil respiration and urease activity increased under WD and CM treatments, whereas dehydrogenase and phosphatase activities generally decreased.These patterns may reflect nutrient imbalances or mild physiological stress in the soil environment.Overall, biochar application improved soil chemical and biological properties and promoted lettuce growth, but the effects differed depending on biochar feedstock and application rate.Therefore, appropriate soil management that considers biochar characteristics and application rates is required to improve soil quality and promote crop growth.