Effect of poultry manure biochar on soil nutrition and carbon improvement in Saemangeum reclaimed soils

Low nutrient and organic matter (OM) contents in reclaimed agricultural soils can hinder crop growth, making it essential to improve the chemical characteristics of reclaimed agricultural soil to maintain crop productivity.Poultry manure (PM) can effectively supply nutrient content by its high nitrogen (N) and phosphorus (P) concentrations, while leads to environmental issues, including odor and greenhouse gas emissions, by improper pre-treatment.This study aimed to evaluate the effect of PM-based biochar containing the varying rate of rice husk on soil improvement in reclaimed agricultural land.Soil samples were collected from the Saemangeum reclaimed land, and biochars were produced using PM as the primary ingreidient, with different proportions (i.e., 0, 10, 30, 50, 70, 90, and 100%) of rice husk.All biochar samples were pyrolyzed at 350℃ for 1 h.Chemical characteristics of biochar showed that increasing the proportion of rice husk decreased the pH electrical conductivity, and nutrient (N, K 2 O, CaO, and MgO) contents, while carbon and OM contents increased.Regarding soil improvement, the nutrient and OM contents significantly increased when biochar was applied at a rate of 5.0 Mg•ha -1 or more.Lettuce yield increased as the biochar application rate increased and the rice husk ratio in the PM-based biochar decreased, with the highest yield (33.52 Mg•ha -1 ) observed in reclaimed soil treated with 10.0 Mg•ha -1 of PM-based biochar without rice husk.Therefore, to improve soil nutrient content, minimizing the rice husk proportion in the PMbased biochar was most effective, while OM improvement was enhanced with increasing rice husk ratios.