Biochar Enhanced Rice (Oryza sativa L.) Growth by Balancing Crop Growth-Related Characteristics of Two Paddy Soils of Contrasting Textures

Rice ( Oryza sativa L . ) growth can be influenced by base cation, plant-available nutrients, and potentially phytotoxic elements in soils. These soil-property groups can be altered by biochar addition, depending on soil textures. The current study aimed to examine the impacts of biochar on rice growth and identify associated mechanisms related to characteristics of soils of contrasting textures. A pot experiment was conducted using clayey and sandy soils added with five biochar rates (0, 0.5, 1, 2, and 5%, w/w) and planted with rice. Rice biomass was measured, and soil samples were taken to be analyzed for ten parameters when the experiment was ended. The base index (BI, average concentrations of exchangeable calcium, magnesium, sodium, and potassium), the nutrient index (NI, average concentrations of NH 4 + and Mehlich-1 P), and the potentially phytotoxic index (PI, average concentrations of exchangeable aluminum, iron, and manganese) were computed for assessment. Biochar improved total rice biomass in the sandy soil (by 55%) more than in the clayey soil (42%). Biochar enhanced properties, the BI, and the NI while reducing the PI in the two tested soils. Total rice biomass was positively correlated with the base ratio (BI/PI) and the nutrient ratio (NI/PI). The findings suggest that mechanisms accounting for improved rice growth could be involved in the enhanced ratios caused by biochar addition. Biochar addition increased rice growth in the sandy soil more than in the clayey soil by raising the base and nutrient ratios of the two soils.