Impact of Rice Husk Biochar on Soil Properties and Microbial Diversity for Paddy Cultivation

Abstract

Utilisation of rice husk biochar (RHB) as an amendment in acidic paddy soil aims to enhance soil properties, microbial composition, and paddy growth parameters during cultivation. A pot experiment was conducted on the Sembada 188 rice variety with rice husk biochar amendments at 5, 20, and 40 t ha-1, with or without the co-application of chemical fertilisers. The agronomic traits (biomass fresh weight and dry weight, shoot length, and chlorophyll content index and yield, including tiller count, grain count, and grain weight) and the soil properties (soil pH, total N, P, and K and microbial diversity) were assessed at final harvest. Additionally, shifts in soil microbiota were analysed via next-generation sequencing. Sole RHB amendments showed little to no positive impacts on the analysed parameters. Still, the co-application of RHB and chemical fertiliser (RHBF) generally improved fresh and dry weight, chlorophyll content, total tiller count, total grain count, total grain weight, and soil pH. The impact of RHBF application was doses-dependent, with optimal improvements and microbial shift seen within RHB20F (combined treatment of 20 t ha-1 rice husk biochar and fertiliser). Current findings revealed a preference for fungi in the acidic soil before the amendment, while bacteria in RHB20F favoured the subsequent pH shift towards slightly alkaline conditions. Proteobacteria, Actinobacteriota, Chloroflexi and Acidobacteriota were dominant among the ten bacterial phyla. In contrast, Ascomycota emerged as the dominant fungal phylum, constituting over 79% of the relative abundance across treatments, with Lecanoromycetes representing most of the class composition. The co-application of rice husk biochar and fertiliser at precisely 20 t ha-1 has improved soil pH, subsequently enhancing the microbial abundance, agronomic parameters, and yield of Sembada 188. This combination retains the benefits of applied fertiliser, thereby offering a prolonged nutrient supply within agricultural paddy soil. Rice husk biochar serves as a liming agent and a growing substrate.