Biochar amendment improves soil properties and augments soil bacteria on continuous maize cultivation over two years

This research aimed to evaluate the effect of cassava stem (CS) biochar on soil properties by applying it to continuous maize cultivated in four crop cycles (2 years), in which biochar was applied only once at the first planting. The fundamental physicochemical soil properties, numbers of soil bacteria and their species, and maize yield and productivity were investigated. The experimental plots consisted of three plots with four replicates per plot: unamended soil (TC), soil amended with CS biochar at 2.5 kg/m², and soil amended with CS biochar at 2.5 kg/m² mixed with fertilizer at 0.56 kg/m² (TBM). The results indicated that CS biochar significantly improved all soil properties without finding a significant difference between the TB and TBM plots except for cation exchange capacity. The TB plots had a significantly higher number and species of soil microbes. Bacillus pumilus was found in the TB plots, while B. megaterium was detected in the TBM and TC. Although the TBM plots provided more maize ears and fresh and dry weight (FW and DW) of kernels than the TB plots, no significant difference was found unless the second crop harvesting, in which case the number of maize ears showed a significant difference. The FW and DW showed significant differences in the last crop harvesting. Maize provided decreased yield and productivity since the third crop cultivation. The research findings recommend that farmers could apply biochar mixed with fertilizer to cultivate every two crop cycles to reduce the frequency of adding fertilizer in real-world cultivation.