Biochar–mycorrhiza synergy: A novel approach for calcareous soil rehabilitation and sorghum yield improvement in semi-arid dryland systems

Abstract

The potential of calcareous soils in semi-arid dryland areas is considerable; however, these soils face major constraints, including high pH, low organic matter content, and limited nutrient availability, which often result in low crop productivity. This study aims to evaluate the effectiveness of the integrated application of locally sourced organic biochar and arbuscular mycorrhizal fungi (AMF) inoculation in improving calcareous soil conditions and enhancing sorghum yield. The field experiment was conducted using a randomized complete block design (RCBD), involving seven types and dosages of biochar and two levels of mycorrhizal application. Biochar was applied prior to planting, while AMF was directly inoculated onto sorghum seeds. The results demonstrated that the combination of biochar and mycorrhiza significantly reduced soil pH from alkaline towards neutral, and increased organic carbon content, total nitrogen, available phosphorus, exchangeable potassium, and cation exchange capacity (CEC) compared to both the control and single-treatment groups. Furthermore, the integrated treatment also led to increases in dry biomass, plant N and P uptake, and sorghum grain yield. These improvements are associated with the release of organic acids from biochar, enhanced soil microbial activity, and the expansion of root absorption zones by mycorrhiza. Thus, the synergy between biochar and mycorrhiza has proven to be effective and sustainable for the rehabilitation of calcareous soils in semi-arid dryland environments.