Targeted regulation of properties and microbial communities in tobacco continuous cropping obstacle soils using different types of biochar.

Continuous cropping obstacle (CCO) is a widespread and intractable issue in crops cultivation. As a green, low-carbon and environmentally friendly material for improving soil quality, biochar has been applied in agricultural production. This study utilized agricultural solid waste to prepare three types of biochar materials (RB: rice straw biochar, PB: pig manure biochar, SB: sludge biochar) and applied them to the improvement of tobacco soil after 15 years of continuous cropping, aiming to investigate their ameliorative effects on soil physicochemical properties and microbial communities. Within a short term (10 days), all three types of biochar effectively increased the pH value of CCO soil, with the PB treatment showing the most significant (32.73%). Compared to CK, the addition of all three biochars increased the content of organic matter (24.37-32.75%), available potassium (25.37-242.58%), available sulfur (13.15-449.30%), and available phosphorus (0.26-4.57%) in CCO soil, and PB and SB treatments reduced the soil water loss by 31.09 and 20.81%. PB showed the most significant improvement in various soil elements, especially in available potassium and available sulfur, followed by RB. Furthermore, biochar exhibits notable improvement effects on beneficial bacterial taxa (Actinobacteriota, Proteobacteria), as well as on bacterial genera (Sphingomonas, Bacillus, Nocardioides). RB significantly increases the relative abundance of beneficial fungal genus Mortierella in CCO soil (31.07%). Therefore, considering the demand of tobacco for soil potassium content and beneficial root microbial community, the combined application of PB and RB in tobacco CCO soil constitutes a moderate, practical, and environmentally friendly strategy.