Preparation and characterization of biochar and its effects on soil properties, rhizosphere bacterial and tobacco yield with reduced compound fertilizer application

Abstract

Biochar is known to have soil-improving effects and has been applied in agricultural production. Continuous cropping of flue-cured tobacco is common due to limited land resources, which can lead to soil obstacles that negatively affect yield. This study aimed to use agricultural waste as raw material to prepare biochar, to improve soil and alleviate continuous cropping obstacles. A 7-year continuous cropping filed of flue-cured tobacco variety ‘yunyan 87′ in Luoshui Town was selected, with four treatments, compound fertilizer (T1) alone, and biochar with 100, 75 and 50% amount of compound fertilizer (T2, T3 and T4), respectively. The physicochemical properties of biochar were studied, its structure was observed under an electron microscope. Its effects with reduced compound fertilizer application on agronomic traits, tobacco yield, soil enzyme activity and rhizosphere bacteria communities were investigated. In the results, biochar increased the tobacco yield (by 10.84%) compared to the same amount of fertilizer without biochar. Biochar application with 75% compound fertilizer (T3) could increase leaf area and yield of flue-cured tobacco significantly. T3 treatment had little effect on the phenoloxidase activity in the rhizosphere soil, however it significantly enhanced the activities of peroxidase, protease and urease by 56.84%, 50% and 11.94% respectively, compared with the T1 treatment. The α-diversity was the highest Under the T1 treatment. Biochar application (T2–T4) increased the soil pH significantly. Under biochar application with the decrease of compound fertilizer, the relative abundance of Proteobacteria improved whereas the abundance of unidentified_Bacteria, Chloroflexi and Gemmatimonadetes decreased. Overall, the study provided evidence that the use of biochar with reduced amount of compound fertilizer could effectively improve the growth, soil quality and alleviate the negative effects of continuous cropping on tobacco. These findings provided a reference for the potential use of agricultural waste and promoting sustainable crop production.