Biochar addition as a strategy for increasing Amorphophallus konjac yield: From the perspective of improving soil physicochemical properties and bacterial community diversity

Biochar produced from agricultural waste shows promise in improving soil properties and the microbial environment. However, the Amorphophallus konjac industry, a vital source of glucomannan, faces challenges of low yield and poor sustainability in China. This study explores the effectiveness of biochar as a soil amendment to mitigate these constraints. A pot experiment was conducted to investigate how different biochar application rates (0, 1%, 2%, 3%, 4%, 5%) affect soil physicochemical properties, enzyme activities, and bacterial diversity in A. konjac cultivation, as well as the crop's agronomic traits, yield, and quality. Biochar significantly improved soil properties, increasing soil pH by 0.45 and cation exchange capacity (CEC) by 4.54 cmol kg-1 at a 5% application rate (B5), and enhancing total nitrogen (TN), available phosphorus (AP), and available potassium (AK) by 18.48%, 12.32%, and 37.28%, respectively, compared to the control (CK). Furthermore, the B5 also elevated soil urease, sucrase, and catalase activities by up to 27.06%, 23.33%, and 9.31%, respectively. At a 4% application rate (B4), biochar increased the soil Shannon diversity index and resulted in a notable increase in the relative abundance of key beneficial genera, specifically Streptomyces (by 19.49%) and Sphingomonas (by 10.68%), compared to CK. Therefore, at a 5% application rate, the yield and glucomannan content increased by 41.64% and 34.05% over the control. The structural equation model further indicates that biochar can significantly enhance the physical and chemical properties and biological characteristics of the soil, thereby promoting the growth, yield and quality of A. konjac.