Response of soil nutrients, enzyme activities, and fungal communities to biochar availability in the rhizosphere of mountainous apple trees

Aims Biochar application is an efficient amendment to improve soil chemical properties. However, its influence on enzyme activities and soil health, especially fungal diversity, is deficient in the rhizosphere of mountainous apple trees. Methods A pot experiment was conducted over the course of a year with six different biochar rates [CK (0), T1 (2), T2 (4), T3 (6), T4 (8), and T5 (10) t ha −1 ] and a basal dose of inorganic fertilizer. Results Experimental findings revealed that: (i) Compared to the CK treatment, the biochar-applied treatment (T5) across the months (3, 6, 9, and 12) significantly improved soil physiochemical properties and enzyme activities [urease (UE), alkaline phosphatase (ALP), catalase (CAT), and sucrase (SC)]. (ii) The T5 of the biochar-applied treatment compared to the CK significantly reduced the dominant relative abundance of the phylum Ascomycota. However, Basidiomycota and Chytridiomycota phyla members showed an optimized trend with biochar-applied treatments. Similarly, the fungal genera with the largest relative abundance in the T5 was Coprinellus , followed by Helminthosporium , Gibberella , Coniothyrium , Paraconiothyrium , and Aplosporella . Furthermore, Alternaria and Amanita were the only genera that showed the lowest trend with the biochar-applied treatments. (iii) The fungal richness and diversity of the biochar-applied treatments exhibited a lower trend than the CK treatment. Moreover, the heatmap correlation was negative between the Ascomycota with soil organic matter (SOM) and total nitrogen (T.N), and Mucoromycota and Olpidiomycota with UE, ALP, and SC activities. Conclusions Biochar-applied treatment (T5) with the required inorganic fertilizer is significant for enhancing soil characteristics, which may aid the productivity of apple orchards.