Mixing of biochar, vinegar and mushroom residues regulates soil microbial community and increases cucumber yield under continuous cropping regime

Abstract

Continuous cropping is a common practice in protected agriculture, although it results in a significant decline in soil quality and crop yield. Considering the large yearly production of vinegar and mushroom residues in China, the current study aimed to investigate the effects of different organic residue amendments on soil quality in the protected cultivation of cucumber under continuous cropping regime. Accordingly, a pot experiment was conducted with the following treatments: soil without amendment (CK), soil amendment with commercial conditioner (C), biochar (B), vinegar (V) and mushroom (M) residue (VM, V:M, 3:1), and the mixtures of vinegar, mushroom residue, and biochar (VMB, V:M:B, 3:1:4). The results showed that the soil pH, soil water content (SWC), and organic carbon (OC) content significantly increased after soil amendments. Vinegar and mushroom residues improved the content of soil N, P, and K. In contrast, biochar substantially decreased the total phenol content and electrical conductivity. Moreover, microbial diversity significantly increased with VMB amendment, and structural equation modeling (SEM) indicated that the microbial Chao1 index was strongly linked to cucumber yield. Furthermore, the yield of cucumber had a strong correlation with microbial diversity compared with soil physico-chemical properties. Chloroflexi, Actinobacteria and Gemmatimonadetes were significantly enriched by different amendments. Our results suggest that soil amendments can directly regulate the soil microbial community or induce compositional shifts of microbes by changing soil physico-chemical characteristics under continuous cropping regime. The coamendment of soil with vinegar and mushroom residues plus biochar is an effective method to reduce the negative effects of continuous cropping in protected cultivation. The study provides convincing evidence that the application of organic amendments and management of residues are potential sustainable strategies to increase agricultural productivity in protected horticulture.