Analysis of specific metabolites in the soil of a sweet cherry orchard withgrass intercropping based on metabolomics

To explore the effects of intercropping grass on soil metabolites in cherry orchards, the metabolomics approach based on Ultra high performance liquid chromatography-quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS) was used. The differences in metabolites between the soil of living cover crop treatments with Vulpia myuros (S) and clean tillage (Q) were examined. A total of 441 metabolites were detected in the two soil samples. Among these, 405 metabolites were shared by both, whereas 427 and 419 metabolites were present in the S and Q samples, respectively. Lipids and lipid molecules were the most abundant, accounting for 33.33% of the identified metabolites. Moreover, organic acids and their derivatives accounted for 23.19% of the total metabolites. In total, 203 (P < 0.01) differential metabolites were identified between the two soil types, accounting for 50.12% of the metabolites common to both soil samples. Among these, two compounds were significantly up-regulated, and 201 compounds were significantly down-regulated. Differential metabolites mainly included fatty acids and their derivatives, amino acids and their derivatives, amines, terpenoids, indoles and their derivatives, steroids, and other substances. KEGG analysis found that 34 differential metabolites were mainly enriched in 20 metabolic pathways, which significantly enriched (P < 0.05) tryptophan metabolism, fatty acid biosynthesis, and the aromatic compound degradation pathways. The different metabolites produced affect soil microbial populations and soil physical and chemical properties by participating in various biological processes. In conclusion, intercropping grass in sweet cherry orchards had a marked influence on soil metabolites, and the types of soil metabolites increased compared with the control. Thirteen metabolites were significantly down-regulated, and they enriched the tryptophan metabolism, fatty acid biosynthesis, and aromatic compound degradation pathways. Phthalic acid was significantly down-regulated in tryptophan metabolism. This study provides a theoretical basis for further research on the influence of grass intercroping on soil microecology in cherry orchards.