Date Palm Waste Compost Application Increases Soil Microbial Community Diversity in a Cropping Barley (Hordeum vulgare L.) Field

SIMPLE SUMMARY: The objective of this study was to determine the effects of compost application on soil bacterial and fungal communities at the tillering, booting and ripening stages of barley plant growth. The two treatments were unfertilized (control) and compost treatment (30 t ha(−1)). The high-throughput sequencing approach and real-time quantitative PCR method were performed to study the characteristics of soil bacterial and fungal communities. Compost addition significantly altered the compositions of bacterial and fungal communities. Our results revealed that the Chao1 index of the fungal community increased at the tillering and booting stage, while that of the bacterial community decreased at the tillering and ripening stage. Moreover, compost decreased the Shannon index of fungal and bacterial communities, especially at the tillering stage. The dominant bacterial phyla found in the samples were Proteobacteria and Actinobacteria while the dominant fungal phyla were Ascomycota and Mortierellomycota. Identified bacteria were mainly involved in energy metabolism, amino acid metabolism, metabolism of cofactors and vitamins and carbohydrate metabolism while fungi were saprotroph, pathotroph symbiotroph and endophyte. Overall, date palm waste compost addition could be considered as a sustainable practice for establishing a healthy soil microbiome and subsequently improving the soil quality and barley crop production. ABSTRACT: Application of date palm waste compost is quite beneficial in improving soil properties and crop growth. However, the effect of its application on soil microbial communities is less understood. High-throughput sequencing and quantitative real-time PCR (qPCR) were used to evaluate the effect of compost application on the soil microbial composition in a barley field during the tillering, booting and ripening stages. The results showed that compost treatment had the highest bacterial and fungal abundance, and its application significantly altered the richness (Chao1 index) and α-diversity (Shannon index) of fungal and bacterial communities. The dominant bacterial phyla found in the samples were Proteobacteria and Actinobacteria while the dominant fungal orders were Ascomycota and Mortierellomycota. Interestingly, compost enriched the relative abundance of beneficial microorganisms such as Chaetomium, Actinobacteriota, Talaromyces and Mortierella and reduced those of harmful microorganisms such as Alternaria, Aspergillus and Neocosmospora. Functional prediction based on Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed that amplicon sequence variant (ASV) sequences related to energy metabolism, amino acid metabolism and carbohydrate metabolism were associated with compost-treated soil. Based on Fungi Functional Guild (FUNGuild), identified fungi community metabolic functions such as wood saprotroph, pathotroph, symbiotroph and endophyte were associated with compost-treated soil. Overall, compost addition could be considered as a sustainable practice for establishing a healthy soil microbiome and subsequently improving the soil quality and barley crop production.