Materials and duration of mulching mediate soil and fruit quality in citrus orchard

AimsMulching is a prevalent agricultural practice in citrus orchards, yet the microbiological mechanisms underlying film mulching require further investigation.MethodsIn this study, five mulching materials (traditional flat planting with no mulching (CK), black film mulching (B), reflective film mulching (R), corn stalk mulching (S), white film mulching (W)) and three mulching durations (3 months (starting in September), 4 months (starting in August) and 5 months (starting in July)) were utilized to investigate the influence on the soil stoichiometric characteristics, microbial community, and fruit qualities in Beni-Madonna tangor (Citrus nanko x C. amakusa) orchards.ResultsIn summary, mulching treatments significantly enhanced both soil quality and fruit quality, a mulching duration of 5 months using corn straw emerged as the optimal combination. However, with the extension of film mulching time, the diversity of soil microorganisms and the abundance of bacteria showed a trend of increasing first and then decreasing, while the abundance of fungi gradually increased. Different mulching materials had substantial impacts on soil microecology. Mulching durations had a more significant effect on bacteria, while the type of mulching material had a greater impact on fungi. There was a strong correlation between dominant flora and soil properties as well as fruit quality. With the exception of Proteobacteria and Chytridiomycota, dominant microorganisms exhibited positive correlations with TSS, TA, and b values of fruit. Acidobacteria, Chloroflexi, and Candidate_division_WPS-1 showed negative correlations with soil available phosphorus (AP), available potassium (AK), while Chytridiomycota was negatively correlated with soil pH. Based on redundancy discriminant analysis (RDA) and random forest (RF) analysis, the contribution of core flora to different indexes was different. Functional prediction revealed that corn straw mulching and extended mulching periods could enhance the abundance of core flora in soil, thereby enriching metabolic pathways such as hydroxypropanoate cycle metabolism, organic acid degradation, and amino acid synthesis.ConclusionsMulching treatment significantly influences the chemical properties of soil, which in turn affects the quality of citrus fruit. Additionally, changes in soil characteristics are influenced by the diversity and abundance of soil microorganisms. Bacteria directly affect more soil properties and fruit color, while fungi have a stronger interaction with pH. The functions of the core microbiota like Bacteroidetes, Chloroflexi, Nitrospirae, Candidate Division WPS-1, Glomeromycota, Armatimonadetes and Aphelidiomycota are highly correlated with the phenotypic characteristics of the soil and fruits. Covering citrus orchards with dry corn stalks for five months each year is the recommended method of mulching.