Effects of mulching with municipal solid waste (MSW)-compost on the soil microbiota and decomposition activity in a productive vineyard in Apulia (Italy)

Abstract

Application of municipal solid waste (MSW)-compost as a mulching material in vineyards supports sustainable practices and aligns with both circular economy and zero-waste principles.

Aim of the study was to evaluate the effects in vineyard of MSW-compost mulching on the bacterial soil microbiota structure and decomposition activity.

The experiment was conducted in a 5-years-old vineyard (cv. ‘Primitivo’) in Salento (Southern Italy). Vineyard implantation consists of rows, vertical shoot positioning with Guyot pruning. Grapevine plants were divided into groups of 6 plants each, subjected to the following treatments (n=3, completely randomized design):

1. Film-black: mulching with traditional black PE film;
2. Film-b/w: mulching with biodegradable film;
3. Compost (8): mulching with MSW-compost, 8 kg plant-1;
4. Compost (15): mulching with MSW-compost, 15 kg plant-1;
5. Compost (22): mulching with MSW-compost, 22 kg plant-1;
6. Control: no mulching.

MSW-compost consisted of a composted mixture of green residues and the organic fraction of municipal solid waste (MSW) produced by a local company.

Metabarcoding was performed on an Illumina Miseq2 machine (paired end sequencing), targeting the V3-V4 region of the 16S rRNA gene, and included both MSW-compost and soil samples collected in March, July and October 2023. QIIME2 and nested plugins were used to analyze the sequence data, inspect alpha and beta diversity, and assign taxonomy.

Soil decomposition activity was assessed by Teabags method on treatments Film-black, Compost (15) and Control.

No significant effects were obtained on both alpha and beta diversity, likely due to a high sample heterogeneity; however, plots showed an impact of the MSW-compost on the soil microbiota structure: compost-treated samples segregated from control in July but notably less in October, indicating a reduction of the effect over time. Some genera contributed more to group stratification, by decreasing in the compost-treated samples: Rubellimicrobium, unidentified genera of the Azospirillaceae family; Candidatus_Alysiosphaera; unidentified genera of Chloroflexi (order Kallotenuales); WD2101 (phylum Planctomycetota); unidentified genera of the Geodermatophilaceae family, and Rhodocytophaga. Pairwise comparisons based on fold change showed significantly increased or decreased taxa.

Teabags index showed that MSW-compost stimulated the soil decomposition activity in the first 3 months after its application.