Microbiota Diversity Change as Quality Indicator of Soils Exposed to Intensive Periurban Agriculture.

In Argentina, periurban agriculture is performed by farmers with inadequate training in the use of pesticides and chemical fertilizers, developing horticulture with serious soil deterioration. The aim of this work was to monitor bacterial diversity of a horticultural soil (S) and a reference soil (R) as quality index for the design of future restoration strategies. As crops changed together with the agrochemical applications, sample collection was before harvest for strawberries, post-harvest for red peppers, pre-harvest broccoli crop and of a resting soil in treatment with poultry litter as a fertilizing amendment. Bacterial diversity was analysed by the use of high throughput sequencing of the V1-V3 region of the 16S rRNA gene. Analysis of R soils seemed relatively constant in time, enriched in Alphaproteobacteria and Acidobacteria consistent with a reference to soil health. The effect of the intensive use of S soils was proved by differences in Chloroflexi, Bacteroidetes and Proteobacteria relative abundances. The main evidence of the alteration of S soils was the increase in Bacteroidetes and Betaproteobacteria. A weak recuperation trend of S soil microbiota was registered during a post-harvest inactive period. A strong influence of the soil use routine-consisting in high crop rotation and short time-rest cycles-on microbial community structure was verified. These results indicate the microbiota perturbation, caused by the intense use of periurban agriculture soils and will contribute for further actions to improve environment quality.