MICROBIAL GROUPS IN A MILPA AGROECOSYSTEM INTERCLASSED WITH FRUIT TREES IN HIGH VALLEYS OF PUEBLA, MÉXICO

Background: Microorganisms play a fundamental role in soil dynamics of agroecosystems. Objective: To determine soil quality parameters and the abundance of functional groups of edaphic microorganisms in eight different contrasting sites evaluated in a milpa agroecosystem interclassed whit fruit trees (MIAF) and in monocultures system. Methodology: Bulk density, humidity, pH, electrical conductivity, percentage of ash, oxidizable organic matter, oxidizable carbon, total nitrogen, inorganic nitrogen and nutrients (NO 3 - , Na + , Ca 2+ and K + ) were determined in composite soil samples by triplicate for each sites, as well as the diversity of weeds and abundance of total actinomycetes, nitrogen-fixing actinomycetes, yeasts, fungi, bacteria, and arbuscular mycorrhizal fungal spores. A principal component analysis was carried out to calculate a soil quality index (SQI). Analysis of variance, Tukey's mean comparison test (P ≤ 0.05), linear correlation, cluster analysis and canonical correlation were performed. Results: A greater amount of total actinomycetes (> 4 Log CFU g -1 soil) and nitrogen-fixing actinomycetes (> 3.8 Log CFU g -1 soil) and fungi (> 1.7 Log CFU g -1 soil) were observed in the MIAF system compared to the monocultures. For the sites with corn-bean association in the MIAF system, a high positive correlation was observed between organic matter content and nitrogen-fixing actinomycetes (r = 0.60) and yeasts (r = 0.73), as well as with the percentage of total nitrogen with yeasts (r = 0.70) and nitrogen-fixing actinomycetes (r = 0.75). Implications: The methodology used allowed the grouping of the sites studied, based on the SQI and a reduced set of variables. Conclusion: The MIAF system favored the abundance of functional groups, soil quality parameters and the availability of nutrients in the soil compared to the monoculture sites.