Abstract

ORTIZ, Jimena et al. Long-term impact of fertilization on the structure and functionality of microbial soil community. Cienc. suelo [online]. 2020, vol.38, n.1, pp.45-55. ISSN 1850-2067.

To understand effects of fertilization on microbial communities and processes a long-term fertilization treatment was performed. Since 1999, a field experiment was conducted and variables of structure (DGGE), enzymatic activity (phosphatase, urease, arylsulfatase), potentially mineralizable nitrogen (NAN) and glomalins were measured at two depths (0-5 cm and 5-10 cm). At both depths, fertilizer rates affected microbiological functions of the biomass community differentially. Urease activity was higher for the Control treatment at 0-5 cm depth, while NAN activity was higher for the Control and the Farmer Rate treatment at 0-5 cm and also in the Control treatment at 5-10 cm depth. Phosphatase and glomalin levels were higher for Reposition Rate treatment. Soil acidity and harvest residue volume generated by fertilization could have caused high phosphatase and glomalins values. NAN decrease at higher fertilization rates could have been caused by the mineralization increase generated by the nutrient addition ("priming" effect). Microbial community structure was affected differently by fertilization according to sampling depth. At 0-5 cm depth, richness and evenness were similar between treatments, while at 5-10 cm depth, both indexes were drastically affected by fertilizer application. Evenness was 2.21 and 2.20 for Control and Farmer Rate treatment, and 1.4 and 1.39 for Reposition Rate treatment. Significant correlations were found between the enzymatic activity and the microbial structure at 0-5 cm depth. The sustainability of agroecosystems depends on the balance between the structure and the biological functions provided by soil microorganisms. We hope this study will be crop management decision tool.

Keywords : Enzymatic activity; DGGE; potentially mineralizable nitrogen; bacterial community.

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