INFLUENCE OF 12-YEARS OF NPS FERTILIZATION ON SOIL QUALITY, MICROBIAL COMMUNITY PROFILE AND ACTIVITY UNDER CONSERVATION AGRICULTURAL MANAGEMENT

Resumen

Microbial parameters are considered to be potential indicators of soil quality since soil microorganisms can respond rapidly to
agricultural management systems. The effect of long-term fertilizer applications on soil, especially nitrogen (N), phosphorus (P),
sulphur (S), and micronutrients (m) can alter soil chemistry, microbial community structure and function. The purposes of this
study were to analyse the long-term effect of chemical fertilizers on soil properties, microbiological communities and function
in relation to grain yields in two growing seasons (2012-2013 and 2013-2014). All fertilization treatments were applied to
a maize-wheat/soybean rotation under no-till farming system. Six fertilization treatments were evaluated: PS, NS, NP, NPS,
NPSm, and CK (unfertilized control). Application of N, P, and S, with several exceptions, tended to increase both total and
available nutrient in comparison with nutrient-deficient treatments. In both growing seasons, CK treatment tended to show
the lowest value of TOC (total organic carbon), whereas NPS and NPSm showed the highest values of grain yield. Except for
dehydrogenase activity, soil basal respiration and enzyme activities tended to increase in fertilized treatments compared to CK.
In 2012-2013, NPSm had the highest abundance of Gram-negative and Gram-positive bacteria. In 2013-2014, CK showed
the highest abundance of actinomycetes and the lowest of Gram-negative bacteria. In addition, NPSm had the highest values of
total PLFA (phospholipid fatty acid) biomass in both growing seasons. Soil microbial enzymes were mainly correlated with soil
pH, indicating that soil alkalinity is a key factor governing soil enzyme functionality.