CONICET | Buscador de Institutos y Recursos Humanos

Microbial parameters are considered to be potential indicators of the 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 analyze 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/soybean rotation with no-till farming system. Six fertilization treatments were evaluated: PS, NS, NP, NPS, NPSm, and CK (control unfertilized). Application of N, P and S, with several exceptions, tended to increase both total and available nutrients in comparison with nutrient-deficient treatments. In both growing seasons, CK treatment tended to show the lowest value of TOC, and NPS and NPSm showed the highest values of grain yield. Except for dehydrogenase activity, soil basal respiration and enzyme activities tended to increase in fertilizer 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 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.