La aplicación de lodos residuales afecta, a corto plazo, la biomasa microbiana y su actividad en suelos sódicos

The effect of applying sewage sludge to sodic soil on C and N mineralization, microbial biomass, microbial enzymatic activity and biological indicators were evaluated. The sodic soil was agricultural, and the incubation experiment was performed at the laboratory level at 56 days with three treatments: control sodic soil group (T1), sodic soil + sewage sludge at 20 Mg/ha (T2) and at 40 Mg/ha (T3). The results obtained for T2 and T3 were: 56.89 and 33.81 % mineralized C, 3.04 and 1.66 % mineralized N, 0.81 and 0.50 % immobilized carbon by microbial biomass in relation to control (T1). The microbial enzymatic activity increased 2.81 and 3.59 times for T2 and T3 with respect to T1. In the biological indicators qCO₂, qFDA and N_min/C_mic, an increase was observed at the beginning of the mineralization dynamics and gradually decreased over time. The application of sewage sludge to sodic soil had a positive effect on the mineralization of C and N, as well as microbial biomass in the short term. The T2 treatment presented a greater efficiency in the mineralization and immobilization of C, but with respect to N mineralization and microbial enzymatic activity no significant differences were found between T2 and T3. It is recommended to evaluate the application doses of the sewage sludge before its application to sodic soils. It is the first time that the use of biological indicators has been reported to evaluate the application of sewage sludge in a sodic soil of Mexico.