Efecto de la actividad microbiana sobre la nitrifiación en suelos cultivados con Brachiaria humidicola (Rendle) Schweicerdt en Cereté, Córdoba

Nitrogen fertilizers used in agriculture have increased the emissions of nitrogen oxides to the atmosphere. This study evaluated the production of NO2 - (nitrite) and N03 - (nitrate) by soilborne bacteria during the dry and the rainy seasons in The Reseach Center Turipana, Corpoica, (Cerete, Colombia). A split plot desing with three accessions of Brachiaria humidicola (CIAT 16888, CIAT 26159 and CIAT 679), three levels of nitrogen (0, 150 and 300 kg ha-1) and two time of applications (rainy and dry season) were used. Unplanted plots were used as a control. The Most Probably Number (MPN) of bacterial colonies (Log NMP/10g of soil) was assessed in the rainy and dry season. In addition, the speed of nitrite and nitrate production (mg N-NO2- kg-1 day- 1 ) by soilborne bacteria was determined at the beginning (May) and the end of the rainy season (September). The results showed that the number of bacterial colonies were directly proportional to the nitrogen levels. Consequently, the highest number of MPN of bacterial colonies was observed at the highest level of nitrogen (300 kg ha-1). The nitrite and nitrate production was higher in planted plots compared to unplanted plots. However, the higher production of oxides of nitrogen was observed at the beginning of the rainy season. B. humidicola CIAT 26159 showed the highest production of nitrite at the level of 300 kg of N ha-1 compared to the other two B. humidicola accessions and the control in May. In contrast, B. humidicola CIAT679 was more efficient in the nitrite production compared to the other treatments.