THE EFFECT OF DIFFERENT SOIL-MANAGEMENT PROCEDURES ON CARBON-CYCLE COMPONENTS IN AN ENTIC HAPLUDOLL

Sampling on different plots of a field located in Pehuajo, Buenos Aire s Province, Argentina, on an Entic Hapludoll, was conducted to determi ne the effect of different soil management procedures on carbon cycle components. The plots studied were: A) eight years of mixed pasture fo llowed by oat (Avena sativa L.) crop, B) five years of mixed pasture f ollowed by maize (Zea mays L.) with direct drilling, and C) five years of mixed pasture followed by maize crop with conventional tillage. Th e sampling was done during the month of June 1994. By that time, plot A was in oat production and plots B and C were in fallow. Microbial bi omass carbon (MBC) values differed significantly between the three plo ts, whereas no differences were found in the organic carbon (OC) conte nt. Plots B and C differed both in respiration and qCO2 (the ratio bet ween C-CO2 released by respioration and the microbial biomass C). For the latter, no differences had been found as a function of the tillage system in a previous work that was carried out on another region of A rgentina. Theoretical calculations on the CO2 release from the soil to the atmosphere were inferred from the respiration values previously f ound.