A field experiment was carried out on a clayey dystrophic Dark-Red Latosol at the Limeira Experimental Station of the Instituto Agronômico (Cordeirópolis, State of São Paulo, Brazil), to evaluate the respiratory activity of the soil when enriched with stillage and treated with the herbicide 2,4D. Stillage was applied three times with a six month interval at 0, 100, and 1,000 m³/ha, and the CO2 evolution measurements began six months after the last application. The soil was maintained free from vegetation all over the experiment. The CO2 was trapped by KOH in PVC cilindric chambers, and collected every 12 hours for analysis, during four days. Highest CO2 evolution rates (77.5mg CO2/m².h) were observed in daytime. Even six months after stillage application, the rate of CO2 evolution was higher in treated soils. The herbicide, applied at 3,0 l/ha, showed no significant influence on soil respiratory activity.
stillage; herbicide 2,4D; soil respiration; microorganisms