ChileanJAR

The effects of tillage (conventional vs no-till), management of residues (retention vs removal), and rotation (continuous wheat, continuous maize, wheat-maize, medicago-wheat, medicago-maize, oats/vetch-wheat and oatslvetch-maize), on C and N microbial biomass in soil. The experiment begun in 1991 and the present work covered the agricultural cycle of 1993 (the third year of the experiment). The C-biomass was affected by both tillage system and management of residues. Microbial biomass increased 30-40% under no-till and 20-30% under residue retention. N-biomass was highly correlated wíth C-biomass (r =0.86**), and no-till with residue retention had the highest values ofthe treatments (38,55 and 92% for no-till/remove, conventionallretention and conventionall remove, respectively). The determination ofmicrobial biomass appears to be easierthan measurement of organic-C and total N to evaluate the effects of management practices in soil.