Chemical and biochemical properties as potential indicators of disturbances

The response of a series of soil microbial, chemical, and enzymatic chacact eristics to two different tillage systems (conventional and no-tillage) and two crop rotations (continuous corn and soybean-corn) was evaluated in a l ong-term field experiment in the Rolling Pampas Region, Marcos Juarez, Cord oba, Argentina. The parameters studied included: oxidizable, soluble and re spiration C, total and hydrolyzable N, microbial activity, ammonifiers, nit rifiers, cellulolytic and total microflora, protease and urease activities. After 15 years, oxidizable C, total N and hydrolyzable N showed no differe nces regarding no-tillage systems. However, differences were found regardin g control soil. While soluble C did not exhibit any significant differences , respiration C and microbial activity were indicators sensitive to differe nt treatments. Enzymatic activities, protease in particular, did reflect ch anges due to management. Fluctuation in microbial population counts were mo re related to plant residues than to tillage systems.