Corn crop residue decomposition and related parameters

The efficacy of no-tillage systems in reducing water erosion depends largely on the soil cover by crop residues. The study was carried out in Santa Catarina State, Southern Brazil, from August 2001 to July 2002, aiming to evaluate the decay of corn residue on the surface of an Inseptisol and its influence on soil properties. The treatments, with three replicates, were: bare soil (BS), 8.77 Mg ha(-1) of air dried corn residue (CR) and 8.77 Mg ha(-1) of air dried corn residue plus 100 kg ha(-1) of nitrogen (CR + N). The remaining residue biomass on soil and its organic carbon and total nitrogen contents were evaluated every 30 days. It was also determined organic carbon, total nitrogen, potassium, pH, soil temperature, and moisture in the superficial 0-0.03 m soil layer. The atmospheric temperature was recorded one meter above the soil surface. The CR + N treatment presented a faster decomposition rate than CR, especially in the first 120 days. The estimated time needed for an almost total decomposition of the corn residue was, approximately, 1300 days for CR and 900 for CR + N.