Disruption of soil aggregates by varied amounts of ultrasonic energy in fractionation of organic matter of a clay latosol: carbon, nitrogen and delta(13)C distribution in particle-size fractions

azote brasil brazil carbon carbone carbono clay soils ferralsol ferralsoles ferralsols fracciones del suelo fraction du sol irradiation nitrogen soil soil organic matter soil separates sol sol argileux suelo suelo arcilloso ultrason ultrasonics ultrasonido