Assessing Stability of Humus in Soils from Continuous Rice-Wheat and Maize-Wheat Cropping Systems using Kinetics of Humus Desorption

摘要

To assess soil quality with respect to carbon sequestration, one should know not only the amount of carbon present in soil but also the strength with which the carbon is held to the mineral surfaces. A chemical method based on batch desorption of adsorbed humus on clay humus complex by sodium hydroxide-sodium pyrophosphate solution was used to assess the stability of humus carbon using soils from two systems of continuous cropping such as rice-wheat and maize-wheat. Humus desorption data were found to be very closely fitted to a linear combination of three first-order equations indicating three different pools of carbon. Humus retention was found to be related to poorly crystalline smectites. Rice-wheat system showed greater contrasting difference in humus stability than maize-wheat system along the depth of the soil profile.