Title: MINERALIZATION IN TALLGRASS PRAIRIE AND AGRICULTURAL SOIL PROFILES
Rice, C - KANSAS STATE UNIVERSITY
Sotomayor, D - KANSAS STATE UNIVERSITY
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 1998
Publication Date: N/A
Interpretive Summary: Changing land use and fertilizer management practices affect decomposition of organic materials in soils. Dissolved organic carbon can percolate from the surface into the vadose zone and groundwater and may affect N in the ecosystem. This study was conducted to determine potentially mineralizable organic C and N and rate constants in the surface and subsurface soils of prairie and cultivated lands. This study found that cultivation and fertilizer application increase the potentially mineralizable organic C and N in most layers of the soil profile. The potentially mineralizable C and N in the surface soil (0-0.2 m) represented 11.6% and 12.2% of the total organic C and N pools for the tall grass prairie soil profile, respectively, and 21.0% and 10.2% of the total organic C and N pools for the agricultural soil profile. Information from this study contributes to our knowledge on the N and C fluxes in the ecosystem. Results can be used to develop long-term management strategies that protect the environment.
In situ mineralization of N may contribute significantly to total inorganic N pools deep in the soil profile. We conducted long-term laboratory incubation experiments to evaluate the net C and N mineralization in soils collected from various depths in tall grass prairie and agricultural fields of the same geological materials and soil type. Samples were packed to a bulk density of 1.4 in 5 cm diameter x 10 cm long cores. The cores were incubated at 35 degrees centigrade for 40 wks in sealed containers. Net C mineralization was measured by evolved carbon dioxide and N mineralized was measured by periodic leaching with ammonia and nitrate measured in the leachate. Carbon and N mineralization in the surface horizon were greater in the tallgrass prairie than in the agricultural soil. In both the tallgrass prairie and agricultural soil profiles, C mineralization was least at the water-table depth. Carbon mineralization was described by a first-order kinetic model, but N mineralization was described better by a consecutive (sigmoidal) reaction model.