Rate of aerobic nitrogen transformations in six acid climax forest soils and the effect of phosphorus and CaCO3 uri icon


  • Nitrogen transformations (mineralization, nitrification, and nitrous oxide production) were evaluated in acid forest floor soils collected from six climax forest sites on Blackhawk Island, Wisconsin. Soils' acidity (CaCl2) ranged from pH 3.9 to 5.1, and organic matter concentrations varied from 2.4 to 59.0 percent. The samples were incubated aerobically for 4 weeks at 30°C under field moist conditions. Treatments were: control; 100 mg P (as KH2P04) kg-1 soil; CaCOa; and P with CaC03.Nitrification of mineralized N ranged from nearly complete in the SM Alfisol to almost nonexistent in the Histosol. Addition of P had little effect on ammonification or nitrification. Liming, however, greatly enhanced ammonification on nonnitrifying or slowly nitrifying soils and both ammonification and nitrification in nitrifying soils. Adding P and lime together did not affect N transformations compared to liming alone. Nitrous oxide emission rates in the soils were related to nitrification. From 0.03 to 0.3 percent of the NH4-N nitrified was released as NzO-N. Phosphorus addition had little effect but liming increased N20 emission rates in soils where nitrification was also enhanced

publication date

  • 1985