Predicting the nitrogen‐supplying power of acid forest soils from data on the release of CO2 and NH3 on partial oxidation

The amounts of CO2 and NH3 released when the soil was digested with a mixture of orthophosphoric acid and chromic acid, or chromate, were used to predict the capacity of forest soils to mobilize nitrogen. By multiple regression analysis, the CO2 and NH3 release data were calibrated against or adapted to the figures of mineral nitrogen accumulation during 9 weeks of incubation at 20°C. The functions so obtained were used to calculate the soil content of “readily mineralizable N”; (=Nmin). For the digestion procedure proposed (Procedure 1) the correlation between the values for mineral N accumulation during incubation and for “readily mineralizable N”; was characterized by the coefficients 0.92 and 0.88, regarding humus and corresponding mineral soils, respectively. The CO2‐C:NH3‐N ratio provided a better estimate of the soil capacity to net mineralize nitrogen than did the ratio of Ctot:Ntot It was concluded, furthermore, that from the data on Ntot and NH3 release on digestion, a reliable estimate of the soil's capacity to accumulate mineral nitrogen during incubation could be obtained.