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

Abstract

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 N. By multiple regression analysis, the CO2 and NH3 release data were calibrated against or adapted to the figures of mineral N accumulation during 9 wk of incubation at 20.degree. C. The functions so obtained were used to calculate the soil content of readily mineralizable N (=Nmineral). 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 N than did the ratio of Ctotal:Ntotal. From the data on Ntotal and NH3 release on digestion, a reliable estimate of the soil''s capacity to accumulate mineral N during incubation could be obtained.