Determination of total phosphorus in soil using simple Kjeldahl digestion

A Kjeldahl digestion method normally used for total nitrogen (N) was compar ed with NaOH fusion and dry ashing met:hods for determination of total phos phorus (P). Overall there was good correlation between the methods (r(2)=0. 996). Results from the digestion method were on average 3.7% lower than the fusion and dry ashing methods, but there were significant differences betw een methods as shown by the regression analysis. The digestion method prove d suitable for analysis of highly organic soils and some soils from the Pac ific Islands. It was also useful for estimation of total P in well-weathere d soils such as Oxisols and in A horizons, but not suitable for less weathe red mineral soils.