A wet oxidation procedure suitable for total nitrogen and phosphorus in soil

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Abstract
A wet oxidation digestion previously developed for plant material was evaluated for a range of British soil types. The traditional Kjeldahl procedure using sulfuric acid, salt and catalyst was modified to include hydrogen peroxide as an additional oxidant. The method is suitable for estimating both N and P in soil and overcomes the need for separate digestion procedures for these elements. It compared favorably with a normal Kjeldahl method for N and with a mixed acid oxidation system for P and recovery was complete after 2 h. Total P and organic N were recovered together with labile NH4-N. NO3-N would require a further modification and the recovery of fixed lattice NH4-N was not assessed. Samples had to be finely ground to achieve good precision and recovery.