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Low-temperature storage gave significant increases in the amounts of extractable ammonium-nitrogen and phosphorus in four soil types. The changes in nitrate-nitrogen and particularly in potassium and calcium were less pronounced and varied according t o the soil studied.Low-temperature storage of soils which had been air-d-ried previously caused similar changes.In view of these findings it is considered that deep-freeze storage should not be used when extractable nutrients are t o be dctermincd.The effects were generally greater in the organic soils.

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A wet oxidation digestion previously developed for plant material has now been evaluated for a range of British soil types. The traditional Kjeldahl procedure using sulphuric acid, salt and catalyst was modified to include hydrogen peroxide as an additional oxidant. The method is suitable for estimating both nitrogen and phosphorus in soil and overcomes the need for separate digestion procedures for these elements. It compared favourably with a normal Kjeldahl method for nitrogen and with a mixed acid oxidation system for phosphorus and recovery was complete after two hours. Total phosphorus and organic nitrogen were recovered together with labile ammoniumnitrogen. Nitrate-nitrogen would require a further modification and the recovery of 'fixed' lattice ammonium-nitrogen was not assessed. Samples had to be finely ground to achieve good precision and recovery. 551