Effects of air‐drying and air‐dry storage on the mineralisable‐nitrogen of soils

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Abstract
Samples of eight soils were air‐dried and stored in brown‐paper or in sealed polythene bags for periods up to 98 weeks. Portions of the fresh and re‐wetted air‐dry soils were incubated at 25° for 10–84 days. the soils were extracted before and after incubation and the increase in mineral‐N (NH4+‐N + NO3−‐N) content (Δ Mineral‐N) was measured. Air‐drying increased Δ Mineral‐N. Air‐dry storage further increased Δ Mineral‐N, the value increasing with the period stored, but the mineralisable‐N of soils kept in sealed polythene bags increased less than that of soils in paper bags, the increases occurring only in the easily mineralisable‐N; most of the extra mineral‐N was formed during the first 10 days incubation and all by 42 days, thereafter the air‐dried soils had the same rate of mineralisation as the fresh soils. the mineral‐N content of the air‐dry soils increased with storage.In a further similar test with 14 soils, air‐dried and stored in brown‐paper bags for periods up to 32 weeks, the mean value of Δ Mineral‐N varied irregularly with time of storage up to 18 weeks but thereafter increased with increasing period of storage before incubation. the mineral‐N content of the air‐dry soils varied, the maximum value being found in the samples stored for 12 weeks.