Nitrogen Transformations and Availability in Soils with Application of Fumigants

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Gross rates of N mineralization, immobilization, and nitrification in soil (Brown Andosol, U.S. Soil Taxonomy : Typic Hapludands), where chloropicrin (28 g m^<-2>) or D-D(1, 3-dichloropropene) (20 g m^<-2>) was applied, were determined using the ^<15>NH_4^+-N isotope dilution technique. Before sowing/planting, the rates of N transformations in fumigated soils were less than 49% of non-fumigated soils. Before harvest, the rates of N transformations in fumigated soil recovered to the level of non-fumigated soil for a sugar beet (Beta vulgaris L.) plot. However, these rates did not recover for spring wheat (Triticum aestivum L.) and azuki bean (Phaseolus anagularis L.) plots. Based on the kinetic analysis of an 84-d incubation, the k(25℃) (rate constant for net N mineralization at 25℃) values of the fumigated soils were 118-123% of the values of the non-fumigated soils and E_a (apparent activation energy) values of the fumigated soils were 82-96% of the non-fumigated soils. Our results indicated that the application of chloropicrin or D-D increased the N availability in soil in spite of a decrease in the gross rates of N transformations.
社団法人日本土壌肥料学会の論文