Mineral nitrogen in tropical forest soils

Abstract

1. Δmin-Nad is the most satisfactory measurement for assessing mineralizable-N in the tropical forest soils used; values are treble those for Δmin-Nf and then increase even further on storage. Comparisons of Δmin-Nad are pointless unless methods of sampling, drying, storing and incubating are standardized.2. Δmin-Nad is correlated with total N and organic C but not pH.3. Undisturbed tropical forest soils can produce very large quantities of mineral N, particularly in their surface layers. This probably accounts for the lack of N responses in these soils. More intensive cultivation of these soils is only possible when organic matter is preserved by protecting cleared soils.4. Added nitrogen was leached more rapidly in these soils than in comparable temperate soils but was not fast enough to prevent absorption by plants.