Interactions of nitrogen fertilizers and forest humus—i fir and black pine |
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| Authors: | G Nakos |
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| Institution: | Soil Science Laboratory, Forest Research Institute, Terma Alkmanos, Athens 615, Greece |
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| Abstract: | In incubation experiments in the laboratory interactions of urea or NH4NO3 with humus from stands of fir (Abies cephalonica, Loudon) growing on soils developed from flysch (shales) and limestone and with humus from stands of black pine (pinus nigra, Arn.) growing on soils developed from peridotites, limestone and schists were investigated.Fir humus from stands on flysch and limestone and black pine humus from limestone showed nitrification but it was absent from black pine humus from stands on peridotites and on schists. Humus from stands on schists showed appreciable ammonification. Increasing concentrations of urea did not initiate nitrification in the latter type of humus. No substantial N immobilization was detected in spite of relatively high P immobilization. Increases in concentration of Ca, Mg and K occurring on incubation of humus samples were related to the ability of a humus type to nitrify rather than to concentrations of added urea-N.Urea was hydrolyzed rapidly to NH+4 during contact with various types of humus, resulting in an increase of pH. Production of NH+4 from urea was only minimally affected by drying the humus samples at 70°C for 20 h before incubation but was reduced to 30% at 1–5°C. |
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