Denitrification in, soils in relation to nitrate source

The effect of different nitrate sources, i. e. Ca(NO₃)₂, KNO₃, and NH₄NO₃ at a level of 2000 ppm nitrate-N on denitrification in starch-amended (0.5 % C) samples of alluvial non-saline (clay), alluvial saline (heavy clay), alluvial alkali (clay loam), and calcareous (sandy loam) soils during incubation at 30 °C and moisture content at the water holding capacity of the soil was studied. Calcium nitrate favoured the reproduction of denitrifying bacteria in the alkali soil, thus organic nitrogen content increased and also more rapid nitrate disappearance occurred, but with subsequent lower nitrogen losses. Potassium nitrate favoured the denitrifying bacteria in each of the non-saline, saline, and calcareous soils; nitrogen losses under this treatment were reduced in both the non-saline and saline soils and increased in the alkali and calcareous soils. Ammonium nitrate inhibited the denitrifying bacteria in all soils tested and thus lowered the intensity of the increase in organic nitrogen content. Inspite of the least rate of nitrate consumption, nitrogen losses were reported to be high. The treatment with NH₄NO₃ resulted in the highest nitrite accumulation in all soils tested. The absolute loss of nitrogen from the differently treated soil samples was highest in the alkali soil, followed by the calcareous, non-salire, and saline soils, respectively.

Drei alluvialen Böden (einem nicht salzhaltigen Ton [I], einem salzhaltigen schweren Ton [II] einem alkalihaltigen tonigen Lehm [III]) und einem kalkhaltigen sandigen Lehm [IV] wurden Stärke (0,5 % C) sowie Ca(NO₃)₂, KNO₃ und NH₄NO₃ in Höhe vom 2000 ppm zugesetzt (Bebrü-tungstemperatur: 30 °C, Feuchtigkeitsgehalt: 100 % WK). Ca(NO₃)₂ begünstigte die Reproduktion der Denitrifikanten in III, Norg. stieg an und Nitrat-N verschwand, wobei die N-Verluste späterhin niedrig waren. KN03 förderte die Denitrifikanten in I, II und IV; die N-Verluste wurden reduziert in I und II, in III und IV jedoch erhöht. NH₄NO₃ inhibierte die Denitrifikanten in allen Böden und erniedrigte daher die Intensität der Zunahme an Norg.- Die N-Verluste waren hoch. Es wurde in allen Böden die höchste Nitritanreicherung festgestellt. — Der absolute N-Verlust aus den unterschiedlich behandelten Böden war am höchsten bei III, gefolgt von IV, I und II.