Nitrogen mineralisation in a sandy soil under native eucalypt forest and exotic pine plantations in relation to moisture content

Abstract

Incubation tests were carried out to identify potential rates of ammonification and nitrification in the surface layer of a sandy soil collected from both a native eucalpyt forest and an adjacent mature Pinus radiata plantation. Tests were conducted over a range of soil moisture contents and incubation periods covering 15-90 days. Ammonification rate was very high despite a C/N ratio in both soils of 31, but extractable nitrate plus nitrite was only dected for the longest incubation period. Ammonification was strongly dependent upon soil moisture content and was slightly higher in soils under eucalypt where up to 135 ppm ammonium was detected after 90 days. The significance of these results in relation to the establishment of P. radiata plantations is briefly discussed.