In situ measurements of soil mineral-nitrogen fluxes in hoop pine plantations of subtropical Australia

Abstract

The dynamics of nitrogen (N) mineralisation, plant uptake of nitrogen, and leaching in the 0-10 cm soil depth were studied in hoop pine (Araucana cunninghamii Ait. ex D.Don) plantations aged 0,3,10,14, and 62 years with in situ incubation cores. Although ammonium-nitrogen was the dominant form of mineral-nitrogen in the 0-10 cm soil depth, nitrification was also an important process in hoop pine plantation soils, indicating that there might be a potential for nitrogen losses through leaching and denitrification, particularly at recently clearfelled sites.
The results indicated that most net nitrogen mineralisation and plant uptake of nitrogen occurred during the growing season between October and May. The amount of nitrogen mineralised from soils during this period ranged between 25 and 53 kg N/ha, representing, on average, 2% of the total nitrogen pool in the 0-10 cm soil depth. Net nitrogen mineralisation was significantly correlated with the soil organic carbon (C), total nitrogen, carbon/nitrogen ratio, and plantation age.