C and N turnover in structurally intact soils of different texture

摘要: The turnover of native and applied C N in undisturbed soil samples different texture but similar mineralogical composition, origin cropping history was evaluated at –10 kPa water potential. Cores structurally intact with 108, 224 337 g clay kg-1 were horizontially sliced 15N-labelled sheep faeces placed between the two halves core. cores together unamended treatments incubated dark 20°C evolution CO2-C determined continuously for 177 d. Inorganic microbial biomass 15N periodically. Net nitrification less amended compared soil. When adjusted NO3-N present before applied, net became negative indicating that had been immobilized or denitrified. most rich nitrified least 15N. amounts retained soils increased content. A maximum 13% recovered soils. content from sandy reduced due to a low potentially mineralizable whereas rate constant mineralization peaked this pool assumed proportional volumetric content, three contained proportions remained highest clay. Thus although availability ensured by their identical matric potential, actual volume seemed determine proportion total mineralizable. (70% C), again higher It is hypothesized constants fluctuate long term result irrespective texture.