Learn more about the NZ-DNDC project


NZ-DNDC is a modified version of DNDC that includes a number of alterations to best reflect the conditions found in New Zealand and was developed by a team at Landcare Research in New Zealand. The presence of distinctive and diverse soil types within a short distance and soils having a higher organic carbon content than the world average; coupled with climatic conditions and grazed pastoral systems which differ from many other countries meant that the application of the DNDC model to New Zealand was challenging. 

Originally, the relationship between air and soil temperatures in the DNDC model was based on northern hemisphere conditions.  This was altered for the New Zealand model, based on calculations using New Zealand specific national soil and air temperature datasets.  The Water Filled Pore Space (WFPS) threshold value to switch dentrification on/off was also altered in this version of the DNDC from a value to 35% to the field capacity value.  Additionally, the model allows soil saturation by simulating drainage followed by infiltration (the reverse of the DNDC), which is representative of the winter months. 

Annual pasture growth rates vary with season in New Zealand, with growth rates typically highest in spring and lowest in winter.  A multiplicative day-length factor was introduced into NZ-DNDC to reflect the seasonal changes and produce N uptake rates typical of New Zealand (more N is taken up on longer days, less on shorter days).  Excretal-N inputs from grazing animals were also included in the model and are described further in Saggar et al. (2004).

Total yearly N2O emission estimates from both grazed and ungrazed pastures in New Zealand were found to be within the uncertainty ranges of measured data.  The model reflected observations due to climatic variations in rainfall and differences in soil texture on field scale experiments; measured emissions changed with varying soil moisture and were approximately 20% higher in silt loam soil (poorly drained) than in sandy loam soil (well drained). Saggar et al. (2004) found the model to effectively simulate most of the patterns in WFPS and nitrous oxide (N2O) emissions observed on grazed and ungrazed land.  The model represented real variability in the processes regulating N2O emissions and is suitable for simulating emissions for a range of New Zealand grazed pastures. 

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