Overseer - South Canterbury Hill Country

OVERSEER® is a nutrient budgeting model that is widely used in New Zealand and is required to be used under some regional council policies. It can be used for in the assessment of a wide range of nutrient and farming systems. Understanding the fate of these nutrients is an important precursor to developing a Nutrient Management Plan.

Environment Canterbury (ECan) and the Lower Waitaki Zone Committee (ZC) have been running a collaborative community process to help decide on water quality and quantity limits for the proposed South Canterbury Coastal Streams (SCCS) area. This case study briefly  describes work undertaken to help provide estimates of nitrogen (N)-loss from the hill country in the SCCS area.

The study aimed to estimate nitrogen loss (N-loss) OVERSEER® predictions for a representative range of land uses on the south Canterbury hill country. This was undertaken to provide estimates of N-loss for land use and soil combinations that had not already been covered in existing studies in an effort to better understand farming practices and nutrient budgets in the region. The aim of this study was to ultimately use OVERSEER® N-loss predictions to inform future planning around water quality and quantity limits throughout SCCS.

OVERSEER case study picture

Catchments and soil classes defined for the SCCS area.

 

For this study information from local farmers, rural professionals and Landcare Research was used to generate a farm system representative of the land use and farm systems found within study area. These inputs to the model went a long way to ground truth the nutrient and financial budgets associated with local properties.

Findings and Conclusions

The OVERSEER® model was used to generate estimates of N loss under two crop types, three soil types and three rainfall scenarios. The results have thus provided estimates of N-loss for land use and soil combinations that were not already covered by the existing Canterbury N-loss look-up tables at the time. The results have been used to help calculate estimates for the total catchment and sub-catchment N loads under current and future scenarios in the SCCS area.

OVERSEER table results

 

The results have thus provided estimates of N-loss for land use and soil combinations that were not already covered by the existing Canterbury N-loss look-up tables at the time. The results have been used to help calculate estimates for the total catchment and sub-catchment N loads under current and future scenarios in the SCCS area.

Associated Models

OVERSEER®

OVERSEER® is a nutrient budgeting model that is widely used in New Zealand and is required to be used under some regional council policies.

References

Fietje, L. (2014): Estimating nitrogen loss from land uses in the hill country of the South Canterbury Coastal Streams (SCCS) area. Environment Canterbury Report No. R14/129