Monitoring stream sediment, nitrogen and phosphorus concentrations research

This is a joint project between Beef + Lamb NZ and Massey University’s Fertiliser and Lime Research Centre (FLRC). The project is monitoring nutrient and sediment concentrations in a hill country stream at Tuapaka and identifying climatic and management practices which increase losses.

Around 60% of land area in the Manawatu catchment is used for sheep and beef grazing and most of this is in hill country. Therefore contributions of nutrients and sediments from grazed hill country to the Manawatu River could be very important, due to large land areas

Why is it important?

This research aims to future-proof farming in the Manawatu. OnePlan nitrate loss restrictions don’t currently cover beef and sheep production, but may apply in the future. The project aims to improve our understanding of nutrient loss in these systems to inform future decision-making in the region.

About the study

This study monitored nutrient and sediment concentrations in selected streams and a seepage wetland on Massey University’s Agricultural Experimental Station at Tuapaka, Palmerston North since April 2013.

The monitoring program covers a catchment area of 137 ha (approximately 25% of the Tuapaka farm area) and monitors stream volumes every 10 minutes and samples for sediment, total nitrogen (N) and phosphorus (P), nitrate and dissolved reactive P (DRP) concentrations every two weeks. This program allows us to examine changes in nutrient and sediment concentration as water moves through the farm. To date it has provided some preliminary insights in to the effects of fertiliser application, grazing and season on water quality parameters. Some water enters Tuapaka from neighboring properties, so it is important that we keep this in mind when interpreting results.

Tuapaka Farm is set up with weirs and water quality monitoring sites in strategic locations – where a stream enters the farm, at the bottom of a paddock (Weir paddock 9), at the bottom of the hills (Main weir) where the stream enters a wetland, where the stream leaves a wetland and at the bottom of the farm on the flats (bottom weir).

Preliminary results

Total N and nitrate

Total N concentrations were generally low (<1 mg N/L), with the exception of when water sampling occurred on the same day that urea was aerially spread over the monitoring area (20/5/2013). As a result of the fertiliser application, stream total N concentrations at the paddock 9 weir increased to 22 mg N/L. The effect of N fertiliser application on stream N concentrations is likely to be short lived, as a subsequent application (2/9/2013) which occurred between water sampling periods, was not detected. Stream nitrate concentrations were generally very low and often below our laboratory detection limit of 0.25 mg nitrate-N/L. An exception to this was when cattle were grazing in the monitoring area, as stream nitrate concentrations appeared to increase to 1-1.5 mg nitrate-N/L as a result, and further investigations are planned for this winter to test this observation.

Total P and dissolved reactive P

Stream total P and DRP concentrations were generally below our laboratory detection limit of 0.03 mg P/L and do not appear to be influenced by cattle grazing. Elevated total P concentrations tended to be associated with elevated sediment concentrations

RESEARCH DATA

Total nitrogen

Nitrate

Total PHOSPHORUS

DISSOLVED REACTIVE PHOSPHORUS

Key contact

  • Dr Lucy Burkitt

    Dr Lucy Burkitt

    Senior Research Officer - Institute of Agriculture and Environment

The team

  • Dr Mike Bretherton

    Dr Mike Bretherton

    Lecturer - Institute of Agriculture and Environment

  • Dr Lucy Burkitt

    Dr Lucy Burkitt

    Senior Research Officer - Institute of Agriculture and Environment

  • Dr Ranvir Singh

    Dr Ranvir Singh

    Senior Lecturer in Environmental Hydrology and Soil Science - Institute of Agriculture and Environment

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