Water

Real-time sensor sheds light on nitrate footprint

A one-year project to study nitrate levels and dynamics has revealed invaluable data to farmers, consultants, and scientists.

The 672ha Wainono Dairy Farm is near Fairlie, Canterbury, bordering the Opihi River, in a high nitrogen concentration area.

With the help of the Our Land and Water Rural Professionals Fund and primary sector consultancy The AgriBusiness Group, Wainono has been evaluating real-time water-quality monitoring, using Lincoln Agritech’s HydroMetrics nitrate sensors.

The findings have been shared with the local irrigation company, catchment groups, community stakeholders, industry representatives, rural professionals, and Te Rūnanga o Arowhenua – the local iwi.

John Wright, Managing Director of Wainono Dairy Farm Ltd, took quarterly water samples for 10 years, but that didn’t provide the information needed to really understand what was happening to nitrate concentrations. “I didn’t know if a spike or a dip was a one-off or part of a pattern,” he says.

Wainono installed three nitrate sensors along the groundwater flow direction, to compare upper, middle, and lower farm nitrate levels and dynamics. The nitrate data uploads to a HydroMetrics-hosted portal and is available in real time.

“I access the data every three or four days, and always before and after a weather event,” John says.

Within two months, John could see the power of real-time information. “Levels are going up and down quite a bit, as we suspected from the quarterly spot samples we took previously, but now we can identify trends. I can see the potential in terms of how we manage grazing and when and where we fertilise.”

AgriBusiness Group consultant Charlotte Senior says the project identified where large nitrate spikes come from. “It was clear drainage from big rainfall events was the main driver behind nitrogen losses.”

The sensors also showed high nitrate levels in the groundwater coming onto the property from upstream, and taking about two days to show up at the bottom of the farm.

John says the sensors have helped Wainono Dairy Farm identify groundwater problems, and probable causes. “We see this data as a way of informing any environmental measures we take, such as riparian planting. Over time, we will be able to see if our planting really does make a difference.”

It also sets the farm up for any future regulatory requirements. “We are creating a rich baseline data set of nitrate levels over time prior to a regulator requiring the information for compliance purposes.

“We will have way more valuable data than that provided by spot grab sampling, and also a thorough understanding of the nitrate levels across our farm.”

At the end of the project Wainono Farm purchased the sensors so it could keep collecting the data and help the local community gain further insight into what affects nitrate levels.