Thursday, 01 March 2018 12:59

Sensors joining the mob to guard waterways

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Cow wearing a urine sensor. Cow wearing a urine sensor.

AgResearch says it has developed world-leading sensors to better understand how nitrogen is being excreted by cows, and so how best to tackle its effects on the environment.

The urine sensors, a work in progress since 2010, are attached to grazing dairy cows to get detailed measurements every time the cow urinates, including volume and frequency, and crucially the concentration of nitrogen in the urine that may leach into soil and waterways, perhaps causing algal bloom.

The urine sensors give much greater understanding of the behaviour of the cows, which can help develop techniques to mitigate nitrogen leaching from farms, says AgResearch senior scientist Dr Brendon Welten.

“Other sensors exist around the world to provide data from livestock, but these sensors we’ve developed are unique in their ability to record nitrogen concentrations each time the cow urinates during grazing,” Welten says.

“We can learn, for example, how different species of pasture affect the amount of nitrogen excreted in urine.”

The sensors weigh about 1.5kg and attach to the cow by a harness connected to a lightweight cow cover. Several instruments record the data (temperature, pressure and refractive index), storing it in a data logger remotely accessed via a wireless network system.  

The sensors have already been used in the UK and Australia. 

“The operation of the sensors is complex, and at this stage we are working towards offering the sensors to other researchers around the world to allow them to use the technology to make similar gains,” Welten says.

“AgResearch will have the expertise to support those researchers to use the technology and maximise the benefits from it.” 

The sensors have contributed to important progress made in the Forages for Reduced Nitrate Leaching (FRNL) programme involving DairyNZ, AgResearch, Plant & Food Research, Lincoln University, the Foundation for Arable Research and Manaaki Whenua (Landcare Research).

DairyNZ senior scientist Ina Pinxterhuis says the results confirm the variability in urinary nitrogen excretion over the day, necessitating many repeated measures. “The sensors make this possible.”

“It is also great to see that the options we examine to reduce nitrate leaching result in lower daily urinary nitrogen excretion and lower nitrogen concentration, if not during the whole 24 hours of the day, at least for some parts. This information provides new options for management too.”


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