Pee is for precision

By Ross Nolly

Using precision tools to apply fertiliser only where it is needed can mean big savings for farmers and reduced nitrogen leaching.

Reducing the amount of nitrogen leaching from farm pasture is an environmental necessity. Not only does it help protect New Zealand’s precious waterways, but from a purely practical standpoint, there’s no point paying for fertiliser that leaches away without growing pasture.

Geoff Bates is managing director of Pastoral Robotics, which has developed Spikey, a precise method of providing pasture with the required nutrients. Spikey is a targeted liquid fertiliser system giving farmers the ability to independently treat urine and inter-urine patches.

“Spikey is a machine that detects and treats urine patches, and applies fertiliser very precisely. The latest iteration applies liquid fertiliser, but doesn’t apply it to the urine patches, so uses 10% less fertiliser for the same growth,” Bates says.

Spikey travels around the paddock and each time it detects a urine patch, it treats it differently. Otherwise it applies bulk fertiliser. This optimises the outcomes for two distinctly different fertiliser requirements as urine already contains large amounts of nutrients such as nitrogen and potassium.

The machine detects urine patches using spiked electrode disks that provide a fast and accurate detection system. Spikey detects and treats the urine patches with NitroStop, which consistently increases grass growth by up to 25% and reduces nitrate leaching by up to 20% on paddock scale.

“On average, the urine patches give you 600kg of extra nitrogen per hectare. That’s a lot of nitrogen, and there’s no question that a plant will grow more, but there will usually be something else that limits its growth,” Bates says.

“If growth is limited, it takes the plant a while to realise that it can take off. The first thing we can do is provide a growth promotant. The next thing is to identify what is limiting the growth. It may for instance be sulphur, which we can add to the mix sprayed on the urine patch. This would give it what it needs to maximise growth.”

Spikey gives farmers the potential to apply 20% less fertiliser and grow more grass. According to Bates, applying low rates of fertiliser more precisely enables a farm to achieve more growth per kilogram of fertiliser, and achieve higher utilisation efficiency.

Contractor Gavin Palmer of Spreading Canterbury uses the liquid fertiliser version of Spikey, recognising that Spikey was the ideal piece of equipment to protect the environment and help farmers comply with the 190kg/ha/year nitrogen cap, he says.

“We chose the liquid fertiliser version because it allows us to only apply nitrogen to the areas outside of the cow urine patch. If a client saves 10% of their available nitrogen, and they’re doing 10 rounds, it equates to them gaining an extra round of nitrogen,” Palmer says.

“We utilise GPS pointing to track where a cow has placed its urine. It’s huge being able to return to that exact point and apply another supplement if needed.”

Contractor Jon Jackson of Jackson Spreading uses the solid fertiliser version of Spikey.

“A farmer trialled Spikey on the worst half of the farm for half a season. By halfway through the season it was growing more grass, and he’d put more cows onto it. Whereas on the other ‘better’ half, he was feeding out silage and running fewer cows,” Jackson says.

Jackson visits his client’s farms every second day because the optimal time to use Spikey is within 48 hours of the cows being in the paddock. This ensures a high urine patch detection rate and gives the treatment the largest possible window to impact pasture response.

Bates predicts that nitrification inhibitors will eventually become available for use on dairy farms.

He believes Spikey is a practical method to minimise the amount that is applied, minimising the risk of residuals in the milk, and maximising their effectiveness.