By: Andrew Swallow

Controlled-release fertilisers are tipped to be an increasingly useful tool in future crop and pasture nutrition as the technology becomes cheaper and trickles down from high-value horticultural niches.

Coated urea product Smartfert is one such product that’s already finding a market in broadacre agriculture as the science behind it accumulates. In 2015 a paper presented to the New Zealand Grassland Association conference in Masterton showed its nitrogen use efficiency in pasture was 5-50% better than uncoated urea’s. That’s since been backed up with results from five more field trials presented to the NZGA’s Whanganui conference in November.

“The results suggest that Smartfert can be used to reduce fertiliser N application costs by reducing the number of applications of soluble N fertiliser and/or reducing pasture N concentrations and hence leaching,” the 2017 NZGA paper* by Edmeades and McBride concludes.

The product’s a biopolymer-coated urea which extends the release of nitrogen from urea’s normal 30-45 days to 90-100 days.

“The coating is modified for New Zealand conditions and 90 to 100 days fits a large proportion of the market,” Bruce Smith, pictured above, of Eko360, says, who has driven Smartfert’s introduction.

It’s available through Ballance Agri-Nutrients at $1154/tonne, though you won’t find it on the co-operative’s standard price list.

“But it does feature on their new e-commerce platform, MyBallance,” Smith says.

Ballance’s innovation leader Jamie Blennerhassett has raised concerns about the rate of nitrogen release from polymercoated products at low temperatures, but Smith says trials show that’s not an issue with Smartfert.

“We got a good response at Wairakei (just north of Taupo) in July. When you walked across the grass in the morning it was crunchy from frost.”

By design, initial pasture response to Smartfert is lower than to the same amount of an immediately soluble nitrogen applied, he says, which is why a blend including 25-50% of such an alternative, such as urea or ammonium sulphate, is usually recommended.

Such blends provide the best of both worlds: an immediate response from the uncoated nitrogen with the Smartfert response taking up where that leaves off at 40-60 days.

Compared side-by-side, total responses to straight Smartfert and urea or SustaiN are similar, it’s just the timing that differs.

“SustaiN and Smartfert gave similar overall yields,” Edmeades and McBride note in the 2017 NZGA paper.

So where does Smartfert fit? Smith says it’s proving popular as a one-pass and shut-the-gate fertiliser application to fodder crops, especially maize, and on pasture where heavy rain regularly increases leaching risk and/or the ability to get on with subsequent applications of nitrogen.

“The beauty in pasture is farmers are using it to get an application on in autumn and the nitrogen is there over winter without them worrying about getting bogged in the paddock.”

In the warm north, the nitrogen’s used over winter as pastures keep growing. In cooler areas further south and west it’s protected until soil temperatures start to increase in spring and the nitrogen is there as the plants need it even though ground may be too wet to travel on, he says.

Assuming a blend is used – “that has an implication on price, because it reduces the overall cost of the nitrogen,” Smith says, the break even point for a Smartfert blend equates to growing about 2.7% more pasture drymatter.

“Farms that are using it recognise that they often lose at least that because, for whatever reason, they can’t get repeat applications of nitrogen on in a timely fashion.”