Smartfert director Bruce Smith said nitrogen use efficiency (NUE) was usually quite low with traditional nitrogen fertiliser, at less than 40%, with much of it lost into the air through volatilisation, leached or tied up in the soil system.
The theory behind the controlled release nitrogen, which has had research done by AgResearch and had an onfarm trial, is that the vegetable oil-based polymer coating will slowly release nitrogen over a three-month period. The farm trial showed the technology had a higher NUE than uncoated nitrogen fertiliser, producing more drymatter for each kilogram of nitrogen applied.
“Because of the low NUE with traditional nitrogen fertilisers, farmers have been applying high rates of nitrogen to get the maximum production with a lot of added cost,” Smith said.
From 50,000 tonnes of nitrogen applied annually onto New Zealand pasture in 1990, farmers today applied 350,000t, with the high-nitrogen regime leading to a reliance on ryegrass that left no room for clover and came at a high cost.
“I see the use of Smartfert as a management tool for controlling the supply of plant-available nitrogen. When applying nitrogen, there’s a lot of parameters to consider to ensure its most efficient use.
“The weather makes a huge difference and you need the thick end of 10mm of rain following an application of urea which is the largest form of nitrogen sold in the country.”
When urea nitrogen sat on the ground without rain, it risked being dissolved by the dew then losing a percentage of nitrogen into the air, he said. In high rainfall areas such as the West Coast, the plants often don’t have the chance to use the nitrogen before it was washed away.
Soil temperature played a big role in nitrogen uptake as the plants’ ability to grow and take up nitrogen diminished with soil temperatures below 10C, he said. Yet having some readily available nitrogen for the plant to take up during these cold periods enabled the plant to be more tolerant to the cold, especially frosts.
“Farmers also need to understand the recycling of nitrogen from stock. For example, the paddocks closer to the dairy are stocked more frequently, so are likely to have higher residual nitrogen.”
As a controlled release nitrogen, Smartfert could be applied in late autumn and spring as part of a farmer’s fertiliser programme rather than a separate nitrogen application, he said. Farmers could mix and match Smartfert with other NPKS fertilisers such as ammonium sulphate as part of their nutrient management. Smith said regulatory requirements would force farmers to change their nitrogen management, but to do that they needed to understand nitrogen.
“The Overseer programme calculates nutrient management on the farm based on rainfall, stock, soil and climate. This also tells them how much nitrogen is theoretically being leached and many are having to reduce their nitrogen to meet their regional requirements.
“Traditionally there has been only the cost of inputs versus the return from outputs to consider, but now farmers have got to recognise the environment and people. So they have to start thinking about their nitrogen inputs more holistically. It’s a balance of profitability, people and planet.”
Soil scientist and Agknowledge managing director Dr Doug Edmeades has done research with Smartfert and said a controlled release nitrogen could be the holy grail of nitrogen fertiliser as it theoretically should make it more effective.
“Now we need to quantify what that benefit is. Is it more efficient and producing more kilograms of drymatter per kilogram of nitrogen applied?”
While he said the concept of a controlled release nitrogen fertiliser was exciting, it was yet to be proved.
