Greenpeace takes aim at nitrogen
Greenpeace wants the Government to ban the use of synthetic nitrogen on New Zealand farms, orchards and market gardens. It has launched a petition which has gained more than 5000 signatures.
What is synthetic nitrogen?
Synthetic nitrogen comes from urea, which contains about 46 per cent nitrogen and is used as a fertiliser. New Zealand’s only urea plant is at Kapuni in South Taranaki, using natural gas from the offshore Ma¯ ui gas field.
Kapuni, owned by Ballance Agri-Nutrients, produced 277,224 tonnes of urea in 2017. To meet the local demand for urea, 640,512 tonnes was imported.
The Fertiliser Association’s latest estimate was for 2015, and was just over 400,000 tonnes a year.
Why is it used?
To boost plant growth.
Why does Greenpeace want it banned?
It says most of the synthetic N – more than 70 per cent – is used ‘‘to drive industrial dairy farming’’. Fifty years ago we used about 6000 tonnes a year, rising to 50,000 tonnes by 1990; today, it’s jumped to over 400,000 tonnes, and numbers of dairy cattle have leapt to 6.5 million.
Not all of the nitrogen put on the soil is taken up by plants but instead travels underground and can pollute aquifers and rivers. When cattle eat pasture, they burp out greenhouse gases such as methane and urinate nitrous oxide – another greenhouse gas.
What are the river trends?
Last year’s report by the Ministry for the Environment on the state of freshwater showed nitrogen levels at over half of monitored river sites were getting worse – on pastoral sites, 72 per cent worsened, while 28 per cent improved.
How else is nitrogen put in the soil?
A number of plants naturally ‘‘fix’’ nitrogen in the soil, but by far the most common in New Zealand is the white clover plant. Rhizobium bacteria form nodules on the roots and convert nitrogen in the soil, which then improves grass growth.
But unlike synthetic nitrogen, which farmers can put on to produce more pasture at critical times of the year, clover is not a convenient quick fix.
So lazy farming then?
Not totally. Clover does not grow at below 9 degrees Celsius, and its success depends on how fertile the soil is and whether there’s enough rain.
But do farmers really need synthetic nitrogen?
Some studies say no. DairyNZ carried out an experiment on two Waikato farms from 2002 to 2011, one applying synthetic N, the other none. For six of the nine years, both farms had the same level of profit. But once the milk price rose over $5.10 per kilogram of milksolids, it became more financially worthwhile to put on synthetic N, because it grows more grass. More grass means more milk.
Would using clover fix the problem of polluted rivers?
Not entirely, it doesn’t matter about the source of the nitrogen, the way a cow processes and excretes the N is identical. Due to its concentrated and localised nature, the urine patches represent a massively higher order of magnitude in terms of risk of nitrate losses than broadcasting synthetic N.
How expensive is fertiliser?
Fertiliser is the single largest fixed farming cost. The average dairy farmer can spend up to $80,000 a year, and sheep and beef farmers pay out $55,683.
So farmers need to be sure of a good payback. When the milk price rises to $8.40, as it did in 2013-14, it pays to put on synthetic N.
Who else uses synthetic N?
It’s extensively used in orchards, arable farms and market gardens to grow fruit, cereals and vegetables. In fact, a crop such as winter lettuce uses about 400 kilograms per hectare – the heaviest use of any crop.
While dairy is still the highest user by sector, that could change if there is a switch to more horticulture and arable farming. Combined, the two sectors take up 297,383 hectares (compared with dairy’s 1.7 million ha). But the Government wants to lift that combined arable and horticulture area to about 500,000ha by 2050.
What’s at stake?
Some say New Zealand’s economic future. In 2017, primary sector exports were worth $38 billion, out of a total $53.7b across all sectors, and production would take a severe dent without synthetic N. Greenpeace contends it is about the future of freshwater, although it also says production need not be impacted by a ban on synthetic N.
What’s Greenpeace’s answer?
‘‘Regenerative’’ farming. It quotes studies showing a farm can do away with 100kg of fertiliser per hectare by simply increasing the varieties of pasture crops from one to 16 species, and still produce the same amount of food.
The counter argument is regenerative farming takes up more land because fields need to be left fallow while nitrogenfixing plants grow. Also, fertiliser companies argue soil testing, modelling software, GPScontrolled spreading and interactive mapping ensure fertiliser is spread at the right rate, time and place.