Pouring down the drain

There seems to be a tacit agreement among many New Zealand scientists that the nitrate pollution of our waterways has nothing to do with the urea being poured on. Somehow they have convinced themselves, and many farmers, that it’s all to do with cow urine.

Poor old cows, suddenly seen as nitrogen factories, when all they are doing is trying to get rid of the overdoses being fed to them through the urea-heavy pasture they are expected to eat these days.

So it was a delight to attend one of Dr Christine Jones’ recent seminars, and be handed a summary document which spells out the real story. According to Statistics NZ, NZ farmers spent $281 million on urea in 2015-16, of which only between 10 per cent and 40 per cent was taken up by plants. The other 60-90 per cent simply sank downwards, through our carbon-light soils into our waterways, representing a wastage of between $168 and $252 million. We then spent more attempting to remove those toxic nitrates from our drinking water sources.

Apparently our urea usage increased by 41 per cent between 2000 and 2010, while over in Europe they maintained high yields using 40-50 cent less fertiliser than used in the 1980s.

Not the worst

Pretty sad stuff really, particularly when the milk payout was less than most farmers’ working expenses during those years.

But that’s not the worst of it. Because all that urea doesn’t allow our soils to make humus or increase soil carbon, many farmers are growing less dry matter per hectare than they were in the 1980s. I am told by both scientists and consultants that these days, growth is only between 10 and 15 tonnes DM/ha. Trying to be profitable on 10 tonnes/ha is difficult to say the least.

In the late 70s and early 80s work done by MAF Ruakura measured pasture averages on different soil types around the Waikato. Monthly cage cuts over four years on what were considered ‘ideal dairy cow grazing systems’ ranged from 15 tonnes on silt loam to well over 18 tonnes on sandy loam or ash soils.

Work being done now, using the same cage system, on farms using only clover to make the N, is being measured at 21 tonnes.

Ignoring reality

The claim is that measurements are done differently now. So either plate meters are measuring short, or somebody is ignoring the new reality. And when I put that to a scientist and some consultants recently, their dirty looks accused me of lying, and I was later assured that I was probably wrong.

And this was at a session where figures were produced to show that many farmers weren’t accurately costing their bought-in supplements, use of which have increased hugely in recent years.

Yes, everyone has more cows, and supplements (particularly PKE) are easily come by, but if the truth is that they are actually growing less pasture, then all the ‘grass first’ hectoring seems a bit of a waste of time.   Perhaps a bit of trusting Nature, and even giving her a helping hand with more of what she uses (mycorrhizae and bacteria), might just solve more than one problem.


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