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Counting the Cost of Nitrogen Depletion

10 December 2013

Any kind of protein producing system is cycling nitrogen, even if you don't apply nitrogen, says pasture expert Neil Griffiths.

Nitrogen is an essential part of animal production, and producers would be better served learning how to manage it efficiently than turning their back on it.

“If you produce protein, you’ve got nitrogen in your farming system,” explains NSW Department of Primary Industries pasture specialist Neil Griffiths.

“Even if you don’t use nitrogen fertiliser or have legumes in your pasture, you still have nitrogen cycling, albeit more slowly, and you’re not immune to the environmental concerns people think they’re addressing by not using it.

“There is a move in some circles to withdraw from using chemical inputs on farms and that’s causing a decline in pasture productivity and soil fertility.

“As well as experiencing lost animal production, having low fertility, low productivity pastures also impacts on water use efficiency and soil erosion.

“So not using fertilisers is potentially just as environmentally damaging as misusing them.”

Neil will deliver two presentations at the Taree Pasture Update being held on 5 December: an overview of ‘efficient nitrogen use’ on both beef and dairy farms and a targeted briefing for dairy farmers on ‘making nitrogen work for you’.

With other speakers to discuss the role of clover and legumes in supplying soil nitrogen, Neil will focus on nitrogen applied as urea – the most cost-effective form of nitrogen fertiliser.

Neil’s tips for achieving efficient urea use include:

  • Responsive pastures – You must have a pasture that responds to nitrogen. In the Taree area that is primarily ryegrass in winter and kikuyu in summer.
  • Climate – There’s no point putting out urea if it’s too dry, too wet, too hot or too cold. Urea needs to be watered in, via rain or irrigation. Ensuring optimal climatic conditions will reduce chances of environmental impacts such as leaching, volatilisation and denitrification.
  • Timing – Apply strategically using split application i.e. small amounts regularly when pasture is actively growing.
  • Rate – 100kg of urea/ha/grazing cycle in the growing season. Split applications help reduce losses/ensure a more efficient response to nitrogen (100kg/ha of urea is equivalent to 46kg of N/ha).
  • Rotational grazing – Urea is not practical in a set stocking regime due to the amount of extra feed produced. Grazing must be managed to cost-effectively utilise feed. Avoid grazing for a week or two after applying urea.

Reaping The Rewards

While some producers have been dissuaded from using nitrogen due to environmental concerns, others are put off by the cost.

“Like all fertilisers, urea prices are up and down,” adds Neil.

“But from trials done a couple of years ago we found urea was costing about $60 to $130/tonne of extra dry matter (DM) produced. Other fertilisers will supply nitrogen but they are generally more expensive.

“That worked out at an average cost of about 10¢/kg of DM. So $1 worth of urea could produce 10kg of good quality dry matter, which in turn could produce about 1kg of beef, or 10 to 20L of milk, provided the feed was used efficiently.

Neil will join a full line-up of speakers at the Pasture Update, which is being presented by The Grassland Society of NSW in conjunction with MLA. A farm tour will be conducted following the presentations.

Further Reading

You can read more about the Taree Pasture by clicking here.

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