N pays off


Nitrogen is still the cheapest form of feed on farm

August 21, 2012


Supplements such as palm kernel extract (PKE) and maize silage are being used in many dairy farm systems to fill feed deficits and boost milk production.

These are sometimes used in place of nitrogen (N) fertiliser which, generally, is a more cost-effective form of feed. To identify the actual cost of additional dry matter (DM) either imported or grown on farm using N we must examine the relative costs of each method.

While PKE, maize and other supplements have a place in dairy farm systems to supplement stock energy intakes or provide a more balanced diet, farmers should consider the true cost of such feeds when deciding how best to boost production.

If we compare fertiliser N (in the form of SustaiN Green) and PKE – based on today’s price of $859 per tonne of SustaiN Green ($1.87/kg N) and an average spot price of $360 a tonne for PKE – SustaiN Green comes out on top as the most cost-effective form of feed. Even with the value of imported nutrients in the alternative supplementary feeds taken into account, N fertiliser is still the cheapest form of feed and, used wisely, is a profitable tool for farmers to increase production that has minimal direct environmental footprint.

For example, taking a conservative 10:1 response rate for N (10 kilogram of extra pasture dry matter for every kilogram of N applied) - easily achievable in typical spring growing conditions - and including $120 per tonne for application and cartage, using SustaiN Green to grow additional pasture means each kilogram of additional dry matter grown costs about 21 cents.

The benefit of using N will vary according to specific on farm conditions, and in particular, the amount of rainfall or irrigation following application. With urea, 10 mm of rainfall within 24 hours of application is necessary to ensure N losses through ammonia volatilisation are minimised, and therefore the pasture response maximised.

If these conditions cannot be guaranteed, this is where SustaiN Green (urea treated with the urease inhibitor Agrotain® nitrogen stabiliser) can help to protect your nitrogen investment. SustaiN Green is less susceptible to ammonia volatilisation if adequate rainfall to prevent ammonia losses is not received following application, offering flexibility around applications.

Comparing N fertiliser to other feeds, PKE ($360 per tonne) at 90% dry matter comes in at 40 cents/kg DM. Other alternative supplementary feeds such as maize or cereal silage present a similar picture, usually costing 30-40 cents/kg DM, often before cartage and feeding out costs have been added on. In addition, without use of a feedpad, high wastage and pasture damage can further reduce the economics of these alternative options.

These calculations demonstrate that using N fertiliser is still 10-20 cents/kg DM cheaper than many other supplementary feeds, or roughly half the price.

PKE and spring N-boosted pasture have similar metabolisable energy (ME) levels at around 11-12 ME MJ/kg DM; hence equal amounts of pasture or PKE on a dry matter basis will provide the same amount of energy. However other factors may impact the decision of which supplement to feed.

If spring pasture crude protein levels are high, maize silage may be a better option (if available) since it is high in ME, high fibre and low crude protein levels will make for a better complementary feed. It all depends on your circumstances.

By Ballance Technical Extension Manager Aaron Stafford

21 August 2012

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