Should I consider applying nitrogen fertiliser in pastures given its high price?  This was a question considered at Southern Farming Systems Nitrogen (N) use webinar.  The answer was a surprising “Don’t rule it out!”

A key consideration in making this decision will be: “Do I expect to have a shortfall of winter feed available for stock?”  And if you do, “Will the cost of the supplementing be cheaper or more expensive than using Nitrogen fertiliser? To work this out you need to know the likely responses to Nitrogen and the proposed cost of supplementation.

With current fertiliser prices, you will need to get a response of at least 8 kg DM for every 1 kg of N applied. The typical response of nitrogen applications is between an extra 5 to 25kg DM/ha for every 1 kg of N applied. Therefore, there are considerations to optimise response.

Know how responsive your pastures are to Nitrogen.  As not all pastures will be responsive because of other factors of nutrient deficiencies, acidity or the pasture species itself, and its propensity to grow in winter. For example, Australian phalaris is semi winter dormant, therefore a response is limited.

At least 50% moisture is required for efficient N use, no moisture equals no growth. On the flip side, apply it to waterlogged pastures, and the nitrogen fertiliser will be lost to the atmosphere as nitrous oxide.

When to apply nitrogen; it is not instantaneous response, so you need to apply well ahead of when you need the feed. Apply it as soon as stock leave the paddock and allow grasses to regrow their full complement of live leaves before re-grazing. Use it or lose it; meaning, the N in the soil doesn’t carry over for later.

A little and often; relates to the application rate and between 25kg to 50 kg of N is advised. Higher rate responses have diminishing returns for cost of application. This is often used in dairy enterprises, but in mixed farming, it’s when N is likely to be deficient and you need the extra feed.

Watch our series of nitrogen use webinars from more information and tips to this season at www.sfs.org.au/communications/media