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Nitrogen not the solution when producing quality hay

By Karl Carrington.

Research funded by the AgriFutures Export Fodder Program as part of the National Hay Agronomy (NHA) Project has shown Nitrogen isn't the be-all and end-all of hay production.

Dr Courtney Peirce, a Senior Research Officer at the South Australian Research and Development Institute (SARDI), who led the South Australian component of the NHA project said the research findings suggested growers wouldn’t be disadvantaged by a conservative nitrogen application strategy in drier growing seasons.

Dr Peirce said:

“The field trials at Hart during the past two seasons mostly produced high quality hay.
“The exception were the trials that were under severe nitrogen stress, but overall, the oaten hay quality and yield did not suffer from a conservative approach to applying nitrogen.
“If your focus is on hay quality, then you don’t want to apply too much nitrogen as higher nitrogen rates can result in lower water-soluble carbohydrates (WSC) and higher fibre content – such as acid detergent fibre and neutral detergent fibre - increasing the likelihood of downgrades in hay quality.”

There have been export hay trials in 2020, at Hart in South Australia.

However they demonstrated no benefit when applying more than 30kg N/ha because of the dry winter, but higher applications were more profitable in the Victorian Wimmera, due to more consistent rainfall during winter and early spring allowing plant uptake of nitrogen.

The “sweet spot” for nitrogen applications strikes the balance between quality and quantity in export hay crops and it’s determined each year by the season. Although weather forecasts for South Australia and Victoria remain variable, Courtney said the research showed more conservative nitrogen applications were best for hay crops after a dry season start.

“This season in many parts of South Australia, there has been limited rainfall, with the moderate season break occurring in late May.
“The growing season rainfall will determine how much applied nitrogen can be taken up by the crop, and our trials suggest that a conservative approach is most likely to be the best-bet.
“Even if we get above average rainfall for the rest of the season, resulting in increased nitrogen mineralization, you could end-up with poorer quality hay because of the timing of when the nitrogen becomes available. Applying nitrogen too late causes it to accumulate as nitrates in the plant.”

The nitrogen strategy for the NHA trials includes top-dressing two-thirds at seeding and one-third six weeks after germination, with the final nitrogen application applied mid-tillering.

NHA project manager Georgie Troup said most export fodder crops throughout Australia require 30- 90kg N/ha, depending on the yield potential and growing season. A trial in Western Australia last year demonstrated a yield increase for an April-sown crop with applications up to 150kg N/ha, but this was detrimental to quality.

The “sweet spot” was 90kg N/ha as this produced 8 tonnes/ha with 25.4 per cent WSC. and was top grade export oaten hay.

Ms Troup said:

“As soon as you apply nitrogen there’s a gradual decline in WSC, so it is about finding the point where you optimise yield without having an effect on hay grade and profitability.
“Last year was the ideal scenario for us to trial gibberellic acid, there were two trials in Western Australia, at Wongan Hills and Merredin, both were under moisture stress from mid-season, and it was a tight finish to the growing season.
“If the gibberellic acid was going to be useful, it would have been apparent there in 2020. But only one variety was able to fully emerge from the boot, and it was the short season variety Durack, which had a maturity advantage over the longer season varieties.”

The National Hay Agronomy (NHA) project is a four-year investment by the AgriFutures Export Fodder Program and aims to address current knowledge gaps in the Australian export fodder industry.

For more information on the program and research visit www.agrifutures.com.au.