Nitrogen your autumn advantage

Nitrogen your autumn advantage

1 March 2017

Pasture-enhancing nitrogen can help you manage autumn’s juggling act.

In late summer through to early autumn, pasture can be very high in fibre and lacking in protein and essential nutrients. Drought can intensify this issue, as can a short growing season, which can then affect the quality of the hay or silage you may be using.

Josh Verhoek, Science Extension Officer at Ballance Agri-Nutrients says “It’s hard for rumen microbes to break down fibre – essentially it is wasted energy at a time when you need to build stock condition or are trying to extend your milking.”

The positive news is that autumn can be a great time to grow grass.

“Rainfall can still be a bit fickle, but soil temperatures are generally good – often warmer than early spring. Using nitrogen (N) to boost grass growth can be an effective way to get the quality feed you need at this critical time.” says Verhoek.

Research indicates you can apply nitrogen straight after the first drought-breaking rain.1 This contrasts traditional advice to wait until later, as the first rain is sometimes followed by a further dry period.

Trials on drought-affected land in Hawke’s Bay and the Bay of Plenty showed that applying moderate rates of nitrogen fertiliser (25 or 50 kilograms (kg) of N per hectare) after the first rainfall produced useful pasture responses just a few weeks after application.

“First harvests yielded between four and 10kgs of dry matter per kg of N applied. Plus the effect of the applied N was not lost if another dry spell followed. The response carried on when more rain arrived.”says Verhoek.

The overall yield over consecutive cuts in the trial was 12kg of dry matter per kg of N applied.

“Whether you’re extending milking, improving condition scores or both, this extra quality feed would help considerably.” he says.

Product choice is critical

Try not to be tempted to interpret the post-drought response research results as a license to apply nitrogen in dry conditions.

“That all-important 5 to 10 millimeters (mm) of rain or irrigation is definitely required within 8 to 10 hours of application to reduce nitrogen loss from ammonia volatilisation,” warns Verhoek. “Getting the nitrogen into the soil is vital.”

Products such as SustaiN and PhaSedN are great choices for autumn. Both have the advantage of Agrotain® nitrogen stabliser, a product that blocks the action of urease enzymes in the soil. This reduces the rate at which the urea converts to ammonium, which in turn reduces volatilisation.

“This gives you more flexibility in terms of the timing of application,” he says.

PhaSedN has the additional benefit of elemental sulphur.

“PhaSedN is a perfect autumn nitrogen option for dairy farms that don’t require phosphate but need to boost or maintain sulphur availability to maximise production,” says Verhoek.

“The sulphur in PhaSedN is in elemental form rather than soluble sulphate. This means if applied in autumn, it will remain in the soil over winter and slowly release to improve supply in spring when pasture starts growing again. It is a great way to make the most of autumn and set the farm up for spring.”

1“The effects on soil, herbage and dry matter responses to applied nitrogen after prolonged low soil moisture conditions,” Research report for Ballance Agri-Nutrients, 2008

For advice on your autumn fertiliser application, contact your local Fonterra Farm Source TSR.

Article supplied by Ballance Agri-Nutrients