Farmers are being advised that maintaining a nitrogen bank, or a small net positive N balance in their soils is one of the best ways to manage their fertiliser strategy.
And similar to maintaining financial bank accounts, a system of small and frequent deposits and ensuring more is going in than is going out is something that can pay dividends.
Speaking remotely at the recent Grains Research and Development Corporation (GRDC) update in Nhill, Birchip Cropping Group (BCG) senior research manager Yolanda Plowman said trial work had demonstrated the best N rate strategies showed a small N positive balance performed better than going into deficit.
“It highlights the need to think of your nitrogen strategy over the long term, rather than just a crop to crop basis,” Dr Plowman said.
She pointed to research that showed 44 per cent of applied N fertiliser was taken up by the crop in the year of application with a further 22pc taken up over the crops over the next two or three years.
“The main take home from this research is not the recovery percentages, but rather the proof that N recovery can occur as long out as three years after application,” she said.
She said the advantages of running a small N positive from fertiliser applications meant there was not the need for a big dump of N in any given year, which increased the risk of crop burn-off or wastage due to volatilisation or leeching.
“Because of those type of risks, overall the evidence shows that farmers in southern Australian cropping systems generally underfertilise.”
However, while the evidence was clear on the benefits of maintaining some sort of an N buffer above the current crop’s needs, Dr Plowman said there were different management strategies to find what that ‘Goldilocks’ application of N was.
“We’ve found that two decision support systems, Yield Prophet and N Banks can both be helpful, which one works better for you will come down to individual preference.”
“Yield Prophet will be the choice for those farmers wanting to have an active plan in place for their N management, it helps match N inputs with potential yield, based on climate modelling.”
“On the other hand, some growers may prefer a more passive method like the N Bank strategy, that simply works on capitalising on year to year N carryover to help support crop growth.”
Dr Plowman said a BCG trial had found a Yield Prophet 50pc treatment and a N Bank 125kg/ha maintenance treatment performed the best in the low rainfall zones of northern Victoria.
“The YP 50pc treatment did best over the life of the trial in terms of maximising crop yields while minimising potential financial losses due to N loss to the environment.”
“Of the N Bank treatments, the NB125 treatment had a good six year average grain yield and a small positive N balance, with a simple decision making process which will definitely have appeal to some growers.”
Article by Gregor Heard, originally published on FarmOnline. For more stories like this, please visit https://www.stockandland.com.au/ and https://www.farmonline.com.au/
