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Nitrogen system trial drawing to a close
RESEARCH WRAP SOUTHERN DAIRY HUB
Story and photos by: Karen Trebilcock
The Southern Dairy Hub is looking to the future as its first major research project draws to a close.
The four-year study comparing fodder beet and kale wintered animals on either a conventional or low input nitrogen system finishes at the end of May so wintering decisions on the 349ha farm near Invercargill have to be made soon.
Current thinking is to focus on reducing greenhouse gas emissions (GHGs) to see whether the farm can meet the Government’s 2030 target and the 2050 target for all dairy farms.
“I think reaching the 2030 targets is doable now,” DairyNZ senior scientist Dawn Dalley said at the Hub field day in July. “But I’m not sure if we have the tools yet to reach the 2050 target.”
Studies could include optimising winter cropping with no-till establishment, the use of oats which grow in cold temperatures and pasture only wintering.
“We may look at feeding fodder beet for the first four to six weeks of winter to achieve body condition scores (BCS) and then no-till kale, oats or Italian and other grass alternatives prior to the springer draft to increase protein intake in late gestation.”
Building an off-paddock wintering structure was still “bubbling away”, Dawn said.
Plantain in pastures and ways of reducing bobby calf numbers may also be looked at.
A secondary focus on animal sentience – how animals responded to different systems, was also being considered.
Final decisions would be made after considering research already done or planned in New Zealand and internationally.
Fonterra would also have a say to make sure outcomes were relevant to its milk markets.
“We can’t do everything but we can drop in and out different research projects as part of a central one,” said general manager of farm operations Louise Cook.
Although the final figures have yet to be collated, the current research is showing fodder beet wintering systems have lower leaching of nutrients than kale.
It was easier to put BCS on cows during winter on fodder beet allowing more days in milk as low BCS did not have to trigger drying-off decisions.
However, cows on fodder beet had a lower six-week incalf rate, a higher not-incalf rate and a lower peak milk production.
Reducing nitrogen fertiliser from 190kg N/ha to 50kg N/ha increased clover content in pastures from 8% to 18%.
Cows on the reduced nitrogen fertiliser input system plus fodder beet had a lower hunger drive reducing grazing intensity.
Profitability was highest on kale with standard nitrogen inputs and lowest in fodder beet with low nitrogen inputs.
Louise said the kale/fodder beet, conventional and low input nitrogen four-way study had proved at times tricky to manage but it was the only place in NZ where such research work was done on a commercial scale.
“You might look at us and say we should be doing things better, or our production should be better, but we are trying these things here so you don’t have to.
“We will take the hit because we can, so you don’t have to on your farms.”
Southern Dairy Hub general manager of farm operations Louise Cook talking at the July field day.
