The first step is to get agreement from the CODEX commission to even look at the issue and put it on the list of compounds to be addressed.
That would involve showing DCD fertiliser has a legitimate use and that a lack of an international standard would have an impact on trade.
The next step is for the expert committee, which advises the CODEX commission on human health risks, to consider the toxicity data on DCD.
That committee only meets once a year and could request more information which could delay an outcome further.
Its findings are ultimately incorporated into a discussion paper supporting the appropriate maximum residue limits which then goes before the CODEX commission for consideration and vote.
The commission also only meets once a year.
Federated Farmers national vice-president and spokesperson on food safety Dr William Rolleston said getting DCD nitrification inhibitors back as a tool for farmers was now a matter of pretty straightforward bureaucracy that would take time.
DCD detections in milk products hadn’t posed any health risk but until the CODEX limit was set farmers had to accept it was off the shelf, he said.
Rolleston urged regional councils to review any base year data they had set for farmers if that data had included the use of nitrification inhibitors.
Now the tool wasn’t available farmers running their operations through programmes such as Overseer would be unfairly disadvantaged in subsequent years.
MeanwhileLincolnUniversity and DairyNZ’s Pastoral 21 (P21) project on the Lincoln University Research Dairy Farm has revealed that pasture species could offer the possibility of a new tool to help slash nitrate leaching – potentially at a similar scale to DCD.
LincolnUniversity professor of dairy production Grant Edwards told the Lincoln University Dairy Farm (LUDF) focus day held on the research farm that trials show using an Italian ryegrass/white clover mix can cut nitrate leaching to similar levels as those achieved using DCD on a more typical perennial ryegrass/white clover sward.
The increased cool season growing activity of the Italian species is likely to be behind the nitrate leaching reduction as the plant takes up more nitrogen (N) through that period leaving less to be leached.
Edwards said over the two years of studies on the research farm nitrate losses beneath Italian ryegrass/white clover pastures were 24-33% less than beneath standard dairy pasture as well as diverse pastures that contain chicory and plantain.
Leaching losses were 50% lower than beneath tall fescue pastures, he said.
Another find from the studies so far is that using herbs such as chicory and plantain along with red clover in the pasture mix can cut urinary N concentrations from cows.
Averaged across two years, which included three trial periods on the research farm, urinary N concentrations were 23% lower from cows grazing the diverse pasture (4g N/litre) than cows grazing a standard perennial ryegrass/white clover sward (4.9g/l).
Importantly there was no apparent difference in milksolids (MS) production between the groups of cows grazing the different pastures providing they were offered the same allowance.
Edwards said there was more work to be done in determining the quantity of herbs needed in the pasture to achieve a reduction in N excretion. Farmers needed to be aware the relationship between height and pasture mass could vary between diverse and perennial ryegrass/white clover pastures which could mean under or over-prediction if using a rising plate meter.
Research is continuing and the Lincoln University Dairy Farm (LUDF) has renovated a pasture using a diverse pasture mix this season.
LUDF has been a user of eco-n, a DCD-based nitrification inhibitor developed at LincolnUniversity. It will be assessing what management practices will be necessary if it’s to achieve desired nitrate leaching limits.
Significant destocking down from 3.95 cows/ha to 3.5c/ha, as in the research farm trials, could be one option. That would see cow numbers go back to 560 cows, down from 632.
