Monday, 25 January 2021

N-loss precision drives Waikato dairy operation’s vision


For Waikato dairy farm consultant Paul Lawrey, precision is a word he circles back to often in conversation, particularly when it comes to on-farm nutrient use. 

Paul oversees the management of two dairy platforms located near Te Awamutu in the Waikato. Bringing their N-use below 190kgN/ha and investigating ways to further reduce their on-farm footprint has been a driving factor behind some of the changes made on the properties over the past three years. 

“Being precise with the nutrients applied and knowing how much feed is actually used by the animals are both key factors in managing our nitrogen use,” he says.  

Keeping in mind that greenhouse gases (GHG) will be an increasing focus across the industry, Paul has been working with Ravensdown’s Waikato-based environmental consultant Adrian Brocksopp. Together they’ve been learning where their farm’s N-loss and GHG numbers sit, as well as modelling different farm management scenarios.  

“We want to know what our N-losses are each year, and even though we are not required to, we do a nutrient budget for each farm annually so that we can understand the effect of the management changes we put in place, and then we are able to review if any adjustments are needed.” 

The nutrient analysis and fertiliser planning are undertaken by Te Awamutu-based Agri Manager Brenna Coleman. The properties undergo whole-farm soil testing every three years, while crop paddocks are soil tested annually. Traditionally, their nitrogen use has sat around 200kgN/ha annually, but they have worked to bring this back over the last three years and now apply 180kgN/ha.  

Modelling good management practice, they have partially achieved this reduction by switching from straight urea to Ravensdown’s N-Protect, a urease-inhibited coated fertiliser.  

N-Protect’s coating helps reduce the amount of N lost to the atmosphere (as nitrous oxide) through the process of volatilisation, meaning more of the N applied remains in the soil for plant uptake. 

“We have a real focus on being more precise with what we apply and when we apply it, and that’s been a big driver behind why we've actually moved from urea to N-Protect,”  

The switch to N-Protect has meant they’ve been applying 5kgN/ha less than traditional uncoated urea. The difference in spreading rate has also meant the cost of N-Protect vs urea is brought to parity.  

In terms of cost per hectare, because we're putting on slightly less N-Protect, our costs stay the same, but we get the benefit of less nitrogen being applied in total.  Applying less product means the N-loss figures are lower, and it also helps with the greenhouse gases, because N-Protect reduces the nitrous oxide losses too. 

Other ways Paul and his team have focused efficiencies include cutting down the N-applications on the effluent blocks to twice a year (some paddocks aren’t done if urine spots can’t be seen) and through regular farm walks (every 10 days), which has allowed the farms to be more precise with when and where they apply nutrients.  

Paul says he is comfortable about operating the farms below the 190kgN/ha N-cap come June 2021, and he’s confident the changes they have implemented will continue to increase on-farm efficiencies.  

“For me, a whole farm soil testing program undertaken every two to three years allows us to be precise with the fertiliser program and treat each paddock individually to maximise its grass growth,” he says.  “In addition, the annual soil testing of crop paddocks, regular farm walks, and  use of nutrient budgets annually will also be key in ensuring both the profitability and the productivity of the farms into the future.