Wednesday, 15 September 2021

Reducing N fertiliser without losing performance


Ravensdown has been involved in a DairyNZ project in Canterbury, looking into ways farmers can reduce N-loss and N inputs without sacrificing on-farm performance. Ravensdown Environmental Principal Consultant Arron Hutton and DairyNZ Farm Systems Developer Phillipa Hedley discuss some of their observations from the project.

Meeting nitrogen (N) loss limits while maintaining profitable businesses under the Canterbury Land and Water Regional Plan is the goal of a two-year, DairyNZ-run project. Forty-five case study farmers located in Canterbury’s Selwyn and Hinds catchments have had their goals and production systems considered, leading to the identification and implementation of appropriate N-loss solutions on-farm. Information gathered from case study farms will then provide a range of options for farmers to consider when meeting targets on their own properties. 

The effect of the 190kg N/ha cap will vary between farms, depending on factors such as the current amount of N applied, its efficiency of use and how the transition to lower use is managed. 

The following tactics have been identified within the project as key to reducing N-use without sacrificing profit. 

    1. Have a plan and monitor so there are no surprises at year-end. 
    2. Identify when to apply to get the best return - the most profitable time to apply N fertiliser is in early spring when there is a genuine feed deficit, the next best times are December to set the farm up for summer and in March when autumn rains arrive, while January and February applications are often not profitable. 
    3. Applications – control the amount of N required and make it easy to stick to a plan. 
      a Monthly – one round of N fertiliser per month. On a 23-day round this means there will be one week where no N fertiliser is applied. 
      b Split monthly applications – 15 days apart e.g. half the farm on the 10th of the month and the balance on the 25th. Lower application rates – apply no more than 40kg N/ha in early spring and drop as low as 0.8kg N/ha per day of round length
    4. N Protect – use 10% less N with N-Protect from September to March, which reduces atmospheric N loss when the urea is not washed in to soil within eight hours.
    5. Real time monitoring– track N use by paddock as provided by HawkEye software.
    6. Increase the round length – use the leaf area to capture light for growth (photosynthesis) rather than relying on N fertiliser. Aim to graze at 2.5 to 3 leaf stage. In Canterbury, if you are grazing on an 18-day round, you may be able to increase this to 22-24 days and eliminate one round of N fertiliser (depending on stocking rate and pasture species)
    7. Optimise pasture/clover growth conditions through:
      a. Soil fertility; soil test for pH, P, K, S, and clover for Mo
      b. Irrigation systems
      c. Intensive soil testing to target nutrients where required
    8. Pasture walks and 'feed the wedge' – no new story here, measuring pasture every week can allow you to better determine the feed supply/feed demand position.
    9. Low rates or no N fertiliser applied in January/February – often N is not the limiting factor, with plenty of mineralised N in the soil.
    10. Staggered reduction – drop to 230kg N/ha this season and 190kg N/ha next season. This gives time for clover to re-establish and for management systems to adapt.

DairyNZ farm case study: Mick and Kirsten O’Connor, Terrace Farm, Dairy Holdings. Selwyn Te Waihora. 

A farm that only fed 20kg DM/cow of supplement on the platform managed to reduce fertiliser N inputs from 270kg N/ha to an average of 182kg N/ha while maintaining production by: 

  1. Following a plan with set N applied per month 
  2. No January or February N applied. While pastures looked N deficient, herbage analysis showed K deficiency 
  3. Effluent paddocks received two spring applications for the season 
  4. Non-effluent paddocks received split monthly applications to December, then monthly (excluding January and February). Weekly pasture data showed no less pasture grown on the effluent and non-effluent areas.