Summer N. Summer milk

Summer N. Summer milk

18 October 2018

A nitrogen (N) boost could be the most cost-effective way to get more milk in the vat this summer.

Ballance Science Extension Officer Josh Verhoek says applying nitrogen to pasture during growth periods encourages tillering. "More tillers mean more cover. You’ll also get larger leaves on each tiller. This makes pasture more resilient to summer grazing, weed invasion and drought and also enables it to recover more quickly for the next season."

Field trials during a dry summer in 1997 revealed nitrogen application as late as December/January boosted shoot numbers by 37 percent – more than double the response achieved through irrigation.

Will this mean more summer milk?

Another trial showed an extra 800 kilograms of dry matter per hectare (kg DM/ha) and 66 kg milk solids (MS)/ha could be produced from December to April by applying 100 kg N/ha, split between December and January. Gains came from having more cows in milk over summer and being able to dry them off later, rather than an increase in daily milk production. "But regardless of the ‘how’, the end result was more milk," says Josh.

Is it economical?

Obviously, production gains are meaningless if the associated costs are too high. The ‘More Summer Milk’ study, carried out in the 1990s, compared cropping, silage and nitrogen use to increase summer food supply, looking at the effects on milk solids production and financial returns. “Applying nitrogen resulted in the most consistent and profitable response,” says Josh.

"Spring-sown crops reduced grazing area at the time of highest feed demand and cultivation costs affected profitability. Silage also proved to be less cost-effective compared to nitrogen."

Tips for success

Right place, right rate, right time, right product

  • You’ll get the best N response from high-fertility paddocks containing productive pasture species.
  • Try Ballance’s My Pasture Planner tool (formerly N-Guru). This uses total soil nitrogen test information to determine where nitrogen will have the biggest impact on-farm and supports variable rate application.
  • Apply N when pasture cover is between 1500 and 1800 kg DM/ha or at 30 to 35 millimetres (mm) high) At these levels there is enough leaf area for effective photosynthesis and plant growth.
  • You need 5 to 10mm of rain (or irrigated water) within eight hours of application to ensure nitrogen gets into the soil effectively and to stop your nitrogen spend disappearing into the air as ammonia gas (volatilisation).
  • Use SustaiN (or SustaiN + K if your soil also needs a potassium boost) to significantly decrease volatilisation loss.

Use the extra growth effectively

  • The pasture response (around 10 to 15 kg DM per kg N, depending on soil moisture levels) will happen four to six weeks after application, so factor this into your feed budget.
  • Graze nitrogen-boosted pastures at the usual height (seven to eight clicks on the plate meter for ryegrass clover pastures). You will get a greater dry matter response if they are spelled for longer but this is likely to be offset by a loss in pasture quality, clover and new grass tillers.
  • Monitor dry matter levels and turn excess feed into supplement if it won’t be eaten. This will help maintain pasture quality.
  • "It’s still important to monitor cow condition closely and dry off if it drops too far to maintain good weights going into winter. However, for many farmers, N-boosted pasture will be the best way to extend your season."

Article supplied by Ballance Agri-Nutrients