Boost nitrogen to boost summer milk

Boost nitrogen to boost summer milk

1 November 2016

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

Field trials1 during a dry summer in 1997 revealed applying nitrogen as late as December or January boosted shoot numbers by 37 percent – more than double the response achieved through the use of irrigation. Josh Verhoek, Ballance Science Extension Officer, says, “Applying nitrogen to pasture during growth periods encourages tillering. You’ll also get larger leaves on each tiller. This will make your pasture more resilient to summer grazing, weed invasion and drought, and enable it to recover more quickly for the next season.”

Another trial2 showed an extra 800 kilograms of Dry Matter per hectare (kg DM/ha) and 66 kilograms of Milk Solids per hectare (kg MS/ha) could be produced from December to April by applying 100 kg of Nitrogen per Hectare (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. With economic value in mind, obviously gains are meaningless if the cost of achieving them is too high. The ‘More Summer Milk’ study3, carried out in the 1990s, compared cropping, silage and nitrogen use as ways of increasing summer food supply, looking at effects on milk solids production and financial returns. “Applying nitrogen resulted in the most consistent and profitable response,” says Josh. “Cropping removed 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.”

To get the best returns from nitrogen there are a few things to consider:

Use the extra growth effectively

  • The pasture response will happen four to six weeks after nitrogen application, so factor this into your feed budget.
  • Graze nitrogen-boosted pastures at the usual height (seven-eight clicks on the plate meter for ryegrass clover pastures). A greater dry matter response can be achieved 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 is not going to be eaten. This will help maintain pasture quality.

Right place, right rate, right time, right product

  • The best response comes from high-fertility paddocks containing productive pasture species.
  • Tailor application to stocking rate. For 2.5 cows per hectare (/ha) or more, use two dressings of 30 kg N/ha. Below 2.5 cows/ha use two dressings of 20 kg N/ha.
  • Apply nitrogen when pasture cover is between 1500 and 1800 kg DM/ha (30-35 mm high). At these levels there is enough leaf area for effective photosynthesis and for plant growth to occur.
  • Watch your soil moisture. You need five to 10mm of rain (or irrigated water) within eight hours of application to ensure the nitrogen gets into the soil effectively and stops your nitrogen spend disappearing into the air as ammonia gas (volatilisation).

Volatilisation can commonly steal around 20 percent of the nitrogen applied.

Losses can be as high as 50 percent. Low soil moisture, organic matter content, cation exchange capacity and crop/pasture cover can all increase the risk of loss. Loss potential also rises with the amount of nitrogen applied.

Using SustaiN or SustaiN K if your soil also needs a potassium boost, can help. The urea in these products is coated with Agrotain™ nitrogen stabliser, which significantly decreases volatilisation losses, giving you more flexibility with the timing of nitrogen application.

“You’ll still need to monitor cow condition closely and dry off if it drops too far but, for many, nitrogen-boosted pasture will be the best way to extend your season,” says Josh.

1DairyNZ Farm Fact 7-16 ‘Nitrogen use going into summer’, DairyNZ 2012

2Penno J.W., Bryant A.M., Carter W.A., Macdonald K.A. 1995. Effect of nitrogen fertiliser and summer rotation length on milk production in a dry Waikato summer. Proceedings of New Zealand Society of Animal Production Vol 55: 64-66

3McGrath, D.F.; Dawson, J.E.; Thomson, N.A.; Simons, H.P. 1998. More summer Milk – the Opportunities Identified. Proceedings of the Ruakura Farmers’ Conference 50: 85-94.

Article supplied by Ballance Agri-Nutrients