Tactical management of nitrogen

Tactical management of nitrogen

27 February 2021

In autumn, there’s a focus on ensuring pasture covers and cow condition are at target levels ahead of winter, but it’s equally important to focus on how you achieve these to reduce potential nutrient losses during what is often a high-risk period of the year. Management decisions made in autumn impact the amount of nitrogen (N) loss that can occur from your farm. The risks linked to these management decisions are reported through your farm’s Environmental Report.

Planning Ahead

When focusing on pasture covers, an excellent place to start is completing a feed budget. Feed budgeting alone won’t directly lower the risk of N loss from your farm, but it will help you take a more calculated approach to fill any feed gaps, particularly if applying N fertiliser. For this reason, we report a feed budget as a management tool to help mitigate N loss from your farm.

Reduce pasture demand

Reducing pasture demand is one way to ensure you reach planned pasture covers. Culling empty or poor performing cows, or drying off those with lower body condition scores (BCS), will reduce your overall pasture demand and ensure more home-grown feed goes into milk production rather than maintenance. The reduced stocking rate will reduce the risk of N loss from stock urine patches. In conjunction with stocking rate, the total amount of dry matter (DM) eaten is a key driver of N loss risk, therefore reducing the number of non-productive dry animals on the farm will lower risk.

Increase pasture covers with strategic nitrogen fertiliser

The strategic use of N fertiliser is an option to increase pasture covers ahead of winter. It’s important to ensure pasture growth conditions are optimum to ensure maximum uptake of any applied N avoiding poor response rates increase the risk of N losses. Some key factors to consider:

  • It can take up to 40 (autumn) days to get a significant yield response to N fertiliser.
  • At low soil temperatures (below 6°C) pasture growth is limited
  • Monitoring moisture levels is important as too dry, and you will not get the response and too wet, you run the risk of N losses
  • The total amount of N applied for the season is an important consideration particularly with the new maximum amount of synthetic N that can be applied to pasture – 190 kilograms of N per hectare (kg/N/ha)
  • Application of fertiliser in high risk (winter) months is reflected as a high-risk activity in the environmental report

Import supplementary feeds

Importing supplementary feed to extend lactation or improve cow condition requires financial consideration to ensure you achieve your production and profit objectives. The purchase price and milk price will dictate if it is financially viable to feed supplements. There are great tools like the DNZ supplementary feed price calculator which allows you to determine how much you can pay for supplementary feed.

Importing supplement also imports N into your farm system. The higher the protein content of the supplement, the more N it contains. It is reported in the efficiency of N imported from the supplements section of the environmental report.

Effluent Management

Autumn is a crucial time for effluent management decisions. You need to ensure you have enough storage so you can differ irrigation during wet weather. Managing your storage as close to empty as possible during autumn will ensure you take the maximum amount of storage possible into winter. The biggest ponds are of no value if they are full at this time of the year. Effluent contains valuable plant-available N and when applied strategically to pasture can help reduce synthetic N applications during autumn. Your effluent area needs to be sufficiently sized to ensure applications don’t exceed regulations or create metabolic issues with animals. The environmental report uses a rule of thumb approach to assess risk, looking at the number of ha per 100 cows that effluent is applied over.

Purchased nitrogen surplus

The purchase N surplus is a key efficiency metric reported in the environmental report. It creates a single metric for the amount of N imported through supplement and fertiliser minus the amount removed in productive outputs (milk, meat, supplements sold). The higher your purchased surplus, the more N that remains in your farm system with the potential to be leached. As the purchased N surplus is a calculation of the inputs within the farmers’ control, the results can easily identify the results of tactical management decisions.

Farm Environment Plan’s are vital for the long term planning of sustainable farms. Our Sustainable Dairying Advisor’s can help develop a Farm Environment Plan that meets the individual’s farm needs and reflects the key issues on farm and any relevant regulatory requirements.

Read more about TIAKI - our sustainable dairying programme.

This article was written by our On-Farm Excellence - Environment Team