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Three Reasons to use Protected Urea in 2022

Protected urea grows more grass in the long term. This is just one of three reasons why farmers should use Protected Urea in 2022. Mark Plunkett, Patrick Forrestal and Siobhán Kavanagh, Teagasc detail these and how to use it while Patrick Forrestal has tips on using protected urea in a video also

At the recent Signpost General Assembly, Dr. Patrick Forrestal provided us with an update on the role of protected urea in reducing emissions. Watch below as he talks about Protected Urea - The fit and tips for your farm (12:47mins)


Reason 1:

Protected urea (protected with a urease inhibitor) is cheaper than CAN and standard urea

Protected urea is cheaper than CAN on a cost per kg of nitrogen basis, and, while it may appear slightly dearer than ordinary urea, it will give the same “effective N” for the plant as urea, at a 12.0% lower spreading rate.

Table 1 summarises the N lost from the three N fertiliser products as ammonia and nitrous oxide nitrogen gases.  The EPA estimates that ammonia loss from urea is 15.5% on average.  Both protected urea and CAN have lower rates of N loss (79% reduction for protected urea = 3.3% loss; 85% reduction for CAN = 2.3% loss).  Published research has quantified direct N loss as nitrous oxide from urea (0.25%), protected urea (0.4%) and CAN (1.49%), when indirect loss through ammonia redeposition is included urea and protected urea are similar.  In summary, protected urea curtails N losses by reducing (1) ammonia N emissions compared with standard urea, and (2) nitrous oxide N emissions compared to CAN. This would make protected urea more cost effective than both urea and CAN.  

Table 1: Percentage N lost from three N fertiliser products through two loss pathways

While the cost per kg of nitrogen is cheapest for standard urea (Table 2), when the extra losses associated with standard urea are accounted for, protected urea is cheaper. See example 1 below.

Table 2:           Relative Cost per kg N for Different Fertiliser Types

Example 1

Assuming a rate of 50 kg of N spread as protected urea or 50 kg of N spread as CAN in March 2022.  The equivalent quantity of N as standard urea that would need to be spread is 57kg to achieve the same plant available N, allowing for the extra losses with standard urea.  If we assume costs of urea = €950/t, protected urea = €1,000/t, CAN = €750/t, Table 2 highlights the difference in cost with protected urea being the cheapest option.

Table 3:           Relative cost of an application of N using different fertiliser types

At these prices, the farmer will get better value for money by using protected urea (as opposed to urea).  The example above, using current fertiliser prices, shows that the extra cost of the urease inhibitor more than covers its cost, if it saves 6 kg of N/ha.  The value of retaining N that had previously been lost as ammonia has increased dramatically in line with the increased fertiliser cost.  Also, in a situation where N application rate is limited, it makes sense to use less of a more effective product. 

Reason 2:

Protected urea grows more grass in the long term

While the quantity of grass grown by using CAN, protected urea and urea was similar across all fertiliser types in short-term Teagasc trials. In a long-term trial at Johnstown Castle, the grass grown by the fertiliser (i.e. net of the zero N control) for protected urea was greater than standard urea in 6 out of 7 years, 2018 being the exception due to drought when water was the limiting factor not nitrogen.  Protected urea grew 13% more grass on average compared to standard urea.  The additional yield is similar in magnitude to the extra effective N level delivered to the plant by protected urea over standard urea. CAN yielded 9% more than standard urea. 

Reason 3:

Potential to reduce farm emissions

By switching to 100% protected urea on dairy farms, total farm emissions have the potential to be reduced by 7-8% at a spreading rate of between 200 to 250 kg N / ha. The equivalent savings on total emissions on suckler farms is  1-2%, at a spreading rate of 60 to 80 kg N / ha. Straight P and K fertilisers or blends such as 0-7-30 or 0-10-20 would be needed to achieve a 100% switch or alternatively use of a split or two of high P-K products such as 18-6-12 +S based on nutrient need opens the opportunity for more straight N slots where protected urea +/-S is a good fit..

Table 4:          Benefits of using different fertiliser types

Unsure which product to use?

There are 20 protected urea products available from 6 companies.  There are straight N options, N+S options as well as N+K+S options. If in doubt on which products to use check the list at https://www.teagasc.ie/crops/soil--soil-fertility/

Supply may be an issue in 2022 but get yosiobur order in early to help reduce farm and overall agricultural emissions.

Practicalities of using it

Precise and ‘even’ spreading of fertiliser is essential.  As protected urea is a high- N product, trial and error is not an option, it must be got right first time.  Key points:

  1. Even spreading depends on the fertiliser physical quality, the spreader, the bout width used, and the adjustment of the spreader. 
  2. All urea fertilisers are lower density than CAN, which makes them a little more challenging to spread wide, making bout width choice and machine setting vital.  Urea from different sources varies in quality. Larger and stronger granules spread better.
  3. Protected urea, will spread similarly to standard urea, provided it is treated and stored well.  Choose a product that has larger and stronger particles. Excessive deposits on the spreading vanes indicates poor quality control in production or storage, impacting on even spreading.
  4. Provided the correct settings and bout width are used, protected urea can be spread evenly with most spreaders.
  5. To set the spreader, match the fertiliser’s quality to a product on the spreader manufacturer’s database (assessing size and strength). Use the manual or phone App or online resource to determine the bout width capability and the spreader settings (disc, vane, hopper height/angle etc) necessary for good spreading.
  6. Use simple tray tests if guided by the manufacturer to verify the spread pattern.

Spreading resources at:  Fertiliser Spreaders

Find out more here about the Teagasc Signpost Programme

Mark Plunkett is a Teagasc Crops Specialist – Soil & Plant Nutrition. Dr. Patrick Forrestal is a Teagasc Research Officer - Soil Science Agronomy and Siobhán Kavanagh is Teagasc Signpost Programme Communications and Engagement Specialist.