April 2019 Monthly Management

Protected Urea for reducing greenhouse gas emissions, Teagasc Pasture Profit Index (PPI) for grass profit metrics

18 April 2019

Protected Urea

What is it?

Protected urea is form of urea which is treated with an active ingredient called a urease inhibitor.
The urease inhibitor can be either:

  • coated onto the outside of the fertiliser granule, or
  • incorporated into the urea granule melt during manufacture.

Urease is the enzyme in the soil that speeds up the conversion of urea to ammonium. It is during this conversion the ammonia gas is lost from untreated urea. The urease inhibitor moderates the rate at which urea converts to ammonium. In doing so ammonia loss is reduced to low levels.

Won’t a slowing of the conversion from urea affect the availability of N for the grass crop?

No, because the conversion of protected urea to ammonium begins as soon as the fertiliser granule starts to melt. The urease inhibitor moderates the rate at which the urea-N converts to ammonium. The result is that the conversion occurs over period of a few days rather than a few hours, as would be the case with conventional urea. Remember, when fertiliser N is applied to soil its aim is to supply the grass or crop with N over a period of days to weeks rather than hours.

Summary of 30 application timings at 3 sites over 2 years
Graph 1.1

Will using protected urea reduce efficiency?

No, published Teagasc trials conducted in different areas of Ireland have shown that the nitrogen recovery efficiency of protected urea and CAN are consistently the same (See graph 1.1 above).

difference in nitrous oxide loss from CAN, Urea and protected Urea
Graph 1.2 shows the difference in nitrous oxide loss from CAN, Urea and protected Urea.

Published Teagasc trials have shown that protected urea has 71% lower nitrous oxide emissions than CAN and ammonia loss is reduced by 79% compared to urea.

Can I spread protected urea throughout the growing season?

Yes, you can spread protected urea across the growing season at times when you would otherwise spread calcium ammonium nitrate (CAN) or unprotected urea.

Is there potential for protected urea to reduce nitrate loss to water?

Yes, during periods when leaching occurs nitrate present in the soil is vulnerable to leaching loss. Protected urea does not deliver N directly as nitrate to the soil, therefore reducing the risk of nitrate losses occurring with rainfall post fertiliser application. Reduced ammonia loss compared to urea will also reduce the risk of ammonia N being deposited from the atmosphere onto sensitive habitats or into sensitive water bodies.

Agriculture accounts for 33% of national greenhouse gas emission and 98% of ammonia emissions and consequently is under the spotlight to reduce emissions. Use of protected urea can reduce agricultural greenhouse gas emissions and ammonia emissions while maintaining yield and saving cost.

Teagasc Pasture Profit Index (PPI)

The 2019 Pasture Profit Index (PPI) is an extremely useful tool when analyzing grass seed as it ranks grass varieties in economic terms. Each variety is valued on its overall contribution to net profit per hectare and is made up of key traits which drive profit including:

Seasonal DM Yield - presents the yield performance of each variety across spring, summer and autumn. Extra grass in the spring of the highest value in the index. Varieties with good spring and autumn growth are desirable to increase grass availability at these key points in your grazing season

Quality - indicates palatability and grass utilization. It is measured across the months of April, May, June and July. Quality is a hugely important trait which has the potential to deliver big difference at farm level.

Persistency - In the PPI, €0 indicates a persistent variety which is expected to last 12 years or longer under good management. Values of –€11, indicate that these varieties will not last over 10 years.

Highest Performing Varieties

Choosing varieties with positive values for quality will help ensure you have a palatable mixture that will increase utilization, intakes and animal performance.
When formulating grazing mixture a blend of late heading tetraploid and diploid varieties are selected

Top top two late tetraploids are:

  1. Abergain - highest ranked variety overall for 2019
  2. Astonenergy – second highest quality of all varieties

The top two late diploids are:

  1. Aberchoice - highest ranked late diploid on yield and quality
  2. Drumbo – excellent yield and the only other late diploid that is positive on quality

The four varieties which make up the Drinagh D74 and Permanent Grazing mixes. Selecting only the best varieties will deliver the best grazing mixes on the market.