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Could you grow 14Ton of grass with 200 units of Nitrogen?


The European Green Deal calls for EU farmers to reduce their chemical Nitrogen inputs by 20% by 2030. Nationally the Ag Climatise document re-iterates this target but also sets an interim target of a 15% reduction by 2025. Joe Kelleher, Dairy Advisor Teagasc, Newcastle West looks at achieving this

Ag Climatise Targets

The Ag Climatise document states “Chemical nitrogen use on Irish farms peaked at 408,000 tonnes in 2018. This must be reduced to a target level of 350,000 tonnes by 2025, with a further reduction to an absolute maximum of 325,000 tonnes by 2030”. While there are no targets at an individual farm level, the figures are being monitored at a national level and it is up to each of us to put our shoulder to the wheel to try hit these targets for the benefit of everyone.

Nationally, Irish dairy farmers are spreading 185kgs/Ha (148units/acre) across the whole farm, but there are huge variations between farms and also between fields within farms. The milking platform typically tends to be fertilised more intensively than outside blocks that may be used for silage or the rearing of replacements.

Under the Nitrate Regulations the maximum chemical nitrogen rate is 282kgs/Ha and many of the more intensive dairy farmers would be spreading close to this limit on the milking platform, and these are the cohort of farmers that are going to come under most pressure to reduce their reliance on chemical Nitrogen over the coming years.

Discussion Group examples

At a recent discussion group meeting of a grass focused discussion group, the farmers growing the most grass were spreading 265kgs chemical nitrogen and growing 15.5Ton of grass dry matter per hectare. Another cohort of farmers within the group were growing 12.5Ton DM/Ha from only 155kgs of chemical N/Ha. This latter group are getting a good response from their Nitrogen use but the key measure of Nitrogen Use Efficiency is how much of the Nitrogen is captured and converted into milk and meat. The group are currently completing an exercise to figure out their individual Nitrogen Use Efficiencies.

So where do these cohort of heavily stocked farmers begin in their attempt to reduce their chemical Nitrogen input? Attempting to drop your chemical Nitrogen by 20% in one year is only going to result in reduced grass growth, increased feed supplementation and reduced profits. In the mid-long term we need to set up our farms to achieve this 20% reduction, but we also need to set our farms up to replace this Nitrogen by other means.

Potential of Clover & Multi Species Swards

Numerous research trials over the past few years have shown  that clover and multi species swards are both capable of growing 12- 14Ton DM/Ha from 150Kgs of chemical nitrogen. Ultimately, we all need to be heading towards these figures, but it is not going to happen overnight. 

Clover has huge potential to deliver, but getting it established, requires considerable effort and perseverance from farmers. At a recent online conference, Michael Egan from Teagasc, Moorepark outlined how we need a clover content of 30% before it starts impacting on herbage production. To attain this level of clover in our swards is going to take time, but by 2025, we are going to have to have a significant portion of our farms at this level to enable cut our chemical inputs significantly, without impacting on grass growth. Michael is recommending that we reseed 10% of our farms with a high clover mix annually and over-sow another 30% of the farm. Over 3 years we could have introduced clover to the entire farm.

Short-term planning

In the short-term what can we do? 250kgs of N/Ha should be capable of growing in excess of 14ton of dry matter per hectare. For those spreading in excess of 250kgs/Ha of chemical N/Ha the target should be to cut back to 250kgs in 2021. This is the equivalent of 200units per acre. Figure 1 shows how this can be achieved across the year on an index 3 soil, by using a combination of protected urea and 18.6.12.

Plan your fertiliser plan now for the year and select the fields you intend getting clover into this year. If we plan now, we can cut our fertiliser usage thereby cutting our costs whilst simultaneously reducing our greenhouse gas emissions. A win win for everyone.

For more on AgClimatise see a recent webinar on the topic here