Tips for fertiliser and grassland management in a changing world

There is nothing like hosting your discussion group to focus the mind on priorities for the month ahead. With over 90pc of our herd calved in the first week of March, the conversations were more about grassland management and nitrogen.

Nitrogen targets for spring are not what they used to be. We have witnessed a big evolution of fertiliser recommendations over the years.

Gone are the simplified routines of a bag of urea to the acre; today’s recommendations are much more considered.

The slogan ‘N is the cheapest feed input you will buy’ papered over a lot of cracks in soil fertility issues. There has been a huge increase in complexity of decision-making around grassland management.

Considerations for clover or multi-species swards, soil phosphorus and potassium indices, pH, slurry analyses, rainfall levels, soil temperature, the fertiliser database and chemical N allowances determine whether the spreader should be hitched up.

This was reflected in a significant number of farms in the group having no chemical N spread by early March.

Here, we had 25pc of the milking platform spread with chemical N in mid-February but had struggled to get conditions for slurry to go out. Slurry had only been spread on replacement heifer ground but a decent response had been seen.

Our plan is to get more slurry out in March once a few dry days come as tanks have been filling steadily.

We will continue with foliar N, building on what we learned from last year. With around 125kgN/ha spread in 2023 while growing similar grass dry matter to when we used conventional N at 170kgN/ha, it’s an experiment worth pursuing.

At a recent soil fertility webinar, Teagasc scientist Dr David Wall addressed the question “When will farmers finally know the N allowances for 2024?”.

We’re well into March and these goalposts are still moving. The current limit for N applications is 225kgN/ha.

Dr Wall explained that the EU Commission’s public consultation on ‘Protecting waters from pollution caused by nitrates from agricultural sources’ was nearing its conclusion, and following that two big questions would be answered:

Firstly, how much the chemical N allowance would be reduced by — anticipated to be a 5pc reduction bringing the limit down to 212kgN/ ha.

Secondly when would this change be implemented? As the nitrates action plan (NAP) which covers the derogation is in place until the end of 2025, it is anticipated that the new reduction would be implemented as soon as possible.

Significant water quality improvements, such as a 20pc reduction in leached N, are required within the time-frame of this NAP in order to secure the derogation beyond 2025.

A strong focus from the conference was around getting the most from soil fertility to grow grass and maximise N use efficiency.

Doing the basics right isn’t sexy, said Dr Wall, hinting at how addressing soil sample results was sometimes seen as a grind. Presentations stressed that huge progress could be attained from getting the fundamentals right: pH, P and K.

The biggest take-home message for me was that for farms operating at low pH and with low soil indices for P and K, 65pc of the N applied to those fields wasn’t making it into the plant at all.

Dead loss

So it’s ultimately a dead loss, both financially and environmentally. A sobering fact.

So how does all that fit into farm N management for the year ahead?

■ Anticipate a reduction in chemical N allowances.

■ Rapidly address soil fertility metrics at the most basic level, dealing first with pH and then with P and K indices.

■ Continue to incorporate clover into grazing swards through reseeding and oversowing.

■ As pH is critical for clover establishment, pushing pH towards 6.8 via liming gives the greatest response in terms of pasture growth in the year of establishment.

■ Utilise slurry via LESS, especially on silage fields as returning both organic matter and nutrient is really important when heavy silage cuts are taken.

In a seemingly endless process of regulatory change our response here is to increase nutrient use efficiency at the three levels of importance: the soil, the plant (clover) and the method of nutrient application.