Welsh Grassland Trial: Foliar Feeding vs Conventional Nitrogen Over Three Years

Same grass. A lot less nitrogen. A Welsh trial worth reading.

A three-year government-backed trial across four dairy farms in Wales set out to answer a straightforward question: can foliar feeding replace conventional granular nitrogen without sacrificing yield?

The short answer was yes. But some of the numbers along the way were harder to ignore than the headline.

What they did

Each farm split one field into three plots. One got conventional prilled nitrogen every 21 days. One got a foliar mix of urea and humic acid on the same schedule. One got nothing. Same grazing management across all three, same timing, same stocking rates. Three years of data across four sites.

The number that matters

At lower foliar nitrogen rates, the foliar plots grew comparable grass to conventional using between 40 and 65% less nitrogen per hectare. Not marginally less. Half, sometimes more.

The researchers measured this as nitrogen use efficiency, essentially how much additional dry matter you get per kilogram of nitrogen applied. Foliar came out two to four times higher than conventional across most sites and years.

By year three, when they pushed the foliar rates up closer to conventional levels, yields were broadly comparable at most sites. Same grass. Still using roughly half the nitrogen.

When conditions got difficult

Two findings from the trial are worth sitting with. In the cool spring of 2019, foliar plots outgrew conventional plots up to the end of April. Cold soil slows microbial activity and root uptake. Leaf uptake doesn’t care.

In the dry spring of 2020, foliar outperformed conventional at two sites. Moving nitrogen through soil into roots needs soil moisture. Foliar bypasses that step entirely.

Neither of these is a surprise if you understand the mechanism. But seeing it show up consistently in replicated farm data is a different thing to reading it in theory.

The clover

This one wasn’t the main focus of the trial, but it showed up in the data anyway. Foliar fed plots had consistently higher clover content than conventionally fertilised plots across most sites and years. In some cases sitting closer to the unfertilised control than to the conventional plots.

The researchers flagged it as worth further investigation. Make of that what you will.

The cost

The foliar ingredients and application cost more per hectare. That’s true and the trial was upfront about it. But the researchers calculated nitrogen cost per additional litre of milk across all sites and years. On average, foliar fed systems came in around 39% cheaper per litre of additional milk produced. The efficiency gap more than covered the higher input cost in most scenarios.

A note on geography

This trial was run in Wales. The biology of foliar uptake is the same wherever you are, but the specific rates, timings, and mixes that work in your system are worth working through with an agronomist who knows foliar programmes. What translates directly is the NUE finding and the performance advantage in cold or dry conditions, both of which are relevant here.

👉 The full technical report is linked below for anyone who wants to go through the data themselves.