By Debbie James

Trials on four Welsh dairy farms have shown that spraying liquid fertiliser directly onto the leaves of grass swards can grow higher dry matter yields from less inputs compared to conventional compound nitrogen.

Standard nitrogen (N) was applied at 50kgN/ha while foliar feed, which is based on urea and humic acid and is more commonly used in horticulture systems, was applied at a rate of 9kgN/ha every three weeks from February 16 to October 30.

Leaves have pores between cell structures which act as the entry point for the foliar feed.

Grass growth was measured weekly with a plate meter from March to October 2019, with twice monthly measurement in February and November and once in January and December.

The product and application costs for each treatment worked out at £26/ha for the foliar feed and £41/ha for conventional fertiliser.

The nitrogen use efficiency – the increase in dry matter (DM) yield achieved per kg of N applied – of both products was compared to the DM yield of a plot on each farm that received no fertiliser

In this comparison, all four foliar feed plots considerably outperformed those that had standard fertiliser applied.

The trial farms involved in the European Innovation Partnership (EIP) Wales project are in Pembrokeshire and Ceredigion and range in height from just 30 metres above sea level to 270 metres.

In the first year of the three-year study, the foliar feed plot on the lowest lying farm grew an additional 52.8kg/DM per kg/N applied compared to 22.4kg/DM in the conventional plot.

Even the farm at 270 metres, which grew the least amount of grass, captured an additional 18.1kg/DM per kg/N applied compared to 8.0kg/DM in the conventional plot.

“The fertiliser efficiency of the foliar feed is about 80-85 per cent in optimum conditions, whereas the efficiency of conventional ground applied products tends to be around 50 per cent-60 per cent,’’ says soil and grassland consultant Nigel Howells, who is advising in the trial.

However, when it came to DM yield overall, the plots treated with the compound fertiliser produced the greatest amount of grass over a 12-month period - 18.8tDM/ha compared to 18.3tDM/ha for foliar feed.

But, since considerably less foliar product was applied, this was not surprising, says Mr Howells, of Nigel Howells Consultancy.

“Between 60-70 per cent less nutrient was used on the foliar feed plots than on the conventional plots, to grow between 12.7-18.3t/DM of grass.

“As it is a three-year project we should have a good idea of the long term effects as far as dry matter yield is concerned and we are also doing detailed soil analysis to examine any effects on the soil.’’

He says the farms, which range in size from a 170-cow unit to 550 cows, had wanted to get involved in the project to examine ways of making artificial fertiliser use as efficient as possible, to reduce the levels they use.

The project not only looked at yields but had also examined how the method of fertiliser application can impact on livestock performance.

Mr Howells says the nitrogen content in the fresh grass on each of the three plots on every farm was monitored.

“To date, levels in the foliar feed plots haven’t exceeded 700ppm (parts per million) post-application whereas in the conventional plots some readings peaked at 1800ppm,’’ he says.

“This is relevant as the higher levels in the grass will require the stock eating it to use more energy to deal with it, making it less available for producing milk and meat or for maintaining condition and fertility.’’

Yield aside, foliar feed could have multiple benefits for grassland farmers going forward, Mr Howells suggests.

Previous trials have proven that foliar feeding can decrease the amount of total nitrogen necessary while minimising nitrogen losses through runoff.

In the case of compound fertiliser, nutrients are applied to the ground before being washed into the topsoil by rain and then taken up by the root system of the plants.