Target fertiliser use on grassland for maximum yields

Treating grass more like an arable crop with targeted compound fertiliser use could lead to significant feed and fertiliser savings and boost grass production. Gemma Claxton reports.

Many dairy farmers are yet to unlock the genetic potential of modern grass varieties, but doing so could lead to high-quality yields nearly double the UK and Ireland average.

The finalists of the Yara Grass Prix, a challenge set to beef and dairy farmers to achieve the highest energy yield from grass, have averaged 13.6t/ha DM and 138,520 MJ/ha of metabolisable energy (ME) this season.

See also: How one organic farmer is maximising yield from forage

Yara area manager Nigel Hester says with the UK and Ireland average at 8t/ha DM and 88,000MJ/ha ME, it is clear grassland can produce more than people think.

“Because so many other things can go wrong, we want to manage things within our control and make sure nutrients are not a limiting factor to grass growth,” says Mr Hester.

He is encouraging farmers to treat their grass more like an arable crop, first by getting their soil analysed. The target is phosphate at index 2, potash at index 2-, magnesium at index 2 and pH 6.5.

Multi-cut grass requires a good supply of nitrogen, sulphur and potash, with potash in particular often not sufficiently replaced, adds Mr Hester.

“Crops will perform best when fresh nutrients are applied six to eight weeks before each cut to avoid potential lock-up in the soil.

“Soil structure is also critical to get right, with damage from machinery or livestock likely in wet conditions. Any compaction will reduce the ability of the plant to root properly and utilise soil reserves of nutrients and water,” says Mr Hester.

Slurry analysis allows farmers to maximise the ready supply of free nutrients before a nutrient management plan highlights any deficits to be topped up by a compound fertiliser, adds Mr Hester.

“Maximising the value from fertiliser by applying a quality compound [not a blend] accurately and evenly will target the chosen nutrient programme and deliver the best return on investment.”

However, he also believes quality of the ley is crucial and must match the farm’s characteristics.

“It’s a false economy to scrimp on quality of the ley. You’ll get a better response from fertiliser with high-quality seed.”

And, as he says, with the difference between the best and worst seed about £20/acre, the decision to buy the best is a “no brainer”. Especially when the cost of the seed is only about a quarter of the total cost of a full reseed, adds Mr Hester.

“What else can you grow for £20/acre? Not even 1t of fresh grass, yet you’ll probably grow over 10t more in the lifetime of a high quality ley at the cost of that one extra tonne.”

Tailored fertiliser use matching the crops needs throughout the growing season allows a more efficient approach and better balance of nutrition.

Farmers who fully exploit all their resources (soil and slurry) should cut the cost of compound fertiliser, while still increasing forage yields and quality, says Mr Hester.

Higher-quality silage should also save money on concentrates, either through the amount needed or protein percentage required, he adds.

Case study: Robert Tilly, Bowgyheere Farm, Penzance, Cornwall

robert tilly

Dairy farmer Robert Tilly is producing nearly 80% more energy from his grass than the national average, making its feed value nearly £400/ha more.

Mr Tilly, who runs a herd of 130 Holstein Friesian cows on 77ha, admits he hadn’t taken a lot of notice of his grass fields, but with an increasing need to tighten production efficiency, making the most out of the cheapest feed was the obvious solution.

“It’s important for grassland management to evolve with the cows. We’ve got higher stocking rates, bigger cows and we need a higher-quality diet to get more litres and improve milk constituents,” says Mr Tilly.

One of 10 contestants in this year’s Grass Prix contest, he aimed to achieve the highest energy yield from grass. The competition is designed to promote the potential of modern grass varieties, applying trial concepts in a real farm situation.

“A lot of livestock farmers are realising grass isn’t just ‘there’, it needs looking after as much as other crops.”

Since correcting his soil pH to 6.5 for optimal nutrient availability by applying 5t/ha of ground limestone, Mr Tilly reseeded a high-quality grass and clover ley in 2012 and used his slurry at 29cu m/ha plus various compound fertilisers to meet crop nutrient requirements.

The combination of soil and slurry analysis with the nutrient management plan has allowed Mr Tilly to make cost savings. Modifying his fertiliser to crop needs, he spread 500kg/ha of 27:5:5 NPK +7.5% sulphate in March and 430kg/ha of 24:0:13 NPK + 5% sulphate in May. This was due to a surplus of phosphorus after the first cut.

Other savings included switching from a 29% to 26% protein blend due to the higher-quality silage produced, saving about £15/t. Mr Tilly has also seen a steady rise in performance, his cows averaging 8,000 litres a year, with 3,000 of these from forage at 4.34% fat and 3.38% protein. And he believes the change in attitude to grassland management has contributed.

“The more milk from forage, the better the health of the cows. If I can push to 4,000 litres from forage on the same concentrate rate, I can move to 9,000 litres and that to me seems like a really good way of increasing output without increasing costs,” says Mr Tilly.

Key to his success were the choice of grass mix and fertilising it well. The ley was chosen to suit the farm system and conditions in the area.

“Our soils are medium clay and prone to poaching. Timothy gives the ley a thick dense bottom, the high sugar tetraploid varieties give the cows their high-energy grazing diet while the clover gives protein in the silage and it helps herd health.”

The results from Mr Tilly’s 3,000sq m sample plot for the Grass Prix were impressive, with first and second cuts yielding 39.1t/ha fresh weight, 10.82t/ha DM and giving 112,699MJ/ha metabolisable energy. That is 28% more energy than the national average of 88,000MJ/ha, giving it a value of £1,803/ha – £395/ha higher than the average.

This was achieved despite unprecedented rainfall delaying manure and fertiliser application, the first cut being taken nearly two weeks late and a following, uneven, manure spread, which reduced second-cut yield.

“There was a lot beyond our control, but that’s farming for you.”

Robert Tilly’s 2014 timeline:

  • 13 January Slurry analused (contains 2.5kg/cu m nitrogen, 
0.86kg/cu m phosphate, 2.57kg/cu m potash, 0.6kg/cu m sulphur, 0.62kg/cu m magnesium)
  • 28 January Soil analysed (P index 3, K index -2, Mg index 3)
  • 22 February 29cu m/ha slurry, chain harrowed and rolled
  • 10 March 500kg/ha of 27:5:5 NPK +7.5% sulphate
  • 16 May First cut taken (27.7t/ha fresh weight, 23.7% DM, 10.1MJ/kg ME, 21.7% CP)
  • 20 May 430kg/ha of 24:0:13 NPK + 5% sulphate
  • 21 May 29cu m/ha slurry
  • 25 June Second cut taken (11.4t/ha freshweight, 37.4% DM, 10.9MJ/kg ME, 23.8% CP)
  • 27 June 29m3/ha slurry
  • 28 June 125kg/ha of 27:5:5 NPK + 6% sulphate (grazing after second cut)