DAIRY SPECIAL: Impact of perennial rye-grass deterioration

Dairy farmers operating a composite-style system, combing an intensive, high output system with grazing have the potential to increase their milk from forage figure.

This was the message from Ben Wixey, of Germinal GB, who said block calving herds knew how to grow and manage grass and high input intensive herds knew how to make quality silage, but often farmers operating a composite-style system were not achieving their potential and there were great gains to be made.

Mr Wixey said it was widely understood that after reseeding with a non-native perennial rye-grass (PRG), deterioration occurred over time and weed grasses took over. Research showed by year 10 there could have been up to 90 per cent weed grasses in the ley.

But recent investment in their research station in Melksham has allowed Germinal to look more closely at the effect this deterioration had on the dry matter (DM) and energy potential of the ley and consequently the financial losses incurred.

Germinal’s research compared a new ley comprising 90 per cent PRG and 10 per cent weed grasses such as Yorkshire fog, rough stalked meadow grass and annual meadow grass whose seeds were naturally in the soil, with a five-year-old ley which had degraded to a 50:50 blend of PRG and weed grasses.

The difference in yield from second cut alone, which was taken in July, six weeks after first cut, meant there was an increased fresh weight forage of over 3.3t/hectare on the new ley versus the older ley, and an increase in DM of over one tonne per hectare.

Mr Wixey said: “There was a 26 per cent increase in the yield of PRG over weed grasses in this field just from having better grasses in a higher population.”

The domination by the energy-rich PRG meant the extra energy per hectare equated to 11,000MJ.

He added: “Because we know it takes 5.3MJ of energy to produce a litre of milk if everything else is the same, this extra energy equates to 2,000 litres more milk, and at 27p/litre that is an extra £550 of revenue.”

The same pattern was seen to a greater extent in a 10-year-old ley, which had just 25 per cent PRG remaining.

There was an additional 5.5t/ha of fresh weight forage which equated to an increase in energy of 18,000MJ/ha which had the potential to produce more than 3,000 litres of extra milk and £920 from the increased production alone.

Mr Wixey said a proportion of the increase in milk from forage target had to be as part of an annual reseeding policy. He said a one year in 10 reseeding policy was adequate but grassland management must be good.