Despite high fertiliser prices, cutting back on nitrogen (N) rates on grassland this year may not lead to lower costs of production, a researcher at the Agri-Food and Biosciences Institute (AFBI) has said.
Presenting data at the last of a three-part ‘Grassland Insights’ webinar series, Dr Paul Cottney showed the economic optimum for N application in a 3-cut silage system at three different CAN prices of £350, £450 and £650/t.
He also split his analysis on the basis of whether fields have very good or average growth potential. Those fields with good potential have been recently reseeded and have the correct balance of pH and key nutrients such as phosphorus (P) and potassium (K).
Estimates from historic data suggest they are capable of yielding an extra two tonned of dry matter (DM) per hectare over and above an average sward.
As shown in Table 1, for CAN priced at £350/t, the economic optimum for a recently reseeded sward is around 220kg N/ha over the three cuts, which drops to 180kg/ha in an average sward.
At a high CAN price of £650/t, this economic optimum for a productive sward is estimated at 170kg/ha, but in an average sward the optimum is only 90kg N/ha.
In a productive sward, the response justifies nearly 5 bags per acre across the three cuts, and again costs per tonne go up either side of this optimum rate.
Current price
Where CAN is bought at current prices of around £450/t, the optimum across three cuts of a productive sward is around six bags per acre, dropping to 4.5 bags per acre in the average sward.
“The economic optimum rate is lower [in the average sward] because of that lower yield potential [of 2t DM/ha]. But what this also shows is that sward production potential has a bigger influence on cost of production than the cost of nitrogen in itself,” said Cottney.
If a farmer has insufficient silage area or is overstocked due to the likes of bovine TB and has to buy in additional silage costing £35/t, it does slightly change the economic optimum. In this scenario, with CAN costing £450/t, the optimum rate across a productive sward is around 250kg N/ha (7.5 bags per acre) and 220kg N/ha for an average sward (6.6 bags per acre).
Payback
The data can also be used to estimate the payback from reseeding and addressing soil fertility. The figures presented by Cottney show the higher response to N fertiliser and the greater yield potential of the sward is worth up to £400/ha, so at a reseeding cost of £1,000/ha, that cost is paid back in just 2.5 years.
“Trying to improve those fields where yield is limited is a key influence in reducing cost of production per tonne of dry matter,” said Cottney.
Protein
The other issue to be aware of if cutting back on N, is the negative implication this will have for crude protein in silage.
“Insufficient N reduces grass protein levels and can mean you could be buying back concentrates to try and supplement that,” said Cottney.
Be ‘fussy’ when selecting new grass
Farmers who go to the expense of reseeding should be “fussy” when assessing the varieties in grass seed mixes, Dr Paul Cottney told last weeks’ webinar.
He said it was important to check performance of varieties on recommended lists and also tailor varieties to land type and management on the farm.
The likes of hybrid ryegrass and Italian ryegrass can deliver a lot of spring growth, but both lack persistency and utilising that spring growth is an issue on heavier land.
As a result, perennial ryegrass tends to offer more versatility and a better combination of quality, yield and persistency.
Early heading perennial ryegrass varieties should deliver improved spring growth, but if cutting date is delayed, silage quality is negatively impacted.
There are also diploid and tetraploid perennial ryegrass varieties. Tetraploids tend to be higher yielding and often have better grazing utilisation scores, but are less persistent and result in a more open sward, so are less suited to heavy land.
As well as diploid varieties, the other option on wetter land is to include some Timothy in the mix.
“Timothy is much better in colder and wetter soils and will perform and persist better than some of these other options,” said Cottney.
Grass measurement will help identify those fields most in need of reseeding. \ Donal O'Leary
Either way, the aim when reseeding is to replace the likes of Rough Stalked Meadow Grass and Yorkshire Fog with something that is more productive. These weed grasses only have 70 to 80% of the production capacity of perennial ryegrass, don’t respond as well to nitrogen and voluntary intakes by grazing animals are lower.
Options to assess sward productivity
There are a number of ways to assess the productivity of swards in different fields, including by counting the number of bales or trailer loads coming off at harvest, or how quick the sward recovers after cutting.
However, the most reliable method is grass measurement by the likes of a plate meter.
“What we have found is that when you actually do measure your grass, you’ll find tremendous field variation and that’s really where you try and use that [information] to target reseeding,” said Co Down dairy farmer, Jason Rankin.
Straight products used on Tyrone farm
During his presentation at the AFBI webinar, Tyrone dairy farmer Andrew Wright highlighted the importance of maintaining nitrogen levels, while achieving a balance of phosphorus (P), potassium (K) and sulphur (S).
He said his target was to have fields at Index 3 for P and K. Given he is running a relatively high input system, most fields are already well supplied with P – only around 1t of Diammonium Phosphate (18.46.0) is applied each year.
However, with a lot of swards cut for silage and the farm in a high rainfall area, there is a much greater need for K, with 6 to 10t of muriate of potash (0.0.60) used annually.
The only issue with that could be luxury uptake of K and potential problems with grass tetany in milking cows or milk fever in dry animals, although Wright maintained that he has experienced no problems to date.
“I’ve done it loads and I’ve never noticed anything,” he said.
When it comes to sulphur, he applies 75kg/ha of polysulphate across the farm each year.
Miracle
With the recent spike in fertiliser prices, he warned farmers to be cautious when it comes to using bacterial or other liquid products which come with claims that they will deliver “miracle” performance.
“If you buy a meter cubed of water with a bit of urea in it, it is not going to grow six times the amount of grass that the granular product at the same rate applied is going to grow. Traditional artificial fertiliser is still the most cost-effective way to get nutrients into your soil,” said Wright.
Over half of Turley farm getting no N
A major focus on reseeding and the use of red and white clover means that over half the farm run by the Turley family outside Downpatrick now receives no N fertiliser.
There are 200 suckler cows kept on the farm in an outdoor system, with cattle grazed on the likes of rape and kale over the winter, alongside grass silage.
At the event last week, Paul Turley said he has gradually shifted away from a high N system, with clovers, lucerne and multispecies swards all grown.
He said the lucerne was not successful and while he does still use some plantain and chicory in mixes, the “Achilles heel” for multispecies swards is weeds, especially docks.
Over the last couple of years, he has had good success with a mix per acre of two perennial ryegrass varieties (each 4kg), along with 4kg of red clover and 2kg of white clover.
“We’ve done those now for the last two or three years and they are bang on the money, hitting the [yield] average for the farm and they’re all on a zero N system,” he said.
Despite high fertiliser prices, cutting back on nitrogen (N) rates on grassland this year may not lead to lower costs of production, a researcher at the Agri-Food and Biosciences Institute (AFBI) has said.
Presenting data at the last of a three-part ‘Grassland Insights’ webinar series, Dr Paul Cottney showed the economic optimum for N application in a 3-cut silage system at three different CAN prices of £350, £450 and £650/t.
He also split his analysis on the basis of whether fields have very good or average growth potential. Those fields with good potential have been recently reseeded and have the correct balance of pH and key nutrients such as phosphorus (P) and potassium (K).
Estimates from historic data suggest they are capable of yielding an extra two tonned of dry matter (DM) per hectare over and above an average sward.
As shown in Table 1, for CAN priced at £350/t, the economic optimum for a recently reseeded sward is around 220kg N/ha over the three cuts, which drops to 180kg/ha in an average sward.
At a high CAN price of £650/t, this economic optimum for a productive sward is estimated at 170kg/ha, but in an average sward the optimum is only 90kg N/ha.
In a productive sward, the response justifies nearly 5 bags per acre across the three cuts, and again costs per tonne go up either side of this optimum rate.
Current price
Where CAN is bought at current prices of around £450/t, the optimum across three cuts of a productive sward is around six bags per acre, dropping to 4.5 bags per acre in the average sward.
“The economic optimum rate is lower [in the average sward] because of that lower yield potential [of 2t DM/ha]. But what this also shows is that sward production potential has a bigger influence on cost of production than the cost of nitrogen in itself,” said Cottney.
If a farmer has insufficient silage area or is overstocked due to the likes of bovine TB and has to buy in additional silage costing £35/t, it does slightly change the economic optimum. In this scenario, with CAN costing £450/t, the optimum rate across a productive sward is around 250kg N/ha (7.5 bags per acre) and 220kg N/ha for an average sward (6.6 bags per acre).
Payback
The data can also be used to estimate the payback from reseeding and addressing soil fertility. The figures presented by Cottney show the higher response to N fertiliser and the greater yield potential of the sward is worth up to £400/ha, so at a reseeding cost of £1,000/ha, that cost is paid back in just 2.5 years.
“Trying to improve those fields where yield is limited is a key influence in reducing cost of production per tonne of dry matter,” said Cottney.
Protein
The other issue to be aware of if cutting back on N, is the negative implication this will have for crude protein in silage.
“Insufficient N reduces grass protein levels and can mean you could be buying back concentrates to try and supplement that,” said Cottney.
Be ‘fussy’ when selecting new grass
Farmers who go to the expense of reseeding should be “fussy” when assessing the varieties in grass seed mixes, Dr Paul Cottney told last weeks’ webinar.
He said it was important to check performance of varieties on recommended lists and also tailor varieties to land type and management on the farm.
The likes of hybrid ryegrass and Italian ryegrass can deliver a lot of spring growth, but both lack persistency and utilising that spring growth is an issue on heavier land.
As a result, perennial ryegrass tends to offer more versatility and a better combination of quality, yield and persistency.
Early heading perennial ryegrass varieties should deliver improved spring growth, but if cutting date is delayed, silage quality is negatively impacted.
There are also diploid and tetraploid perennial ryegrass varieties. Tetraploids tend to be higher yielding and often have better grazing utilisation scores, but are less persistent and result in a more open sward, so are less suited to heavy land.
As well as diploid varieties, the other option on wetter land is to include some Timothy in the mix.
“Timothy is much better in colder and wetter soils and will perform and persist better than some of these other options,” said Cottney.
Grass measurement will help identify those fields most in need of reseeding. \ Donal O'Leary
Either way, the aim when reseeding is to replace the likes of Rough Stalked Meadow Grass and Yorkshire Fog with something that is more productive. These weed grasses only have 70 to 80% of the production capacity of perennial ryegrass, don’t respond as well to nitrogen and voluntary intakes by grazing animals are lower.
Options to assess sward productivity
There are a number of ways to assess the productivity of swards in different fields, including by counting the number of bales or trailer loads coming off at harvest, or how quick the sward recovers after cutting.
However, the most reliable method is grass measurement by the likes of a plate meter.
“What we have found is that when you actually do measure your grass, you’ll find tremendous field variation and that’s really where you try and use that [information] to target reseeding,” said Co Down dairy farmer, Jason Rankin.
Straight products used on Tyrone farm
During his presentation at the AFBI webinar, Tyrone dairy farmer Andrew Wright highlighted the importance of maintaining nitrogen levels, while achieving a balance of phosphorus (P), potassium (K) and sulphur (S).
He said his target was to have fields at Index 3 for P and K. Given he is running a relatively high input system, most fields are already well supplied with P – only around 1t of Diammonium Phosphate (18.46.0) is applied each year.
However, with a lot of swards cut for silage and the farm in a high rainfall area, there is a much greater need for K, with 6 to 10t of muriate of potash (0.0.60) used annually.
The only issue with that could be luxury uptake of K and potential problems with grass tetany in milking cows or milk fever in dry animals, although Wright maintained that he has experienced no problems to date.
“I’ve done it loads and I’ve never noticed anything,” he said.
When it comes to sulphur, he applies 75kg/ha of polysulphate across the farm each year.
Miracle
With the recent spike in fertiliser prices, he warned farmers to be cautious when it comes to using bacterial or other liquid products which come with claims that they will deliver “miracle” performance.
“If you buy a meter cubed of water with a bit of urea in it, it is not going to grow six times the amount of grass that the granular product at the same rate applied is going to grow. Traditional artificial fertiliser is still the most cost-effective way to get nutrients into your soil,” said Wright.
Over half of Turley farm getting no N
A major focus on reseeding and the use of red and white clover means that over half the farm run by the Turley family outside Downpatrick now receives no N fertiliser.
There are 200 suckler cows kept on the farm in an outdoor system, with cattle grazed on the likes of rape and kale over the winter, alongside grass silage.
At the event last week, Paul Turley said he has gradually shifted away from a high N system, with clovers, lucerne and multispecies swards all grown.
He said the lucerne was not successful and while he does still use some plantain and chicory in mixes, the “Achilles heel” for multispecies swards is weeds, especially docks.
Over the last couple of years, he has had good success with a mix per acre of two perennial ryegrass varieties (each 4kg), along with 4kg of red clover and 2kg of white clover.
“We’ve done those now for the last two or three years and they are bang on the money, hitting the [yield] average for the farm and they’re all on a zero N system,” he said.
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