In episode one of Virtual Machinery Day 2021, we look at the various different low-emission slurry spreading (LESS) systems. Many farmers have availed of grant-aided support through the Targeted Agricultural Modernisation Scheme (TAMS) to make the move to LESS technology, with over 2,800 systems funded to date under the scheme. In order to meet our emission targets, reduce ammonia losses to the atmosphere and to become more sustainable as an industry, it is important we make the transition.
From the start of this year 6,786 derogation farmers going forward are required to spread all slurry using LESS technology. From 15 April, this requirement will be extended to an extra 5,511 farms stocked above 170kg N/ha across the whole farm prior to exporting slurry from 2021.
We compare and contrast each different system under the criteria of power requirements, weights and running costs, ease of use and of course growth and contamination results. The three LESS systems are the dribble bar, trailing shoe and shallow disc injection system, alongside the traditional splash plate as a benchmark.
Each system was used to apply slurry to a test plot in two different grass covers, the first being 400kg/DM/ha (plot A) and the second 800kg/DM/ha (plot B). Each slurry tanker was calibrated using the Teagasc calibration tool so that an even rate of 2,500gals/acre was applied by each of the four systems.
The trailing shoe results in higher Nitrogen uptake and reduced leaf contamination over the dribble bar.
Dribble bar
The dribble bar is the cheapest, most common and easiest LESS method used with the lowest associated running cost compared to the others. Slurry is pumped into the macerator and from there through a series of outlet hoses and on to the surface.
The only service point is the macerator and after a number of years, possibly the distribution hoses. If left outdoors, direct sunlight can eventually cause these hoses to go brittle and crack. That said, macerator and hose-related maintenance will be applicable to all.
A typical 7.5m retrofit system will weigh in the region of 450kg to 650kg depending on mounting type and brand. A 7.5m dribble bar with break-back protection, which we strongly advise, will cost around €13,000 to €14,000 fitted including VAT, before grant aid.
Tractor requirement: For a 2,750-gallon tanker, similar to what we used on the day, a minimum of 120-130hp is required and ideally a tractor nearing 6,500kg.
Obviously a smaller tanker will have lower power requirements, but not lower hydraulic flow.
Once in working position a flow of 65l/min is sufficient to run the macerator.
The trailing shoe leads to reduced contamination compared with the splash plate or dribble bar.
Advantages:
Cheapest LESS system.Easiest system used.Only LESS method grant-aided for retrofit under TAMS II.Lowest running costs.Disadvantages
Highest leaf contamination after splash plate.Lowest degree of N made available and recovered over other LESS methods. Trailing shoe
The trailing shoe was next to be tested. The principle here is that a wearing metal coulter (shoe) separates the sward canopy, allowing the slurry to be applied to the soil surface, thus avoiding contamination.
Maintenance is similar to the dribble bar, aside from the wearing metal shoes which will eventually need replacing. Lifespan again is dependent on a number of factors including metal type, soil type, level of downward pressure placed on each shoe and how much the system is used.
Each of these shoes will cost in the region of €25 to €50 each plus VAT to replace. A typical 7.2m unit will weigh in the region of 650kg to 750kg and cost anywhere from €15,000 to €18,000 including VAT before grant aid.
Tractor requirement: A slightly larger tractor will be required for this system, but again it depends on tanker size. These systems will be slightly heavier and harder to pull considering each shoe has a downwards pressure applied.
A 2,600gal tanker similar to what we used for our demonstration would require 140-150hp up front, again weighing in or around the 6,500kg mark. Once in working position 65l/min is the hydraulic flow required to run the macerator.
The disc injection is the most costly LESS system but provides the best uptake of slurry nutrients.
Advantages:
Reduced losses of ammonia.Higher N uptake.Reduced leaf contamination.Disadvantages:
More expensive over a dribble bar.Higher running costs.The unit has to be raised for reversing to avoid damage.Not grant-aided for retrofit through TAMS II.Shallow disc injection
The shallow disc injection system is the most complex of the three LESS systems. Here, a series of steel discs slit the ground to a depth of 20mm-60mm. Behind each is a coulter which allows slurry to flow out and into the slit.
This way the slurry has the least amount of exposure to the air, reducing volatilization and odour. As a result, a higher level of nitrogen and ammonia is retained. Given the complexity of injection systems there is naturally a higher running cost.
The life span of the unit aside from typical macerator maintenance will again depend on use and soil type. It is also important to note that such systems do not suit all soil types. The cost of replacing an entire disc section (two disc sets with springs) is in the region of €200 plus VAT. A 5.2m machine similar to what was used for our demonstration will cost an additional €26,000 to €30,000 plus VAT on top of the tanker new. This size of unit alone will weigh in the region of 1,500kg to 2,000kg and requires a purpose-built tanker with a rear linkage system.
The working widths of tanker-mounted systems tend to be a lot less in comparison to the other LESS methods. This is entirely down to their weight.
The injection system uses a series of discs to slit the surface from 20-60mm which slurry is then placed in.
Tractor requirement: Given that there are a series of discs engaging up to 60mm deep in the soil, quite a pull is required even taking into account the narrower working width of 5.2m. Tanker size again will play a part in tractor requirements. A minimum of 170hp to 180hp is required in good conditions and again a tractor weighing 7,000kg or over.
Advantages:
Best uptake of slurry nutrients.25%-30% more nitrogen recovered over splash plate.Nitrogen value available in kg/ha more than doubled.No leaf contamination and minimal odour.Disadvantages:
Most expensive LESS system.Not suited to all soils.Larger power requirement.Reduced working width, higher forward speed. Highest running costs.
Slurry applied using the injection method leads to no leaf contamination and reduced odour.
Results
After slurry had been applied to both trial plots, we closed the gate for five weeks before returning. The weeks of February and March that followed presented unfavourable grass-growing conditions.
Grass growth in general this spring on Tullamore Farm has been slow due to heavy rainfall and cold weather.
Leaf contamination
However, there were results, albeit not to the extent we would have liked. The major observation was the different levels of leaf contamination. As expected, the trailing shoe and disc injection systems offered practically no leaf contamination while the dribble showed contamination mainly in lines where slurry was distributed and the splash plate showing high levels of contamination throughout. On the higher cover of plot B this was clear as day. Lower contamination levels will lead for a quicker turn out and better clean out from grazing.
Using the splash plate as a bench mark, plot A at time of application had a grass cover of 400kg/DM/ha and plot B a cover of 800kg/DM/ha.
The growth results observed upon return are noted in Table 1 opposite.
Plot A (kg/DM/ha) Plot B (kg/DM/ha)
Splash Plate 600 1100
Dribble Bar 620 1100
Trailing Shoe 630 1200
Shallow Disc Injection 620 1250
Results table
Points to note
Research shows that by using a LESS method the N fertiliser replacement value of slurry increases by 10% to 15% due to increased N uptake and reduced ammonia (NH3) losses. Remember, that the narrower working width of a LESS system will result in an increased forward speed for the same application rate.Dribble bars are the only LESS system grant aided for retrofit.Weigh up the different options and see what works best for you.Most macerators will have a constant hydraulic requirement of 65l/min during operation. Calculations
We used an application rate of 2,500gals/acre, calculated using the Teagasc online calculator. The variables needed for the calculation include tank size, working width, time to empty and the target application rate.
Major 3,100gal and 5.2m injector = 5.8km/h.HiSpec 2,600gal and 7.2m trailing shoe = 8.1km/h.SlurryKat 2,750gal and 9m dribble bar = 7.0km/h.SlurryKat 2,750gal and splash plate = 3.2km/h.
In episode one of Virtual Machinery Day 2021, we look at the various different low-emission slurry spreading (LESS) systems. Many farmers have availed of grant-aided support through the Targeted Agricultural Modernisation Scheme (TAMS) to make the move to LESS technology, with over 2,800 systems funded to date under the scheme. In order to meet our emission targets, reduce ammonia losses to the atmosphere and to become more sustainable as an industry, it is important we make the transition.
From the start of this year 6,786 derogation farmers going forward are required to spread all slurry using LESS technology. From 15 April, this requirement will be extended to an extra 5,511 farms stocked above 170kg N/ha across the whole farm prior to exporting slurry from 2021.
We compare and contrast each different system under the criteria of power requirements, weights and running costs, ease of use and of course growth and contamination results. The three LESS systems are the dribble bar, trailing shoe and shallow disc injection system, alongside the traditional splash plate as a benchmark.
Each system was used to apply slurry to a test plot in two different grass covers, the first being 400kg/DM/ha (plot A) and the second 800kg/DM/ha (plot B). Each slurry tanker was calibrated using the Teagasc calibration tool so that an even rate of 2,500gals/acre was applied by each of the four systems.
The trailing shoe results in higher Nitrogen uptake and reduced leaf contamination over the dribble bar.
Dribble bar
The dribble bar is the cheapest, most common and easiest LESS method used with the lowest associated running cost compared to the others. Slurry is pumped into the macerator and from there through a series of outlet hoses and on to the surface.
The only service point is the macerator and after a number of years, possibly the distribution hoses. If left outdoors, direct sunlight can eventually cause these hoses to go brittle and crack. That said, macerator and hose-related maintenance will be applicable to all.
A typical 7.5m retrofit system will weigh in the region of 450kg to 650kg depending on mounting type and brand. A 7.5m dribble bar with break-back protection, which we strongly advise, will cost around €13,000 to €14,000 fitted including VAT, before grant aid.
Tractor requirement: For a 2,750-gallon tanker, similar to what we used on the day, a minimum of 120-130hp is required and ideally a tractor nearing 6,500kg.
Obviously a smaller tanker will have lower power requirements, but not lower hydraulic flow.
Once in working position a flow of 65l/min is sufficient to run the macerator.
The trailing shoe leads to reduced contamination compared with the splash plate or dribble bar.
Advantages:
Cheapest LESS system.Easiest system used.Only LESS method grant-aided for retrofit under TAMS II.Lowest running costs.Disadvantages
Highest leaf contamination after splash plate.Lowest degree of N made available and recovered over other LESS methods. Trailing shoe
The trailing shoe was next to be tested. The principle here is that a wearing metal coulter (shoe) separates the sward canopy, allowing the slurry to be applied to the soil surface, thus avoiding contamination.
Maintenance is similar to the dribble bar, aside from the wearing metal shoes which will eventually need replacing. Lifespan again is dependent on a number of factors including metal type, soil type, level of downward pressure placed on each shoe and how much the system is used.
Each of these shoes will cost in the region of €25 to €50 each plus VAT to replace. A typical 7.2m unit will weigh in the region of 650kg to 750kg and cost anywhere from €15,000 to €18,000 including VAT before grant aid.
Tractor requirement: A slightly larger tractor will be required for this system, but again it depends on tanker size. These systems will be slightly heavier and harder to pull considering each shoe has a downwards pressure applied.
A 2,600gal tanker similar to what we used for our demonstration would require 140-150hp up front, again weighing in or around the 6,500kg mark. Once in working position 65l/min is the hydraulic flow required to run the macerator.
The disc injection is the most costly LESS system but provides the best uptake of slurry nutrients.
Advantages:
Reduced losses of ammonia.Higher N uptake.Reduced leaf contamination.Disadvantages:
More expensive over a dribble bar.Higher running costs.The unit has to be raised for reversing to avoid damage.Not grant-aided for retrofit through TAMS II.Shallow disc injection
The shallow disc injection system is the most complex of the three LESS systems. Here, a series of steel discs slit the ground to a depth of 20mm-60mm. Behind each is a coulter which allows slurry to flow out and into the slit.
This way the slurry has the least amount of exposure to the air, reducing volatilization and odour. As a result, a higher level of nitrogen and ammonia is retained. Given the complexity of injection systems there is naturally a higher running cost.
The life span of the unit aside from typical macerator maintenance will again depend on use and soil type. It is also important to note that such systems do not suit all soil types. The cost of replacing an entire disc section (two disc sets with springs) is in the region of €200 plus VAT. A 5.2m machine similar to what was used for our demonstration will cost an additional €26,000 to €30,000 plus VAT on top of the tanker new. This size of unit alone will weigh in the region of 1,500kg to 2,000kg and requires a purpose-built tanker with a rear linkage system.
The working widths of tanker-mounted systems tend to be a lot less in comparison to the other LESS methods. This is entirely down to their weight.
The injection system uses a series of discs to slit the surface from 20-60mm which slurry is then placed in.
Tractor requirement: Given that there are a series of discs engaging up to 60mm deep in the soil, quite a pull is required even taking into account the narrower working width of 5.2m. Tanker size again will play a part in tractor requirements. A minimum of 170hp to 180hp is required in good conditions and again a tractor weighing 7,000kg or over.
Advantages:
Best uptake of slurry nutrients.25%-30% more nitrogen recovered over splash plate.Nitrogen value available in kg/ha more than doubled.No leaf contamination and minimal odour.Disadvantages:
Most expensive LESS system.Not suited to all soils.Larger power requirement.Reduced working width, higher forward speed. Highest running costs.
Slurry applied using the injection method leads to no leaf contamination and reduced odour.
Results
After slurry had been applied to both trial plots, we closed the gate for five weeks before returning. The weeks of February and March that followed presented unfavourable grass-growing conditions.
Grass growth in general this spring on Tullamore Farm has been slow due to heavy rainfall and cold weather.
Leaf contamination
However, there were results, albeit not to the extent we would have liked. The major observation was the different levels of leaf contamination. As expected, the trailing shoe and disc injection systems offered practically no leaf contamination while the dribble showed contamination mainly in lines where slurry was distributed and the splash plate showing high levels of contamination throughout. On the higher cover of plot B this was clear as day. Lower contamination levels will lead for a quicker turn out and better clean out from grazing.
Using the splash plate as a bench mark, plot A at time of application had a grass cover of 400kg/DM/ha and plot B a cover of 800kg/DM/ha.
The growth results observed upon return are noted in Table 1 opposite.
Plot A (kg/DM/ha) Plot B (kg/DM/ha)
Splash Plate 600 1100
Dribble Bar 620 1100
Trailing Shoe 630 1200
Shallow Disc Injection 620 1250
Results table
Points to note
Research shows that by using a LESS method the N fertiliser replacement value of slurry increases by 10% to 15% due to increased N uptake and reduced ammonia (NH3) losses. Remember, that the narrower working width of a LESS system will result in an increased forward speed for the same application rate.Dribble bars are the only LESS system grant aided for retrofit.Weigh up the different options and see what works best for you.Most macerators will have a constant hydraulic requirement of 65l/min during operation. Calculations
We used an application rate of 2,500gals/acre, calculated using the Teagasc online calculator. The variables needed for the calculation include tank size, working width, time to empty and the target application rate.
Major 3,100gal and 5.2m injector = 5.8km/h.HiSpec 2,600gal and 7.2m trailing shoe = 8.1km/h.SlurryKat 2,750gal and 9m dribble bar = 7.0km/h.SlurryKat 2,750gal and splash plate = 3.2km/h. 
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