Now is a good time to take a look at setting up the fertiliser spreader for work.
Fertiliser remains one of the most expensive and beneficial inputs on all farms. Timing and application methods are crucial to maximise the returns from broadcasting fertiliser.
The accuracy of application is essentially down to the setup and operation of the fertiliser spreader. There are a number of factors that can influence how effective application of fertiliser is on the farm:
Tractor setup and forward speedFertiliser spreader mechanism checksCalibrationReducing driver errorExamining fertiliser qualityFinancial loss
Poor setup and maintenance of the fertiliser spreader is literally throwing money away. A study in the UK suggested that a coefficient of variation value (CV) of 30%, which is not that difficult to achieve, gives a financial loss of €31/ ha in winter wheat.
I have carried out a number of tray tests on machines over the years, with results from 5.5% CV to 29% CV. The CV value is an indication of how even fertiliser is applied across the field. A CV value above 15% can result in visual differences in the crop striping and lodging in cereals.
Take a farmer with 50ha of grass who over the course of the year, with five applications, applies two bags per hectare too much. That is 100 extra bags to be paid for, or 5t at €350, which amounts to €1,750. The life cycle of that machine on the farm could be 10 years. So if the problem is not corrected, that is €17,750 overspent on fertiliser in 10 years.
Breaking it down, it is just less than 7kg over-applied to every acre over 10 years. This could also happen if using contractors.
The cost of the fertiliser is offset by extra grass growth. However, if this grass is not needed for grazing, what happens to the grass? From an environmental point of view, is the farm now compliant with Nitrates if extra fertiliser is applied?
Tractor setup and forward speed check
The tractor setup checks ensure the linkage is the correct category for the machine and the lift capacity is adequate.
For safety reasons, the tractor should have enough front ballast to cope with the weight of a rear-mounted fertiliser spreader. The lift arms on the tractor should be level and all PTO guards in place.
Checking the forward speed is a simple task. Nearly all modern tractors will display the forward speed in km/h. However, if you suspect a faulty reading, the following technique can be used to check the reading:
Measure a distance of 100m in the field.Select the appropriate gear to give the correct forward speed at the desired PTO rpm.From a rolling start, record the time in seconds to travel 100m.The formula below is used to calculate forward speed in km/h.Forward speed (km/h) = 360/time taken in seconds to travel 100m
Fertiliser spreader checks
The parts of the spreader that should be inspected at the start of the season include the following:
The shutter opening and closing needs to be free from obstruction and moving smoothly.The agitator in the bottom of the hopper will have an effect on flow rate – if worn, it may not be able to sufficiently stir the fertiliser and break down small lumps.The discs need to be checked – a damaged disc may cause vibration or disrupt the spreader’s performance.
The veins on the disc are critical to send the fertiliser from the machine in the correct pattern. Wear on veins is not uncommon, especially when they are required to broadcast fertiliser over wide working widths. Channels and ruts can often be seen on the veins, which will affect the spread pattern.The hopper itself should be clean and secure to carry the fertiliser load.Hydraulic hoses and couplings should be examined and replaced if damaged.Lights and safety rails need to be in good working condition.Calibration
Calibration of fertiliser spreaders is the only way to calculate an accurate application rate in kg/ha.
Farmers need to apply fertiliser accurately and evenly to comply with crop nutritional requirements. Application rate is affected by:
Bout width.Forward speed.Regulator setting.Technology and calibration aids from manufacturers have greatly helped this process.
Most manufacturers offer online support and mobile phone apps to help farmers calibrate their machines.
Other manufacturers have introduced flow-rate kits to calculate fertiliser output. The operator needs to know what the calibration method is for the machine that is being used.
High-spec machines at the top of the market offer self-calibrating options, which involve weight cells and forward speed sensors, to monitor and adjust the regulator setting on the machine while in work.
Year-on-year, fertiliser characteristics will change. Humidity and other factors will influence the flow rate. The setting used last year on the machine will not guarantee the same application rate this year.
The static calibration method described below will calibrate most machines. The problem is how to collect the fertiliser from the machine.
Some manufacturers will provide collection buckets or trays and the best advice is to contact the dealer for the options available.
Static calibration
To calculate the target output of spreader per minute, attach the calibration collection device to the spreader and ensure it is operating at a PTO speed of 540rpm.
Set the metering mechanism to the recommended setting from the manufacturer’s guidelines. Open the metering mechanism and allow the product to flow for one minute.
Weigh the fertiliser and confirm the flow rate per minute.
Use this figure in the following formula to calculate application rate in kilogrammes per hectare.
The 600 figure in the formula is a constant that will never change – the variable figures are forward speed, bout width and flow rate.
Application rate kg/ha = (600 X flow rate kg/min)/(forward speed (km/h) X bout width (m))
Driver error
With the machine calibrated, the last link in the chain is needed to execute the job – the driver. Poor driving can account for variations in the application of fertiliser and the problem is that these variations may never be known.
Marking out fields and turning off the machine at the right time are basic skills. The development and availability of GPS technology and sectional control machines takes the risk out of leaving it all to human instinct.
Investment in this technology depends on the scale of the farm and perhaps the payback on the technology may not be as long as you think.
Fertiliser quality
No matter how good an operator or machine performs, poor quality fertiliser will always cause problems. Light grains of fertiliser are almost impossible to broadcast over the working width of the machine.
Force equals mass by acceleration, but the trouble is that the acceleration speed generated by the veins on the disc is not matched by the mass in the light granules to generate enough force to throw the granules over the working width.
The ideal fertiliser will have a rounded granule shape sized between 2mm and 4mm and will be able to withstand the force vein on impact.
Think safety
Remember the risks when applying fertiliser:
Crushing injuries under bags or machinesManual handling with small 50kg bagsGuards, PTO, shaft covers and beware of spinning discsWatch out for tractors manoeuvring in yards.This article was first published in the Irish Farmers Journal in January 2016.
Read more
EU fertiliser price scandal uncovered
Now is a good time to take a look at setting up the fertiliser spreader for work.
Fertiliser remains one of the most expensive and beneficial inputs on all farms. Timing and application methods are crucial to maximise the returns from broadcasting fertiliser.
The accuracy of application is essentially down to the setup and operation of the fertiliser spreader. There are a number of factors that can influence how effective application of fertiliser is on the farm:
Tractor setup and forward speedFertiliser spreader mechanism checksCalibrationReducing driver errorExamining fertiliser qualityFinancial loss
Poor setup and maintenance of the fertiliser spreader is literally throwing money away. A study in the UK suggested that a coefficient of variation value (CV) of 30%, which is not that difficult to achieve, gives a financial loss of €31/ ha in winter wheat.
I have carried out a number of tray tests on machines over the years, with results from 5.5% CV to 29% CV. The CV value is an indication of how even fertiliser is applied across the field. A CV value above 15% can result in visual differences in the crop striping and lodging in cereals.
Take a farmer with 50ha of grass who over the course of the year, with five applications, applies two bags per hectare too much. That is 100 extra bags to be paid for, or 5t at €350, which amounts to €1,750. The life cycle of that machine on the farm could be 10 years. So if the problem is not corrected, that is €17,750 overspent on fertiliser in 10 years.
Breaking it down, it is just less than 7kg over-applied to every acre over 10 years. This could also happen if using contractors.
The cost of the fertiliser is offset by extra grass growth. However, if this grass is not needed for grazing, what happens to the grass? From an environmental point of view, is the farm now compliant with Nitrates if extra fertiliser is applied?
Tractor setup and forward speed check
The tractor setup checks ensure the linkage is the correct category for the machine and the lift capacity is adequate.
For safety reasons, the tractor should have enough front ballast to cope with the weight of a rear-mounted fertiliser spreader. The lift arms on the tractor should be level and all PTO guards in place.
Checking the forward speed is a simple task. Nearly all modern tractors will display the forward speed in km/h. However, if you suspect a faulty reading, the following technique can be used to check the reading:
Measure a distance of 100m in the field.Select the appropriate gear to give the correct forward speed at the desired PTO rpm.From a rolling start, record the time in seconds to travel 100m.The formula below is used to calculate forward speed in km/h.Forward speed (km/h) = 360/time taken in seconds to travel 100m
Fertiliser spreader checks
The parts of the spreader that should be inspected at the start of the season include the following:
The shutter opening and closing needs to be free from obstruction and moving smoothly.The agitator in the bottom of the hopper will have an effect on flow rate – if worn, it may not be able to sufficiently stir the fertiliser and break down small lumps.The discs need to be checked – a damaged disc may cause vibration or disrupt the spreader’s performance.
The veins on the disc are critical to send the fertiliser from the machine in the correct pattern. Wear on veins is not uncommon, especially when they are required to broadcast fertiliser over wide working widths. Channels and ruts can often be seen on the veins, which will affect the spread pattern.The hopper itself should be clean and secure to carry the fertiliser load.Hydraulic hoses and couplings should be examined and replaced if damaged.Lights and safety rails need to be in good working condition.Calibration
Calibration of fertiliser spreaders is the only way to calculate an accurate application rate in kg/ha.
Farmers need to apply fertiliser accurately and evenly to comply with crop nutritional requirements. Application rate is affected by:
Bout width.Forward speed.Regulator setting.Technology and calibration aids from manufacturers have greatly helped this process.
Most manufacturers offer online support and mobile phone apps to help farmers calibrate their machines.
Other manufacturers have introduced flow-rate kits to calculate fertiliser output. The operator needs to know what the calibration method is for the machine that is being used.
High-spec machines at the top of the market offer self-calibrating options, which involve weight cells and forward speed sensors, to monitor and adjust the regulator setting on the machine while in work.
Year-on-year, fertiliser characteristics will change. Humidity and other factors will influence the flow rate. The setting used last year on the machine will not guarantee the same application rate this year.
The static calibration method described below will calibrate most machines. The problem is how to collect the fertiliser from the machine.
Some manufacturers will provide collection buckets or trays and the best advice is to contact the dealer for the options available.
Static calibration
To calculate the target output of spreader per minute, attach the calibration collection device to the spreader and ensure it is operating at a PTO speed of 540rpm.
Set the metering mechanism to the recommended setting from the manufacturer’s guidelines. Open the metering mechanism and allow the product to flow for one minute.
Weigh the fertiliser and confirm the flow rate per minute.
Use this figure in the following formula to calculate application rate in kilogrammes per hectare.
The 600 figure in the formula is a constant that will never change – the variable figures are forward speed, bout width and flow rate.
Application rate kg/ha = (600 X flow rate kg/min)/(forward speed (km/h) X bout width (m))
Driver error
With the machine calibrated, the last link in the chain is needed to execute the job – the driver. Poor driving can account for variations in the application of fertiliser and the problem is that these variations may never be known.
Marking out fields and turning off the machine at the right time are basic skills. The development and availability of GPS technology and sectional control machines takes the risk out of leaving it all to human instinct.
Investment in this technology depends on the scale of the farm and perhaps the payback on the technology may not be as long as you think.
Fertiliser quality
No matter how good an operator or machine performs, poor quality fertiliser will always cause problems. Light grains of fertiliser are almost impossible to broadcast over the working width of the machine.
Force equals mass by acceleration, but the trouble is that the acceleration speed generated by the veins on the disc is not matched by the mass in the light granules to generate enough force to throw the granules over the working width.
The ideal fertiliser will have a rounded granule shape sized between 2mm and 4mm and will be able to withstand the force vein on impact.
Think safety
Remember the risks when applying fertiliser:
Crushing injuries under bags or machinesManual handling with small 50kg bagsGuards, PTO, shaft covers and beware of spinning discsWatch out for tractors manoeuvring in yards.This article was first published in the Irish Farmers Journal in January 2016.
Read more
EU fertiliser price scandal uncovered
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