As fertiliser is an expensive input that impacts on yield, quality, profitability and the environment, substantial research effort continues to determine the optimum level of crop nutrition for specific crop and soil situations.
However, this improved level of precision in fertiliser recommendation is of little use if the fertiliser is applied unevenly or the incorrect rate is applied.
Uneven spreading is often seen as striping in a crop. However, crop yield and quality are frequently affected at levels of unevenness that are not as obvious as a crop colour difference.
In an eight-year life of a fertiliser spreader working on a 100ha tillage farm, poor spreading could cause a crop loss of €40,000. To avoid these losses, four critical factors must be considered:
Correct choice of machine for the fertiliser being used at the chosen bout width.Use of fertiliser with good physical quality characteristics.Correct setting of the machine for fertiliser and bout width using setting resources based on comprehensive tests .Correct setting and use of the machine on the field headland and narrow bout widths.Wide bouts and windy conditions
Today’s spreaders have a huge challenge, with most tillage farmers using 24m bout widths and some up to 36m. Broadcast spreaders rely on forming an overlapped pattern (Figure 1) to give an even spread.
Figure 1: Basic (shaded area) and overlapped (line) spread pattern at 18m: good pattern.
Some 24m spreaders need to spread fertiliser almost 48m, with fertiliser just visible in the next tramline, to give the correct overall spread pattern.
Even with a good-size distribution, it is vital that the correct spreader setting is used and that the bout width limitations of the spreader with urea are observed
While spreaders, and their setting for bout widths, are developed in perfect conditions in indoor test halls, field conditions with wind and undulating ground can cause a huge deterioration in spreading evenness. The impact of wind on wide bouts should never be underestimated.
Machine design
Today, there is a huge emphasis on spreader control technology and this has increased, with TAMS grants available for position-based control systems and weighing systems.
However, while this technology can help even spreading in certain situations, the most important aspect of a spreader is the basic design of the spreading elements and how it impacts on the spread pattern.
Features such as paint quality, hopper design and robust construction, etc, are all important, but the ability to spread evenly must be the first factor to be considered.
Full spread test reports
Machine design has a huge impact on how evenly the fertiliser is spread. The only way to assess a particular model is to have a spread test report where evenness of application is measured.
While the major fertiliser spreader manufacturers have their own test-hall facilities capable of giving very accurate test results, they only put the best results in their brochure.
Results from independent test halls are of far more value, but these tests are increasingly rare. You should look for an independent test result and always favour a manufacturer who provides one.
The evenness of spread is frequently summarised by a single figure: the coefficient of variation (CV) – the lower the CV percentage, the better the spread pattern.
A CV value of less than 15% would be acceptable in the field, but figures of 5% to 10% should be demanded from a test hall, where perfect conditions prevail.
But the CV does not tell the full story. The shape of the basic spread pattern determines how likely good spreading will be achieved in the field.
A triangular shape like the one in Figure 1 tells us that the spread will be a little less sensitive to wind or fertiliser variation than the more shouldered pattern of Figure 2.
Figure 2: Basic (shaded area) and overlapped (line) spread pattern at 18m: shouldered pattern.
The spreader producing a pattern like Figure 2 would need to be very carefully set to suit the fertiliser characteristics and spreading conditions. Better spreaders should have both a low CV and a good basic spread pattern.
Fertiliser quality
The physical characteristics of the fertiliser will affect how evenly it spreads and the spreader settings required and should be considered when purchasing.
Fertiliser quality will affect how evenly it spreads.
The key factors are:
Size of the granules: generally, larger particles will throw further. Where most particles are in the 2mm to 4mm range, it’s easier to achieve a good spread, but larger diameters (3mm to 4.5mm) may make it easier to achieve wider spread widths. The component parts of blends should have similar size distributions. Shape of the granule: rounded particles will roll off the disc more predictably. Density of the fertiliser: low-density fertiliser such as urea is more difficult to throw. Strength of granule: strong particles will resist break-up on the disc.Spreading urea
Urea will be more widely used across all farm types in the future. Its lower density (80%) presents a greater spreading challenge and it usually will not spread as wide as denser material. Urea with larger particle sizes is easier spread.
Even with a good-size distribution, it is vital that the correct spreader setting is used and that the bout width limitations of the spreader with urea are observed.
Wind will affect urea more than denser products, so spread in calm conditions if possible.
Blends of urea and conventional density fertiliser need to be considered very carefully. Proper size matching of particles (larger urea with smaller dense fertiliser particles) can help even spreading, but the onus is on the fertiliser supplier to show that this can be achieved.
Machine setting for evenness
The bout width being used and the physical quality of the fertiliser will determine the setting or adjustment required.
Spreader manufacturers have a database of settings for different fertilisers and the setting process increasingly requires the operator to match the fertiliser to be used to one in the database, by measuring size distribution, strength, density and shape.
Using a smartphone app, website or detailed brochure, the appropriate setting for the bout width being used is determined.
The components that are adjustable vary between manufacturer and model, but include one or more of the following:
Disc type, disc speed, vane type and position on disc. Position of fertiliser drop point on to disc.Disc height over crop or soil, or spreader or disc angle.Rate setting and calibration
Getting the correct rate of fertiliser out (kg/ha or bags/acre) is also important and while manufacturers’ setting guides are a starting point, some level of field calibration is usually needed.
Some makers have very useful setting aids such as calibrated flow bags which can be accurate, while others make full calibration through the spreader easy.
On-board weighing systems can make calibration very easy. Whatever system is used, it is important to establish the correct rate setting before field-scale errors are made.
Headland spreading
Headlands present particular problems for broadcast spreaders. Recent Oak Park research indicates that fertiliser distribution in the headland areas of fields on tillage farms is quite uneven compared with the in-field area, contributing to yield loss.
There are two challenges: spreading to the boundary, and merging the in-field runs with the headland runs.
To spread evenly to the field margin, the pattern to the headland side has to be completely different from the normal in-field pattern, to apply the desired rate up to the boundary without spreading past that boundary.
Different manufacturers use different techniques to achieve this altered spread pattern, such as deflectors dropped into the fertiliser flow; altered disc speed and fertiliser drop point, etc.
Recent Oak Park research indicates that fertiliser distribution in the headland areas of fields on tillage farms is quite uneven compared with the in-field area, contributing to yield loss
Many allow the pattern to be altered if yield optimisation is prioritised over fertiliser loss across the boundary. Operators need to ensure that the headland settings are correct.
Merging the in-field runs with the perpendicular headland runs requires operation of the shutter opening and closing at a precise distance from the headland.
This can be very difficult to achieve with modern spreaders, which throw fertiliser considerable distances. Accurate GPS systems can automatically control the on-off point, making this more precise than can typically be achieved manually, thus avoiding fertiliser waste and crop lodging at the headland. These need to be set carefully.
Conclusion
Spreading fertiliser evenly over wide bout widths is a challenge. To achieve this:Choose a spreader that has a good basic pattern and can achieve the bout width with a low CV value.Value fertiliser which has good physical quality and will spread evenly at wide bout widths.Use the manufacturer’s resources to identify the correct settings for the fertiliser and bout width being used.Ensure the headland spreading mechanism is properly set up.Consider technologies such as GPS headland switching and dynamic weighing to ease the task of headland operation and calibration. Read more
Crops & Spreaders event offers something for everyone
As fertiliser is an expensive input that impacts on yield, quality, profitability and the environment, substantial research effort continues to determine the optimum level of crop nutrition for specific crop and soil situations.
However, this improved level of precision in fertiliser recommendation is of little use if the fertiliser is applied unevenly or the incorrect rate is applied.
Uneven spreading is often seen as striping in a crop. However, crop yield and quality are frequently affected at levels of unevenness that are not as obvious as a crop colour difference.
In an eight-year life of a fertiliser spreader working on a 100ha tillage farm, poor spreading could cause a crop loss of €40,000. To avoid these losses, four critical factors must be considered:
Correct choice of machine for the fertiliser being used at the chosen bout width.Use of fertiliser with good physical quality characteristics.Correct setting of the machine for fertiliser and bout width using setting resources based on comprehensive tests .Correct setting and use of the machine on the field headland and narrow bout widths.Wide bouts and windy conditions
Today’s spreaders have a huge challenge, with most tillage farmers using 24m bout widths and some up to 36m. Broadcast spreaders rely on forming an overlapped pattern (Figure 1) to give an even spread.
Figure 1: Basic (shaded area) and overlapped (line) spread pattern at 18m: good pattern.
Some 24m spreaders need to spread fertiliser almost 48m, with fertiliser just visible in the next tramline, to give the correct overall spread pattern.
Even with a good-size distribution, it is vital that the correct spreader setting is used and that the bout width limitations of the spreader with urea are observed
While spreaders, and their setting for bout widths, are developed in perfect conditions in indoor test halls, field conditions with wind and undulating ground can cause a huge deterioration in spreading evenness. The impact of wind on wide bouts should never be underestimated.
Machine design
Today, there is a huge emphasis on spreader control technology and this has increased, with TAMS grants available for position-based control systems and weighing systems.
However, while this technology can help even spreading in certain situations, the most important aspect of a spreader is the basic design of the spreading elements and how it impacts on the spread pattern.
Features such as paint quality, hopper design and robust construction, etc, are all important, but the ability to spread evenly must be the first factor to be considered.
Full spread test reports
Machine design has a huge impact on how evenly the fertiliser is spread. The only way to assess a particular model is to have a spread test report where evenness of application is measured.
While the major fertiliser spreader manufacturers have their own test-hall facilities capable of giving very accurate test results, they only put the best results in their brochure.
Results from independent test halls are of far more value, but these tests are increasingly rare. You should look for an independent test result and always favour a manufacturer who provides one.
The evenness of spread is frequently summarised by a single figure: the coefficient of variation (CV) – the lower the CV percentage, the better the spread pattern.
A CV value of less than 15% would be acceptable in the field, but figures of 5% to 10% should be demanded from a test hall, where perfect conditions prevail.
But the CV does not tell the full story. The shape of the basic spread pattern determines how likely good spreading will be achieved in the field.
A triangular shape like the one in Figure 1 tells us that the spread will be a little less sensitive to wind or fertiliser variation than the more shouldered pattern of Figure 2.
Figure 2: Basic (shaded area) and overlapped (line) spread pattern at 18m: shouldered pattern.
The spreader producing a pattern like Figure 2 would need to be very carefully set to suit the fertiliser characteristics and spreading conditions. Better spreaders should have both a low CV and a good basic spread pattern.
Fertiliser quality
The physical characteristics of the fertiliser will affect how evenly it spreads and the spreader settings required and should be considered when purchasing.
Fertiliser quality will affect how evenly it spreads.
The key factors are:
Size of the granules: generally, larger particles will throw further. Where most particles are in the 2mm to 4mm range, it’s easier to achieve a good spread, but larger diameters (3mm to 4.5mm) may make it easier to achieve wider spread widths. The component parts of blends should have similar size distributions. Shape of the granule: rounded particles will roll off the disc more predictably. Density of the fertiliser: low-density fertiliser such as urea is more difficult to throw. Strength of granule: strong particles will resist break-up on the disc.Spreading urea
Urea will be more widely used across all farm types in the future. Its lower density (80%) presents a greater spreading challenge and it usually will not spread as wide as denser material. Urea with larger particle sizes is easier spread.
Even with a good-size distribution, it is vital that the correct spreader setting is used and that the bout width limitations of the spreader with urea are observed.
Wind will affect urea more than denser products, so spread in calm conditions if possible.
Blends of urea and conventional density fertiliser need to be considered very carefully. Proper size matching of particles (larger urea with smaller dense fertiliser particles) can help even spreading, but the onus is on the fertiliser supplier to show that this can be achieved.
Machine setting for evenness
The bout width being used and the physical quality of the fertiliser will determine the setting or adjustment required.
Spreader manufacturers have a database of settings for different fertilisers and the setting process increasingly requires the operator to match the fertiliser to be used to one in the database, by measuring size distribution, strength, density and shape.
Using a smartphone app, website or detailed brochure, the appropriate setting for the bout width being used is determined.
The components that are adjustable vary between manufacturer and model, but include one or more of the following:
Disc type, disc speed, vane type and position on disc. Position of fertiliser drop point on to disc.Disc height over crop or soil, or spreader or disc angle.Rate setting and calibration
Getting the correct rate of fertiliser out (kg/ha or bags/acre) is also important and while manufacturers’ setting guides are a starting point, some level of field calibration is usually needed.
Some makers have very useful setting aids such as calibrated flow bags which can be accurate, while others make full calibration through the spreader easy.
On-board weighing systems can make calibration very easy. Whatever system is used, it is important to establish the correct rate setting before field-scale errors are made.
Headland spreading
Headlands present particular problems for broadcast spreaders. Recent Oak Park research indicates that fertiliser distribution in the headland areas of fields on tillage farms is quite uneven compared with the in-field area, contributing to yield loss.
There are two challenges: spreading to the boundary, and merging the in-field runs with the headland runs.
To spread evenly to the field margin, the pattern to the headland side has to be completely different from the normal in-field pattern, to apply the desired rate up to the boundary without spreading past that boundary.
Different manufacturers use different techniques to achieve this altered spread pattern, such as deflectors dropped into the fertiliser flow; altered disc speed and fertiliser drop point, etc.
Recent Oak Park research indicates that fertiliser distribution in the headland areas of fields on tillage farms is quite uneven compared with the in-field area, contributing to yield loss
Many allow the pattern to be altered if yield optimisation is prioritised over fertiliser loss across the boundary. Operators need to ensure that the headland settings are correct.
Merging the in-field runs with the perpendicular headland runs requires operation of the shutter opening and closing at a precise distance from the headland.
This can be very difficult to achieve with modern spreaders, which throw fertiliser considerable distances. Accurate GPS systems can automatically control the on-off point, making this more precise than can typically be achieved manually, thus avoiding fertiliser waste and crop lodging at the headland. These need to be set carefully.
Conclusion
Spreading fertiliser evenly over wide bout widths is a challenge. To achieve this:Choose a spreader that has a good basic pattern and can achieve the bout width with a low CV value.Value fertiliser which has good physical quality and will spread evenly at wide bout widths.Use the manufacturer’s resources to identify the correct settings for the fertiliser and bout width being used.Ensure the headland spreading mechanism is properly set up.Consider technologies such as GPS headland switching and dynamic weighing to ease the task of headland operation and calibration. Read more
Crops & Spreaders event offers something for everyone
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