Variable-rate fertiliser spreading can be described as controlling the inputs applied to a field by varying the amounts spread in different areas of the same field based on soil fertility results.
Brian Reilly is an agronomist with Drummonds in Ballough, Lusk, Co Dublin. He has helped to launch the variable fertiliser spreading service in Drummonds’ Lusk branch. The service is becoming popular among Drummonds customers, with 25 farmers in the area participating.
Brian explains: “Over the years, we were getting feedback from vegetable growers and tillage farmers about the variability in crops that got a broadcast treatment of lime, phosphorus and potassium on the interpretation of ordinary soil test results.” He was looking for a way of correcting that variability and he claims that variable-rate fertiliser spreading – correcting the variability resulting from fertility – is working for his customers.
How does it work?
Firstly, the boundaries of the field are mapped with a global positioning system (GPS) device to give an accurate area reading for the field. Reilly says a company specialist drives a utility vehicle hooked up to a GPS around the field.
Once the field area is identified, it is mapped into hectare plots. Each hectare plot is labelled with a grid name; 16 soil cores are taken from each plot to make up a sample representative of that plot. The samples are numbered according to the plot they were taken from. Drummonds sends the soil samples and field map to SOYL, a company based in the UK which specialises in precision farming. SOYL analyses samples for phosphorus, potassium, magnesium and pH.
A report is sent back to Drummonds, usually within two weeks. This report includes a map displaying nutrient variation across the field. SOYL also sends back fertiliser recommendations for the planned cropping strategy of the field. Variable-rate spreading data files are created and emailed to Drummonds. Tailored fertiliser rates are allocated for each hectare plot, depending on its soil fertility results. The data is then uploaded to an app called ISOYL and used in the tractor on an iPad. The iPad uses a smart cable and adaptor to connect to all popular fertiliser spreaders that are variable-rate compatible. When the soil fertility results are uploaded on to the iPad, work can then be carried out in the field.
Only one nutrient can be applied at each application as the spreader works by varying the rate of application on the basis of the level of requirement in different parts of the field. In the field, the contractor works in the same way as any fertiliser contractor would. Using a GPS device, he follows the line set out by the GPS. The difference here is that the iPad is feeding information to the spreader telling it the rate of application needed according to the results of the different zones that were mapped out and tested originally.
As the spreader enters each zone, the controlled application rate automatically changes to that of the new zone and any exclusion zones recorded in the map will stop the spreader’s application, thereby only applying nutrients to those predefined areas. Fertiliser is not applied where it is not needed.
Field variability
According to Reilly, there can be huge nutrient variability in a field. He showed me some of the map reports of north Dublin farms that came back from SOYL and showed significant variation.
Figure 1 illustrates a field (6.53ha) that had one area with a pH of almost seven, while other areas in the same field were as low as 4.7pH.
Reilly says that, in the vegetable business, this can have a huge bearing on productivity and can result in variable crops.
Cost
Reilly says that for a farmer to set up his spreader to accommodate variable-rate spreading, it cost €600 for the iPad and leads to connect with a compatible spreader.
To provide the service to farmers, Drummonds charges €30/ha to test the pH level, or €35/ha to test for phosphorus, potassium and pH. This includes mapping the fields into hectare zones. To spread the different nutrients (phosphorus, potassium or lime) on the field using the variable rate spreading technique, Drummonds charges €30/t plus vat. Reilly says that farmers using this system are not solely looking at costs of spreading and savings made on fertiliser spend – they are more interested in correcting field variability.
Lessons learned
After four years of using the system, Drummonds found that the biggest issue is the amount of times you need to enter a field to apply each nutrient. “You might have to go into a field an extra one to two times to get all the nutrients in, because compounds can’t be spread in the variable-rate system,” he explains. Spring workload and issues with compaction can be problematic with this system, but Reilly says they have learned to split the times of the year when the nutrients are applied.
Limitations
There is no doubt but this system is a step in the right direction when it comes to correcting field variability for soil fertility. However, there is still variability even in the hectare plots that the system cannot account for.
Carl Cooney is a tillage and dairy farmer from Townrath, Drogheda, Co Louth. He is farming 700 acres which is a combination of tillage and grassland. Six years ago, he decided to trial variable-rate spreading for his phosphorus and potassium applications with Drummonds’ new service.
After the first year of use, the main thing he noticed was that the yield monitor on the combine had a consistent reading from one end of the field to the other. “In the past, I could never get my top-end yields over 3.6t/acre for winter barley but, after my first year of variable-rate spreading, my top yields were at 4.1t/acre,” he explains. Carl says that it takes a good bit of getting used to when the variable-rate spreader is in the field as it cuts in and out as it spreads according to the prescription rate based on soil test results for each plot.
He gets soil tests done every four years using the GPS system. He says the variability in the field’s fertility has decreased each year. He is milking 180 cows and plans to convert more of the tillage ground to dairying and expand cow numbers.
Carl wants to continue using variable-rate spreading because he finds it a good way to improve his soil indices quickly rather than traditional broadcast spreading. He says he has smaller fields that he doesn’t spread with a variable-rate fertiliser spreader and says these fields are much slower to climb indices. By variable-rate spreading, he says he doesn’t think he has saved any money on fertiliser but he is looking at the long-term investment and likes the fact that fertiliser is being targeted more in the areas that need it most. He says fields less than 10 acres in size do not warrant variable-rate spreading.
A field has to be mapped out with GPS into hectare plots and soil samples have to be taken from each of these plots.Results of soil tests come back from a UK-based company with crop specific fertiliser application for each plot.An iPad with a specialised app feeds information to the belt of the fertiliser spreader and tells it to speed up or slow down, depending on the precise location of the spreader in the field.
Variable-rate fertiliser spreading can be described as controlling the inputs applied to a field by varying the amounts spread in different areas of the same field based on soil fertility results.
Brian Reilly is an agronomist with Drummonds in Ballough, Lusk, Co Dublin. He has helped to launch the variable fertiliser spreading service in Drummonds’ Lusk branch. The service is becoming popular among Drummonds customers, with 25 farmers in the area participating.
Brian explains: “Over the years, we were getting feedback from vegetable growers and tillage farmers about the variability in crops that got a broadcast treatment of lime, phosphorus and potassium on the interpretation of ordinary soil test results.” He was looking for a way of correcting that variability and he claims that variable-rate fertiliser spreading – correcting the variability resulting from fertility – is working for his customers.
How does it work?
Firstly, the boundaries of the field are mapped with a global positioning system (GPS) device to give an accurate area reading for the field. Reilly says a company specialist drives a utility vehicle hooked up to a GPS around the field.
Once the field area is identified, it is mapped into hectare plots. Each hectare plot is labelled with a grid name; 16 soil cores are taken from each plot to make up a sample representative of that plot. The samples are numbered according to the plot they were taken from. Drummonds sends the soil samples and field map to SOYL, a company based in the UK which specialises in precision farming. SOYL analyses samples for phosphorus, potassium, magnesium and pH.
A report is sent back to Drummonds, usually within two weeks. This report includes a map displaying nutrient variation across the field. SOYL also sends back fertiliser recommendations for the planned cropping strategy of the field. Variable-rate spreading data files are created and emailed to Drummonds. Tailored fertiliser rates are allocated for each hectare plot, depending on its soil fertility results. The data is then uploaded to an app called ISOYL and used in the tractor on an iPad. The iPad uses a smart cable and adaptor to connect to all popular fertiliser spreaders that are variable-rate compatible. When the soil fertility results are uploaded on to the iPad, work can then be carried out in the field.
Only one nutrient can be applied at each application as the spreader works by varying the rate of application on the basis of the level of requirement in different parts of the field. In the field, the contractor works in the same way as any fertiliser contractor would. Using a GPS device, he follows the line set out by the GPS. The difference here is that the iPad is feeding information to the spreader telling it the rate of application needed according to the results of the different zones that were mapped out and tested originally.
As the spreader enters each zone, the controlled application rate automatically changes to that of the new zone and any exclusion zones recorded in the map will stop the spreader’s application, thereby only applying nutrients to those predefined areas. Fertiliser is not applied where it is not needed.
Field variability
According to Reilly, there can be huge nutrient variability in a field. He showed me some of the map reports of north Dublin farms that came back from SOYL and showed significant variation.
Figure 1 illustrates a field (6.53ha) that had one area with a pH of almost seven, while other areas in the same field were as low as 4.7pH.
Reilly says that, in the vegetable business, this can have a huge bearing on productivity and can result in variable crops.
Cost
Reilly says that for a farmer to set up his spreader to accommodate variable-rate spreading, it cost €600 for the iPad and leads to connect with a compatible spreader.
To provide the service to farmers, Drummonds charges €30/ha to test the pH level, or €35/ha to test for phosphorus, potassium and pH. This includes mapping the fields into hectare zones. To spread the different nutrients (phosphorus, potassium or lime) on the field using the variable rate spreading technique, Drummonds charges €30/t plus vat. Reilly says that farmers using this system are not solely looking at costs of spreading and savings made on fertiliser spend – they are more interested in correcting field variability.
Lessons learned
After four years of using the system, Drummonds found that the biggest issue is the amount of times you need to enter a field to apply each nutrient. “You might have to go into a field an extra one to two times to get all the nutrients in, because compounds can’t be spread in the variable-rate system,” he explains. Spring workload and issues with compaction can be problematic with this system, but Reilly says they have learned to split the times of the year when the nutrients are applied.
Limitations
There is no doubt but this system is a step in the right direction when it comes to correcting field variability for soil fertility. However, there is still variability even in the hectare plots that the system cannot account for.
Carl Cooney is a tillage and dairy farmer from Townrath, Drogheda, Co Louth. He is farming 700 acres which is a combination of tillage and grassland. Six years ago, he decided to trial variable-rate spreading for his phosphorus and potassium applications with Drummonds’ new service.
After the first year of use, the main thing he noticed was that the yield monitor on the combine had a consistent reading from one end of the field to the other. “In the past, I could never get my top-end yields over 3.6t/acre for winter barley but, after my first year of variable-rate spreading, my top yields were at 4.1t/acre,” he explains. Carl says that it takes a good bit of getting used to when the variable-rate spreader is in the field as it cuts in and out as it spreads according to the prescription rate based on soil test results for each plot.
He gets soil tests done every four years using the GPS system. He says the variability in the field’s fertility has decreased each year. He is milking 180 cows and plans to convert more of the tillage ground to dairying and expand cow numbers.
Carl wants to continue using variable-rate spreading because he finds it a good way to improve his soil indices quickly rather than traditional broadcast spreading. He says he has smaller fields that he doesn’t spread with a variable-rate fertiliser spreader and says these fields are much slower to climb indices. By variable-rate spreading, he says he doesn’t think he has saved any money on fertiliser but he is looking at the long-term investment and likes the fact that fertiliser is being targeted more in the areas that need it most. He says fields less than 10 acres in size do not warrant variable-rate spreading.
A field has to be mapped out with GPS into hectare plots and soil samples have to be taken from each of these plots.Results of soil tests come back from a UK-based company with crop specific fertiliser application for each plot.An iPad with a specialised app feeds information to the belt of the fertiliser spreader and tells it to speed up or slow down, depending on the precise location of the spreader in the field. 
This is a subscriber-only article
SHARING OPTIONS: