Fertiliser Spreader Calibration and Tray Testing: An Assessment of Accuracy and Financial Impact
Key results:
Application accuracy was improved with 60% of spreaders requiring adjustment to correct issues such as overthrowing, underthrowing, or imbalance. Early identification of 21 mechanical faults including worn vanes, misaligned apertures, and faulty agitators. Many were resolved on-site resulting in:
- Financial losses avoided ranged from £1.19 to £26 per hectare, depending on the product and machine condition.
- Reduced risk of nutrient leaching through improved spread accuracy helps prevent fertiliser reaching hedgerows, field margins, or watercourses, supporting responsible nutrient management.
- Improved farmer understanding of how to identify common problems and understand the impact of spread patterns on yield and cost.
Background:
When the accuracy of fertiliser spinners is less than optimum it creates a spread pattern that results in:
- Fertiliser being thrown directly into water courses, hedgerows and buffers, as operator is not aware of overthrow.
- Financial losses – cost of the wasted fertiliser & crop premiums will be missed.
- Problems at harvest (grass lying flat etc).
- Additional applications by operator as they notice stripes in crops - this causes more damage, increased cost and can result in surface runoff.
Purpose of the work:
- Determine the financial savings that could be achieved across a number of the Farming Connect Our Farms through correct calibration and tray testing of fertiliser spreaders.
- Reduce the risk of leaching to ensure high water quality in water catchments across Wales.
- Ensure fertiliser is used as effectively as possible on Welsh farms to ensure operator safety and optimum crop yield.
What we did:
As part of this Our Farms pan-Wales project, 15 farms received fertiliser spreader calibration and tray testing. This service followed a structured process designed to assess both the condition of the machine and the accuracy of fertiliser application through the following steps:
- Machine MOT
- Fertiliser Analysis
- Fertiliser Tray Test
- Tray Test Report
Where a machine gives an unacceptable spread pattern, the machine is adjusted and re-tested until an acceptable spread pattern is achieved.
Outcomes:
The main issues caused by poor machine maintenance and inaccurate spreading of fertiliser are, operator safety, agricultural pollution, and loss of yield. The spread pattern must be even across the whole bout width, for all types of fertilisers being spread. The settings for one type of fertiliser will not provide an even spread for another, each fertiliser has unique ballistic characteristics which affect how the machine should be set up to achieve optimal accuracy.
The main ways that fertiliser can be inaccurately spread are:
- Overthrowing: the machine is throwing the fertiliser too far, meaning excess fertiliser which the plant cannot utilise halfway between each tramline.
- Underthrowing: the machine is not throwing the fertiliser far enough, meaning excess fertiliser adjacent to each tramline where the tractor drives. Again, the excess fertiliser cannot be utilised by the plant.
- Unbalanced left to right: the machine is applying different amounts of fertiliser on either side of the bout width, meaning that excess fertiliser on one side of the tramline compared to the other.
Of the machines tested, four machines were adjusted for overthrowing fertiliser, four machines were adjusted for under throwing fertiliser, and one was adjusted for an unbalanced pattern left to right.
The financial implication of an uneven spread pattern can be assessed to identify the loss as cost per hectare. Figure 1 shows the financial loss through uneven spreading of fertiliser at different coefficients of variation.
Figure 1. Financial loss through uneven spreading of Nitrogen fertiliser at £380/t
For the 9 tray tests that did not have satisfactory spread patterns, Table 1 highlights the financial savings based on 1st cut silage, representative of the most common crop grown by the farms tested. The fertiliser products noted are based on the farms buying choices and preference and were not influenced by this project.
Table 1. Financial loss that has been mitigated by improving the spread pattern
Product | First run CV | Second Run CV | CV Reduction
| Savings assuming spread on 1st Cut | Total annual area spread with machine (Ha) |
Overthrowing spread pattern | |||||
CF Nitram 34.5%N | 15.10% | 8.26% | 6.83% | £4.41/ha | 280 |
Glasson Fertilisers 27N 10S* | 16.81% | 10.34% | 6.47% | £4.85/ha | 100 |
Origin 40N + 14SO3* | 9.67% | 5.83% | 3.84% | £1.64/ha | 100 |
Glasson Fertilisers 20-7-10+7.5* | 31.82% | 8.43% | 23.39% | £26.00/ha | 200 |
| |||||
Yara Bela Prilled N 34.5%N | 8.08% | 4.72% | 3.36% | £1.19/ha | 400 |
Yara Bela Prilled N 34.5%N | 17.45% | 6.10% | 11.35% | £7.38/ha | 1200 |
Achema LithAN 34.4%N | 16.12% | 6.56% | 9.56% | £5.99/ha | 120 |
Origin Granular Urea 46%N | 16.65% | 5.52% | 11.12% | £6.81/ha | 500 |
Unbalanced left to right spread pattern | |||||
Yara Bela Extran 33.5%N | 14.39% | 10.88% | 3.52% | £2.45/ha | 600 |
*Product is not a straight Nitrogen, financial loss is likely to be less than for straight Nitrogen, however analysis is indicative that loss would still be present.
How to apply on your farm:
- Wearing parts should be monitored regularly and replaced as soon as required as these are the most common cause of inaccuracy.
- Annual testing will increase the likelihood of the machine being maintained properly and thus reduce the chance of agricultural pollution when in use.
- If you wish to apply to our own farm, please contact your local Development Officer to discuss how Farming Connect can support you via an on-farm fully funded clinic.
Please contact timtechnegolcff@mentera.cymru if you would like to receive a copy of the full final report for this project.