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Preparing for Spring Fertiliser Applications

27 February 2023

With spring just around the corner, attention will turn once again to land work. One of the most important tasks for both arable and grassland farmers alike is spreading fertiliser. The basic mantra for applying fertiliser is often quoted as being the 4Rs- the right product, at the right time, at the right rate and the right place. Achieving this is only possible if application equipment is correctly set, fit for purpose, and used by a skilled operator.

Firstly, think about the tractor that you will be using –

  • Is the tractor size and weight proportionate to the spreader when full. The tractor needs to be a stable and steady platform for spreading and ballast should be used on the front of the tractor to help avoid “bouncing”.
  • Look at tyres and pressures- early applications can be made in less than ideal conditions. This can cause ruts in tramlines and compaction in cropping and grassland fields alike.

When attaching the spreader consider the following –

  •  Safety is paramount so make sure all guards are in good condition and fitted correctly including those around the PTO area.
  • Is the back of the spreader level from left to, right? If not, adjust the link arms accordingly.
  • Spreader height relative to the crop is important for achieving the desired spread width. Refer to the manufacturers guidelines and remember the overall height of the machine above the ground will change through the season depending on the crop and growth stage, so carry a tape measure to make sure the correct gap between top of the crop and spreader is maintained when in the field.

The spreader itself should also be checked over-

  •  Is the spreader structurally sound? Fertiliser is corrosive and regular washing can also see moisture gathering in enclosed areas. This combination can take its toll on the framework, hopper and moving parts. In addition, electricals should also be checked over to ensure controls are functioning correctly with attention also paid to lighting.
  • Discs should be in good condition and move round freely and smoothly. Gearboxes and bearings should also be checked for the absence of any play.
  • Look at the condition of the vanes. Wear and tear from spreading fertiliser can leave its mark (literally) on vane surfaces. Vane surfaces should be as smooth as possible to allow fertiliser to be thrown to the correct width with damage such as pockmarks disrupting the transfer and flow along the vane as energy is lost. Condition should be monitored through the season with damaged vanes replaced. It is not just damage that can affect vane smoothness, with some fertiliser types also leaving a coating of dust, so wiping and cleaning regularly, even between fills may be necessary particularly if conditions are damp or humid.
  • Headland control systems should be checked over to make sure they are free from damage and in good working order. This is important as this prevents fertiliser being spread outside the crop, reducing waste and protecting non-target areas such as hedgerows, margins and watercourses. In addition, field border systems ensure that the outside pass receives the correct rate of fertiliser in an even manner.
  • Inside the hopper, shutters and their control mechanisms as well as agitators should also be in good working order. Fertiliser characteristics can change with conditions and keeping a steady flow of fertiliser is vital to maintain spreading rate and prevent uneven spreading.

Operators are also advised to refer to the manufacturer’s manual for regular and annual maintenance procedures.

With the machine now ready to spread, attention focusses to settings and calibration. At the start of the season it can worthwhile taking the time to look up the machine setting for each fertiliser. In recent years these can most easily be found by using Apps created by the fertiliser and spreader manufacturers and are easily accessed using smart phones or similar devices. Calibration should be done to assess the spreading rate of each fertiliser to allow for the distinctive characteristics in terms of flow behaviours with most modern spreaders having kits to make the process quick and simple. Fertiliser differs in size, shape, and density with variation in particle size all impacting on spreading.

It is also worthwhile getting spread pattern assessed by tray testing. Kits can be bought to allow self-testing, or a specialist company can be used. This involves driving the spreader once it is set up and running over a line of trays spaced at regular intervals perpendicular to the direction of travel. To replicate spreading in the field three passes are made, one down the middle and one each side to simulate adjacent tramlines. Each tray is then collected, and volume compared to assess the accuracy of spreading pattern across the full width. Differences across the spreading width are expressed as the Coefficient of Variation (CV) with results over 20% leading to visible striping in the field along with yield and quality penalties. Adjustments should be made, and the spreader retested with a CV of around 10% being as good as most farms can achieve in the field.

Spending time now going over your spreader and preparing for the season ahead can help ensure you get the best from this year’s fertilisers.

tractor spreading fertiliser on wheat crop

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