Fertiliser application: Headland Spreading

Headlands make up a large proportion of a field. Headlands often display the greatest variation in fertiliser application.Dermot Forristal outlines why is it important to spread fertiliser evenly on headlands?

Spreading fertiliser evenly on field headlands is hugely important, yet we may not be doing what’s required to achieve that.   But why should we focus on field headlands?

• Field headlands often display the greatest variation in fertiliser application as evidenced by crop colour and other indicators such as lodging.
• Headlands make up a large proportion of a field. A 4 ha square field with a 24m tramline would have almost 50% of the area in that 24m headland area.
• In a survey of 17 farms PhD candidate Mark Ward found that 70% of growers had uneven spreading on their headlands.
• Half of these had low rates towards the field edge, the other half had variable rates in the turning area near the tramline and in the transition area where the standard field spreading bouts merge with the headland bout and can be at a distance of from 8 to 30m from the field edge depending on the spreader.

While some spreaders have spreading patterns that can spread headlands more evenly than others, two factors contribute to the risk of uneven spreading:

• The spreader’s border or headland spreading mechanism
• The operator picking the correct point to turn on and off the spreader when merging the in-field and headland runs.

Border spreading

To spread evenly to the field edge, the spreading pattern on the edge side must be radically altered from the normal wide-overlapping pattern to an abrupt non-overlapped ‘box-shaped’ pattern at the field edge.  This is achieved by either altering/changing:

• The discs, the disc vanes, disc speed, fertiliser drop point onto the disc, tilting the spreader or dropping a trimmer into the fertiliser flow.

Because there is no overlap at this side, the spread pattern is more susceptible to wind, spreader angle, fertiliser quality, etc.  Consequently they need to be set/adjusted very carefully to ensure they are spreading accurately.  Some spreaders which are very easy to set-up for in-field setting require quite a bit of checking on the field headland, and they often don’t receive that attention!   The edge pattern can also be adjusted to avoid any fertiliser passing the boundary if there is a water-course nearby or, alternatively, to maximise yield to the field edge.  The key to setting the headland components correctly is to consult the manufacturers resources, whether on-line, or the instruction manual.  The edge pattern can also be checked using test trays.

Merging headland and in-field runs

Achieving the correct positions for turning on and off the spreader, to allow it match the in-field and headland pattern, is vital to avoid over- and under- spreading.  Teagasc research has shown position errors on farms of from 1 to 12m.  The biggest challenge is determining the ‘turn-on’ point when moving away from the field headland, as modern wide-spreading spreaders with good overlapped patterns spread quite a distance back from the machine.   For some machines with a 24m bout width for example, the correct ‘on’ position may be 26m from the headland tramline.  This is very difficult to judge from the tractor seat while travelling at speed. It’s important to:

• Consult the manufacturer’s resources for the correct turn on and off points which may be affected by:
• Bout width
• Fertiliser quality
• Tractor forward speed
• Control type (hydraulic, electric servo etc.)
• If using automated GPS controlled systems ensure they are set-up correctly.
• With manual systems, place a marker in the field for the correct ‘on-point’ to assist or ‘train’ the operator. This should be repeated each spreading day!

Attention to detail in all of these areas will improve yields, fertiliser use efficiency and reduce the risk of crop lodging. 

Headland spread pattern is different