A broadcast spreader does not place material in a perfectly even rectangle.

As the impeller turns, it throws material outward and forward in a fan-shaped pattern creating two spread widths: the effective working width and the full spreader width . The outer edges receive less material and are often referred to as the feathered edge of the pattern.

The outer edges (which form part of the full spread width) receive less material and are often referred to as the feathered edge of the pattern.

That lighter edge is normal. Broadcast spreading relies on overlap. The light edge from one pass is meant to overlap with the light edge from the next pass.

If passes are too far apart, the light edges do not overlap enough. The result is striping and missed areas, creating visible strips of underapplication.

There are two different widths to understand.

When the effective working width of each pass overlaps correctly, the full spread width is achieved.

To achieve this, ensure you don’t set pass spacing from the furthest granules or material you can see. Those granules/material are too sparse to define the effective working width.

Use the effective working width: the part of the pattern that can then overlap with the next pass to produce even coverage.

Pass spacing is the centre-to-centre distance between walking lines. It is also called bout width or lane spacing.

Correct pass spacing is narrower than the full visible spread.

The aim is not to avoid overlap. The aim is to overlap deliberately and consistently.

Spread width tells you how far material travels. Pass spacing tells you how far apart each walking line should be. Spread pattern balance tells you whether the material is landing evenly left-to-right across the working width.

A spreader can have the correct application rate and sensible pass spacing, but still leave uneven results if the pattern is heavier to one side.

Before changing the aperture setting or narrowing pass spacing, check:

• whether border control is active;
• whether the correct slider is fitted;
• whether material is flowing consistently;
• whether the spread pattern needs balancing.

Some Cresco models include spread-pattern balancing features that help adjust how material reaches the impeller before it is thrown outward.

For a fuller explanation, see: **Understanding Spread Pattern and Balance Transfer**.

Walking speed is one of the biggest practical factors.

A Cresco spreader should be operated at a steady, purposeful walking pace of about 5 km/h / 3 mph, unless model-specific guidance says otherwise.

At a slower speed:

• the impeller turns more slowly;
• material carries less far;
• the spread pattern narrows;
• more material may be applied per square metre if the setting is unchanged.

At a faster speed:

• material may be thrown slightly farther;
• output per square metre can reduce;

The most important thing is consistency. Speed changes during a pass create rate changes and pattern changes.

Use a phone walking-speed app, or mark out 10 metres on a flat surface.

At 5 km/h, 10 metres takes about 7.2 seconds. At 3 mph, it takes about 7.5 seconds.

Practical target: walk 10 metres in about 7–8 seconds.

Check this before loading material. Most people walk more slowly than they think when pushing a loaded spreader.

Larger and denser particles usually travel farther. Smaller, lighter, dusty, or irregular particles usually produce a narrower spread pattern.

Particle size is often expressed as SGN.

SGN means Screen Guide Number. As a practical guide, SGN is approximately the average particle diameter in millimetres multiplied by 100.

Examples:

Do not treat these descriptions as exact. Shape, weight and density matter as well as size. A round, dense, heavy granule may travel farther than a flat, light, or irregular particle of a similar SGN sized material

Material condition changes spread behaviour.

Watch for:

• damp fertiliser;
• clumped salt;
• dusty material;
• broken granules;
• mixed particle sizes;
• foreign debris;

Poor material condition causes uneven flow affecting application uniformity and pass spacing

Wind can move fine particles and distort the spread pattern.

If fine fertiliser or seed is drifting, stop and reassess. Do not assume the pass spacing is wrong if wind is visibly carrying material sideways.

Avoid spreading fine materials in conditions where wind drift is likely.

Aperture setting controls flow rate, not spread width.

Higher settings can sometimes make a pattern appear slightly wider because more material is visible coming off the impeller, but this is an illusionary effect.

Opening the aperture more will not correct a narrow spread pattern. That changes application rate and risks over-application.

If the spread width is narrower than expected, check speed, material, and pass spacing.

The ranges below are practical starting points, not guarantees. Actual width should be checked with the material being used.

Assumed conditions: dry material, correct slider, steady 5 km/h walking speed, level ground, and no significant wind.

These ranges should be treated as planning estimates. A measured pattern on the ground will be more accurate than the SGN category.

Use the overlap rule as a starting point:

• Fine material: pass spacing ≈ two-thirds of measured full spread width.
• Coarse material: pass spacing ≈ three-quarters of measured full spread width.
• Mixed or uncertain material: start with two-thirds.

More overlap is usually safer than a gap. A modest overlap is less visible than an underaplied strip.

If measured full spread width is 3 m with fine fertiliser:

• 3 m × 2/3 = 2 m pass spacing

If measured full spread width is 4 m with coarse material:

• 4 m × 3/4 = 3 m pass spacing

These are starting points. Confirm by a test pass.

A short test prevents most striping problems.

Use a dry driveway, yard, path, or other hard surface where material can be seen and swept up.

Sweep up the material after the test, especially salt or fertiliser.

Note when spread testing on a hard surface be aware of bounce of the material off the hard surface (excess scatter) particularly with heavy granulated material.

Tip 1: It can be beneficial to go over the same test area more than once so the volume of material on the ground is increased making it easier to see the materials distribution on the ground.
Tip 2: Having an assistant watching from in front of the spreader at the end of the 10 metres can be beneficial, the person can visually mark the point at which the effective width is seen.

An alternative option is to use collection trays or shallow pans placed across the expected spread width.

This gives a clear picture of the transverse distribution: how much material lands at each point across the pass.

A tray test is a good method of checking calibration and provides an alternative way of accurately calculating spread width. It is also effective for

• training operators;
• comparing material spread characteristics;
• investigating persistent striping or over application;
• setting up the spreader for repeated professional work.

The goal is not a perfectly flat single-pass pattern. The goal is a pattern that achieves uniform distribution after adjacent passes correctly overlap.

Correctly calculated pass spacing only works if the operator consistently keeps the correct spacing while walking.

Reliable options:

• canes or marker flags;
• string lines;
• chalk marks on hard surfaces;
• fixed visual references such as posts, kerbs, or path edges;

For ultimate accuracy, use physical markers. Estimation is usually the reason spacing drifts.

Uneven coverage often starts at the beginning and end of a pass.

Do not open the aperture while stationary. That causes material dumping and local over-application resulting in potential surface damage.

If stripes appear, check in this order.

Was speed consistent from start to finish?

Slowing down narrows the pattern and increases application rate. Speed variation is one of the most common causes of visible striping.

Return to a consistent 5 km/h / 3 mph pace.

Was spacing based on the correct effective working width?

If the spacing used is too wide, the sparse edges do not overlap enough.

Reduce spacing slightly via a re-test to confirm correct spacing.

Is the material dry and free-flowing?

Damp or clumped material causes surging, stopping, or side-to-side inconsistency.

Correct the material issue before changing any settings.

Is the correct slider fitted? Is the aperture and impeller clean and moving freely?

A blockage, excess debris, moving parts, or incorrect slider can look like a spread-width problem when the real issue is inconsistent or incorrect flow.

Wind can push fine material sideways. Rough ground can change wheel speed leading to decreased impeller speed. Slopes can affect operator pace and pattern control.

Adjust working conditions where possible.

Diagnose the issue before a second use or a corrective application .

Do not adjust randomly or estimate. That usually creates a second problem on top of the first.

If fertiliser striping becomes visible and the affected area is significant, correct carefully after the main pass pattern is understood and the corrected spread width is established. Use a light, targeted correction rather than applying a full-rate pass over already treated ground.