Slashing and mulching pastures

Slashing and mulching can help you get the most out of your pastures, especially when used with other techniques like fertiliser application and grazing management.

Benefits of slashing and mulching

Slashing and mulching to remove dead standing matter can help to:

• reduce low-quality pasture that livestock avoid
• improve access to sunlight for new growth
• improve the effectiveness of herbicides and gibberellic acid (via droplet contact with growth points)
• minimise shading and smothering of desirable species
• support even grazing and better feed utilisation.

Even well-managed pastures can become dominated by dead stalks and low-nutrient material, especially after seasonal flushes followed by drier periods or season change. Slashing or mulching helps reset the pasture and prepare it for productive regrowth.

Example analysis of slashing vs mulching

This information was taken from a demonstration trial paddock at Orange Agricultural Institute in March-May 2023. 

The paddock originally had a total herbage mass of approximately 8 tonnes per hectare. Out of this, only about 2 tonnes per hectare were green, while the remaining consisted of dead stalks, leaves, and detached plant material. Thick Phalaris grass made it difficult to see or move around the paddock. 

Before introducing cattle to the paddock, two treatments were applied: slashing and mulching. Both methods involved cutting the vegetation at approximately 15 centimetres high. 

• The slash treatment left a small windrow to one side, resulting in uneven residue distribution across the area.
• The mulched treatment evenly spread the residue, chopping it into smaller segments. 

After the slash and mulch treatments, the Angus heifers were allowed to graze the paddock three times and the following results were shown after laboratory testing.

The most notable distinction among the treatments was the availability of high-quality green growth. Cattle were able to select a superior diet in the slashed and mulched treatments.

Key takeaway from this example

The biggest improvement was the amount of accessible green feed available after treatment with gains in both digestibility and metabolisable energy. Livestock could better select higher-quality feed in both slashed and mulched areas compared with untreated pasture.

Considerations before you slash or mulch

The following key points should be considered when deciding to slash or mulch:

• adjust stocking rates and grazing intervals to match pasture growth for effective grazing management
• conduct a pasture budget in early September, considering peak livestock demands during calving/lambing
• use tools like Farming Forecaster to help determine a spring pasture feed supply and if a surplus is available
• allocate paddocks for fodder conservation in the event of a surplus, with contingency plans if surplus herbage mass cannot be cut
• slashing and mulching should be employed as a last resort due to the associated costs of time, diesel, and machinery wear and tear
• a significant amount of dead grass residue can lead to reduced soil nitrogen levels
• slashing and mulching treatments can substantially increase the availability of green pasture regrowth, leading to improved animal performance
• it is essential to consider paddock suitability for slashing and mulching as rocks, stumps, and uneven ground can pose challenges for machines.

Timing slashing or mulching

• In high altitude and high rainfall regions, enabling sunlight to reach new growth in pastures is preferable to shading caused by tall temperate grasses during cooler months.
• Ideally, slashing or mulching should be completed before the end of December to allow residue to break down over summer.
• Mulching in late summer or early autumn may reduce sub-clover germination in some productive pastures.
• If you're in a cooler or warmer climate zone, the decomposition rate and impact on germination may differ. 

Your Local Land Services' office can provide tailored advice about what best suits your region and climate.

After slashing or mulching

Fertiliser is one of the most effective ways to boost pasture growth following slashing or mulching, but it’s also one of the most expensive. With prices changing and seasons shifting, always review your fertiliser strategy before use. 

Livestock grazing after slashing or mulching helps trample dead material, reducing shading effects. 

Alternative to slashing or mulching

Using grazing management techniques with dry adult livestock can also achieve similar outcomes as slashing and mulching. It's important to monitor the condition of this livestock class to prevent excessive weight or fat loss when using livestock in place of slashing or mulching techniques.