Pests (insects and  birds), diseases (mainly fungal) and frosts (radiation) are the three banes of horticulture. These risks are all minimised if the inter-row grass is kept very short and if the within-row grass is very short or absent. This is especially important in spring/early summer, when the risks are highest and the grass growth most vigorous. Grass is usually mowed sixteen times a year and the within-row is usually treated with week killer five times a year.

Mowing and weedkilling are costly ($1,000 per hectare per year and bad for the environment – soil compaction, soil erosion, reduced soil health, reduced organic matter, reduced aeration and drainage, high consumption of non-renewable resources, high CO2 emissions – and dangerous – mowing machinery, storage, handling and use of dangerous chemicals. Where pest, disease, or frost risks are especially high, orchard floor maintenance is especially important and these penalties are all increased.

Using sheep to manage an orchard floor has a long history and  holds good promise - free grass management for the orchardist and free grass for the grazier. Nevertheless, it is not popular in spite of our 50,000,000 sheep and large land areas under tree and vine horticulture (63,000 ha).

THE PLUSSES

Access: With so many sheep around, most fruit growers should be able to borrow a few sheep from a nearby grazier - an obvious, cash-neutral, synergism where extra feed is traded for its regular removal.

Reduced risk: If properly managed, sheep keep grass very short - especially on uneven or soft ground, which prevent short mowing. Very short grass reduces risk from birds (seed), pests (habitat), diseases (humidity) and frost (warmer soil).

Increased safety: Reduced storage, handling and usage of dangerous chemicals and mowing machinery makes your orchard a safer place for kids and pets to live  and staff to  work.

Market access/price: Lower inputs and more sustainable production usually improves market acceptance.

Short grass vs bare soil: Bare soil increases erosion – especially on light soils and slopes. It also degrades soil structure with reduced organic content and increased compaction interfering with healthy root growth - about half of every tree lives underground.

Canopy: Sheep trim the lower canopy to about 1 m increasing air flow around the tree base so speeding canopy drying and reducing disease.

Soil compaction: Regular mowing compacts the soil – especially in spring when the ground is soft.

Nutrient translocation: Sheep feed mainly in the inter-row where grass growth is strong and they urinate and defecate mainly beneath the trees. This moves soil nutrients from the inter-row and deposits them within the row. Inter-row grass growth is slowed and trees are fertilised.

THE MINUSES

Bark damage: If a complete ring of bark is removed from the trunk, the tree dies. Structural branches usually emerge about 1.2 m from the ground and are just out of reach. Even if some structural branches are a little lower, only their lower bark is damaged, so they are not ring barked and so not killed.

Root damage: Sheep may want to scratch (skin parasites). If your young tree is the scratching post, the rocking motion damages the roots slowing growth and possibly killing the tree. Young tree canopies are often too low to allow sheep orchard access anyway. Rocking is not a problem for larger trees.

The ‘plusses’ outweigh the ‘minuses’ with the exception of the bark damage risk. This is the one, key issue deterring most growers from allowing sheep into their orchards.

Because sheep attack is so serious, it is worth making doubly sure your trees are safe. We suggest (a) good stock management (break feeding, good husbandry) and (b) the installation of plastic tree protectors.