Well-grassed interrows have become the drainage lines in this Bangalow orchard.

Macadamia orchards often experience high levels of soil erosion because of poorly designed drainage and lack of ground cover.

North Coast macadamia growers are now working to reduce erosion by managing water flows through their orchards and establishing shade-tolerant ground cover.

NSW Department of Primary Industries (DPI) is overseeing several erosion projects in the macadamia industry as part of its 2006-7 Soil Erosion Solutions (SES) program.

In one Dunoon orchard the trees are 20 to 30 years old. Tree rows had been placed across the farm without consideration of the natural drainage lines running through the property.

These watercourses have cut paths through the orchard and formed into unstable gullies.

During rain, these gullies scour out the bare earth on the flow lines and carry substantial amounts of soil down the slope into the farm dam.

Using SES funds, the grower is creating defined watercourses through the orchard.

In some areas the watercourses will be grassed, so trees will be removed to provide enough light, and the soil will be initially protected with erosion matting which the grass grows through.

In one area where tree rows run across the slope, small rock check dams will be built within tree rows to slow the water velocity and trap sediment without restricting machinery access along the interrows.

At an orchard at Brooklet, erosion has caused concentrated run-on water from upslope.

The orchard owner and upslope neighbour are working together to remove a weed dominated windbreak along the boundary and create a grassed waterway that will divert water around the tree rows of the down-slope orchard and deliver it safely to a farm dam.

Early in 2006 a Bangalow grower reshaped the interrows of his orchard to ensure water flowed down a broad grassed spoon drain rather than down the bare soil tree rows.

These spoon drains were planted with sweet smothergrass, a shade tolerant species able to persist as light levels reduce in the maturing orchard.

The reshaped rows have now been well stabilised with grass cover, the smothergrass dominating closer to the trees.

SES is funded by the Northern Rivers CMA.

Contact Abigail Jenkins, (02) 6626 1357, abigail.jenkins@dpi.nsw.gov.au