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Tasmanian Institute of Agriculture

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Published: 6 Sep 2018

John McPhee & Bill Cotching

With winter now behind us, we are once again seeing the effects of soil erosion from the North-West Coast hinterland visible in Bass Strait and farm dams. Wet weather at this time of the year is a normal part of our climate and preparing for it should be a standard part of farming practice.

Soil Researchers, Bill Cotching and John McPhee from the Tasmanian Institute of Agriculture (TIA), said planning to minimise soil erosion needs to start in late summer and autumn, instead of waiting until the rain starts.

“The reasons for soil erosion are usually fairly obvious – bare paddocks, saturated soil, steep slopes and heavy or frequent rainfall greater than the capacity of the soil to absorb it,” Mr McPhee said.  

“Some areas along the North-West Coast experienced higher than normal rainfall, but the past few months have not been much higher than the long-term average. There shouldn’t be any excuses as processes and technologies are available to help farm managers prevent soil erosion.”

Dr Cotching said strategies to reduce the risk and severity of soil erosion were well known and have been used successfully by many farm managers. However, he said there was still a long way to go to achieve wider option of these methods.

“Farm managers use strategies to reduce soil erosion, have used them, or may no longer be using them for whatever reason, but something like the rip mulcher has been around for many years. There is really no reason for it not to be more widely used,” he said.

“Cover crops are another important tool in preventing soil erosion. Living cover crops are best, but if managing the growth is an issue coming into cropping season, spray them off early. A dead mulch cover on the soil is far better than no cover at all.”

Soil forms at a rate of 0.2 tonnes per hectare per year. In severe erosion events, it could be washing into dams and the ocean at rates of over 100 tonnes per hectare per year. That sort of loss would take 500 years to get back by normal soil formation processes.

“It’s not only soil that is lost during erosion, it's also hundreds of dollars per hectare in lost nutrients and those nutrients are never coming back,” Mr McPhee said.

Dr Cotching said property management planning was an essential starting point of an integrated approach to soil erosion.

“The causes and effects are not confined to paddock or farm boundaries. A farm plan allows integration of soil erosion control measures into the farming system, and can accommodate off-site influences,” he said.

“For those cropping steeper land, it is essential to install soil erosion control measures. Minimisation and control of surface water are key elements in preventing soil erosion.”

Farmers can follow these steps to reduce soil erosion:

  • Use diversion (cut-off) drains to prevent runoff from upslope paddocks, roads and tracks coming onto cultivated ground.
  • Sow grass to protect and stabilise natural drainage lines.
  • Use mulched rip lines to shorten the length of slope and control surface flow
  • Establish grassed buffer strips between cropped areas and waterways or dams.
  • Increase infiltration and reduce erosion by:
    • Retaining crop residues after harvest.
    • Cultivating across the slope following harvest to increase surface roughness.
    • Sowing a green manure (such as short rotation ryegrass) immediately after harvest, and keep as ground cover for as long as possible before establishing the next crop.
    • Strip-tilling to allow crop establishment without removing all the cover crop.

For more information, contact John McPhee or Bill Cotching

This article was published in The Advocate & The Examiner Newspapers on 6 September 2018

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