EFFECT OF GROUND COVER AND REDUCED CULTIVATION ON RUNOFF AND EROSION
SUMMARY
Good ground cover...
EROSION PROBLEM
In their natural state, most soils in Far North Queensland are fairly resistant to erosion. Trouble starts when land is cleared and cultivated. The natural ground cover is destroyed and soil particles are pulverised by excessive cultivation.
Our rainfall pattern doesn't help. Of an average annual rainfall of about 2,000 mm, 87% or 1,750 mm falls in the 6 months between mid-November and mid-March. About 65% or 1,300 mm falls in the 3 months of January, February and March.
Not only can storm rain be intense early in the wet season, but long periods of wet weather saturate the soil. Saturated soil particles are easily washed away by the excessive amounts of runoff water.
Maintaining a good ground cover of living or dead material and reducing cultivation, particularly during the erosion-prone months of the year, will reduce the erosion problem.
DEMONSTRATION
The dramatic effect of ground cover in reducing runoff and erosion is easily demonstrated using a rainfall simulator. A rainfall simulator produces artificial rainfall on small plots. Peter Rudd and Brian Prove will demonstrate this machine as part of the soil conservation display. These demonstrations will show landholders the benefits of keeping a good ground cover on their soil.
When used in field trials, this machine showed that by increasing ground cover, four things happened.
This means that more water soaked into the soil for crop growth and less soil and fertiliser was lost through soil erosion.
EROSION
Covering the soil surface reduces erosion in several ways. Firstly, it stops raindrop impact on the soil surface. This prevents the break-up of soil particles which causes surface sealing. More water soaks into the soil. Also, ground cover controls the runoff water and catches silt for cultivated land.
Cultivation pulverises the soil. Reducing or eliminating cultivation leaves the soil with a better soil structure and less able to be moved by runoff water.
SOIL LOSS TRIALS
To measure the benefits of increased ground cover and reduced cultivation on commercial farms, trials have been set up on cane farms in Far North Queensland.
Four treatments were used.
These trials showed that on average:
Trials are continuing but the benefits of increased ground cover and reduced cultivation has been clearly demonstrated.
So remember before the next wet season
DATE: September 1987
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