Good ground cover...

Reduces runoff and erosion by
-Protecting the soil from raindrop impact
- Improving infiltration
- Reducing rate and amount of runoff
- Reducing sediment concentration
- Saves money by
- Reducing cultivation
- Improved weed control
- Improved soil structure
- Improved soil moisture
- Reducing erosion losses (soil and fertiliser)
Reducing or eliminating cultivation
- Improves soil structure
- Reduces erosion
- Saves money

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.

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.

- The start of runoff was delayed
- The rate of runoff was reduced
- The amount of runoff was reduced
- The amount of silt in the runoff water reduced.

This means that more water soaked into the soil for crop growth and less soil and fertiliser was lost through soil 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.

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.

Conventional - No surface cover - normal cultivation
BCTB Some surface cover - reduced cultivation
Zero Tillage - No surface cover - no cultivation
GCTB - Complete surface cover - no cultivation

These trials showed that on average:

- Little erosion occurred on GCTB plots where the ground cover was complete and no cultivation took place.
- Twice as much erosion occurred where surface cover was reduced or removed and/or some minor cultivation took place.
- A massive ten times as much erosion occurred on the conventionally-treated plots which had no ground cover and were cultivated normally to fertilize and control weeds.

Trials are continuing but the benefits of increased ground cover and reduced cultivation has been clearly demonstrated.

So remember before the next wet season

Cover up your soil

Put away your plough

Save all that toil

Even better - do it now!
P.J. Rudd
District Experimentalist
Kamerunga Horticultural Research Station Centenary Open Day on 21st May, 1987

DATE: September 1987

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