Soil erosion

What kind of erosion does rain cause?

Gully erosion.

What happens to soil every year?

Every year the world loses fertile soil the size of South Korea.

Costs $400 billion a year.

What does grass do?

Shield soil from the elements.

What strategies are used to prevent soil erosion?

• Aforestation

• Contour farming

• No till farming

• Cover crops

What was afforestation?

The process of establishing a forest in an area where there was no forest before.

What is contour farming?

Practice of plowing and/or planting across a slope following its elevation contour lines.

What is soil erosion?

The removal of soil (usually permanent) by both natural and human processes.

What factors effect soil erosion?

• salinisation

• waterlogging

• wind erosion

• compaction

What is salinisation?

Water and salts move upwards from a high water table. The water evaporates and salts remain behind.

What happens o soils over time?

Soil minerals weather and release salts.

What happens when there is poor drainage?

Waterlogging is caused, meaning the water table will rise, bringing dissolved salts towards the surface.

What is explicit to salt-tolerant crops?

Salt-tolerant crops, such as cotton, can withstand salinisation.

What happens if salts in soil are very acidic or alkaline?

Crops will fail.

Acidic - cannot absorb nutrients.

Alkaline - plants become infertile.

When does waterlogging occur?

Whenever the water table rises to the point of soil saturation and there is insufficient oxygen in the pore spaces for plant roots to respire adequately.

What do many farmers not realise about waterlogging?

Many farmers do not realise that a site is waterlogged until surface water appears, by which time the roots may already be damaged and the potential yield severely affected.

When does waterlogging happen?

• When rainfall exceeds the rate that soils can absorb or the atmosphere can evaporate.

• When relief basins or depressions encourage accumulation of water.

What are most farmers aware of?

How soil texture (proportion of sand, silt and clay) influences its characteristics and workability.

What is just as important as soil texture?

The structure (how the particles are grouped together) is just as important as the texture - 2 soils with the same texture can behave very differently depending on their structure.

How does strip cropping reduce soil loss?

Groundcover plants such as grasses are planted in strips between fields of crops.

The strips of groundcover soak up rain and slow runoff.

How do windbreaks reduce soil loss?

Rows of trees are planted between fields.

The trees slow down the wind and reduce wind erosion.

How does terracing reduce soil loss?

Step-like terraces are built on slopes.

They prevent runoff from rushing downhill and carrying away the soil.

How does contour cropping reduce soil loss?

Crops are planted in curving rows to follow the contour of hills.

This slows runoff and reduces erosion.

What solutions are there for waterlogging?

• Drainage pipes or ditches to prevent water being absorbed and held in the soil.

• Avoid over-watering crops.

What solutions are there for salinisation?

• Avoiding over-irrigation of crops by using techniques such as drip irrigation, soil moisture monitoring and accurate determination of water requirements.

• Good crop selection - use deep-rooted plants to maximise water extraction.

What are the solutions for structural deterioration?

• Avoid compaction by moving livestock clearly.

• Change the structure of soil by adding sand to clay soils.