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Fact Sheet 1- What happens to rainfall on your paddocks?
Fact Sheet 2- Does summer weed control save soil water?
Fact Sheet 3- Calculating maximum plant available water of your rootzone
Fact Sheet 4- Increasing Plant Available Water
Fact Sheet 5- Properties of a healthy soil
Fact Sheet 6- Root Facts
Fact Sheet 7- Soil Pit Checklist
Fact Sheet 8- Soil Water Facts

Fact Sheet 6: Root Facts


  • For most plants, there is as much growth above the soil surface as there is below as roots.

  • Dryland crops grow 90 percent of their roots in the top 10 cm of soil. 

  • The remaining 10 percent of roots may grow as deep as 2m to tap deep water for 'survival and insurance'.

  • In ideal conditions, roots can grow up to 1cm/day.


  • Roots grow easily where the soil strength is less than 3 Mega Pascals (3 MPa).

  • Fibrous rooted plants e.g. grass and cereals can penetrate 5 MPa soil strength with difficulty.

  • Plants with large diameter roots including those with tap roots are more sensitive to soil strength than those with fine fibrous roots.

Growth Patterns

  • Roots grow randomly but grow faster and branch more where conditions are good - i.e. adequate moisture and fertiliser, low soil strength.

  • Roots do not grow towards water or fertiliser but cluster around these areas as they promote growth. 

  • Roots grow randomly with a slight tendency to go grow down, shoots grow up, drawn towards the sun. 

  • As soil clay content increases, less roots are required to fully explore soil water. This is because clay can conduct water to the roots.


  • Roots absorb the majority of their water and fertiliser a few millimetres behind the growing tip.

  • Older roots act as pipes to transfer the water and nutrient to the plant.

  • Where root growth is restricted or disease attacks the root tip uptake will be restricted.

Rainfall Frequency

  • Plentiful early season rainfall will lead to rapid and prolific root growth of dryland crops and pastures. 

  • If there is no follow-up rainfall, the lush growth will rapidly remove soil moisture leaving a moisture shortage later in the season. This may affect seed set and grain fill and result in 'haying off' in cereals. 

  • A plant can survive with only a fraction of its root system if rain falls regularly through the growing system. In this situation root disease may not affect yield.


Fact Sheet 6: Root Facts

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