SHELTERBELTS

The benefits of shelter to the land whether it be broadacre or the small landholder have long been recognised and include protection of crops, livestock, and the home, reduction of soil erosion, salinity control and biodiversity improvements.

Shelterbelts are vegetative barriers that are designed to reduce wind speed and provide sheltered areas on the leeward (the side away from the wind) and windward (the side toward the wind) sides of the shelterbelt.

PALS will design a belt to suit soil types rainfall and above all what the belt aims to protect (eroded zones, capital assets or paddock shelter) Parameters of the design include:

  • height
  • density
  • number of rows
  • species composition
  • spacing between the trees or shrubs.
  • Paying attention to the length, orientation and continuity of your shelterbelt will also improve its efficiency.

 Case study : Mullewa, West Australia 

Problem

The Midwest of West Australia grows some of the best cereal and lupin crops in Australia. However the soils are very fragile with the dominant soil type being non-wetting sand. Soil erosion is a major problem, especially when the paddocks have just been sown to crop and at the end of summer when the stubbles have deteriorated.

The top few centimetres of soil is usually the most fertile and most valuable for crop and pasture production. While the loss of a few millimetres of soil during a heavy downpour or windstorm may not seem critical, the impact over time on farm productivity and fertiliser requirements over a generation can be devastating.

Solution

A series of strategic belts were planted across the prevailing winds and to follow the working pattern of the paddocks to help with the overall paddock management efficiency ie control traffic and GPS guidance

PALS recommended each belt was to be four lines wide with the outside lines containing mallee trees in conjunction with low shrubs so to add low shelter and prevent further land loss to root penetration out into the crop. Taller Eucalyptus specie to add height through the central rows.

Alternative design options: Where possible fodder shrubs are integrated. This adds shade and low shelter and increases the grazing capacity of the belts. Mixed with mix of tall, deep-rooted native Eucalyptus and mallees is the ultimate in shelterbelt design. Fodder shrubs are also less sensitive to chemical drift, a major consideration on broadacre cereal properties