Guideline Index

Chapter 4: Soil Properties

4.1 Introduction

In this Chapter;

The components which make up a mineral based soil include inorganic particles or minerals, organic matter, living organisms and water and air (pore spaces) as shown in Figure 4.1.

Figure 4.1  Composition of a loam surface soil when conditions are good for plant growth (adapted from Brady and Weil 1999, pg. 15)
Figure 4.1 Composition of a loam surface soil when conditions are good for plant growth (adapted from Brady and Weil 1999, pg. 15)

Each soil has different types and arrangements of these components which creates unique soil properties or ‘soil types’. Soil properties affect;

  • plant growth responses
  • fertiliser requirements
  • the soils’ response to management
  • land use capability (i.e. suitability for different land uses such as grazing versus cultivation)
  • drainage and water runoff
  • nutrient loss and leaching
  • soil erosion

Understanding soil properties is essential for nutrient planning and can be applied to land-use decisions.

Soil properties such as soil structure, depth, texture, salinity, acidity, waterlogging or compaction can limit plant growth even when the soil has adequate nutrients. Before applying fertiliser, consider what is actually limiting plant growth. Is it really a nutrient deficiency or is it a soil property? Soil properties can be observed in the paddock or measured through soil testing.

A soil’s properties are largely determined by its parent material and weathering during its formation (Refer to section 4.6). Topography, age and agricultural practices can also affect a soil’s properties.

Three groups of soil properties influence plant growth:

  • Physical, or the texture and structure of the soil.
  • Chemical, which affects both the fertility of the soil and its physical properties.
  • Biological or the organisms in the soil, such as bacteria, fungi, insects and earthworms – See Chapter 5 for more information on soil biology.

It is the combination of these properties that determine soil health and the ability of the soil to provide ecosystem services.

Soil properties influence plant growth and guide fertiliser decision making. Information relating to soil properties can be used to help guide investment decisions on-farm to maximise the benefit, for minimal investment.