1. DKO Soil Management Practices
AS 90919
Level 1 Ag Hort Sci External Exam
4 Credits

2. Contents What is the soil made of? What can we measure in the soil?
How can we change the soil?
Irrigation?
Drainage
Crop rotation
Fertiliser or compost application
Liming
Cultivation
Effluent application

3. What is soil made of? M A L O W
Have a go at answering this question. There are 5 components: M A L O W
INERALS IR
IVING ORGANISMS
RGANIC MATTER
ATER

4. Mineral components
When rocks/ stones get broken down they create the mineral part of the soil. These ‘bits’ are the sand, silt and clay particles.
Clay = < mm
Silt = – 0.02 mm
Sand = > 0.02 mm
The mix of sand silt and clay determines soil texture (More on this latter)

5. Air
Contains oxygen which is necessary for plant roots and the living soil organisms. No oxygen in the soil = no life in the soil.
Air travels into the soil from the surface through the pores (holes) in the soil.
Air is sucked into the soil by water as it drains downwards.

6. Living organisms
Living organisms include:
Bacteria
Fungi
Nematodes
Worms
Ants
Centipedes
Slugs…
Soil organisms are more important than everyone thinks…
They improve soil structure (worms dig holes)
And they breakdown (digest) the OM to release the nutrients to the plant.
Micro
Macro

7. Organic matter
If it was once living then it is now dead .Organic matter (OM) is dead plants and animals. It can be large particles down to very small particles.
The very small particles of OM are called humus

8. Water Essential for: photosynthesis Plant turgidity Nutrient uptake
The only way water can get into the plant is via the roots (root hairs).

9. Plant Nutrients
Macro Nutrients
N NH4
P H2PO4
K K+
Ca Ca2+
Mg Mg2+
S SO42-
Micro Nutreints Fe Mn Zn Cu B Mo Cl
There are 16 essential plant nutrients. 13 of these come from the soil and are absorbed as ions.
These soil nutrients (ions) are ‘chemically held’ by the soil minerals (sand silt clay).
As OM breaks down it eventually will be broken down into the ions and absorbed by the plant.

10. Plant Nutrients availability
Four factors decide how much of a nutrient is available to the plant
How much enters the soil (from fertiliser or compost)
How much leaves the soil (from plant uptake or leaching)
How much the soil can hold onto (it needs a high surface area to hold the ions)
The pH (acidity) of the soil.

11. Soil pH
The correct pH …
Allows plant nutrients to be released by the soil
Encourages living organisms

12. Soil pH Different plants have different pH preferences.
The pH of most vege gardens should be about This is a good pH for most vege plants.
However if you had a crop of potatoes – the best pH would be…

13. Soil texture The % of sand silt and clay determine the soil texture
Soil texture determines a lot of soil characteristics
The ideal soil is a loam
You tube and soil texture measurement
You tube – soil texture the feel test

14. Soil structure
Macro/ micro pores, Porosity,
Peds

15. Water Holding Capacity

16. Cultivation
Compaction is when the soil has been compressed and the pores squashed so that air can no longer enter the soil

17. Topography Browning off on the ridges of the hills.
Irrigated grapes in the foreground

18. Soil Amendments
Lime – artificial fertiliser – organic fertilisers

19. Drainage To improve drainage… Lay pipe drains or open drains
Signs of poor drainage
Yellowing of plants
Mottled subsoil
Pugging of surface
Poor structure
To improve drainage…
Lay pipe drains or open drains
Plant in raised beds
Improve soil structure
Add lime to clay soils (floculation)

20. Irrigation

21. Crop rotation

22. Revision Questions Name the 5 components of soil
What three particles define the soil texture?
Place the following in order of smallest to largest
Sand clay silt
What 2 functions do living organisms perform in the soil?
In an ideal soil, what proportion of the soil is air?

23. Activity – The perfect soil
What percentages of each of the soil components would be in the perfect soil? M A L O W
INERALS IR
IVING ORGANISMS
RGANIC MATTER
ATER