Soil testing basics

Why test soil?

Before you commit to a piece of land, understanding the soil is one of the most important things you can do. Soil testing tells you about pH, nutrient levels, organic matter, and potential contaminants.

What to test for

• pH: Most crops prefer pH 5.5 to 7.0. Too acidic or too alkaline and nutrients become unavailable.
• Nutrients (NPK): Nitrogen, phosphorus, and potassium are the big three. Low levels mean you'll need to amend.
• Organic matter: Higher organic matter means better water retention and soil structure.
• Heavy metals: Especially important on land with a history of industrial use, orchard spraying (arsenic), or mine proximity.
• Salinity and sodicity: Common in drier areas. High salt can make land unsuitable for many crops.

How to take a sample

1. Take 15 to 20 sub-samples from across the paddock in a zigzag pattern.
2. Mix them in a clean bucket.
3. Send a portion to a NATA-accredited soil testing lab.

Your state agriculture department can recommend labs. Many offer subsidised testing for new growers.

When to test

Test before you sign any agreement, and again at the start of each season. Soil changes over time, and you want a baseline to measure against.