Soil Sampling: Best Practices - Target Fertilisers

There are significant economic gains to be made by having soil at the correct level for pH, P and K, as you optimise the efficiency of all nutrients therefore maximising growth rates for whatever crop you wish to grow. Teagasc research shows that by simply correcting the soil pH, you can grow up to 20% more grass. Soil sampling ensures you are applying the right nutrients where they are required, when they are required and at the rate they are required.

Improving soil fertility management is a key step for improving the agronomic, economic and environmental performance of Irish farms. The principle of soil analysis is to determine the nutrient status of your soil and to give a measure of the available nutrients in the soil.

Late autumn/early winter is an ideal time to soil sample your land. Allow a minimum of 3 months after the last P and K application and a minimum of 2 years after lime application before taking samples. Having a farm map with field area and numbers clearly marked is important when taking soil samples as it aids in comparing results and helps you identify which field corresponds to a specific sample.

How to take a soil sample

To address deficiencies accurately it is fundamental that soil samples are taken accurately. Below are 9 pointers on how to accurately take a typical soil sample.

Each sample should be 0.25 – 0.5 kg of soil.
Ensure a consistent dept of 4 inches is being achieved with your soil corer.
Take a sample every 2 to 4 ha. (5-10 acres)
Avoid sampling unusual spots such as old fence lines, ditches, drinking troughs, dung or urine patches or where fertiliser or lime has been heaped or spilled in the past.
Take a representative sample by walking in a W-shaped pattern across the field.
Take a minimum of 20 soil cores per sample, mix them together, making sure the soil sample box is full.
Sample fields at the same time of the year to aid comparisons against previous soil sample results.
Place the soil sample in a soil box or a bag to avoid contamination and write the field number on it with a black permanent marker. So, when you pick up the result for this year or in three years’ time you know exactly what field each result corresponds to.
Repeat samples every 3-4 years to see if the actions you are taking to correct soil fertility are working. Derogation farmers must take a soil sample every 4 years from a maximum area of 5 ha.

Managing your soil starts with taking a representative soil sample. Knowing what nutrients are required by your soil eliminates the guesswork. There is little to be achieved by applying additional fertiliser to soils where the underlying problem is soil pH. Therefore measuring, correcting and maintaining soil pH and Indexes should be the first consideration in soil fertility management. Managing the fertility of your soils begins with measuring the fertility of your soils. After all, you can’t manage what you don’t measure!

More information

For more information on utilising your soil sample results and developing a farm fertiliser plan for 2022, please contact a member of the Target Fertiliser team here.