Why soil sampling should be on every farmer’s autumn checklist

An up-to-date soil test will help ensure that lime and fertiliser decisions for 2027 are based on what each field actually needs, Veronica Nyhan, Soil and Plant Nutrition Specialist, and the NMP Online team explain why soil sampling should be on every farmer’s autumn checklist.

After a difficult growing year, with drought putting pressure on grass and cereal crops, autumn is a good time to take stock of soil fertility and identify which fields need to be sampled in preparation for 2027.

Soil sampling provides a field-by-field picture of soil pH, phosphorus (P) and potassium (K), helping to target lime and fertiliser where they are needed and avoid applications where they are not.

For nutrient planning purposes, soil test results are valid for four years. Farmers should check now for samples that have expired or will need to be renewed for 2027. Using out-of-date results can give a misleading picture of soil fertility and lead to poor nutrient management decisions.

There is also an important regulatory reason to have valid soil samples. Farms with a grassland stocking rate above 130kg organic N/ha, and land growing cereal crops, cannot apply chemical P fertiliser where valid soil test results are not available. Farmers affected should ensure the relevant areas are sampled to establish a P allowance for 2027.

Use NMP Online

The Soil Sample Expiry colour layer in Teagasc NMP Online provides a quick way of identifying fields where soil samples are out of date or approaching expiry (see figure 1 below). Ask your advisor to produce this map and use it to plan your autumn sampling programme.

Where the NMP Online organic matter map indicates that a sampling area may contain high-organic-matter or peaty soil (>20% organic matter), talk to your advisor about including an organic matter test, as different nutrient advice may apply.

Figure 1: Soil Sample Expiry colour layer in Teagasc NMP Online

Don’t forget lime

Soil pH should be one of the first things considered when results come back. Lime improves nutrient availability and helps crops make better use of applied fertiliser.

Teagasc research has shown an average grass production response of around 1.5t DM/ha from lime alone, with an estimated return of €6–€10 for every €1 invested. On tillage farms, an average cereal grain response of at least 1.5t/ha has also been recorded.

With fertiliser transactions now recorded through the National Fertiliser Database, it is more important than ever that farmers know their fertiliser allowances and keep track of fertiliser use to ensure these limits are not exceeded.

This autumn, check your soil sample expiry dates, identify the fields that need to be resampled and get the job done. An up-to-date soil test will help ensure that lime and fertiliser decisions for 2027 are based on what each field actually needs, supporting production while avoiding unnecessary expense.

For more on soil fertility including soil analysis, fertiliser advice and crop nutrition, visit here

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