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Get to Know Your Soil Fertility


It is well known that grass is the cheapest source of feed on our farms. It is up to 3 times cheaper than silage and up to 5 times cheaper than concentrates. Advisor Patricia Lynch gives information on the importance of soil sampling to optimise grassland performance.

A valid soil sample result will give you real time accurate data on the nutrient status of your soil.

By taking the guess work out of the fertiliser plan, soil sampling will allow you to focus on where your chemical and organic fertilisers are most required. This will give you the best return for your money and avoid wasting valuable nutrients by applying them to ground where they are not needed. This will also avoid potential pollution risks by avoiding the application of excessive nutrients to areas where there is already a surplus.

Achieving maximum growth rates

To achieve maximum growth rates you need to have optimal soil fertility. Maintaining a soil pH of 6.2-6.5 is a critical starting point for maximising the value of your fertilisers. If the pH of your soil is not in this range then there will not be optimum uptake of expensive fertilisers. This is critical to understand with the expected rise in fertiliser prices over the coming years.

Taking a soil sample

Soil samples should be taken up to a maximum area of 4ha.  They are good value when you consider the valuable information that will be retrieved. A standard soil sample result will provide you with a phosphorus, potassium and the soil pH reading (lime requirement).

It is important to note that the results of a soil analysis are only as good as the sample on which it is based. To give reliable advice, a soil sample must be representative of the area sampled and soil cores should be taken to a uniform depth of 10cm. Do not sample a field until 3 to 6 months after the last application of P and K and 2 years where lime was applied. Grouping 2 or 3 fields or paddocks together is acceptable as long as the samples are uniform and fields have being treated the same in previous years. 

Separate samples should be taken from areas with different:

  • soil types
  • cropping history
  • slope
  • drainage
  • fields with persistent poor yields.

Avoid any unusual spots such as old fences, ditches, drinking troughs, dung or urine patches or where fertiliser, manures or lime has been heaped or spilled in the past. Take a representative soil sample by walking in a W shaped pattern across the sampling area. Sample fields at the same time of year to aid comparisons of soil sample results.

DAFM soil sampling programme

Recently the DAFM closed a free soil sampling programme where farmers could avail of up to 16 free soil samples. For farmers who will be accepted into this programme it is important they interpret the soil samples and act on the results. 

Any farmers who did not apply to this scheme but who still wish to get soil samples taken can call their local Teagasc office. Prices may differ depending on what nutrients the sample is being tested for.

Find you local Teagasc office here