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Teagasc report: Considerations on soil sampling


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Now is a good time to plan soil-sampling requirements for 2023 and have results on time to plan fertiliser requirements.

Under cross-compliance, the prohibited application period for chemical fertiliser and slurry is an ideal opportunity to have soil samples taken for the whole farm.

While some farmers might find managing appropriate timings of fertiliser or slurry applications challenging for various reasons such as weather conditions or contractor availability, under no circumstances should fertiliser or slurry be spread during the prohibited application period.

Mainly because there is little or no crop uptake, therefore nitrates will leach to ground water in freely draining soils and P will be lost due to surface run-off.

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The quality of the fertiliser plan is dependant on soil samples being taken correctly, which includes sampling to the correct depth of 10 centimetres, every two to four hectares, and taking separate samples from areas that are different in soil type, previous cropping history, drainage or persistent poor yields.

Information on soil PH, lime, P and K indexes will allow for a targeted application of slurry, and choosing a fertiliser that has the correct balance of Nitrogen, Phosphorus, Potassium and Sulphur.

Allow three to six months between fertiliser P and K applications and taking fresh soil samples.

For non-derogation farmers and farmers stocked below 170kg N/ha in GLAS to remain Nitrate compliant, original soil samples taken, if not in date for 2022 or not replaced by a new set of soil samples, P Index 1, 2, and 3 lands reverted to P index 3 and P index 4 land will remain at P index 4 until the end of the GLAS extension year 2022.

From January 1, 2022, all farmers above 170 kg N/ha must take soil samples.

Where soil samples are not undertaken, Index 4 for Phosphorus will be assumed.

From January 1, 2023, all farmers above 130 kg N/ha must take soil samples.

Where soil samples are not undertaken, Index 4 for Phosphorus will be assumed.

All arable land sown from January 1, 2023, must take soil samples. The soil-sample results will allow the advisor and the farmer to tailor a fertiliser plan for the coming year to match the needs of the soil and the crop.

The number of soil samples to be taken and how many years between each sampling will depend on whether you are a Nitrate Derogation farmer or not, and this should be discussed with your advisor.

Your soil-sample analysis will show the rate of lime required depending on the soil type, soil pH and crop type.

In any case, the maximum that can be applied is 7.5 tonne/hectare and apply the balance after two years.

The advice given on the soil test report should always be cross-checked against an estimate of the total fertiliser allowance for the farm under the nitrates regulations.

There are cases where the full P advice may not be permitted on the farm under the regulations, so it is important to check this before you purchase or apply fertiliser.

Knowing the farm soil-fertility status, field by field, is the starting point to control fertiliser costs.