Time for Soil Sampling

Under the new nitrates directive all tillage farmers are required to take soil tests. For 2023 if an up to date soil test for P is not available then P is assumed to be index 4 (no P allowance). Now is the ideal time to identify fields on the farm that require fresh soil samples.

Ensure soil samples are taken correctly and take a soil sample every 4ha (max 5ha) where soil type and cropping of lands were similar during the previous five years. This will provide the basis for lime, P, K & Mg applications for the next 4 years.

Crop yields from this harvest were above average for most crops. This will have resulted in increased off takes of P and K’s, so it is very important to assess crop P and K offtakes and soil fertility over the coming weeks.

Teagasc analysed 3,794 tillage soil samples in 2021 and the results show a slight decline in soil fertility on tillage farms when compared to the previous year.

• 18% of soils have optimum pH, P & K (6 % Decrease)
• 61% of soils with a soil pH >6.5 (13% Decrease)
• 57%of soils at P index 1 & 2 (7% Increase)
• 32% of soils at K Index 1 & 2 (2% Decrease)

Soil test reports are central to nutrient management planning. Each farm needs to have an up to date nutrient management plan in place for 2023 to establish allowances for each crop and overall limits for the farm. The fertiliser database is due to commence in January 2023.

Soil Sampling Technique

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 be taken to a uniform depth (10cm).

The principle of soil analysis is to determine the average nutrient status of an area and to give a measure of the available nutrients in the soil. A sample normally consists of 0.25 – 0.5 kg of soil and this is taken to represent the entire sampling area or field.

1. To take a soil sample it is essential to have a suitable soil corer
2. Ensure soil cores are taken to the correct sampling depth of 100 mm (4”)
3. Take a soil sample every 2 to 4 ha. (5-10 acres)
4. Take separate samples from areas that are different in soil type, previous cropping history, slope, drainage or persistent poor yields
5. 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.
6. 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.
7. Take a minimum of 20 soil cores, mix them together, and take a representative sub-sample for analysis, making sure the soil sample box is full.
8. Take a representative soil sample by walking in a W shaped pattern across the sampling area.
9. Sample fields at the same time of the year to aid comparisons of soil sample results and avoid sampling under extremes of soil conditions e.g. waterlogged or very dry soils.
10. Place the soil sample in a soil box to avoid contamination and write the field number and advisor code on the soil box with a black permanent marker.

Soil Sampling Pattern

In this short clip, Mark Plunkett, Soil & Nutrition Specialist with Teagasc runs through why its so important to be testing your soil and what best way to do it.

Get more information and advice from the Teagasc Crops team here
Find your local Teagasc office here