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Soil Sampling, Methods and Analysis Guide

As customers seek advice on soil nutrients and recommended fertiliser application rates the first piece of advice is to conduct soil sampling methods and analysis.

Importance of Soil Sampling

Soil sample results provide a sound basis for efficient and targeted application of lime, manure and fertiliser. This is more crucial than ever as lower commodity prices for grain, milk and beef are predicted to leave lower margins in all sectors this coming year.

This makes efficient and targeted use of fertiliser and lime even more important as fertiliser is not a cheap product anymore but lime is the value product relative to its importance in the system. As the Americans like to say “more bang for your buck” will be a very important slogan for the coming year as it will be unwise to take a sabbatical on inputs such as lime P and K! I cannot stress enough that yield will still be one of the most important factors in determining profitability on farms this year.

A typical standard soil analysis will test for major soil nutrients such as soil P, K and Mg with pH measurement taken for soil acidity. For tillage fields it is advisable to also test for some of the minor trace elements such as manganese, zinc and copper.

There are a number of recommendations when taking soil samples to ensure that the results you get back are accurate and reflective of the overall area being tested.

Soil Sampling Techniques

A soil sample should be taken to a depth of 10cm using a suitable soil corer. It is worth remembering that for grassland soils, P tends to stay in the top few centimetres of soils and by not sampling low enough into the soil you will get an inaccurate reading.

Taking soil samples for analysis and testing in tillage soils is not an issue as the soil and presence of P tends to be more uniform. A soil sample should be taken every two to four hectares, walking in a W shaped pattern avoiding any unusual spots such as drinking troughs, rung or urine patches.

Soil Sampling Analysis

A minimum of 20 soil cores should be taken and then mixed together to get a representative sample ready for analysis.  Allow at least two years after latest lime application and three months since last application of fertiliser or slurry three months.

I recommend sampling every three to five years. Regular soil sampling provides up to date field by field information providing an opportunity to monitor farm soil fertility changes over time, and show the speed of change in soil pH, P and K relative to nutrient management practices for the soils and fields within a farm.

For further advice on soil sampling or interpreting your results, contact any member of the Connolly’s RED MILLS agronomy team.

  • Tags:
  • Agri
  • fertiliser
  • lime
  • nutrient management
  • PH
  • slurry
  • soil sampling
  • tillage farming