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Profit from Soil Nitrogen Sampling

How to take an N-Min Sample

When and how to sample?

Best time to sample is in the spring before the first fertiliser application and at least six weeks after the last manure application.


The quality of the soil sample is critical, so plan the sample well:

  • Take 10 to 15 cores (up to 20 cores for fields >20ha) from a ‘W’ shape pattern across the field

  • Avoid areas such as gateways, headlands, old manure heaps

  • Do not pick up any crop residue or manure

  • Soil cores should be taken at a depth of 60cm (or max rooting depth, if less than that)


Push the auger in firmly and measure how deep it goes:

  • If the field varies, test in a few places and take an average

  • Make sure you record the actual sample depth


Once collected, the cores should be combined together (but not overmixed):

  • Keep the sample cool with frozen gel packs and send to the lab within 1-2 days.


Before leaving the field, make an estimate of amount of Nitrogen already in the crop:

  • By counting the tillers in cereals or

  • Measuring the Green Area Index (GAI) in oilseed rape.


Within two weeks, the results will return from the lab:

  • Feed them into CF Fertilisers Nitrogen calculator; N-Calc

  • Add target yield, keeping it realistic

  • Obtain result- optimum amount of Nitrogen fertiliser to apply with timing guidance on applications.

Contact CF in order to become a CF N-Min approved provider:

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