ARCHIVE: Fertiliser Manual (RB209)

Checklist for Decision Making

Individual decisions for fertiliser use must be made for each field on the farm. Where more than one crop is grown in a field, these areas must be considered individually.

  1. Confirm the crop to be grown and the intended market. Identify any crop quality requirements required by this market. For the purposes of this guide, winter sown is defined as sown before 1st January and spring sown as in January or after.
  2. Identify the dominant soil type in the cropped area (see page 86 and Appendix 1).
  3. Carry out soil analysis for pH, P, K and Mg every 3-5 years (see page 35). Target values to maintain in arable rotations are:

    Soil pH 6.5 (5.8 on peat soils)
    Soil P Index 2
    Soil K lower Index 2 (2-)
    Soil Mg Index 2
  4. Identify the Soil Nitrogen Supply (SNS) Index of the field either by carrying out analysis for soil mineral nitrogen (the Measurement Method) (see page 95) or by using the Field Assessment Method based on previous cropping, previous fertiliser and manure use, soil type and winter rainfall (see page 86). Sampling and analysis for SMN is recommended where nitrogen residues are expected to be moderate or high (e.g. following previous manure use or crops receiving high rates of nitrogen fertiliser or following a dry winter).
  5. Calculate the nutrients that will be available for crop uptake from organic manures that have been applied since harvest of the previous crop, or which will be applied to the crop being grown (see Section 2). Deduct these nutrients from the recommended rates given in the tables.
  6. Decide on the strategy for phosphate and potash use. This will be building up, maintaining or running down the soil Index (see pages 38-41). Allow for any surplus or deficit of phosphate or potash applied to previous crops in the rotation.
  7. Calculate the amount of phosphate and potash removed in the harvested crop according to expected crop yield (see pages 38-41 and Appendix 5). This is the amount of these nutrients that must be replaced in order to maintain the soil at the current Index. Remember that some of these nutrients will also be removed in straw.
  8. Using the tables, decide on the required rate of each nutrient. Decide on the optimum timings for fertiliser application, then find the best match for these applications using available fertilisers (see page 102).
  9. Check that the fertiliser spreader or sprayer is in good working order and has been recently calibrated (see page 49).
  10. Keep an accurate record of the fertilisers and organic manures applied.
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