Nutrition check list

Good crop nutrition will help to achieve maximum crop productivity for maximum profits with minimal impact on the environment while adhering to all legislation. Some basic principles should be followed to achieve these goals:

  1. Identify the soil type in order to understand nutrient requirements.

  2. Analyse soil for nutrient content every 3-5 years and adapt nutrient inputs to maintain values of:

    pH 6.5 (5.8 peat soils)
    P Index 2
    K Index 2-
    Mg Index 2
  3. Determine the Soil Nitrogen Supply (SNS) either by Field Assessment Method or by sampling and analysis for Soil Mineral Nitrogen.

  4. Determine nutrient supply from organic sources and deduct available nutrient sources from total crop requirement.

  5. Apply Phosphorus and Potassium to maintain nutrients from crop removal and apply additional quantities if soil indices are low.

  6. Apply nutrients at the correct timing to match plant demand.

  7. Check that the fertiliser spreader or sprayer is calibrated to deliver nutrient accurately.

  8. Record all fertilisers and organic materials used.


N Max limit

For crops grown in Nitrate Vulnerable Zones (NVZs) there are rules limiting the amount of nitrogen that can be applied. These limits are not necessarily the optimum for agronomic performance but are the maximum allowable in these areas.

In NVZ zones, the average nitrogen application rate (from manufactured fertiliser and crop-available nitrogen from any organic manure) must not exceed the N Max limit. It is also good practice to follow these guidelines for land outside of NVZ zones. The N Max limit applies to the average across the farm.

For full details of N Max limits please refer to the DEFRA document; Guidance on complying with the rules for Nitrate Vulnerable Zones in England for 2013 to 2016.

The table below highlights the N Max limits.

Crop Expected yield N max limits
Potatoes n/a 270

Nitrogen Input

The tables below highlight the nitrogen inputs required based on SNS, variety and length of growing season.


SNS Index

Length of a) growing season and b) variety group 0 and 1 2,3 and 4 5 and 6
    kg N/ha
<60 days - Variety group 1 100-140 70-110 40-60
  - Variety group 2 80-120 50-80 0-40
  - Variety group 3 60-100 40-70 0-40
  - Variety group 4 N/A N/A N/A
60-90 days - Variety group 1 160-210 130-160 90-120
  - Variety group 2 100-160 60-120 40-80
  - Variety group 3 60-140 40-100 0-60
  - Variety group 4 40-80 20-40 0-40
90-120 days - Variety group 1 220-270 190-220 150-180
  - Variety group 2 150-220 110-160 80-120
  - Variety group 3 110-180 80-100 40-60
  - Variety group 4 80-140 40-60 0-40
>120 days - Variety group 1 N/A N/A N/A
  - Variety group 2 190-250 150-180 120-150
  - Variety group 3 150-210 120-140 80-150
  - Variety group 4 100-180 60-80 20-40

N/A - Not Applicable

a. 50% emergence to haulm death

b. Examples of varieties to in each variety group are as follows:

Group 1 Short haulm longevity (Determinate varieties) Accord, Estima, Maris Bard and Premiere
Group 2 Medium haulm longevity (Partially determinate varieties) Alantic, Lady Rosetta, Marfona, Maris Peer, Nadine, Saxon, Shepody and Wilja
Group 3 Long haulm longevity (Indeterminate varieties) Maincrop varieties such as Desiree, Flanna, Hermes, King Edwards, Maris Piper, Rooster, Russet Burbank, Pentland Dell, Pentland Squire and Saturna.
Group 4 Very long haulm longevity Cara and Markles




Crop nutrient removal

Significant nutrients are removed from the field during crop removal. The levels of these nutrients that are removed from the system will vary significantly depending on yield. In order to maintain soil nutrient levels the nutrients that are removed with the crop need to be replaced by either fertiliser applications and/or organic  additions.

The table below indicates the level of nutrients required to maintain soil indices at target Index 2 across a range of yield levels:

    Nutrient requirement (kg/ha)  
Crop Yield (t/ha) P2O5 K2O MgO
Potato 50.0 170 (50 crop removal) 300 40
60.0 170 (60 crop removal) 358 43
70.0 170 (70 crop removal) 416 46
80.0 170 (80 crop removal) 474 49


Please note that phosphate recommendations are based on yield response rather than crop uptake. At soil P Index of 2  170kg P2O5/Ha  should not be adjusted if yield above or below 50t/Ha. This rate is required to ensure adequate phosphorus is available to the crop.

On soils at P Index 2 or below it is important that the phosphate fertiliser is of highly water-soluble.


For K requirements above 300kg K/Ha apply half in autumn/winter and the balance in the spring.


Sources of magnesium are very important and preferably those with high water solubility such as kieserite should be used.