Forage Maize

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
Forage maize n/a 150

Nitrogen Inputs

The table below highlight the nitrogen inputs required based on SNS.

SNS Index
  0 1 2 3 4 and higher
kg N/ha
Nirogen (N) all mineral soils 150 100 50 20 0



Crop nutrient removal

Significant nutrients are removed from the field during crop removal and levels of P, K and Mg 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 highlights the nutrients required for soils at target Index 2 at different crop yields and to maintain the soil at the target Index.

    Nutrient requirement (kg/ha)  
Crop Yield (t/ha) P2O5 K2O MgO
Maize Silage (30% DM) 40.0 55 175 48
50.0 69 219 60
60.0 83 263 72
70.0 97 307 84
80.0 111 351 96
90.0 125 395 108