How to Correctly Apply Fertiliser?
As an essential part of crop production, fertiliser application is a well-established method of increasing crop yield.
Supplying the right balance of nutrients to the crop and soil lead to not only increase in yields but also improves overall crop health.
Four factors of fertiliser success
Before selecting the correct method of fertiliser application, it is important to note the four factors that will support in the success of applying fertiliser to crops.
- Nutrient contents
- There are many types of fertiliser, with options to supply a multitude of different nutrients in a variety of different formats. So, it’s important to understand what your crops and soils need before applying, this can be done by soil or tissue testing
- One you know which fertiliser to use, you can decide how to correctly apply it
- For guidance on the value of nutrients, soil and nutrient management, see AHDB’s Nutrient Management Guide (RB209)
- Nutrients should be applied depending on when crops need them – your local agronomist should be able to advise for your specific farm
- Split applications are typically more successful than one application, as crop uptake, soil supply and nutrient loss risks are all at play during application
- Right rate
- Tailor the amount of nutrient to the needs of the crop – do not run short or apply to much, as this can be costly not only in terms of wasted fertiliser, but also have negative impacts on the environment
- Fields vary within and between themselves, so manage the discrepancies and differences to meet site specific crop needs – again, your agronomist can support with field mapping to establish areas of differing nutrient needs
Top Tip: Before applying, check the spreader calibration (found in the spreader manufacturer’s handbook) to ensure the fertiliser goes exactly where it is needed.
With regards to application, there are a variety of methods each suited to different farm locations, crop varieties and the requirements.
The most common application methods are: broadcasting, foliar, placement, and fertigation. Methods can also be divided into two subgroups depending on their form – solid or liquid.
To start with solid form, there are two main types; broadcasting and placement – about 90% of fertilises are applied as solid granules.
- Fertilisers, such as well-decomposed manure, granules and lime are applied by a spreader throughout the whole field before or after drilling
- During planting, fertiliser is applied by drilling into the soil below the surface, which allows for crop roots to easily uptake nutrients and reduces the risk of drift
- Often, the fertiliser is placed one to two inches below the seed row
- Localised placement
- Not to be mistaken for placement, localised placement similarly applies fertiliser into the soil, but with special reference to the location of the seed or plant
- This is a more technical method that requires special precautions but requires less fertiliser as nutrients come in easy reach of crop roots
There are two main types of liquid fertiliser; fertigation and foliar – these are both tailored towards very specific application options.
- Foliar spraying of nutrient solutions
- For established crops, foliar applications apply liquid fertiliser in a spray allowing it to settle on plant leaves and efficiently move through the plant
- For seedlings, starter solutions (usually containing nitrogen, potassium and phosphorus) are applied to wet the field, allowing seedlings to quickly establish
- This method of nutrient application prevents nutrients from being locked up in the soil
- Used in surface, sprinkler or drip irrigation systems, generally for specialist crops, fertiliser is dissolved into water to drip in the channels via the pre setup irrigation system
- Caution must be made in relation to flooding, as excess water may lead to physiological problems in crops
Avoiding spreading fertiliser in unfavourable weather conditions such as in wind, high rainfall levels and damp and humid conditions.
Spreading fertiliser during heavy rainfall in particular can pose several environmental risks, including the following:
- Runoff: can carry nutrients, especially nitrogen (as nitrate) and phosphorus, into nearby water bodies.
Nutrient runoff can cause eutrophication in rivers, lakes, and ponds, leading to harmful algal blooms, fish kills, and a reduction in water quality.
These algal blooms can produce toxins harmful to aquatic life, humans, and animals.
- Leaching: in sandy soils or those with poor structure, heavy rain can cause fertilisers to leach deep into the soil profile, beyond the root zone of plants.
This can contaminate groundwater with nitrates, posing risks to human health when consumed and harming aquatic habitats when this groundwater flows into surface water.
- Erosion: if fertiliser is applied to bare or sparsely vegetated soil, and there’s heavy rain or strong winds, it can lead to soil erosion.
The eroded soil particles treated with fertiliser can end up in water courses, adding to the sediment load and further contributing to nutrient pollution.
- Ensure you have a clean spreader: Over time, fertilisers can leave deposits on the spreader vanes which can build-up or cause blockages leading to un-even spreading.
- Check your speed: Speed affects the application rate, so ensure to drive forward in a consistent speed to ensure even coverage.