TIME4 ACCURACY: Improving fertiliser use efficiency

Experts indicate that around 40% of nitrogen fertiliser that’s applied to agricultural land isn’t utilised because plants aren’t able to use the available mineral nutrients.

As fertiliser prices remain high, read our reminder guide for helpful tips on how to improve nutrient use efficiency, without compromising yield.

Soil analysis

Soil sampling provides a representative view of soil fertility and condition which will help to improve nutrient use efficiency. It will also inform accurate fertiliser calculations and costings by ensuring the right fertiliser is spread at the right time, in the right amount.

This is because soil testing results will show:

Soil nutrient level – Basic soil analysis will show magnesium (Mg), phosphorus (P) and potassium (K) levels. More advanced soil tests will show levels of other elements and trace elements such as calcium (Ca), boron (B), copper (Cu) and manganese (Mn)
Nitrogen (N) levels are tested separately from other elements and trace elements. An estimate of nitrogen levels can be calculated from analysing soil type, rainfall and previous cropping
Soil indices – Potash and phosphate should be at index level 2 for grassland to ensure nitrogen can be used efficiently, which will drive higher levels of daily dry matter production
Soil pH levels –Different crops have different pH requirements but the optimal range for most plants is between 5.5 and 7.0. Soil pH is important for increasing the response to chemical or organic fertiliser as it maximises the availability of nutrients to plants. Apply lime if soils are too acidic to prevent yield losses.

Top tip: Lime applications should only be based on soil tests taken within the last four years. Target the most acidic fields with lime first as they may need more than one application to reach the optimum pH range

Soil sampling top tips:

Take samples when it’s dry
Test all silage fields every three years and permanent pasture every five years (this can be achieved by sampling around 20% of your farm every year)
Avoid nitrate-release tests in grass grazed by livestock because manure and urine can create false readings
Take multiple samples within the same field
Use soil sample results to inform precision spreading
Assess soil compaction and condition when soil sampling. Consider using a harrow, plough or aerator to break up and add oxygen to compacted soil. This encourages root growth, supporting fertiliser uptake and sward health
Watch our ‘how to’ soil sampling video here

Make use of slurry or manure

Organic manure is the obvious substitute to reduce use and reliance on chemical fertiliser. But as stipulated by the updated ‘Farming Rules for Water’, you must plan how much fertiliser or manure to use to not exceed the needs of the soil and crop on the land. This can be achieved by:

Analysing slurry or manure before application to understand the nutrients within it to make sure nutrient requirements (based on soil analysis) are met
Calculating the phosphate and potash levels to maintain ideal soil indices (as outlined above)
Calculating the application rate. Nitrogen application rates should be calculated separately to other elements and follow Nitrate Vulnerable Zones (NVZs) standards where applicable.

Top tips:

Two slurry or manure samples should be taken per year, coinciding with the main spreading periods
Stir slurry, or break up any lumps if using solid manure, and thoroughly mix, before taking the sample to achieve representative results
Make sure you’re familiar with the Farming Rules For Water
Any nutrient shortfalls can be made up with chemical fertiliser
Retrofitting a tanker dribble bar to your slurry spreader is a quick, cost-effective, and low-cost method of optimising your slurry application. Contact us here to find out more.

Seek advice

Our FACTS-qualified advisers can help with creating nutrient and manure management plans. Speak to your local on-farm specialist if you would like assistance with this.

Check the most cost-effective application rates of nitrogen, slurry or manure for your crops by consulting AHDB’s recommendations in the Nutrient Management Guide (RB209).

Top tips:

As part of a longer-term plan to improve fertiliser efficiency, consider adding nitrogen fixing crop varieties, such as clover or other legumes, into your rotation. Read our Grass and Forage Guide 2021 to learn more.
Calibrating your fertiliser spreader, using dribble bars or slurry injectors will improve accuracy. Contact your local on-farm specialist if you’d like assistance with this and read more on this here: Fertiliser spreader checks should be prioritised to reap financial rewards