Policy is paving a path to reduced artificial fertiliser use and if decreases are not seen in the near future, then regulation is likely to force a reduction in use.

This does not have to be seen as a negative on farms. More efficient fertiliser use can lead to savings and a more sustainable farm system.

The basics should always be tackled first when deciding on fertiliser use. Of all soils in Ireland, 80% are not in optimum condition and need soil pH, phosphorus (P), potassium (K), or a mixture of all three, to be corrected. Those three characteristics provide a solid foundation for efficient fertiliser use, so before considering a big investment or a big switch in system on the farm, sort out soil indexes and pH.

GPS fertiliser spreaders

The announcement last month that the TAMS grant towards GPS fertiliser spreaders will be rolled out to all farms, not just tillage as had been the case, is a welcome one and has the potential to dramatically increase fertiliser efficiency on many farms.

The first step of automatic shut-off can avoid overlaps on headlands and turns, while rate control can also be achieved. The use of driving guidance and automatic shut-off can result in savings of approximately 15% in fertiliser use.

It is of course essential that a cost-benefit analysis is carried out ahead of a purchase, as the technology adds significantly to the cost of spreading, but can also significantly reduce the bill for the product spread.

While the spend required may not be practical on many farms, it is certainly something to think about and is worth considering hiring a contractor with the equipment for some jobs.

Variable rates

Maps to guide P, K and lime application are the next step up. Variable-rate spreaders have the ability to spread nutrients at different rates across fields where GPS soil samples have been taken to create a variable-rate map.

This technique is particularly beneficial on soils where the index is low. The nutrient can be spread at higher rates where levels are low in the soil and at lower or zero rate where the fertility is adequate.

On land where soil nutrient levels are depleted, spreading P and K as straights at variable rates could help to improve these levels quickly.

It should be noted that variable-rate spreading will not necessarily reduce your fertiliser bill, but it will put the P and K where it is needed most and where it will be used most efficiently.

While P and K at variable rates might be a stretch for some, as it usually involves spreading straights and more passes of the machine, variable-rate lime spreading is an investment worth thinking about and is easily accessible to most through a lime spreading contractor.

Many contractors who spread lime are already kitted out with the equipment, so getting land sampled and the variable-rate map created is the main investment for the farmer.

Fields can vary hugely in soil pH across different areas and correcting those areas could lead to improved productivity in those patches of fields that were most likely under-performing. For this reason, it may also be best to tackle soil pH and lime before tackling P and K levels.

Improvements in technology from steering guidance and automatic shut-off to variable rate application not only saves on the fertiliser bill, but it also means that all fertiliser will be used more efficiently.

Doing this should reduce the risk of excess nutrients making their way to waterways or escaping to the atmosphere.

TAMS grant

GPS fertiliser spreaders are available to all participants in the current TAMS tranche (Tranche 21), which opened on 16 January and is due to close on 16 April.

Under the scheme, fertiliser spreaders must be GPS-controlled (controlling the application rate) and have headland management.

The GPS unit must also have:

  • A display screen.
  • GPS receiver and control unit.
  • It should also be able to record the location, the fertiliser path (to within 200mm of the actual location), the application rate and the spreading width across the field.