The impact of Brexit on any business is not known and there is much uncertainty for farmers, including around potential volatility within import and export markets. Fertiliser costs are lower than this time last year but as much fertilisers is imported, and from a range of EU and non-EU countries, the impact on future price is unknown. However whilst the price is unclear, what is known is that the creation of optimum soil conditions will maximise the benefit of fertilisers – increasing the impact they have on grass or crop growth.
The natural pH of soil depends on the nature of the parent material from which the soil was developed, the soil profile age and climatic weathering. There are also regional differences in soil acidity occurring due to differences in soil type and land uses. Lime is not a fertiliser but the application of lime is vital to create the optimal soil conditions for nutrient uptake, healthy productive plant growth and efficient fertiliser use. The optimum availability of most plant nutrients in soil occurs in a small range of soil pH values. For mineral soils, this is a pH of between 6 and 6.2.
If the pH of soil is 5.5 and lower, then the yield potential can be lower by up to 20% in grass, 30% in winter wheat and 50% in spring barley even with adequate PK fertilisers.
As can been seen from the table above the lower the pH of the soil the less Nitrogen, Potassium and Phosphorus is available to the crop thus limiting the yield of the crop.
Soils should be sampled every 4 to 5 years and analysed for soil pH, extractable P, K and Mg. This allows the application of lime and fertilisers at the correct levels to the field requirements. Farms can develop a sampling programme setting up a system that fields are sampled in a rotation with 20 to 25% of fields sampled annually – spreading the costs of lime and application.
Lime takes time to work- it does not have an instant effect on the pH of the soil. Guidance for timing of lime application is to spread before ploughing in the autumn or spread after ploughing for spring crops and after ploughing for autumn crops.
Prilled lime works very quickly and is short acting making it expensive compared to ground lime, but can save crops and could be used to sort out a pH problem.
Ground lime is a natural occurring product quarried in the United Kingdom. As lime is a naturally occurring product, all ground limestone differ. Amounts of calcium and magnesium vary and they all have different neutralising values. Liming materials should be purchased based on the price relative to the neutralising value and the fineness of the products on offer.
“Cost per tonne of product including delivery and spreading divided by the Neutralising Value.”
Although the UK left the EU on 31 January 2020 but Brexit will remain at the forefront of farmers’ minds as crucial trade deals are negotiated. Imported fertiliser prices will be influenced by exchange rates and potential tariffs and there isn’t much farmers can do to influence this. However what they can do is make sure that their soil will make the best use of any fertiliser applied.
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