Improving soil pH has a real impact on realising the potential of the soil, improving the effects of mineral fertilisation, organic fertilisation and other agronomic treatments, resulting in an improved bottom line.
pH regulation consists of bringing the soil pH to a level suitable for the soil category. This is achieved by applying an appropriate dose of lime fertiliser. In Poland, almost 60% of land has a very acid or acid reaction, and only 18% of soils do not require liming.
The optimum pH for soils of different soil categories is for very light soil: 5.1 – 5.5; light soil: 5.6 – 6.0; medium soil: 6.1 – 6.5; heavy soil: 6.6 – 7.0. Mineral fertiliser doses shall be determined on the basis of a reliable soil analysis result. The amount of calcium application is usually determined by the degree of acidity of the soil and its granulometric composition.
For example: if you have a field with light soil and a pH of 4.8 according to the table above, you need to apply 2.5 tonnes of CaO, i.e. 5 tonnes of lime with 50% CaO. The dose is large, so it should be divided into 2 smaller doses applied at different times; the first can be higher, e.g. 3 tonnes, and after 1-2 years the second – 2 tonnes. Sometimes, when neglect is severe and soils are heavy, it can take up to 5 years to reach the correct soil pH.
In addition to the correct doses, the location of the lime placement is important. Lime should be well mixed into the soil, bearing in mind that it will move down the soil profile over time. Therefore, the best method of application is to apply lime under the cultivator, although satisfactory results can also be obtained by applying lime under post-harvest cultivation or by mixing well throughout the soil profile.
An important factor in successful liming is the correct choice of fertiliser. The market offers calcium and calcium-magnesium fertilisers in oxide or carbonate form. Oxide fertilisers – for example quicklime – are characterised by their rapid action and are therefore recommended for heavier soils and very low pH. On light mineral soils, oxide fertilisers can be used interferingly in very moderate doses, while their use on organic soils can lead to rapid degradation. Due to their scorching properties, they can only be applied post-emergence in exceptional situations, for example on grassland, lawns and perennial plantations. It is safer to use carbonate lime, which is a naturally occurring form of calcium with a slower but also effective action. The fastest-acting carbonate fertiliser is fertiliser chalk. The carbonate form of lime is recommended for use on light to medium mineral soils, as well as organic and organic-mineral soils, as it is safe, even in post-harvest applications on perennial plantations. It is also recommended for the conservative liming of heavier soils. Lime and magnesium fertilisers should be used on magnesium-deficient soils, as it is the cheapest source of this nutrient.