Liming

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Carbonate of lime from natural degradation has a slow and lasting effect in the soil and is particularly well tolerated by soil organisms. The sample contains 90% calcium carbonate and 2% magnesium carbonate

Under liming or liming is meant the application of powdered limestone ( calcium carbonate CaCO3 or calcium carbonate ), or more rarely burnt lime ( calcium oxide CaO , to neutralize) the acids in the soil and the pH increase of the soil. Liming is carried out to counteract soil acidification and to maintain or improve soil fertility.

In order to contain or compensate for massive forest soil acidification, soil protection liming has been carried out in German forests since 1980. As a rule, the forest liming is now carried out with helicopters , as they can distribute the lime in a targeted and very evenly over the forest. For the various locations, it must be checked and weighed up whether or not liming should be carried out. For forest liming, carbonic acid magnesium limes with more than 15% magnesium content are usually used in order to increase the magnesium supply and base saturation in addition to improving the pH value. Usually three tons of lime are spread per hectare. On average, this is sufficient to compensate for the acid accumulation of around ten years.

Lime fertilizer

Market importance of lime fertilizers in Germany

Lime fertilizers such as carbonate, quicklime, slaked lime, convert lime, carbolime or other residual limes not only increase the pH value, but also improve the soil structure and supply the plants with calcium and, in some cases, magnesium . They are also often referred to as fertilizer lime.

Natural limes (Ca carbonates) are extracted from natural deposits and ground. Limestone (e.g. chalk , marl , marl , dolomite ) is widespread and has been used in agriculture for centuries to improve soil fertility. In addition to natural limes, there are industrial limes as well as calcareous nitrogen fertilizers (calcium ammonium nitrate, calcium cyanamide, calcium nitrate) and phosphate fertilizers ( superphosphates ) that contain calcium.

Lime fertilization causes CO 2 emissions and is therefore climate-relevant, but the emissions of approx. 1 million tons per year for Germany are low compared to the total emissions (approx. 900 million tons / a).

Lime requirement and pH range

Liming a field in Devon

The correct dosage of lime fertilization requires a soil analysis and a target value for the desired soil reaction ( soil pH ). A slightly lower pH value (5.0 to 6.0) is sought for light soils than for heavy soils (5.5 to 7.0). Some plants are so closely adapted to certain acid ranges that they can serve as indicators of the current pH value.

Depending on the purpose, a distinction is made between recovery liming to cover pent-up demand and maintenance liming. Depending on the buffer capacity of the soil, fast-acting forms of lime such as quicklime CaO or slaked lime Ca (OH) 2 are preferred for heavy soils, while mixed lime , carbonate lime or converter lime is used on lighter soils in order to achieve sustainable liming.

When setting a soil-specific optimal pH range, the direct effects of the H + ions are less decisive than the availability of nutrients for the cultivated plants and the structural properties of the soil at the respective pH value. In strongly acidic soils, in addition to calcium , magnesium , potassium , phosphorus and molybdenum are significantly less available to plants due to leaching (impoverishment) or retention. From a value of pH <3.5, the H + and Al 3+ ions have a toxic effect on root growth and many microorganisms in the soil.

In the case of over-lime formation at pH values ​​above 8.0, however, iron, manganese and boron are fixed. From a value of pH> 9, OH - toxicity can occur as primary damage.

See also

literature

  • Arnold Finck : Plant nutrition in brief . 3rd revised edition. Hirt, Kiel 1976, ISBN 3-554-80197-6 , ( Hirt's key word books ), p. 130.
  • Martin Greve: Long-term effects of forest liming on the material balance. Trippstadt, 2015. Download .
  • Max Schmidt: Lime fertilization - healthy arable soils - optimal yields . 1st edition. DLG-Verlag, Frankfurt 2013, ISBN 978-3-7690-2017-5 , ( series: Agrarpraxis compact )

Individual evidence

  1. ↑ Thünen Institute: Calculation of gaseous and particulate emissions from German agriculture 1990 - 2016. Accessed on May 22, 2018 (German, English, zip file).
  2. ↑ Federal Environment Agency: Emissions development 1990 to 2015 with near-term forecast 2016. Accessed on May 22, 2015 .