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Clay application on sandy soils

Sandy soils have a low water and nutrient storage capacity. Due to the lack of clay, it also has a very limited capacity for enrichment with soil organic matter. In a practical trial, the application of clay from a clay pit 9 km away was tested on soils with the soil type sand or loamy sand.

In variant 1, 225 kg clay/ha were applied. This corresponds to about 0.001 % clay to the total soil mass at 0-20 cm depth. In variant 2, 500 t clay/ha were applied. This corresponds to about 1.8 % clay to the total soil mass at a depth of 0-20 cm. A clay mineral analysis of the clay used showed a mineral composition accentuated by smectite and illite/muscovite.

One and a half years after application, sufficient mixing had not yet taken place in the soil; small clay lumps were still clearly visible. After about 30 months, isolated clay lumps were no longer visible in soil samples. In variant 2, a significantly higher cation exchange capacity of 86 mmolc/kg was measured compared to 80 mmolc/kg in the untreated soil. The pH value was found to have increased by 1.1. The water content in the soil had also increased by 1 %. No differences were found between variant 1 and the untreated soil.

The high one-time cost of the initial expenditure is compensated by the extremely long-term effect of the measure. With the help of cover crops and a supply of organic material, it should now be possible to increase soil organic matter even on this type of soil.