Over de ontzilting van den bodem in de Wieringermeer : een studie over de zout- en waterbeweging in jonge poldergronden

The initial concentration of salt in the soil moisture of the Wieringermeer (reclaimed from the sea in 1930) was about 2 %. The moisture content of the soil and hence the salt content in dry matter increased with increasing clay content.
Percolating rainwater attained the concentration of the soil moisture within a depth of 25 to 50 cm. Diffusion hardly influenced salt movement as such, but was highly instrumental in equalizing the salt concentration of the percolating rainwater and of the soil moisture.

In comparable leaching conditions the topmost layer of sandy soils was leached faster than of clay soils. For the deeper layers the reverse was true. Usually the low permeability of the clayey subsoils hampered passage of water. In soils with vegetation upward capillary transport did not exceed about 50 mm a year. Seepage retarded desalinization considerably.

The better the drainage the faster the leaching. After laying an adequate field- drainage system the rains of one winter leached sufficient salt from sandy soils to allow crop growth; for a comparable leaching of clay soils the rains of two to three winters were required.