RETENTION OF IONS BY VOLCANIT SAND USED IN HYDROPONIC CULTURES

Volcanic sands were treated with nutrient solutions for a period of six weeks and were washed with deionized water (until constant conductivity) for several weeks.
These basaltic materials had been used in commercial hydroponic cultures for 6-, 5-, 4-, and 1 year, while another, as control, had not been used before.
The activity of the materials on the NH⁺₄-, NO^–₃-, H₂PO^–₄-, K⁺-, Ca⁺⁺-, Mg⁺⁺, and Na⁺ contents of the nutrient solution was examined.
All material had retention of NH⁺₄ and H₂PO^–₄, and released K⁺, Ca⁺⁺, Mg⁺⁺ and Na⁺. The non used material is the one which had the lowest activity in the nutrient solution composition.
The pH of the material decreased about 1 unit (from 8 to 7). The NH₄-Acetate extractable Ca⁺⁺, Mg⁺⁺, and Na⁺ and the NaHCO₃ extractable P increased after treatments.
There was also a nitrification of the NH⁺₄ retained, increasing the NO^–₃ in the nutrient solutions except in the non-used material.

Symposium on Substrates in Horticulture other than Soils In Situ

A. Luque

https://doi.org/10.17660/ActaHortic.1982.126.8