Ph effects: The difference between soil grown and aquaponics

Cultivating on aquaponics is not the same as growing directly in the soil. What kind of approach do you need to take in regards Ph? 

This year the Dutch trial center Proeftuin Zwaagdijk is doing research, on the effects of pH in aquaponic cultivation of lettuce. The research looks the production, the development of fertilizer concentrations in the nutritional solution and the absorption by the plant.

In the first test, the pH in the range from 5.2 to 7.1 did not significantly affect the harvest percentage and the harvest weight. Effects on fertilizer concentrations in the nutritional solution were observed in this test, in particulars for calcium and phosphate (decrease at pH above 6.5), iron (decrease at pH higher than 6.8) and manganese (decrease as pH rises).

Significant effects on the nutritional intake were observed for zinc and copper (less uptake at rising pH) and manganese. In the latter, the intake appears to be optimal in the pH 5-6 range, with a peak at a pH of around 6.5.

In the test, nutritional solutions with an EC of about 2 mS/cm were used. In this nutritional solution all essential elements are abundantly present, more than the plant actually needs.

An additional number of tests will be carried out this year in order to substantiate the observed effects.