Focus on nutritional elements: sulfate

In addition to the other nutritional elements, a plant also needs sulfate (SO42-) in order to grow properly. Sulfate in the plant is mainly found in the proteins of the leaf green and in the cell fluid.

Sulfate (SO42-) is the oxidized form of sulfur and is absorbed by the plant roots. A plant can also absorb sulfur dioxide (SO2) from the air. Too high concentrations of these can be toxic to plants. Sulfate does not move easily through plants. In the plant it is mainly found in the proteins of the leaf green and in the cell fluid. The sulfate content in the dry matter of the plant is low and is around 0.1 percent.

Sulfate is added to most potting soil basic fertilizers. The sulfate content in a substrate must, according to the RHP standards, increase with higher EC. Sulfate is a so-called anion and is not bound to the adsorption complex. So it remains in the solution. Only in very high concentrations (above 14 mmol / l in the soil moisture) does it precipitate with calcium as gypsum.

A lack of sulfate rarely, if ever, occurs in practice. The images resemble that of nitrogen deficiency. The only difference lies in the fact that sulfate deficiency can be found in the youngest parts of the plant. This is because sulfate does not move that easily through the plant. Sulfate excess is also a rare phenomenon. Plants that get too much sulfate are dark in color and do not grow well. This is comparable to the effect of a too high EC.

Sulfate is present in most potting soil basic fertilizers. RHP-certified products are checked for use in a substrate for, among other things, the sulfate content. For substrates with the RHP Horticulture quality mark, the substrate producer and grower together determine what the sulfate content should be, appropriate to the crop.