How do plants obtain sulfur from soil?

Plants obtain sulfur from the soil primarily through the action of soil organisms, which facilitate the sulfur cycle.

While sulfur is abundant in soil within organic matter such as proteins, it is not immediately available for plant uptake in these complex forms. Soil organisms break down these sulfur-containing proteins into constituent amino acids. Subsequently, a series of microbial transformations converts the sulfur into sulfates, which are the inorganic forms that plants can absorb through their roots.12

The process generally follows these steps:
* Degradation: Soil organisms decompose organic tissues, releasing sulfur from proteins into amino acids.12
* Conversion: Through microbial action, the sulfur is converted into hydrogen sulfide.1
* Oxidation: In the presence of oxygen, sulfur bacteria oxidize hydrogen sulfide into sulfur and eventually into sulfate, the form usable by plants.1

Once converted into these inorganic salts, sulfur is absorbed by the plant root system alongside other essential macroelements.34