Nitrogen gets built into the plant. Potassium never does — it stays a free ion that runs the grass: water pressure, drought and disease toughness, the pores on every leaf. Follow it out of the clay's hidden pools, and when you reach the root, tap the glowing spot to zoom in and watch it slip through its own doorway.
ZOOM: ~1 mm · a pinch of soil
No sound? On iPhone, flip the silent switch off (side of the phone) and turn the volume up — Safari mutes audio when it's on.
K⁺
Potassium. A positive ion (cation). The plant's regulator — runs water pressure, the leaf pores, and stress toughness.
CEC
Cation Exchange Capacity. How many + nutrients your clay can hold — the size of the pantry. Sandy soil = small pantry.
H⁺
Proton. A hydrogen ion. The root pumps these out to build the "current" that pulls K⁺ in.
ATP
Energy. The cell's battery. The pump spends ATP to build the charge across the membrane.
Do something — watch the soil react
Potassium isn't made or lost by biology like nitrogen — it just moves between pools in the clay. Pull a lever and watch it move.