We've talked a bit in the past about how nutrient deficiencies can devastate your garden. And that's absolutely true. But, we only talked about the heavy hitters then. Secondary nutrients – if your plants don't have enough of them – can wreck your garden just as easily.

Just what are these secondary nutrients? Calcium, magnesium, and sulfur.

These nutrients are necessary in amounts that are less than the primaries but more than the micronutrients. They're all taken up via mass flow, aka bulk flow or mass transfer.

Mass flow is defined in biology as the movement of fluids down a pressure or temperature gradient. In simpler terms, nutrients moving by this mechanism are taken up by the roots via a pressure gradient. This assumes that the soil pH allows for this. These three nutrients, along with most of the others, are readily taken up by the roots in a pH range of 6.0-7.5.