Feed directly, or pre-water first?

[Ray]

I know this has been discussed, and I stand by my recommendation to NOT pre-water, but I was challenged on that by someone who had “275+ppm” mineral-laden tap water, so I thought I’d share my logic:

When using non-purified water supplies, I think the concept still applies - maybe even more so. In my mind, there are two processes to deal with: saturation and ion capture, and both have limits.

Scenario 1 - one watering with pure water and fertilizer: the roots become saturated with the solution and as many nutrient ions as possible are captured by the available sites.

Scenario 2 - initial, plain, pure water irrigation, followed up with fertilizer solution: the roots become saturated, reducing the absorption of the fertilizer solution, so fewer ions are captured.

Scenario 3 - one watering with “275+ ppm” water and fertilizer: the roots become saturated with the solution and as many dissolved mineral- and nutrient ions as possible are captured. Yes, it will be less nutrition, as the dissolved mineral in the water will occupy some of the “capture sites”.

Scenario 4 - initial, “275+ ppm” water irrigation, followed up with fertilizer solution made with the same water: the roots become saturated and capture as many of the dissolved mineral ions as possible with the first watering, reducing both the absorption of the fertilizer solution at the second, which already allows fewer ions to be captured, but the sites available to capture more are already occupied, so even fewer nutrient ions can be captured.