i grow outdoors
i have a question about how soil buffers work, so i've been growing for a few years using terra canna professional which has a ph of around 5.8
i was told that soils have buffers that make it so the ph always stays the same, if that's so, what's the point of adjusting ph before watering? if the soil adjusts itself?
how long do these buffers last? do they get used up with time?
does flushing a plant use up the buffer? i wanna do a flush before up-potting my girls to get rid of excess salts, when i flush i usually run tap water trough the soil for half an hour or so, until the water comes out clear and not yellow
would this consume the ph buffer? i wanna flush before uppotting from a 3gal container to a 10 gal one, and then do another flush a week or so before they switch to flowering.
There is a lot of confusion out here about soil and how it is supposed to work. Every time I do this it starts an argument, but let me explain how soil was described to me, and why it is designed the way it is at the manufacturer.
First buffers. Buffers are not there to keep the soil at a certain pH. Within limits, we really don't care what the soil's pH is, but designers of soil have built in a tool that lets you work with common synthetic nutrients with ease. There are buffers in the soil that can be at both the upper and lower ends of the usable pH scale. Lower end buffers are mostly used in hydro situations where the working pH is 5.1-5.9 and are designed to pull the pH up from the lower end to around 5.9 pH. The goal is to adjust your fluid to 5.5 and then let the buffers and the nutes being used up, slowly drift the pH of the medium up to the high end, sweeping through the entire pH range as it happens. There is an advantage gained by sweeping through the entire range since some elements are more able to get up into the plant at different pH levels.
Soil is usually buffered to the high end of the usable pH range in soil, 6.2-6.8 pH. The intent of this is to allow the gardener to adjust the incoming fluids to 6.3, and then the buffers will slowly drift the pH up to the high end, again drifting through the entire working pH range. Your buffers allow the nutrients to break free of their bonds that keep them stable in the bottle, and then be available to the plant for the maximum amount of time.
Soil has been used like this for at least 100 years. Farmers will add dolomite lime to "sweeten" the soil (or raise its base pH) and it has been commonly known all these years that in a closed container grow, it was best to come in at the low end and let the soil do its thing to drift your nutrients through the entire range. Soil used in this way is a tool, one that has been intentionally built into soil since commercial soils began to be manufactured.
Don't let anyone tell you that soil pH needs to be adjusted down from where the factory put it, or that you even need to run pH tests on your soil. Almost every soil out there is pH buffered to 6.8 for a reason. This nonsense that you never have to adjust the pH of your fluids if you get your soil right is simply a fad, carried on by a few online personalities in the last 5 years or so. While this newfangled method might work, the age old advice is to always pH adjust your incoming fluids to 6.3, the point where the most nutes are the most available to the plant, and then let the soil do the job it was designed to do.
This advice however is only for someone using common EDTA chelated synthetic nutes, that are designed to free themselves of their chelation only within that working 6.2-6.8 pH range. If you are growing organically, or with amino acid chelated nutes, pH doesn't matter much and wherever your soil happens to be should be fine.
Yes, flushing will dissolve some of the dolomite lime, and your buffering will reduce a tiny bit. This is no crisis, at least in a normal flush. What you are doing is excessive. To clear soil of salts we know that it takes about 3x the volume of the container to do so. Running the hose for a half hour is overkill and I would advise against it.
