Can you please clarify what you mean by adding ferts to the sediment? Does this mean adding root tabs? Or are you referring to using an enriched substrate such as Aqua Soil? Or would either of these work?
What Hoppy stated.
However, you may still do EI, or a modification thereof.
EI is just a modification of PMDD. It lost the testing requirements/suggestions, used the very same serial dilutions(see practical PMDD near the bottom for Fe, same can be applied to any nutrient) to do so. It also added PO4, and raised the ppm's much higher as at the time, PMDD was done at about 1.5-2w/gal of low output old school T12 lighting, folks with T5, PC, MH's etc, even at those same wattages/gal will need more nutrients.
However, as is the case with any method that's widely used, it must be flexible. There's no requirement to use less ppm's if you have ADA AS, or MS..........however, you generally can or may do so without issue.
The beef I have is when folks claim otherwise.
Many say or suggest outright that adding non limiting nutrients to the water column is "bad". I cannot find any verification to the contrary in my aquariums and the same can be said for thousands of other aquarists.
What specifically is bad?
If I have 10ppm or 40ppm of NO3, how is it bad?
What might I see?
Some claimed algae, some claimed fish issues, yet neither has ever been shown. they guess that's the reason, then my fish and shrimp breed and are fine and no algae, wimpy plants grow well etc. Falsifies the claims pretty fast. Some claimed that they need to do more water changes if they dose this way.
EI does not say you cannot use test kits.
Only that using a little math, it will give a range of ppm's for a given dosing rate and given % water change. If you want to tweak it to reduce water changes, that's fine. No method gets away entirely without any water changes for everyone, except perhaps non CO2 methods.
Some skilled folks and those that can watch their tanks well can avoid water changes for long time frames as well as reduce or not use test kits at all.
But this takes time, experience and I do not suggested it for most folks unless you have gotten pretty good and know the tank well. Few folks asking about fert routines are anywhere near that level of horticulture.
I can do that, but it's not what I'd suggest.
While you can avoid water changes with test kits, you also have to look at the trade off in dealing with multiple test and calibrating them since now your entire dosing routine relies solely on the results of your water testing.
So you have to buy and purchase these test kits, added expense.
Next you have to learn how to make a calibration curve with 2 or more known reference standards. Many just guess and by pass this step, so they really do not know either way and are guessing.
If you cannot commit well to weekly water changes, then it's very unlikely you may commit to weekly testing either IME and IMO and the stat's have long shown this about aquarist (who are honest).
Water changes are just simple easy step to re set things, and every method uses them, including PPS. I see folks messing and struggling with all that to avoid the work, yet spend far more time in the long run. Spend a dime to save a penny.
The actual "target level" is not "better" if it's lower either. In many cases the opposite is true. It's harder to maintain a lower level since it's used up and then there's little/none left. If you add enough to buffer a few days' worth, then it's a more robust target.
You can still add it daily if you want, or perhaps 2-3 x a week, or even weekly etc in lower light tanks. But.............adding sediment ferts adds more robustness either way, as does adding water column ferts extends the life of the sediment source as well and reduces the energy to transport ferts up through the sediment to the growing tips.
Sediment + water column source are complementary, not antagonistic, either/or etc.
Same deal with water changes, many aquarist wanna avoid that chore/work, but trading it in for more work and more technical aspects of chemistry does not seem like a good trade off, no matter how you slice it.
So if you focused on sediment ferts, less light intensity(Stop HLD!), then automated, or hard plumbed a fill/drain with a valve, or simply got a garden hose that adapts to the shower head, a U shaped PVC "hook" for the water changes, they are hardly any chore, even my 7 year old nephew can change his 20 Gal tank in 10 minutes and never lifts a bucket.
Drains the water outside for the landscape or in the drain in the home etc, then switches the hose end to the shower and refills in a 5 minutes.
How hard is hooking up the ends of a hose vs learning all this mish mash about reference standards, calibrations, micromanagement of chemistry?
Try teaching that
to my nephew.
See how far you get.
"Where's my DSL Nintendo?"
Too late, you lost him.
So sediments offer a good alternative to avoiding the water change without the added labor and hassles of testing and then doses lightly to the water column(fish also add a good source). ADA does this but also still suggest frequent water changes, they also use less light intensity that you might think based of testing of light with PAR meters.
More light= more demand for CO2 and nutrients, less light, less demand.
If usuing less is honestly your goal, including water changes, and labor in general, then start with light, then consider CO2/Excel options, non CO2 methods, plant choice considerations, automation of water changes etc, then lastly mess with dosing.
It's the last thing on the list if you approach it logically, not the first.