That link seems to be for hydroponics
For soil, I find that ALWAYS keeping the runoff PPM (capture the run off from watering) under 900 is a good idea, I hit 1400 and my plants were burnt to a god awful crisp, after copious amounts of flushing, I got them under 600 and most to 300. I would say get a PPM meter (nothing too fancy), nute every other watering, and always test the runoff every watering. Just toss a gallon or so in the pot, lift it up, left it seep out for a while (until it starts to slow its flow), then capture the water seeping out in a container and test that for both pH and PPM. That is more of an indicator of how your soil is doing than simply measuring the PPM of the water you are putting in.
Plants absorb nutrients and water at different rates, so you can end up leaving a lot of excess nutes and salts in the soil even though the plant has absorbed/transpired all of the water you added, testing the run off is a better way of telling how the nutrient and salt levels look
Rep this man for awesome link!