Just checked garden with soil tester. Both potash and phosphate read high. How much and type of harm can this can do to a vegetable garden? A good way to lower both ? ? ? How important is it to do ? Tnx.
Which garden tester? What water did you use? What else did you test to prove your test worked and reads true? K leaches almost as fast as N in some soils. What kind of soil do you have? Is it amended with anything particular? Here is some detail on phosphorus. What is your pH?
You may want to get a laboratory soil test done. I've read that the test kits are not very accurate when it comes to NPK (though they are supposed to be pretty good for pH). This will also gives you values for things like calcium, magnesium, sulfur, etc. Your local Extension office should be able to point you to a lab in your area that does soil testing.
There is a growing problem, nationwide, of phosphorus reaching toxic levels in garden soils. The reason being that the old advice was to use a balanced fertilizer (like 10-10-10). Phosphorus leaches less quickly than nitrogen and plants don't use as much as we may think they do. So phosphorus is building up. Often we are dumping in balanced fertilizers when we would be better off with fertilizers high in nitrogen (which is what usually leaches) and lower in phosphorus.
If you get a soil test done and then compare it to the values you got with your home kit I would be curious as to how they stack up.