Slurry test question(don't roast me)

[Ezdeezy89]

So I've seen guides and videos posted, but I always wondered something.

Why dont slurry guides or videos ever mention the starting pH of the water they're mixing in with the coco/soil? If I'm doing a 1:1 mix of 7.0 pH water with the coco/soil, surely the results would be different than if I were to use 5.0 pH water instead. Unless I'm tripping, how is it possible to get an accurate result without knowing the pH of the water you're using? Does it not matter?

 

[Oldchucky]

I think you always use distilled to do a slurry test. At least I always have.

 

[Ezdeezy89]

So I see. So just 7.0 straight up. Got it

 

[hoobastank_enthusiast]

Distilled water doesn't automatically come out at a pH of 7.0... the purpose of using distilled water is that it removes almost all the impurities that contribute to EC, which is what the slurry test is actually about: you're trying to measure the EC of what's in the media to figure out if it needs to be buffered or not. The pH of your media is going to fluctuate quite a bit throughout the growing process and unless you're starting with some radically dirty coco, any initial pH testing of the media itself is arguably unimportant.

 

[Oldchucky]

Slurry’s come in handy if you cook your own soil during the off-season. At least give you a rough idea in the spring how much npk your soil has in it. When, like me, you are too cheap to send it out and have a proper analysis done of it!

 

[hoobastank_enthusiast]

I'd argue further than handy and say you should absolutely be doing a slurry test on your coco media, whether it's the highest-quality prebagged or the cheapest bricks off Amazon. You always want to rule out a bad starting EC from your list of coco problems. FoxFarms, Canna, doesn't matter what I've used, I always slurry them just to make sure that the factory did its job correctly.

 

[Oldchucky]

Yeah, it’s nice to have some kind of a baseline to work from.

 

[Ezdeezy89]

Thanks for the replies. I was bulk ordering floraflex nutes cause they were like $8 a bag, but kept having problems. Turns out the ppm was anywhere from 1100-1500 ppm out of the bag. Went to my main hydro store and asked if they could pull out samples from 4-5 diff coco brands. Best one I got wasa brand called char coir with roughly 400ppm and 6.0 out the bag. Been using them the last couple months with no issues in veg.

 

[hoobastank_enthusiast]

That makes sense. In my experience with a 1:1 slurry, I've seen that a high-quality prebagged product will land somewhere in the general area of 600 μS/cm on average and anything over 1000 μS/cm should be throwing off alarm bells. So depending on which ppm scale you use, those bad bags could have been 50-150% over that value.

 

[Ezdeezy89]

That makes sense. In my experience with a 1:1 slurry, I've seen that a high-quality prebagged product will land somewhere in the general area of 600 μS/cm on average and anything over 1000 μS/cm should be throwing off alarm bells. So depending on which ppm scale you use, those bad bags could have been 50-150% over that value.

Yeah dude my plants were getting waxed. Tested my pH with a medium pen and after mixing in 5.6 Ph'd water to fill pots, my pH was reading around 8.0 before transplant. In fact most of the brands I tested were all near 1000ppm on 700 scale.