Soil water retention

If I choose to use soil, should I be looking for one with high or low water retention?

Low =water often with easy oxygen access for roots.

Plenty of DIY soil recipes for cannabis use and they will out perform any shop bought.

Bio green top mix is pretty good straight out the bag

newGrows said:

If I choose to use soil, should I be looking for one with high or low water retention?

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You want to water every 2-3 days. I use Pro-Mix HP (high porosity, which means it has perlite already added to the what is otherwise pure peat moss). I add 20% perlite to that. If you're under HPS lights you may want more retention due to the heat of the lights. I've read HPS users recommend Pro-Mix BX which has vermiculate, which retains moisture.

I would err on the side of drying too quickly.

I've got some really high quality organic soil (at least thats what the price would lead me to believe...). It contains some kind of seed hulls and woodchips in addition to dirt (is what i can tell is in it by eye)
I'm afraid the water retention is too high for seedlings though for the reasons oilmaker suggested. The only other stuff i've got is called Holly Tone, but it's slightly acidic and I dont have a reliable way to measure ph to get the balance right.

Would adding sawdust be a good idea, i've heard mixed opinions about perlite on this site but i would consider trying it if thats the best answer?

I'm in cfl so heat isnt an issue a z2000.

Can i just crush up any rock and mix it with soil? Does it have to be store bought perlite?

A good soil can provide good drainage and retain water. Add perlite for drainage and coir for water retention.

i'd use a good amount of perlite too...

newGrows said:

Would adding sawdust be a good idea, i've heard mixed opinions about perlite on this site but i would consider trying it if thats the best answer?
Can i just crush up any rock and mix it with soil? Does it have to be store bought perlite?

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I wouldn't add organic material like sawdust will consume nitrogen from the soil as they decompose. You'd need some time to "cook" it into compost.

It seems like most people use perlite. It's more than just introducing solids like crushed rock. It's pourous and allows water to pass through. (I suspect organic growers would emphasize a properly composted, living soil for drainage. Maybe that's the mixed opinions you've read. Perlite with soilless media such as Pro-Mix or coco is like doing hydro without all the hydro equipment. It's "drain to waste." You can do a degree of organic in it that you can't do in hydro. But, if your goal is organic, then you'd probably do soil not soilless. Then the organic growers have a point that perlite is inorganic and doesn't contribute to the soil the way organic amendments would. So, I guess it depends on how you want to feed your plants. Synthetic? I wouldn't worry about using perlite.).

here's some good perlite info.

https://www.icmag.com/ic/showthread.php?t=42002

newGrows said:

If I choose to use soil, should I be looking for one with high or low water retention?

Click to expand...

might be an idea i put coco in my soil to hold the water in only reason i do this is so i can leave them for up to a week somtimes 2 without any water i use it indoors aswell same reason as the amount of lights i run tends to dry shit out in about 2 days with the coco i can get away with about 5 days without water

Thanks for all the information.

I'm running into some problems that seem to be caused by overwatering (bending stems, yellow drooping leaves). I just got a water meter and even days after just lightly misting my pots the meter is at about a 5/10. Probably because i'm just using cfl's so there isnt really any heat to dry it up.

Going to try adding about 20% perlite (don't have the luxury of being an organic purist).

If that doesn't work i'm not sure what to do next, maybe calcium/magnesium?