ppm? Newb Q.

[primitive]

Hi people,
I'm just into my 2nd grow now, and I admit I don't really understand why, or rather how ppm matters. I use sensigrow A+B and their online nutrient calculator to determine how much to feed of what. It gives a target ppm, but that includes all of the products they suggest to compliment sensigrow. I use a few, but was told most are basically unnessecary by the local hydro store guy. His explanation of ppm, and most I've read, are a bit beyond me still. Perhaps due to overindulgence in the bounty of my first grow. Can anyone give a dumbed down explanation so I can better understand, like is it just the incrimental difference in ppm over the life of the plant that matters or does the actual number play a large factor as well? Since it doesn't determine what is actually in the liquid, what info should I be gleaning from these readings, just that the ppm is stable?

Also, my local water runs about 220ppm, 7.4 ph on average. Would getting an RO unit make a serious difference? And for that matter does it do anything to ph?

 

[Growdude]

Since it doesn't determine what is actually in the liquid, what info should I be gleaning from these readings,

PPM or parts per million is just a measurement method of TDS or total dissolved solids. Or basically the concentration of nutes in the water.

I use a ppm meter in hydro when I mix my nutes in the rez, once i add water I measure the ppm and top off the nutes to obtain whatever PPM,s im shooting for (stage of growth).

As the water evaperates the ppms rise and i top off with more water to lower ppm to the desired target.

220 ppm is hard water but not terible bad, the RO unit will give you a purer starting point and a better grasp on what is in your nute solution (only what you have added).

 

[primitive]

I'll try that with topping it off, though I've found my ppm tends to drift up only slightly, maybe because I'm changing it more often than I need to? I've been flooding ebb/flow tray 30 minutes twice a week in coco(sun,thurs), then flush(sat), then change the rez and start again.

I had assumed the ppm was staying relatively stable because the coco material was adding dissolved solids as the roots were eating the nutes. My assumption is based on absolutely nothing though. Am I throwing out my solution to early?

 

[primitive]

Bump.

Am I wasting solution?

 

[Growdude]

Bump.

Am I wasting solution?

I dont do ebb-flow but Stony says you never have to change your rez in ebb -flow.
I go about 10 day average in my drip system.

 

[greenfriend]

I had assumed the ppm was staying relatively stable because the coco material was adding dissolved solids as the roots were eating the nutes. My assumption is based on absolutely nothing though. Am I throwing out my solution to early?

if your using plain coco coir the medium should have no effect on ppm or pH

i start clones with 0 ppm distilled water, then 200ppm and gradually increase to 700-800ppm in the middle of flowering. i never change my res but thats cus the plants drain my entire 115 gal res in one watering, then i refill/pH/ppm and let the solution circulate and oxygenate for a day to get rid of any chlorine/other chemicals in the tap water

you should also pH down the 7.4 to bout 5.8 if you havent already

 

[primitive]

Thanks, yeah I've been keeping the pH to 5.8-6.0, it seems to drift down a bit after each of the two weekly feedings so I let it start at 6.2.

I'm not quite sure what you guys mean though by never changing your res, my 30 gallon res only drops by about 3-5 gallons each flooding/feeding(what soaks into the coco), so after two feedings from one full res, it lowers by about 1/3 volume. After the two feedings each week I've been tossing the 2/3 res solution left. Then fill with plain water, flush, and mix new solution. Is that 2/3 left still actually any good?

 

[greenfriend]

Thanks, yeah I've been keeping the pH to 5.8-6.0, it seems to drift down a bit after each of the two weekly feedings so I let it start at 6.2.

I'm not quite sure what you guys mean though by never changing your res, my 30 gallon res only drops by about 3-5 gallons each flooding/feeding(what soaks into the coco), so after two feedings from one full res, it lowers by about 1/3 volume. After the two feedings each week I've been tossing the 2/3 res solution left. Then fill with plain water, flush, and mix new solution. Is that 2/3 left still actually any good?

if you only have two feedings a week you could probably keep the solution at least 2 weeks. i would just top off the res once a week with plain water when its at 2/3 full. the water evaporating from the res probly caused the solution to become more acidic over the week

when you do change the res i would flush the plants with plain pH'd water for a minute before you water them with the new full strength solution

 

[NewbieG]

Thanks, yeah I've been keeping the pH to 5.8-6.0, it seems to drift down a bit after each of the two weekly feedings so I let it start at 6.2.

I'm not quite sure what you guys mean though by never changing your res, my 30 gallon res only drops by about 3-5 gallons each flooding/feeding(what soaks into the coco), so after two feedings from one full res, it lowers by about 1/3 volume. After the two feedings each week I've been tossing the 2/3 res solution left. Then fill with plain water, flush, and mix new solution. Is that 2/3 left still actually any good?

Hey man. I'm currently running a smaller ebb and flo of 5 plants and I must say you do it very differently. I flood for 15 minutes every three hours day or night. I honestly thought the plants would be dead feeding them once every 3 days. But hey if its working thats great. Good to know.

As far as the res. I changed mine at when i started flowering, thats it, and it probably wasn't necessary. I'm sure they would have been fine just drinking off the veg. nutes and starting on flower nutes. I do think i will continue that as im sure its better for the pump and may help the plants. You really don't have to throw yours away every time my plants seem to be doing ok as a few have more than trippled in size just like they should in flower and the other shorter ones are indicas.

As far as your pH going down after feedings, I must say that from what i've heard its suppose to go up and your ppms should be going down if you have your mix locked in properly. That just sorta makes sense as the plants should be drinking nutrients thus lowering the ppms, and are releasing waste that increases the pH. Don't quote me on this being correct, but its what I have seen said online.

Last thing, I've heard coco after a month or two locks out some essential nutrient(s) that us ganja guys need, so you may want to google that or something. Just a heads up incase ya didn't know. Hope I said something useful in all this talk

 

[primitive]

@greenfriend: Yeah I'm going to try keeping the solution two weeks next crop I think, I'll be doing the same strains so comparison shouldn't be hard. I have been flushing once a week at res change, pH'ed water with a touch of florakleen , though I'm not sure how much the florakleen helps.

@NewbieG: w/ straight coco flooding even once a day gives you a swamp, as I learned in my first few weeks of my first grow, I had a swarm of fungus gnats, roots getting no oxygen, bad situation. A few flushes, gnatrol, and giving them two days to dry out a bit saved them from oblivion, but as I'm seeing from this soon to be finished second grow my yield was stunted quite a bit. As for lockout and pH changes from coco, I'm still to new to growing to make much of the conflicting opinions I've read on forums and growguides regarding this. Some have real headaches it seems and others think it's a myth that these problems even occur. My pH sags after each feeding but I have no idea if it's the medium or, more likely, the grower causing it. Kinda wish I had started with hydroton now.

@Any&Everyone: I think I nailed what is confusing me. An example of some collected wisdom found online, "The optimum flood is just long enough to allow the flood to reach the correct flood depth, plus a few minutes to allow the nutrients to wash thru the planters, carrying away accumulated salts from the planters."

Accumulated salts, I'm not 100% clear how this fits into reading TDS. If every flood carries some of these salts back to the res each time, shouldn't that skew the ppm, or are these accumulated salts not dissolved solids, not adding to the ppm reading? I assumed these "salts" were raising the ppm each feeding while the plants absorbing nutrients lowered it, rendering the readings kinda pointless.

Are accumulated salts just the slightly granular scummy crap that settles to the bottom of the res?