Res/Nutes Change Frequency

P

petedavid

Member
Hi guys,

I run a flood and drain systems, with 100gal res's that I change every 2 weeks. Recently, in a veg tent, I have seen slow/miscolored growth towards the end of a 2 week cycle (with E.C and PH are fine). I feel like I need to drop the res change frequency to every 10 days and see if this phenonemon shows again, however, I don't want the extra work of more res changes.

How often do you guys change your nutrients? Should I investigate changing every 10 days, or even less?
 
rkymtnman

rkymtnman

Well-Known Member
Keesje said:
Is this because the nutes can go bad?
If so, do you think all brands have this 'problem'?
Click to expand...
don't know for sure if they go "bad" but most nute mfgs recommend a week to 10 days. i think alot depends on how much ph down or up you need to add during that time too.
 
Keesje

Keesje

Well-Known Member
Manufacturers also advice to add x ml to a liter, but we all know it is often only half of that :)
So perhaps they advice to change after 1o days is because they want to sell more nutes..

With the ph - and + you might have a valid point.

I think that with DTW you could more easily test if your plants would get problems after 2 weeks.
Because the EC will stay the same, and you know what are the origins of this EC.

With E&F this is different.
The EC might be the same but you have no clue what makes up this number.
Because when the nutes go to the roots, the roots do not take up every single element in the same percentage.
So what returns to your rez?
There might be a dis balance of elements, but still a nice EC number.

If it has to do with a dis balance, there are a few solutions:
- More changes of res > more work.
- Bigger res, so it will take longer before the dis balance is gonna hurt your plants.

If the nutes last only 10 days anyway, then you have to cope with more work.
 
rkymtnman

rkymtnman

Well-Known Member
Keesje said:
With E&F this is different
Click to expand...
i agree. with anything other than DTW, i would personally change every 7 days.

my system is setup so i can go away for 14 days without touching it. it required me to find a slightly different nute recipe that is pH stable for 14 days. when i'm home, i use additives that affect my pH and require me to adjust.
 
P

petedavid

Member
Keesje said:
What is the size of the plant surface?
Click to expand...
Scrogged at 1m2.
rkymtnman said:
10 days max. that's for a DTW res.
Click to expand...
If that is true, then flood and drain would be, for sure, less? With "tainted" water returning to res, the flood and drain res must get worse faster than water that does not circulate.

rkymtnman said:
don't know for sure if they go "bad" but most nute mfgs recommend a week to 10 days. i think alot depends on how much ph down or up you need to add during that time too.
Click to expand...
I haven't had to touch PH/UP down once it is set.

Keesje said:
With E&F this is different.
The EC might be the same but you have no clue what makes up this number.
Because when the nutes go to the roots, the roots do not take up every single element in the same percentage.
So what returns to your rez?
There might be a dis balance of elements, but still a nice EC number.
Click to expand...
I think this disbalance is what I am seeing. The EC drops slightly throughout the 2 weeks but growth gets "weird" towards the end of that period. I think a 10 day switch is a good compromise. I will have to start playing around with some different feeding schedules too.

Thanks both for the response.
 
N

newbplantgrower420

Well-Known Member
I change once in the middle weeks and once at the end before restarting. Been doing that for the past yr now.

Im not sure if my yield would increase if I went back to weekly or every other week water changes. But my job is a helluva lot easier now.
 
S

StrawberryOzark

Active Member
I change mine twice a week and run water one day a week. Now debating if im doing more then I need to but makes me feel better to keep fresh h202 and nutes every few days
 
Keesje

Keesje

Well-Known Member
GBAUTO said:
I typically run my RDWC on a 2-week cycle.
I used to do 10 days and found I got the same results on a 14-day cycle.
Click to expand...
What brand of nutes do you use?
No funny smell?
No signs on the leaves of anything missing?
 
klx

klx

Well-Known Member
Keesje said:
Manufacturers also advice to add x ml to a liter, but we all know it is often only half of that :)
So perhaps they advice to change after 1o days is because they want to sell more nutes..

With the ph - and + you might have a valid point.

I think that with DTW you could more easily test if your plants would get problems after 2 weeks.
Because the EC will stay the same, and you know what are the origins of this EC.

With E&F this is different.
The EC might be the same but you have no clue what makes up this number.
Because when the nutes go to the roots, the roots do not take up every single element in the same percentage.
So what returns to your rez?
There might be a dis balance of elements, but still a nice EC number.

If it has to do with a dis balance, there are a few solutions:
- More changes of res > more work.
- Bigger res, so it will take longer before the dis balance is gonna hurt your plants.

If the nutes last only 10 days anyway, then you have to cope with more work.
Click to expand...
This comment pretty much covers it.

In a perfect world weekly changes would be best for F&D imo
 
TintEastwood

TintEastwood

Well-Known Member
Keesje said:
Because when the nutes go to the roots, the roots do not take up every single element in the same percentage.
So what returns to your rez?
There might be a dis balance of elements, but still a nice EC number.
Click to expand...
This!

That's the way I understand it...
As time passes, because of plants consumption, the ratio and balance of elements in solution is going to change.
 
Keesje

Keesje

Well-Known Member
TintEastwood said:
This!

That's the way I understand it...
As time passes, because of plants consumption, the ratio and balance of elements in solution is going to change.
Click to expand...
There is also something that is called the build-up of plant exudates, which can be toxic.
I do not really understand this.
Are they the same elements that were already in the nutes, but now disproportional?
Or are it new elements, created by chemical reactions inside the roots or plants?
I suck at chemistry!
 
Bluehillsmoker

Bluehillsmoker

Well-Known Member
GBAUTO said:
I typically run my RDWC on a 2-week cycle.
I used to do 10 days and found I got the same results on a 14-day cycle.
Click to expand...
Totally agree, I used the stinkbud aeroponic system and two weeks is perfect, I would have to add fresh water because they were drinking so much. Be careful though, fresh water raises the PH!
 
DarthVaper84

DarthVaper84

Active Member
Keesje said:
There is also something that is called the build-up of plant exudates, which can be toxic.
I do not really understand this.
Are they the same elements that were already in the nutes, but now disproportional?
Or are it new elements, created by chemical reactions inside the roots or plants?
I suck at chemistry!
Click to expand...
I don’t know anything myself about “exudates”, but I can answer one of your questions.

New elements will never appear overtime that aren’t included in the original liquid nutrients (or dissolvable). It is possible that different compounds/molecules could form I suppose, but e.g. having a bunch of nitrogen won’t spontaneously create phosphorus.
 
You must log in or register to reply here.
Top