Over Fertilization?

Hank · Mar 29, 2014

Edges of leaves curling. This is a relatively new problem. Started a 2 to 3 weeks ago thinking it was heat stress I raised my light as high as I could and removed the 1.5in of SM from under the pots and dropped the light to 1000w. Temps are around 25 to 29c and humidity is quite low in 30s.
Not all the plants are affected to this extend some with just a few leafs some with none. So I don't think its heat related. I'm thinking its over fertilization. I have been dropping the EC, the last watering's have been 1.4 1.6 1.8 and 2.0 but sometimes I'm not getting enough runoff. The last watering at 1.4 EC had 30% runoff.
Still I think I might have a salt buildup. Dropping to 1.2 EC next watering.

Natural · Mar 29, 2014

I've seen 3 things cause taco leaves...low humidity, over-feeding, and heat from the lights. If it was PH she would twist too. All she is doing is trying to slow down her transpiration..for whatever reason. Sounds like you're gearing for lower feeds..should get her back on track.

Hank · Mar 29, 2014

I hope so. Considering dropping down to 1 EC next watering.

Natural · Mar 29, 2014

Hank said:
I hope so. Considering dropping down to 1 EC next watering.

ya that is pretty low..but you're right you are probably a little built up with salt..since you can take her out no problem you could even do a proper run off flush with even lower nutes..I started noticing the tips a little better and you might be on the edge of burn.

Hank · Mar 30, 2014

Thanks Natural, maybe I should flush them all. How does flushing at 0.6 EC with say 50% runoff sound would that be enough?Canna suggests never using straight water and flush with no less than 0.6 EC.

Natural · Mar 30, 2014

Hank said:
Thanks Natural, maybe I should flush them all. How does flushing at 0.6 EC with say 50% runoff sound would that be enough?Canna suggests never using straight water and flush with no less than 0.6 EC.

Ya definitely..never hurts to flush, especially in coco. Canna seems like a good line. She might have been crispy critters with something saltier. By the looks of things she's gonna put out some chunks.

Chrondondalae · Mar 30, 2014

That does not look like over fertilization to me. Looks like heat and low humidity/VPD. Always check your run off if you think the ppm's are too high. Raise your humidity to 50-60%, if you can, and you'll see a big difference.

Natural · Mar 30, 2014

Chrondondalae said:
That does not look like over fertilization to me. Looks like heat and low humidity/VPD. Always check your run off if you think the ppm's are too high. Raise your humidity to 50-60%, if you can, and you'll see a big difference.

That's good thinking Chrondon..he should check some run-off..fo sho. But I think it's a combo of all 3 issues to an extent..because I've seen plants taco in perfect temps and humidity...makes sense that heavy feeds can have that effect as well. It's definitely a defense mechanism..related to transpiration...and that pheno could be more sensitive to humidity..food..and heat at the same time.

Hank · Mar 30, 2014

Chrondondalae said:
That does not look like over fertilization to me. Looks like heat and low humidity/VPD. Always check your run off if you think the ppm's are too high. Raise your humidity to 50-60%, if you can, and you'll see a big difference.

That's problem, I really don't have any control over the humidity in my tent, its basically whatever the humidity is in the house. The humidity does rise to 65% when the light is off for 12hrs. No difference in the leaves though.
As for checking the runoff all I've done is taken a sample from each plant and checked it with the pH and truncheon meter, seems ok always lower than whats going in. Not sure if these readings are accurate Canna says you cant do it this way, they say to take a sample of the coco in the root zone and mix with distilled water let it sit for bit then filter it then measure for pH and EC.
Chrondondalae you could be right about the heat thinking about going to 825W on the light and adding a oscillating fan.

Chrondondalae · Mar 30, 2014

If the ppm's are lower coming out I highly doubt you are over fertilizing them. I know Canna's runoff procedure but you're still getting some info from the run off.

A night time humidity of 65% is not going to help when the lights are on, hence no change in the leaves. Check out a Vapor Pressure Deficit chart. Basically, at those temps with that low humidity the air is sucking the moisture from your plants.

Natural · Mar 30, 2014

Chrondondalae said:
If the ppm's are lower coming out I highly doubt you are over fertilizing them. I know Canna's runoff procedure but you're still getting some info from the run off.

A night time humidity of 65% is not going to help when the lights are on, hence no change in the leaves. Check out a Vapor Pressure Deficit chart. Basically, at those temps with that low humidity the air is sucking the moisture from your plants.

maybe a swamp cooler would work..or a cheap humidifier

Hank · Mar 30, 2014

Chrondondalae said:
If the ppm's are lower coming out I highly doubt you are over fertilizing them. I know Canna's runoff procedure but you're still getting some info from the run off.

A night time humidity of 65% is not going to help when the lights are on, hence no change in the leaves. Check out a Vapor Pressure Deficit chart. Basically, at those temps with that low humidity the air is sucking the moisture from your plants.

I'm off the VPD chart, not good. Great info Chrondondalae, I think your bang on about this. Check out this link I found on the inter web.

"When humidity gets too low plants will really struggle to grow. In response to high VPD plants will try to stop the excessive water loss from their leaves by trying to avoid light hitting the surface of the leaf. They do this by rolling the leaf inwards from the margins to form tube like structures in an attempt to expose less of the leaf surface to the light"

Hank · Mar 30, 2014

Natural said:
maybe a swamp cooler would work..or a cheap humidifier

Natural I've tried a ultrasonic humidifier inside the tent with no success plus I really don't have the room. For now I'll try and raise the humidity with the whole house humidifier that's on the fan the furnace it has a flow through humidifier. We heat our house most of the time with a wood insert so it can get dry in the house if the furnace doesn't come on.

Seamaiden · Mar 30, 2014

Hank, there are a few ways you can raise RH. If nothing else, you can soak a towel or three and hang them along the sides of the tent. Putting a tray of pebbles under the plants and fill it with enough water that it hits *just* below the top of the gravel is an old school method.

Chrondondalae said:
That does not look like over fertilization to me. Looks like heat and low humidity/VPD. Always check your run off if you think the ppm's are too high. Raise your humidity to 50-60%, if you can, and you'll see a big difference.

Same here.

Hank · Mar 30, 2014

Tried some old school with the towels today plus with the furnace humidifier running the RH came up to 35% thanks for the tips Seamaiden.
Doesn't help that the 3 humidity meters I own all read different. Junk!!
I was looking into swamp coolers when I can across this home made industrial ultrasonic humidifier. I think I could rig this up to pump right into the tent. Check it out.

Hank · Apr 2, 2014

No real change, basically its only the one plant that's in bad shape. Watered yesterday with an EC of 1.2 going in and 1.0 to 1.2 EC coming out and pH 6.2 to 6.5 but I don't think its an accurate way measure. I do a 3 point calibration on my meter whenever its out the slightest.
At the moment my temp is 27c and RH is 32%

These are my RH meters all different readings lol

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