Backyard Aquaponics
A place to discuss aquaponics

Hi Could the turning in of tomatoes leaves be due excess heat, sun?

I have a gravel growbed with in a IBC cut 30/70 with tilapia at the bottom.

i have covered with 20% shade netting but the leaves keep on turning.

Lettuce leave at the bottom dies off as well, I assume the gravel in the growbed is too hot?

i have aflood and drain system with a bell siphon,

Any Suggestions?

Welcome to the forum MA .

Pictures would definitely help in this case. Several things can cause this issue in tomatoes. Wind, nutrition, and viruses all come to mind. Sounds like it must be hot there and that's another thing that sometimes can cause this.

Cheers

a hot dry heat could do this, particularly a hot spell among cooler temperatures and the plants are not acclimatized to it.
yes the media getting hot can be an issue.
your temps would need to be 30deg+ I have seen that occur to my tomatoes here in Perth in late spring/early summer which can get dry hot days before shade cloth goes on. Dry hot wind is a big factor and you wont be getting much protection from 20% shade.
However still quite early on in the hot season I would have thought.... usually closer to summer.


but as Scotty notes, could be a few things, so best to post some pictures.

We are situated North of Pretoria South Africa

it is the beginning of our summer and no rains as yet this season, so it is blazing hot..max tems are between 29 and 38deg c in the day.

The system is quite new, 3-4 weeks, and I think only starting to cycle now. In the last week the plants were doing better, i can see new growth and stems thickening, However the leaves still remains partially rolled up.

I have started to take the sump water and spraying the plants down to "wet" them and the gravel growbed, and have added more shade netting....I hope this helps.

Your lettuce will probably bolt at those temps. I think I'm already seeing a slight elongation in that first pic of the lettuce. Since it gets bitter when it bolts you may want to harvest it (you could also let it go to seed if you want some for next time). Glad you put some shade cloth up. Don't be surprised if you don't get much fruit set on the tomatoes at these high temps. They'll get back at it when the temp goes down . Here's an explanation of what's going on with the tomatoes - the technical term is Physiological Leaf Roll -

http://mtvernon.wsu.edu/path_team/PhysiologicalLeafRollOfTomato-PNW_VEG_FactSheet.pdf

Thank you very much!

my next question would be how you are running the system.
Temps already in high 30's means you must be looking at a fairly brutal summer ??
(bit like our Australian interior) or does it cool a bit and go humid when/after rains come ?.
Wikepedia suggests November is the hottest month for Pretoria- for us it is February.

You will find that you need to keep the media wet and try and prevent it heating up too much.
Maybe even go constant flood over the hot months.

one option may be to keep the stones below water level and look at something a bit more inert on top that holds a bit of moisture and doesn't heat up as much. Or maybe just go to DWC's for most things, buckets for tomatoes (with the lids on like hydroponics have) and use some form of filtering for the system.

I suspect you will need 50-70% shade cloth and wind protection if 35+ is going to be the norm for the next few months.
Tomatoes and most veg don't like hot dry wind. May even be worth looking at some form of sunlight in early AM and late PM and perhaps some shading during the hottest parts of the day.

It does get better when it rains but we generally have hot dry heat in summer.

Would it be better to have the Aquaponics inside a tunnel or hothouse? Perhaps the humidity will be helpful?

But I suppose one will still need to cover with shade cloth in selected areas?

not really sure, you may have to ask around your area for what commercial growers etc do.
I know with my limited exposure to greenhouses that they are a challenge in very hot weather.
need a lot of venting to avoid becoming stiffling - of course a bonus in the cooler months.

in places like Geraldton in mid-west WA and inland WA simple shade houses work pretty well.
basically a frame with 50-70% shadecloth on top and sides seems to be ok.

If hot wind is an issue then a solid side / fence etc can be used.
Though most simply put on the protected side of a building.

Thank You Darren

At least with hot and dry climates you can do something about it. It may not be enough for lettuce but look into swamp coolers/evaporative coolers. You can also make your own -

https://www.youtube.com/watch?v=A67u3NyC9w8

>> swamp coolers/evaporative coolers.

commercial greenhouses and seedling operations in Aust hot conditions do this + water misting.
but quite a large overhead - coolers are still quite a few watts
(but cheaper than heating a basement/greenhouse in minus temps).

mostly the shade houses and blocking the dry winds is 95% of solution.
very common for gardens and vegies out in the interior on farms etc.

AP helps as well since plants dont tend to get water stressed.
DWC work better than media for some leafy types IMO.
in really hot conditions just go with constant flood to keep media cool.