Tomgrow
Full Member
Posts: 10
Joined: Tue Dec 12, 2017 12:03 am

Growing outside in the summer

We get some pretty brutal Australian summers over here. Temperatures can get into the 40°c+ 104°f range in my area. As a mostly new hydroponic grower I was wondering if I could get some feedback on my idea for an outdoor set-up?

The plan is to set up a 500 litre container made out of plywood and coated with water potable bitumen on the inside. It would have a second layer of roofing insulation on the outside, covered by another layer of white painted plywood. I also plan to use a swamp fan and white shade cloth to protect the plants from the heat.

I want to use this to work with something like a nutrient film solution, but with much more than a film. More like a 5cm/2inch high reservoir of circulating water.

I have two questions:
- If my plan is to grow tomatoes does anyone think that this set-up would work under these conditions?
- If tomatoes wouldn't work is there anything else that might be able to survive in a hydroponic system?

Thanks in advance. I look forward to posting my progress if any of it goes ahead.

imafan26
Mod
Posts: 13961
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

I am more familiar with tomatoes in dutch buckets. The beds that are used for hydro are usually shallow no more than 6-8i nches deep. Tomatoes and cukes make a lot of roots and need a lot of space. A box or rail system is best used for short crops that can be spaced closer and harvested in 50-60 days.

The dutch buckets we used were 15 gallons, but I know some people have gone with as little as a 5 gallon container. You will have to train the tomatoes on a wire and prune them if you put the buckets a couple of feet apart.

We switched from a raft to a media based aquaponic set up, however if you want to do a raft system your method will work.

Our was set up using a 4x8 ft pressure treated plywood as a base with 2x4 or 2x6 sides. It was lined with a waterproof plastic liner and it was just folded in the corners and stapled on the outside. 4 inch pvc was the main water line from the reservoir.
This was an ebb and flow system using a siphon valve to trigger the drains. The main reservoir (fish tank) was underground) the smallest was 700 gallons and the larger one was 100,000 gallons. This was on a commercial farm.

We do have a demonstration Kratky system at the garden where I volunteer. It is a 4x4 plywood and 2x6 frame with a plastic waterproof liner. It has a floating styrofoam raft. Holes are drilled 8 inches apart. They are 3 inch holes to suspend a 3 inch net pot. The seedlings are grown in oasis media in a plug tray and when they are 2 inches tall (lettuce) seedlings are put in the net pots. The tank is filled with a master solution and water. This system is very low tech. It works better with an aerator but does not require a pump. It only works for short crops like lettuce that can be harvested in 30-50 days. It is filled once and should last until harvest. Because this is a stagnant system unless you use an aerator, and if you live in the tropics like I do, mosquitoes can be a problem. Easily solved with BT. The other problem we encounter is that hydroponically grown produce can grow faster than in ground, but because they are in a more confined space and have a lot of green growth, pests were a big problem. We did have more problems with pests when plants were grown outside of the shade house. When pests got inside the shade houses, it got so bad that the whole house had to be sterilized and cleaned to get rid of them. Consider using shade cloth, phylon roof so you can control over head rain as well as light and insect netting for the sides to keep birds, and other pests out. We also had problems with rats and mongoose coming in the shade house from the drains, so they had to be screened off. We had fans inside the shadehouse but they really should be on the ends one fan blowing into the house and the other pulling air out as well as roof vent (We had an off set roof, it also had to be screened to keep the birds out, but it allowed hot air to rise and escape.

Kratky did come up with a solution for tomatoes which requires more nutrients than lettuce.

https://www.ctahr.hawaii.edu/hawaii/dow ... matoes.pdf
https://www.ctahr.hawaii.edu/hawaii/dow ... ettuce.pdf
https://www.ctahr.hawaii.edu/hawaii/dow ... ulture.pdf
https://www.ctahr.hawaii.edu/hawaii/Vegetable.aspx

Tomgrow
Full Member
Posts: 10
Joined: Tue Dec 12, 2017 12:03 am

Hi imafan, thanks for the detailed response!

Come to think about it I have been warned about tomato’s deep roots. I was originally planning to use a deep water culture system but the sheer amount of aeration required put me off. I had a perception that it's more efficient to aerate with a water pump rather than blowing air bubbles. I don't know whether or not that's correct though.

The Kratky method had interested me as well. Especially when there's such detailed information available. My main concern was the stagnant water issue, but in the scheme of things, I think it may be the easiest option. I might bury some pots for insulation and give it a go.

Thank you for the input. I'll take those things into account. I should start setting up pretty soon.

Manpalace
Newly Registered
Posts: 3
Joined: Mon Mar 05, 2018 3:42 pm

The Kratky Method would be possible as long as you can ensure mosquitos aren't getting into the stagnant water. The best way to do this is to simply cover the interface between the water and air with mosquito mesh or netting
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imafan26
Mod
Posts: 13961
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

The Kratky plants grew better with aerators. The aerators are big and while it does not circulate the water it does keep it moving so it is not that stagnant. If the cover is snug and you are using hydroton or rockwool for media you don't need a large cover. You might be able to get away with screen material around the top of each cup.



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