Hydroponics in a polytunnel

Hi,

I wonder if anyone uses a hydroponics system in their polytunnel and if so - what type and how are the results? I'm thinking about growing tomatoes peppers and chillies using this method. I realise that the start up costs are a bit more - but I believe that the upkeep thereafter is much less.

many thanks

 

@hydrogardener is the one to answer that question

Not sure about that ... the nutrient solution needs to be kept in balance. Typically this is done by adding more concentrate using a meter to measure the "salt" level, but individual nutrients can get out of whack. Amateurs often solve that by throwing away the nutrient solution periodically (or even "frequently"!) and starting with fresh nutrients, but I reckon that works out pretty expensive.

If you use a system that involved circulation then you are at risk from pump/electricity failure and so on. But ... done right ... I suspect you would be able to have an automated system that allowed you to go away for a long weekend where the rest of us would be panicking and worrying whether the neighbour watering our plants was going to kill everything!

I've worked in commercial horticulture growing using NFT hydroponics growing Tomatoes, Lettuce and Peppers and we got great yields, but we have a whole chemistry lab that was able to check the individual nutrients' balance etc., and although I like playing with Boy's Toys and automation I grow everything at home using conventional methods.

 

Thanks for that.

I've used a greenhouse for conventially growing tomatoes and peppers etc, before, but I'm thinking of putting up a large polytunnel to really expand. (probably 18 x 40 feet). This is getting to the size where daily maintainance could be an issue (particually as I'm away to work from 6 to 6 every day).

I'm somewhat lucky in that the site I have ear marked will have water plumbed into it and I could also get electric to it cheaply (I have a solar PV system installed), but I was thinking more about a gravity system so pumps shouldn't be an issue.

Nothing much exciting will happen until the end of the year I expect - but I'm looking into my options now

thank again.

 

Dutch buckets are probably the most versatile for bigger plants. In a power cut you can water by hand or have a 12v pump/battery for backup. I have chillies in 10L manual flood and drain buckets filled with hydroton, they are happy with 4 hourly floods during the day (8am, noon, 4pm). I run 2 kinds of aeroponics outdoors but the hardware is more involved so its not really suitable for a new hydroponic grower.
Whatever you do, dont buy nutrients from a hydroponic shop, you`ll pay a fortune. For an outlay of £100 you can get at least 25,000L of nutrient solution suitable for tomatoes, which are one of the heavier feeders, chillies need lower strength.
Here`s the chillies (the buckets were free for the asking from lidl`s cut flower department).

 

Mine is 10' x 30' - so also a bit larger than a regular garden greenhouse

I use the greenhouse soil (changed annually). I have leaky hose matching the plant rows along the greenhouse, watering on a timer from a water butt (gravity fed) and that water butt is linked (by hose / syphon) to some further IBCs (1,000L each) and then to a water butt on the house downpipe - which replenishes the whole storage (and I get a bit from the greenhouse gutters too, of course). I feed with a watering can when I remember, generally between once a week and once a fortnight.

My greenhouse "soil" is 50:50 well rotted manure (stacked for a year) and my homemade compost ... well ... I say "made" I just pile everything up, and after 12 months whatever is there is what I use, its pretty rough still, but when it comes out of the greenhouse borders it is beautifully friable, and I use it for various potting and mulching tasks. The compost / manure combination if much lighter than my regular clay soil, so its not hard work to change each year, but changing it annually is overkill (I do it that often to have a steady supply of the nice fine friable compost that the process produces ) and you could use grafted plants instead (which will tolerate soils that have disease buildup / nutrient deficiency from mono-cropping).

Plants need attention with hydroponics of course - picking fruit, training up strings, side-shoot removal, so the only thing you are saving on is irrigation and in the case of hydroponics feeding. You might get significantly higher yields with hydroponics (if done well ), but some may say that you will get watery tasting fruits. Supermarket tomatoes are mostly grown in hydroponics, and folk will base their experience on those - but supermarkets' growers will choose varieties that suit the commercial process - disease resistant, thick skins so they don't bruise in transit, and so on - whereas home growers choose on flavour - and tolerate lower yields and so on - so I doubt anyone has trialled best-flavour varieties side-by-side with soil grown & hydroponics to be able to say if they can taste the difference. What folk do so is "grow Tomatoes mean" for flavour, and you can't do that with hydroponics - the plants will have everything they want, in particular water, "just so" ...

If you want a project then don't let me stop you!! but if you want minimal maintenance cropping then soil-based (rather than container or bag) would be a whole pile cheaper to start with, and less risk of crop-loss due to equipment failure / power outage.

 

Sorry @Hex_2011 - forgot to mention your name earlier. Too old to be able to remember that you grow Hydroponics too

 

No worries, Kristen, i`m at that age too lol
Power cuts wont affect manual flood and drain buckets. Its not very hi-tech,
lift watering can, pour into FD bucket, drain FD bucket back into watering can. Wait 4 hours and repeat
A hydro pepper plant (variety unknown) on its 5th season in the same wilko`s hexagonal planter filled with hydroton. The nutrients are delivered via a 10L B&M watering can. It was literally just a stick in a big planter up until april, now its 4ft around with hundreds of pods.

 

That's the sort of results I'm hoping for.


Some great advice / tips there.

I'd like to give hydroponics a go - though next year. I think the flavour,as you say, is determined mostly by variety and supermarkets do choose their stock based on transit capability, uniform ripening and shelf life, while a variety that has better flavour should be better regardless of the medium it's grown in. And then there is all the pesticide / preserative messing around that may go on. There could be an experiment there in future, to compare them, though

I'm more interested in peppers and chilies than tomatoes at this stage.

Manure I have a lot of. The farmer who rents my land dumps the cow shed cleanings within wheelbarrow distance ....


Where would be a good source for the nutrients though?




Thanks again all - that's very helpful

I'll post pictures when I have something exciting to show.

 

I think Peppers / Chillies will do better in hydroponics than Tomatoes (flavour-wise) due to the water content of Tomatoes which goes hand-in-hand with a reduction in sweetness.

 

The thing about supermarket toms is its all about cost and productivity, just halve the feed and you`ll deliver something that looks like a tomato but it wont taste of anything
You cant really blame the lack of taste on a particular growing method as there`s likely the same kind of taste difference between a tom grown in some top notch homemade organic compost.and another of the same variety grown in some naff shop bought compost, fed with MG

 

I'd like to see some side-by-side trials - how come those students that pitch up here saying "Can you vote for the new [useless!!] garden tool I've designed for my horticulture diploma" don't arrive saying "Any ideas for a project?"

In the absence of a direct comparison my gut feeling is that the amount of water [in hydroponics] may make a difference. I also think that amateur hydroponics nutrient solutions are likely to have incorrect nutrient ratios at times. For example, when I worked on a commercial hydroponic site the lab found that Tomatoes would strip all the Potash out of solution within a few hours at particular times of the fruiting cycle - i.e. selective feeding - I presume it would be impossible to detect this in an amateur setup, and just relying on dosing via salt level metering would then cause disproportionate imbalance of the other nutrients - until the next time the solution was dumped and replenished. Having said that it would be much the same for container grown plants, and for all I know, absent a comparative experiment, may be no different in a soil-based setup either

Again just a gut feeling, but I think that would be too rich for tomatoes. The plants would look great, and fruit profusely, but I think they might lack sweetness.

Where is that student wanting an idea for a project when I need one?!!

 

I make my own nutrients so i`m not restricted to whats available but there`s really only 3 elements that change throughout the life of the plant, nitrogen, potassium and calcium. The uptake begins to ramp up rapidly from the 4th true leaf and peaks when the first flowers appear. There is a well defined drop in Ec and ph as the plant stockpiles what it needs but theres no outward signs from the plant. Its very hard to miss if you track the Ec/Ph daily.
To get an idea of the N, K and Ca ratio`s and changes,
upto the 4th true leaf 275, 400, 240.
From 4th true leaf 330, 500, 280, ramping up to a peak of 550, 900 and 480 just before the first flowers appear.
From the first flowers to 2-3 weeks before you pick the first tomato the levels ramp back down to 330, 500, 280.
From that point until frost kills the plant, they are back where they began, 275,400, 240.
Sounds like a nightmare but you only need to adjust the amount of calcium and potassium nitrate to alter the N, K and Ca levels.

I run aeroponics so the roots arent submerged or constantly soaked (pic attached). It may be a contributing factor to the taste but i`ve used flood and drain and they werent watery or tasteless either. I`ll have to send you some for a taste test

 

Is there a simple test for the ratio of main nutrients then? I assumed Ec was all you had if you know the actual K levels then that's much better than what I expected an amateur could do. Can't remember the name of the gear we had, back then, but it was whatever was a more modern, and automated, equivalent of gas chromatography. From recollection it came from Perkin Elmer ... anyways, it told us the concentration of all the elements in the solution in only a few minutes - great piece of Boy's Toys kit You'd probably pick one up on eBay for $9.99 now !!

Not such a daft idea ... if others in the taste test were growing the same variety. I've swapped fruit with other growers for a taste test before now

 

If you use reverse osmosis water with <10ppm, the elemental content will be what you add. The aero runs drain to waste, so nothing comes back to alter the feed makeup. The rhubarb usually gets whats in the runoff tub each morning but it doesnt fill a 2L jug..
Drain to waste with a commercial NFT isnt too viable, it makes sense they`d invest in expensive lab gear to check and replace only what has been removed by the plants..
I guess they`d still have to periodically change the water out or run it through an osmosis system to prevent unwanted elements from building to toxic levels. Sodium springs to mind, but anything in the makeup water the plants didnt need or use would gradually accumulate in the solution.

I put the surplus cuttings in the raised beds and a few in 10L pots of B&Q Verve MP compost, i`ll have a few off each of those plants for the taste test.

 

Some very interesting points made in this thread - especially the N, K and Ca ratio changes.

Where is the best place to purchase the nutrients (mineral) other than a hydroponics shop - yes they do seem to be expensive there ...

I'm not afraid to have a go at mixing my own

many thanks