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Battling Heat Stress in Hydroponics · Hydroponics Daily

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Hello and welcome back to Hydroponics Daily.
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Today we're talking about heat stress. In the UK it's been unseasonably warm
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or hot for the time of year and it's definitely been unseasonably dry. There's been no rain.
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Maybe where you are it's also unseasonably warm
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and as we get into summer it's that's going
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to be even more of the case this i always say the
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best time to start hydroponics is in the winter because it's
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a lot easier all of your problems get a lot
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more severe in the summer and it
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becomes a lot harder to control the environment and heat
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stress is the main cause of this and obviously
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other issues around just going on holiday lots of
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people go on holiday during the summer so that can mean that your grow
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room gets left unattended however it's the
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heat that we're going to concentrate on today so most plants
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like a temperature between 20 to
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25 degrees celsius i don't know what that is
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in american probably 80 to
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90 fahrenheit something like that please get in touch
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if you go above 30 degrees celsius
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most crops will suffer there will be
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some that like to grow in very very hot conditions like the c4 plants or cacti
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things like sugar cane and things like that but most plants will start to suffer
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and the symptoms you'll get are the flowers and the fruits will suffer first
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you'll get scorch and you might get flower drop and fruit drop.
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Whereas at the other end of the scale, you're not going to get much damaged
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until you get to about five degrees Celsius for most plants.
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So the upper limit for plants is quite low.
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Then you've got to remember that your plant may be hotter than the air temperature.
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So if your plants are running a slight water deficit in the soil.
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Then the stomata will be closed.
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And that means that the leaf temperature could be five degrees Celsius warmer.
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So suddenly 30 becomes 35 or
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35 becomes 40 and your plant will start to
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cook it'll start to scorch yeah photosynthesis
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will stop it will become a lot less efficient flowers
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and fruits will become malformed and may
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drop but scorch is a big danger there so
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always the first tip is always make sure your plants are extremely
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well watered i've talked in the past about
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how there can be benefits from running a deficit irrigation system
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but if it's really high temperatures
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you want to avoid that so make sure that ample water throughout
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the day as well so if your water once a day and you're
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in a greenhouse with really low humidity and high airflow they're
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going to dry out during the day significantly so maybe
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look at installing a a irrigation
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system and this is hydroponics daily so this should be this should
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that's for cocoa growers and soil growers for hydroponic growers
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you're an advantage because you can supply fertigation constantly
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with an ft system or with flood and drain
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you could up the number of floods gwc again
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the thing you need to be careful of is your reservoir going to be running dry
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and as the plants suck up lots of water is the ec level going to rise significantly
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during the day obviously you can top it up when you get in later in the day
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but or you get or you get around to that task but just make sure your ec levels
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don't go too high as the plants suck up so much water. In your hydroponic systems.
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Other things you can do, if it's going to be a really, really hot day and it's
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going to be the exception for the norm, you could lower the light intensity
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if you're growing indoors.
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Most lights now, hydroponic lights, are dimmable. So you might want to lower it for a day or two.
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Yes, you might not get the same amount of light, but photosynthesis might suffer
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because it's such high temperatures.
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If you had those high light levels, they would just be doing something
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called photorespiration and damaging plants so
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lower your light intensity if you're growing auto flowering
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or non-photoperiodic varieties and strains
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you can lower the photoperiod so the lights aren't on during the day during
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the peaks of high temperatures that's not going to affect yield dramatically
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if you are growing photoperiodic plants that's less of an option but just look
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at the minimal what we call the critical day length for that plant for that variety.
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If it's say 16 hours and you're running at 22 hours day lengths you could drop
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that by four hours per day and there wouldn't be an issue.
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Now obviously don't drop that four in the middle of the day but either side
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you know it's still really really hot that's an option.
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Now two really key things to coping with heat stress. The first one is CO2 enrichment.
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Now obviously don't use a heater but based
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a burner type co2 enrichment because that's going to be adding temperature but
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a canister type co2 would be ideal in this situation
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enriching co2 really helps with plants cope with
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heat stress and one of the
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issues with canisters can be that they they the ice
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up they freeze up in if you use too much of it too
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quickly but in you know above 30 degrees celsius that's
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not going to be a problem unless you're using serious amounts of co2 now one
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of the other ways you can cope with high temperatures is to increase your airflow
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bump up the speed of your inlet filter and your outlet filter move the air around
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the growing faster with your circulatory fan however if you're enriching with co2.
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You might want to experiment with that because you don't want to just be enriching
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with CO2 and then sucking all that air out straight away.
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You want to get bang for your buck with that CO2. So there's a game to be played there.
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Another issue, another way you can help the plants cope with heat stress is
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to increase the humidity.
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So dial the humidity up to the upper limit that is safe for your crop.
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Don't be going too high because high temperatures and high humidities can
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promote powdery mildew growth and so
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but if you're at the lower end of your humidity air
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range for that crop at that temperature then
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then look at increasing the humidity consult a vpd
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chart work out whether the prevailing temperature is going to be in your grow
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room and then take it to the top of the humidity that keeps you in the green
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zone most vpd charts the central zone the central curve is the green zone so
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have a look at that as i said increase air movement look at installing an air
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conditioning unit to lower the temperature.
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If it's your first time grow don't go out and buy an air conditioning unit but
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if you're a medium-sized grower or you've thought about air conditioning in
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the past and you think that you might lose your crop or it would significantly
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affect your crop then air conditioning could be an option.
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Especially where you're thinking about like one of the problems with
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high temperatures is your terpenes can be can volatilize
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off they can they can evaporate off the plants you can lose
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if you're growing a terpene based like a scent crop
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a flower crop that that needs scent then
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that can be an issue things like lots of
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plants produce terpenes and iso what's
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the word isoprenes isoprenes and they
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in really high temperatures photosynthesis rather than producing sugars
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produces gases that that volatize off
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and and you lose carbon into the air and that's
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one of the components of smog and also global warming
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is these isoprene emissions so high temperatures
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you can lose crop quality if you're
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not if you're not careful so an air conditioning unit might
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be for high value crops air conditioning unit might be something
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to look at i said increase your outflow and your
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inflow rates make sure if you've got an inflow filter
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that it can cope with that extra pressure that it'll
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be under doesn't just pop off the filter that would
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be the worst case scenario because you come back in and you
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find that your grow room has been sucked in a load of fungus gnats
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and aphids and white flies that'll be
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flying around in the high temperatures because they love those sorts of conditions
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and again your outflow filter make sure your outflow filter
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can cope with that airflow if you're trying to scrub the
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air going out there are a number of biostimulants that
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you'll see sold that claim to help plants.
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Cope with heat stress and there's some
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that claim to help plants deal with cold
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stress more often than not these are biostimulants sold
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under the guise of being like a fancy product more fancy than they are they
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might be a seaweed extract or a glycine betaine or something like this some
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source of biostimulant that that has one of the benefits is that it helps plants
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cope with heat stress. But.
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Unless you're in America they might not say what's
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in the product on the label certainly won't say it in the
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safety data sheet unless it's hazardous so be careful
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you're not overpaying for what is a basic buyer stimulus with that
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if you're interested and you want to know more about those
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sorts of products and you you want your advice on say a product
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feel free to email me and I will cast my
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eye over the product and say whether it's a good investment or
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not because then we can look at it and see what it's
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potentially made of and it might be really good value for
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money I don't know some of them are obviously certain
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plants are going to like high temperatures but you can't really choose certain
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varieties based on you know a weather
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forecast most weather forecasts only go for 10
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days so you can't really that's the problem with a
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lot of environmental stresses you can get varieties that
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cope well with flooding or drought or heat stress or
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cold stress or other things like high wind even like
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lodging and things like this but you you don't know what
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the weather you're going to get until you get it so that's why plant
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breeders don't really breed for environmental stress resistance so
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that's been hydroponics daily for today if you're growing in nft
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systems make sure your nutrient tank doesn't run out dwc
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again dwc and ebb and flood make sure
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that your tank doesn't go to the point where your plants
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aren't your roots aren't being submerged to
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the same point every day because you get really bad stress levels
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from those roots that aren't submerged so make sure you can.
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Top that level up some people have automatic pumps that.
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Work from the mains water that will pop a top a.
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Tank up it'd be going to be a fairly big grower to do
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that and what other systems could we look at talked.
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About cocoa and how you you know you you might
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want to water the source if you're growing in cocoa and you're hand watering
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you might want to put some water in the sources below the plants
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bottom feeding as it were i tend to.
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Not recommend that as a daily routine because you get root
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rot at the bottom however if it's on periods of
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extremely high temperatures then you
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could do that obviously that's how an autopot or
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a passive system works is it feeds from the bottom so autopots
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would be fine under high temperatures just making sure that
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the tank isn't getting too dry in
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24 hour period or however many days you
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leave it before filling it up and make sure you really look in
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all systems make sure you look at the ec level because as
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it's sucking all that water out of the fertigation system your ec levels can
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be getting really high okay another key issue during high temperatures is the
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the fertigation tank when it gets hot it will start to encourage microbial growth
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and so it might get a dinky during high temperatures.
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Certain nutrients might start to interact at high temperatures as well.
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So just keep an eye on your tank, make sure that you've not got any biofilms
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developing, you haven't got any nutrients locking out.
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You might want to add a bit of peroxide just to keep the bacterial levels low.
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And you can buy cooling systems for fertigation tanks.
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And the added advantage of that is that when that fertigation solution goes
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through to your plants, then it keeps the root system cool as well.
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If you're running a system with lights indoors, you could also look at putting
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the lights on during the night and then having the lights off during the day.
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In many countries you can also save on electricity costs
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because electricity is cheaper during the night as well so that's something to
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look at that helps with high temperatures it also helps in
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the winter because if you're growing in in say
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like a shed based system or in a
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conservatory you'll grow rooms there then the low
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temperatures at the night if you have the lights on during the
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night that helps just take off those really low minimums
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and so you get much more of an even temperature obviously it's
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not very conducive to actually you going out there
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and measuring and looking at your plants because you
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have to be a night owl you have to be on nights then
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because unless you've got a green safe light you can't really go
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in when the when the lights are off if it's photoperiodic okay
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so it makes things more difficult to do that so I
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appreciate that but it might be a good option if you get really bad
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heat stress so hopefully we don't
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get really extreme heat waves this year and everyone's
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crop looks amazing if you think i've missed something about
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growing hydroponically in a in a what do you call it a heat wave that's the
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word then let me know if not then give this podcast a like and share it with
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your friends and all the other good ones that i tell you to do every week thank
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you very much for listening until tomorrow that's been hydroponics daily.