Can light intensity and duration affect how much nitrates are used by plants?

[AJ Grottke]

I want to c what others have to say, but i was thinking about that question in relation to indoor growing under lights, but it can be fore sun-driven systems too.  I have noticed running my light for 20 hrs a day as opposed to 10 doubles the growth of plants in hydroponics. Also i have noticed that using a 600Watt HID will get about double the growth rates and yields as a 250Watt HID.  (All this info i have gotten from  personal experience in my 4 years of extensive hydroponic growing.)   So i would think this would increase the amount of nutrients absorbed, possibly allowing one to have less plants for filtration, or more fish.  What do yall think???

[David Nabong]

I am not absolutely certain, but I believe this has been touched on before in these forums.  The down and dirty is yes, by changing one input factor you affect many.  This has been shown many times in conventional greenhouse horticulture settings.  The amount of light provided will cause the plants to grow based on the amount of nutrients available,  if light availability falls off, plants can be affected by nutrient toxicity (salt injury), if there is too much light, the plants will grow until the nutrient availability is too low to support active growth.  The most reasonable way to monitor this is checking and charting nitrate levels and only changing the light levels, of course since many of us grow inside, light is our limiting factor and not nutrients.

[RupertofOZ]

"So i would think this would increase the amount of nutrients absorbed, possibly allowing one to have less plants for filtration, or more fish."

 

If the nutrient absorbtion is increased as you suspect... it doesn't follow that can have less plants for filtration... or more fish...

 

For the possibility of increased nutrient absorbtion... supposes that there was an excess of nutrients available...

 

Normally we'd actually increase our plant load to utilise any excess.... lessening your plant load would only increase the level of excess nutrients... It wouldn't affect your filtration at all..

 

Similarly, increasing your fish load... might well mean that you reach a point where you're effectively under-filtered... and even with a corresponding increase in plant load... you could still well end up with excess nutrients...

 

Or more probably.. just a messy water quality.. and/or dead fish...

 

Apples are apples... oranges are oranges...

[tilly the tilapia]

hi ya

stronger lighting and longer duration  will increase nutrient absorbtion for most plants
I have used hid's extensively  for over 26 years on a commercial scale
RupertofOZ said:

"So i would think this would increase the amount of nutrients absorbed, possibly allowing one to have less plants for filtration, or more fish."

 

If the nutrient absorbtion is increased as you suspect... it doesn't follow that can have less plants for filtration... or more fish...

 

For the possibility of increased nutrient absorbtion... supposes that there was an excess of nutrients available...

 

Normally we'd actually increase our plant load to utilise any excess.... lessening your plant load would only increase the level of excess nutrients... It wouldn't affect your filtration at all..

 

Similarly, increasing your fish load... might well mean that you reach a point where you're effectively under-filtered... and even with a corresponding increase in plant load... you could still well end up with excess nutrients...

 

Or more probably.. just a messy water quality.. and/or dead fish...

 

Apples are apples... oranges are oranges...

[RupertofOZ]

tilly the tilapia said:

hi ya

stronger lighting and longer duration  will increase nutrient absorbtion for most plants
I have used hid's extensively  for over 26 years on a commercial scale

I have no problem accepting that increasing the light cycle allows for extra growth and absorbtion of nutrients... indeed in order for extra growth to occur, there must be available nutrients for it to occur...

 

In hydroponics, there is of course always an excess of nutrients... in aquaponics, depending on number/type of plants... there may be...

 

However to postulate that utilisation of excess nutrients can be in some way tied to modification of your filtration capacity.. is wrong... and potentially dangerous...

[tilly the tilapia]

yes i agree totally

RupertofOZ said:

tilly the tilapia said:

hi ya

stronger lighting and longer duration  will increase nutrient absorbtion for most plants
I have used hid's extensively  for over 26 years on a commercial scale

I have no problem accepting that increasing the light cycle allows for extra growth and absorbtion of nutrients... indeed in order for extra growth to occur, there must be available nutrients for it to occur...

 

In hydroponics, there is of course always an excess of nutrients... in aquaponics, depending on number/type of plants... there may be...

 

However to postulate that utilisation of excess nutrients can be in some way tied to modification of your filtration capacity.. is wrong... and potentially dangerous...

[Ryan Chatterson]

These statements are far to vague.

"I have noticed running my light for 20 hrs a day as opposed to 10 doubles the growth of plants in hydroponics."
Completely crop specific. It's not simply double the light equals double the growth.

"Also i have noticed that using a 600Watt HID will get about double the growth rates and yields as a 250Watt HID"

This will have to do with the Lumen output from the specific bulb and how far the light source is away from the plants. You can have a 250w bulb 2 ft from a plant and a 600w 4 ft from the plant. If the lumen output is the same at the plant, the growth rates will be the same. Again, not really a standardized rule for all plants.

I do agree that faster growing plants will absorb more nutrients, They are photosynthesizing faster, growing faster, and using more nutrients to fuel that. Which nutrients will they be using more of? Depends on the plant species and where it is in its growth cycle. What you theorize is a possibility but it would take a lot of testing and plotting results against each other to put it into any kind of meaningful terms.

[AJ Grottke]

Great responses.  This thread is more of a theoretical one; im not willing to risk my system with experimentation.  Maybe some time in the future.  By posting this discussion I was seeing what others thought about it; or to see if anyone has grown the plants in their AP system with a 400Watt HPS at 1 ft above plant canopy, then switched to a 1000Watt HPS at 2 ft above the canopy (for example).  If anyone has done something like this, im curious about nitrates levels, and the corresponding amount of fish feed to produce those nutes. How were these parameters affected by this increase in light or "Lumens" while using the same spectrum or type of bulb.  Has anyone increased the light in their system without changing anything else and recorded the results?

[TCLynx]

Provided the filtration is ample to handle whatever you are throwing at it.  Yes, I expect better lighting for the plants can cause them to take up more of the nutrient (provided there is excess.)

 

But as Rupe said, plants taking up nutrient is not actually filtration so make sure the bio and solids filtration is up to the task.

[Chi Ma]

Think of light as the gas pedal and nutrients as the fuel. Increase light you increase nutrient consumption.

[TCLynx]

Chi Ma said:

Think of light as the gas pedal and nutrients as the fuel. Increase light you increase nutrient consumption.

 

In that case, the filtration is the fuel filter. If there isn't enough filtration, the gunk gets out of hand and the car dies.  Seeing as we add the fuel in a form that won't drive it until it is filtered properly.

[AJ Grottke]

Good analogies Chi and TC.  For some reason ive always loved analogies. :)