# Is there a best time of the day to add fertilizer?



## littlecich

cmax916 said:


> Hi,
> 
> Right now, I am adding fertilizer at night because I am not home during the day. Will this be a problem to plant growth?
> 
> Thanks!


I really don't think time of day makes a difference. Aquariums are really an artificial setting, with lights on at times other than during daylight hours without problems. When fertilizers are added shouldn't make a difference. What would be a problem is if they weren't added and it was a high tech tank.

Just my opinion.


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## pvtschultz

I agree. Adding them at some time during the day is much better than not adding them at all. So picking a time of day that is most convenient for you is better over the long haul because it promotes consistancy and longevity.


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## macclellan

If you are following EI dosing, it's best to fertilize before lights on. This can be the night before; you may always be "one day ahead" but that's fine as long as it is consistent and proper quantities.


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## plantbrain

Plants take up nutrients 24/7.
I think adding them at a consistent rate is more important.
You can dose daily, 2x a day 3x a day, whatever............or 3x a week, or none at all in a non CO2 tank(well, the fish food waste is a form of "dosing").

I think the whole at the nutrients in the morning or early part is plain rubbish, there's no support for this.

CO2 is the only "nutrient" that's day/light time dependent really, some plants will take some nutrients at a slightly higher rate depending on the time of day and the demand.

Plants gear up for the day's growth by taking in nutrients first/or they already have them stored, this process obviously takes time to take them in, then process them, then transport them where they need to go and modify them into parts the plant needs. This is not an instantaneous process. Then they start to grow once light hits and they take up CO2 (add reduced carbon to their biomass), then they will still take up nutrients during that process as well(during the daylight).

At night, they continue to do so.
What makes folk's honestly believe they might stop?
Plants store nutrients, reserves etc and respiration does occur (even if no CO2 is being fixed) which requires nutrients and helps store the next day's nutrient supply. 

If you where a plant, would you only regulate yourself to taking up nutrients during say 40% of the day? Obviously that would be a disadvantage if another plant could take up nutrients 24/7.


In most growth studies I've read, the timing of growth far exceeds the demands one simple dose might yield in the morning. It takes time, energy and processing to get everything in place in a plant right before the light hits.

It takes a lot of energy to assimilate and provide uptake.
Now if this all happened all at once, say during the first hour of the day, the plant would really have to change things, take nutrients up super fast and store even more nutrients.

Otherwise it would reduce growth.

Now if a plant had all day and night, then they could supply and process all the nutrients at as much more stable rate.

While the notion that adding the nutrients in the beginning of the day might seem quaint, if you ask yourself what would be best based on how a plant grows, then it;'s pretty apparent it's best to take up nutrients consistently day/night, or as I've long said, 24/7.

http://www.jstor.org/pss/2258287

Here we see only a morning maxima, however, let's look at this paper:

In the submersed state, CO2, not nutrients like N and P are far more limiting.
Since we add N, P, and CO2 to many such tanks, the paper really does not answer the question.

Also, the light intensity far exceeds anything we have in our tanks, so the speed of growth is driven much faster and CO2 is depeleted and becomes limiting much faster.

Recall growth is a function of light, CO2, and nutrients, not just nutrients.
And you cannot say much about growth at that one point in time because plant metabolism occurs 24/7. You need a more holistic view of plant physiology over time. Plants can handle a pure DI water solution for a few days as the plant has some reserves. Or a blackout etc.........

But over time, things will suffer.
Same type of thing here.
So it's not so much the time of day, rather, are you adding enough and consistently so.

Now if adding then in the morning and feeding your fish at that time works for you, then that's when you should add them, but you should mention that this is a human habit issue, not a plant growth issue..................



Regards, 
Tom Barr


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## plantbrain

Plants take up nutrients 24/7.
I think adding them at a consistent rate is more important.
You can dose daily, 2x a day 3x a day, whatever............or 3x a week, or none at all in a non CO2 tank(well, the fish food waste is a form of "dosing").

I think the whole at the nutrients in the morning or early part is plain rubbish, there's no support for this.

CO2 is the only "nutrient" that's day/light time dependent really, some plants will take some nutrients at a slightly higher rate depending on the time of day and the demand.

Plants gear up for the day's growth by taking in nutrients first/or they already have them stored, this process obviously takes time to take them in, then process them, then transport them where they need to go and modify them into parts the plant needs. This is not an instantaneous process. Then they start to grow once light hits and they take up CO2 (add reduced carbon to their biomass), then they will still take up nutrients during that process as well(during the daylight).

At night, they continue to do so.
What makes folk's honestly believe they might stop?
Plants store nutrients, reserves etc and respiration does occur (even if no CO2 is being fixed) which requires nutrients and helps store the next day's nutrient supply. 

If you where a plant, would you only regulate yourself to taking up nutrients during say 40% of the day? Obviously that would be a disadvantage if another plant could take up nutrients 24/7.


In most growth studies I've read, the timing of growth far exceeds the demands one simple dose might yield in the morning. It takes time, energy and processing to get everything in place in a plant right before the light hits.

It takes a lot of energy to assimilate and provide uptake.
Now if this all happened all at once, say during the first hour of the day, the plant would really have to change things, take nutrients up super fast and store even more nutrients.

Otherwise it would reduce growth.

Now if a plant had all day and night, then they could supply and process all the nutrients at as much more stable rate.

While the notion that adding the nutrients in the beginning of the day might seem quaint, if you ask yourself what would be best based on how a plant grows, then it;'s pretty apparent it's best to take up nutrients consistently day/night, or as I've long said, 24/7.

http://www.jstor.org/pss/2258287

Here we see only a morning maxima, however, let's look at this paper:

In the submersed state, CO2, not nutrients like N and P are far more limiting.
Since we add N, P, and CO2 to many such tanks, the paper really does not answer the question.

Also, the light intensity far exceeds anything we have in our tanks, so the speed of growth is driven much faster and CO2 is depeleted and becomes limiting much faster.

Recall growth is a function of light, CO2, and nutrients, not just nutrients.
And you cannot say much about growth at that one point in time because plant metabolism occurs 24/7. You need a more holistic view of plant physiology over time. Plants can handle a pure DI water solution for a few days as the plant has some reserves. Or a blackout etc.........

But over time, things will suffer.
Same type of thing here.
So it's not so much the time of day, rather, are you adding enough and consistently so.
What about fish waste?
Does this contribute to plant growth?
Should we feed them to only allow their waste during the day?

Now if adding then in the morning and feeding your fish at that time works for you, then that's when you should add them, but you should mention that this is a human habit issue, not a plant growth issue..................

In some plants, like Elodea, PO4 uptake appears to be strongly driven by photosynthesis, so day time drives uptake for this nutrient and this species, but unless you test for it and can show it increased the total biomass, it's really not affecting long term growth. Some species might have different responses. Still, the leaf uptake is driving the PO4 uptake there, not roots.
Photosynthesis is not occurring in the roots. Many claim plants prefer root uptake, yet also want to argue in favor of the time of day for dosing being a strong dependence.

Here's a good paper that is very recent that looks at PO4 and time of day in *one species* without CO2 and without looking at the other nutrients.

http://www.int-res.com/articles/ab2008/3/b003p209.pdf

But it does not mention anything about dry weight differences between dosing during the day vs night.

Which is the real question here...............

I think folks lose track and get messed up searching for answers that fit their conclusions. Not results that answer their question specifically.

Even if the PO4 is not being taken up by some species, others very well might be, and it's not going anywhere either, once the lights do come on, the plants will suck it out. 

For NO3, a similar issue arises. We should see more uptake when there's more demand for N, this is well correlated with CO2, the plant balances the demand for N based on how much CO2 it has and fixed. So during the light cycle, many of the nutrients are depeleted and thus uptake tries to keep up with demand. You will get a higher rate of uptake, but this does not imply that the nutrients are not being used or taken up at night nor that you gain anything is only adding it early right before the lights come on, or an hour afterwards.

The nutrients are still there if they have not been taken up correct?
Then it should not matter when you dose, only that you add enough to prevent limiting amounts and use lower light(which would drive larger differences in demand).

So either way, there's not going to be any noted reason to add it at some particularly point in time during the day. Our dosing observations also match this logic and reasoning as well. 


Regards, 
Tom Barr


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## cmax916

Ok, thanks for your input everyone!

-m


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