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lvumlow
Well-Known Member
I have some new data to share...
One of the main challenges I have experienced with this grow is determining the optimal feeding schedule. There are many posts with references to mister timings but I have not been able to find a source that appears to be using any type of scientific method. Some say they can read the plant while others just use what someone else was using in terms of cycle times so it appears that most people are guessing. I can't help but to remind myself that the plant will grow even if the roots are submerged in solution so how are we to understand the impact of providing the optimal levels? I would feel better if I could quantify this data a little more so this I would like to explore this in more detail...
First, find your starting point. This should be based on the strain, quantity of plants, light intensity, brand of nutrients, growth stage and overall environmental conditions. If you do your research, you will likely get somewhere close but I believe this should only be your starting point and as I share this story further I think you will see how a little tweaking can go a long way to unlocking potential in your plant.
OK, so for my case I started with pretty aggressive cycle times in the early stages of growth and this is mostly because you have a relatively small footprint to absorb nutrients with when your plant is small and has a undeveloped root structure. As the plant grows, you should have more surface area available in the root zone so most people will want to make some changes as you push through various stages of growth (each phase will have different demands for nutrients). For most of my grow, I have been using a 5 second on and 5 minute off cycle. This is pretty common but I believe most people are unaware of many variables out there like the number of misters, the flow rate of those misters, number of plants being fed, appetite for those specific plants, etc... In my example,, 5 seconds on is about 23ml but that is unique to my specific hardware and configuration whereas you may need more or less depending on yours. I am confident we can benefit from zeroing in on optimal levels but how do we do this? I really don't know, but below is the best solution I have found for moving in the right direction.
Once you have a starting point and you feel like your plants are at least looking healthy, it is time to see if you can zero in on the optimal needs for your specific environment. I did this by monitoring both the waste EC levels and the overall consumption by the plant. In my case, it may be a little easier as I have only one plant so the math is basic. I have weeks of logged journals that tell me exactly how much nutrient solution my plant consumes (and I have zero evaporation) so this can be calculated easily by documenting the levels in your reservoir at various points in time. If you are using a drain to waste solution, consider draining to a second stage reservoir where you can make some calculations before you dispose of it.
Remember, everyone will have different numbers so don't use mine; yours will be different. I have one Northern Lights Autoflower that is in week 8 of flower so I have plenty of data collected from the grow to help me feel confident that my plant is consuming 1.25 gal (4721ml) daily (at this phase). This has been very consistent for the last 2 weeks of growth but remember this would change when transitioning from seedling to veg, and then to flower. So now I know how much nutrient is being consumed so the next piece of the puzzle is to understand how much you are delivering to the plant. If you have specs for your pump/nozzles you may be able to use documented numbers but my recommendation is the take your own measurements and do this often to identify trends or changes over time. You can even diagnose a clogged nozzle without ever looking in the root chamber if your measurements are precise.
I did this by removing my nutrient reservoir return line from the root chamber and turned on my misters. I left them on long enough to essentially get a steady stream coming out of the root chamber return line. You want this to be steady so give it time to stabilize and then use a small jar to collect the run-off for a 10 second interval. Take a couple of samples and average them for an overall flow rate. Mine was 45ml/10 seconds. This equates to 4.5ml/second. Now, make some calculations using your current timer settings to determine how much nutrient you are spaying on the plant over a 24 hour time period. A simple formula is (86400/<off timing in seconds>*amount of ml delivered during the <on timing cycle>). This should give you the total nutrient delivered in 24 hrs. Using this data along with your actual quantity returning to your reservoir will tell if how much your plant is absorbing .vs how much you are delivering. In my case, I was delivering 25% more nutrient than the plant was consuming.
This is where I think things get a little interesting. Most of our hydro guys out there will say no bid deal, it returns to the reservoir to be reused on another cycle right? I have to say no, and I believe this because there is a big difference between aeroponics and DWC even though both are classified as a hydroponic solution. The concept of aeroponics is to provide a very specific amount of moisture to the roots. If you exceed this amount, I personally believe you are drifting towards the efficiency zone of a hydroponic style grow (to a degree that can be argued). If you are getting enough moisture to allow it to combine and drip down the root structure, that is too much and the reason why I believe we see the standard "fishbone" style of photos of roots. With that in mind, my plant was only able to absorb 75% of what was coming out of the misters. That other 25% is doing exactly what I don't want - it is combining with other moisture molecules and forming a droplet that is running down the root structure to drain. I believe on a macro level this is limiting the amount of oxygen the roots can absorb and limiting your plants potential. That is what we are talking about here right? - POTENTIAL.
To close on this, I used all the data referenced above and reduced the total amount of nutrients delivered (in a 24 hr. period) by 20% and at the same time made some new calculations to deliver that quantity evenly over the 24 hour time period so this means I reduced my mister on time and also reduced my off time but made sure the overall numbers still give the plant what it needs over the time period. The result: My plant still consumes 1.25 gal. but with my new timer settings the plant is now consuming 95% of what is coming out of the sprayers. I do not want to skirt the line too close just yet but I am planning on seeing how close I can get and observing the impact it has on the plant. My best guess is that it is more efficient and should unlock more potential from the plant.
I will be the first to say this is totally experimental, I wish it was as easy as someone giving me numbers to use but this is the best I can come up with to zero in on the best timer cycles for my specific conditions. Don't forget, your numbers will be totally different so you can't use mine. You have to make your own calculations but I can say this. After making the changes I referenced I can see a significant change in my plants growth and appearance (even this late in flower) - I have brand new buds popping out the top of my current buds. This is all in the last 24 hours! I wish I had considered some of this theory earlier but I am new and this is my first attempt at something like this so take the information with a grain of salt and apply what is helpful and discard the rest.
Here are some pics of where she sits today but not much overall change from recent photos...
One of the main challenges I have experienced with this grow is determining the optimal feeding schedule. There are many posts with references to mister timings but I have not been able to find a source that appears to be using any type of scientific method. Some say they can read the plant while others just use what someone else was using in terms of cycle times so it appears that most people are guessing. I can't help but to remind myself that the plant will grow even if the roots are submerged in solution so how are we to understand the impact of providing the optimal levels? I would feel better if I could quantify this data a little more so this I would like to explore this in more detail...
First, find your starting point. This should be based on the strain, quantity of plants, light intensity, brand of nutrients, growth stage and overall environmental conditions. If you do your research, you will likely get somewhere close but I believe this should only be your starting point and as I share this story further I think you will see how a little tweaking can go a long way to unlocking potential in your plant.
OK, so for my case I started with pretty aggressive cycle times in the early stages of growth and this is mostly because you have a relatively small footprint to absorb nutrients with when your plant is small and has a undeveloped root structure. As the plant grows, you should have more surface area available in the root zone so most people will want to make some changes as you push through various stages of growth (each phase will have different demands for nutrients). For most of my grow, I have been using a 5 second on and 5 minute off cycle. This is pretty common but I believe most people are unaware of many variables out there like the number of misters, the flow rate of those misters, number of plants being fed, appetite for those specific plants, etc... In my example,, 5 seconds on is about 23ml but that is unique to my specific hardware and configuration whereas you may need more or less depending on yours. I am confident we can benefit from zeroing in on optimal levels but how do we do this? I really don't know, but below is the best solution I have found for moving in the right direction.
Once you have a starting point and you feel like your plants are at least looking healthy, it is time to see if you can zero in on the optimal needs for your specific environment. I did this by monitoring both the waste EC levels and the overall consumption by the plant. In my case, it may be a little easier as I have only one plant so the math is basic. I have weeks of logged journals that tell me exactly how much nutrient solution my plant consumes (and I have zero evaporation) so this can be calculated easily by documenting the levels in your reservoir at various points in time. If you are using a drain to waste solution, consider draining to a second stage reservoir where you can make some calculations before you dispose of it.
Remember, everyone will have different numbers so don't use mine; yours will be different. I have one Northern Lights Autoflower that is in week 8 of flower so I have plenty of data collected from the grow to help me feel confident that my plant is consuming 1.25 gal (4721ml) daily (at this phase). This has been very consistent for the last 2 weeks of growth but remember this would change when transitioning from seedling to veg, and then to flower. So now I know how much nutrient is being consumed so the next piece of the puzzle is to understand how much you are delivering to the plant. If you have specs for your pump/nozzles you may be able to use documented numbers but my recommendation is the take your own measurements and do this often to identify trends or changes over time. You can even diagnose a clogged nozzle without ever looking in the root chamber if your measurements are precise.
I did this by removing my nutrient reservoir return line from the root chamber and turned on my misters. I left them on long enough to essentially get a steady stream coming out of the root chamber return line. You want this to be steady so give it time to stabilize and then use a small jar to collect the run-off for a 10 second interval. Take a couple of samples and average them for an overall flow rate. Mine was 45ml/10 seconds. This equates to 4.5ml/second. Now, make some calculations using your current timer settings to determine how much nutrient you are spaying on the plant over a 24 hour time period. A simple formula is (86400/<off timing in seconds>*amount of ml delivered during the <on timing cycle>). This should give you the total nutrient delivered in 24 hrs. Using this data along with your actual quantity returning to your reservoir will tell if how much your plant is absorbing .vs how much you are delivering. In my case, I was delivering 25% more nutrient than the plant was consuming.
This is where I think things get a little interesting. Most of our hydro guys out there will say no bid deal, it returns to the reservoir to be reused on another cycle right? I have to say no, and I believe this because there is a big difference between aeroponics and DWC even though both are classified as a hydroponic solution. The concept of aeroponics is to provide a very specific amount of moisture to the roots. If you exceed this amount, I personally believe you are drifting towards the efficiency zone of a hydroponic style grow (to a degree that can be argued). If you are getting enough moisture to allow it to combine and drip down the root structure, that is too much and the reason why I believe we see the standard "fishbone" style of photos of roots. With that in mind, my plant was only able to absorb 75% of what was coming out of the misters. That other 25% is doing exactly what I don't want - it is combining with other moisture molecules and forming a droplet that is running down the root structure to drain. I believe on a macro level this is limiting the amount of oxygen the roots can absorb and limiting your plants potential. That is what we are talking about here right? - POTENTIAL.
To close on this, I used all the data referenced above and reduced the total amount of nutrients delivered (in a 24 hr. period) by 20% and at the same time made some new calculations to deliver that quantity evenly over the 24 hour time period so this means I reduced my mister on time and also reduced my off time but made sure the overall numbers still give the plant what it needs over the time period. The result: My plant still consumes 1.25 gal. but with my new timer settings the plant is now consuming 95% of what is coming out of the sprayers. I do not want to skirt the line too close just yet but I am planning on seeing how close I can get and observing the impact it has on the plant. My best guess is that it is more efficient and should unlock more potential from the plant.
I will be the first to say this is totally experimental, I wish it was as easy as someone giving me numbers to use but this is the best I can come up with to zero in on the best timer cycles for my specific conditions. Don't forget, your numbers will be totally different so you can't use mine. You have to make your own calculations but I can say this. After making the changes I referenced I can see a significant change in my plants growth and appearance (even this late in flower) - I have brand new buds popping out the top of my current buds. This is all in the last 24 hours! I wish I had considered some of this theory earlier but I am new and this is my first attempt at something like this so take the information with a grain of salt and apply what is helpful and discard the rest.
Here are some pics of where she sits today but not much overall change from recent photos...
