CannaStats - Control Track
One reason many indoor gardeners decide to grow with hydroponics is to relieve themselves of the time consuming manual chores associated with watering plants. Automated irrigation has a strong attraction, but not many beginners realize that tradeoffs are involved and often find themselves swapping one maintenance chore for another unanticipated chore. Being freed from the chores of checking plants to see when they need to be watered, and from the actual watering when that time comes, is indeed a welcome time savings anyone can appreciate. However, aside from the time saved performing those chores, does your new schedule really give you any free time you can spend doing other things besides tending to your garden? Not surprisingly, for many people the answer is.... no!
The time tradeoffs for eliminating the need to check and water plants manually is the maintenance involved in seeing that the hydroponic nutrient solution remains fit for the plants to use. Many find soon enough that the fitness of their nutrient solution isn't a static unchanging entity, but rather a moving target that constantly changes positions throughout the entire day-to-day life cycle of the crop. The pH and TDS maintenance of the nutrient solution often unnecessarily keeps hydroponic gardeners captive to their systems. For those who had expectations of freeing up their time, this maintenance often becomes an unanticipated ball & chain. A ball & chain for one gardener can be a welcome opportunity for another to tinker with some new toys, however, in the end, the difference is only one of endurance. Sooner or later the joys of tinkering with meters and solutions wears off and evolves into the humdrum routines we call work. This article is meant for those who can admit they have a ball & chain, and for those who want to put some direction behind their tinkering so they have a handle on reservoir maintenance when the ball & chain are eventually noticed.
Having the ability to predict pH/TDS changes in your nutrient solution is a means of extending your free time away from the garden by reducing those uncertainties that keep you tied to it. To say the least, pH is the most elusive item we need to test for in hydro systems, with TDS being next in line. Through tracking pH/TDS changes, one is able to effectively predict where the pH/TDS will be at any point in the life of a nutrient solution. It should go without saying that anyone reading this article has a unique situation on his hands. Every indoor garden has things about it that make it different from other indoor gardens, this is especially true of hydroponic gardens. Your environment, your choice of nutrients, and your source water all come together to serve you with your own custom brand of required nutrient solution maintenance. This article will show you how to use your environment, your nutrients, and especially your source water, to your advantage. Instead of allowing those variables to control you and put you at a disadvantage, you will learn how to control them by anticipating their next move and be better able to predict where those moving targets known as pH and TDS will be at any given time.
Before one can predict, one must first track a solution to record its habits. This is the control track by which future solutions will be compared, predicted, or formulated.
First I should mention a few things that contribute to the accuracy of the control track when it's applied to the nutrient solution it will be predicting:
Source water is an eternal variable, especially if you use tap water or well water. It can be one of the most influential factors on the life of your nutrient solution and how it behaves. You should know if your water supply is reasonably consistent, and be aware that seasonal changes are not at all unusual. Seasonal changes can affect predictability to some degree, but usually it's a small one. Always test your source water pH/TDS before mixing in the nutrients so you will be alerted to any appreciable departure from your norm. When you know your source water it can be used to your advantage instead of fighting against its influences.
Environment - If the lighting, reservoir capacity, canopy size, or other environmental factors change, and are much different from those used when the control track was created, the effective predictability of the control track will be compromised. These factors can affect the pH/TDS in profound ways.
Species - I can't say if, or how much, the plant variety (same species) would affect predictability if all other factors where the same. My observations so far say, if it does it's not much at all to be concerned about. For example, different tomato varieties would have similar nutritional needs. However, because different species often have unique nutritional requirements, I wouldn't use a control track for one species with another without first investigating the possible differences.
Substrate - Because there is always some old solution remaining in the growing media during a reservoir solution replacement, I try to end a solution's life close to the pH & TDS of what the new solution will be. I do this because the solution left in the substrate during a reservoir change, if it's much different from the newly mixed solution, can affect the pH/TDS outcome of the new solution once the first irrigation has mixed the two together then drained back into the reservoir. The degree to which it would affect the outcome would depend on the amount of medium you use, its solution holding properties, and the capacity of the reservoir. Examples of two extremes would be a system using a handful of grow rocks or one 4 inch rockwool cube for each plant, versus a system that grows plants in large rockwool slabs.
Predictability is based on using the control track for the same nutrient formula mix, and for a given stage of growth. The stage of growth is the prime moving target, for it drives the changes taking place in the nutrient solution. For example, the formula mix used in one of the examples below was mixed from General Hydroponics Flora Series components using 6.0 Micro/10.0 Bloom/2.0 Grow (ml/US gallon). The stage of growth is the 4th thru 7th week of induction (days 47 thru 68), and with a full canopy. If the same formula is used on successive crops at that stage of growth the control track will be the same, with all other things mentioned above being equal. It it were used starting on day 7 the control track would be completely different.
This method of using a control track is best suited for those who endeavor to grow with the same system (lights, nutrients, canopy size, etc.) over an extended period of time, and find predictability a definite advantage to have from crop to crop. Highly evolving gardens undergoing constant major changes from one crop to the next will need new controls when changes occur. Having said that, it should be apparent that this method would appeal to the more experienced hydroponic gardener who, through trial and error, has finally arrived at the garden configuration and hardware that best meets his needs.
The only difference between a control track and what you probably do now is that it entails recording daily pH/TDS tests. The end result is to be able to go for long periods of time without taking solution tests because you'll know what pH/TDS will be from the control track. I'm in the habit of taking daily pH/TDS tests of the solution mainly because I'm often experimenting with different mixes to find ways to manipulate pH to my advantage (more on that later). But when I plan to be elsewhere for an extended period of time (vacations, long weekends, etc) I use a mix I can predict from a control track, and it works very well.
I was convinced of the efficacy of control tracks when I went on a 10 day vacation during the time when a crop's peak water uptake was approaching. Knowing from previous crops that approximately 1.25 gallons per day would be used while I was away, I asked a friend to stop by only once during my absence, on the fifth day, with instructions to simply fill the reservoir up to the full line with plain tap water. To make things easy, I had 7 sealed gallon jugs prepared for her to use. When I returned on the 11th day, the reservoir needed 6 gallons (only 1/4 gallon from predicted), pH was just -0.02 from predicted, and TDS was +35 ppm from predicted. At one time, I never would have dreamed that a non-technical friend would be able to maintain my reservoir without knowing how to use a pH meter or make pH adjustments. Predictability paid off very well.
Control tracks can also provide other benefits. They allow you to actually see how the pH/TDS is affected by the addition or deletion of certain nutrients, not just at the time they're mixed into the solution, but over the next few days. This is apparent with the General Hydroponics Flora Series three part formula because it allows one the flexibility to manipulate the nutrient configuration and pH behavior in delicate ways. A benefit is that the nutrients can be used to control or adjust pH as well as to add back depleted nutrients, as is the case in one of the below examples. Also, when your growing environment does change substantially, rerunning a control track taken while the old environment was in place will give you a clue to the subtle differences occurring in the new environment because of that change.
One reason many indoor gardeners decide to grow with hydroponics is to relieve themselves of the time consuming manual chores associated with watering plants. Automated irrigation has a strong attraction, but not many beginners realize that tradeoffs are involved and often find themselves swapping one maintenance chore for another unanticipated chore. Being freed from the chores of checking plants to see when they need to be watered, and from the actual watering when that time comes, is indeed a welcome time savings anyone can appreciate. However, aside from the time saved performing those chores, does your new schedule really give you any free time you can spend doing other things besides tending to your garden? Not surprisingly, for many people the answer is.... no!
The time tradeoffs for eliminating the need to check and water plants manually is the maintenance involved in seeing that the hydroponic nutrient solution remains fit for the plants to use. Many find soon enough that the fitness of their nutrient solution isn't a static unchanging entity, but rather a moving target that constantly changes positions throughout the entire day-to-day life cycle of the crop. The pH and TDS maintenance of the nutrient solution often unnecessarily keeps hydroponic gardeners captive to their systems. For those who had expectations of freeing up their time, this maintenance often becomes an unanticipated ball & chain. A ball & chain for one gardener can be a welcome opportunity for another to tinker with some new toys, however, in the end, the difference is only one of endurance. Sooner or later the joys of tinkering with meters and solutions wears off and evolves into the humdrum routines we call work. This article is meant for those who can admit they have a ball & chain, and for those who want to put some direction behind their tinkering so they have a handle on reservoir maintenance when the ball & chain are eventually noticed.
Having the ability to predict pH/TDS changes in your nutrient solution is a means of extending your free time away from the garden by reducing those uncertainties that keep you tied to it. To say the least, pH is the most elusive item we need to test for in hydro systems, with TDS being next in line. Through tracking pH/TDS changes, one is able to effectively predict where the pH/TDS will be at any point in the life of a nutrient solution. It should go without saying that anyone reading this article has a unique situation on his hands. Every indoor garden has things about it that make it different from other indoor gardens, this is especially true of hydroponic gardens. Your environment, your choice of nutrients, and your source water all come together to serve you with your own custom brand of required nutrient solution maintenance. This article will show you how to use your environment, your nutrients, and especially your source water, to your advantage. Instead of allowing those variables to control you and put you at a disadvantage, you will learn how to control them by anticipating their next move and be better able to predict where those moving targets known as pH and TDS will be at any given time.
Before one can predict, one must first track a solution to record its habits. This is the control track by which future solutions will be compared, predicted, or formulated.
First I should mention a few things that contribute to the accuracy of the control track when it's applied to the nutrient solution it will be predicting:
Source water is an eternal variable, especially if you use tap water or well water. It can be one of the most influential factors on the life of your nutrient solution and how it behaves. You should know if your water supply is reasonably consistent, and be aware that seasonal changes are not at all unusual. Seasonal changes can affect predictability to some degree, but usually it's a small one. Always test your source water pH/TDS before mixing in the nutrients so you will be alerted to any appreciable departure from your norm. When you know your source water it can be used to your advantage instead of fighting against its influences.
Environment - If the lighting, reservoir capacity, canopy size, or other environmental factors change, and are much different from those used when the control track was created, the effective predictability of the control track will be compromised. These factors can affect the pH/TDS in profound ways.
Species - I can't say if, or how much, the plant variety (same species) would affect predictability if all other factors where the same. My observations so far say, if it does it's not much at all to be concerned about. For example, different tomato varieties would have similar nutritional needs. However, because different species often have unique nutritional requirements, I wouldn't use a control track for one species with another without first investigating the possible differences.
Substrate - Because there is always some old solution remaining in the growing media during a reservoir solution replacement, I try to end a solution's life close to the pH & TDS of what the new solution will be. I do this because the solution left in the substrate during a reservoir change, if it's much different from the newly mixed solution, can affect the pH/TDS outcome of the new solution once the first irrigation has mixed the two together then drained back into the reservoir. The degree to which it would affect the outcome would depend on the amount of medium you use, its solution holding properties, and the capacity of the reservoir. Examples of two extremes would be a system using a handful of grow rocks or one 4 inch rockwool cube for each plant, versus a system that grows plants in large rockwool slabs.
Predictability is based on using the control track for the same nutrient formula mix, and for a given stage of growth. The stage of growth is the prime moving target, for it drives the changes taking place in the nutrient solution. For example, the formula mix used in one of the examples below was mixed from General Hydroponics Flora Series components using 6.0 Micro/10.0 Bloom/2.0 Grow (ml/US gallon). The stage of growth is the 4th thru 7th week of induction (days 47 thru 68), and with a full canopy. If the same formula is used on successive crops at that stage of growth the control track will be the same, with all other things mentioned above being equal. It it were used starting on day 7 the control track would be completely different.
This method of using a control track is best suited for those who endeavor to grow with the same system (lights, nutrients, canopy size, etc.) over an extended period of time, and find predictability a definite advantage to have from crop to crop. Highly evolving gardens undergoing constant major changes from one crop to the next will need new controls when changes occur. Having said that, it should be apparent that this method would appeal to the more experienced hydroponic gardener who, through trial and error, has finally arrived at the garden configuration and hardware that best meets his needs.
The only difference between a control track and what you probably do now is that it entails recording daily pH/TDS tests. The end result is to be able to go for long periods of time without taking solution tests because you'll know what pH/TDS will be from the control track. I'm in the habit of taking daily pH/TDS tests of the solution mainly because I'm often experimenting with different mixes to find ways to manipulate pH to my advantage (more on that later). But when I plan to be elsewhere for an extended period of time (vacations, long weekends, etc) I use a mix I can predict from a control track, and it works very well.
I was convinced of the efficacy of control tracks when I went on a 10 day vacation during the time when a crop's peak water uptake was approaching. Knowing from previous crops that approximately 1.25 gallons per day would be used while I was away, I asked a friend to stop by only once during my absence, on the fifth day, with instructions to simply fill the reservoir up to the full line with plain tap water. To make things easy, I had 7 sealed gallon jugs prepared for her to use. When I returned on the 11th day, the reservoir needed 6 gallons (only 1/4 gallon from predicted), pH was just -0.02 from predicted, and TDS was +35 ppm from predicted. At one time, I never would have dreamed that a non-technical friend would be able to maintain my reservoir without knowing how to use a pH meter or make pH adjustments. Predictability paid off very well.
Control tracks can also provide other benefits. They allow you to actually see how the pH/TDS is affected by the addition or deletion of certain nutrients, not just at the time they're mixed into the solution, but over the next few days. This is apparent with the General Hydroponics Flora Series three part formula because it allows one the flexibility to manipulate the nutrient configuration and pH behavior in delicate ways. A benefit is that the nutrients can be used to control or adjust pH as well as to add back depleted nutrients, as is the case in one of the below examples. Also, when your growing environment does change substantially, rerunning a control track taken while the old environment was in place will give you a clue to the subtle differences occurring in the new environment because of that change.
