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fatman
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Myth Free Water Nutrient Temperature Level Information
:fixed:
This write up is on chemical nutrients systems not organic nutrient systems or a hydro system using organic growing media.
Oxygen is an essential plant nutrient – plant root systems require oxygen for aerobic respiration, an essential plant process that releases energy for root growth and nutrient uptake. In many water-based hydroponic systems, (non medium pressure, or high pressure or air atomized aero) the oxygen supplied for plant root uptake is provided mostly as dissolved oxygen (DO) present in the nutrient solution.
Oxygen requirements for plants in flower tend to be more demanding in comparison to vegetative states. This is due to the size of the root system, temperature, and nutrient uptake rates, not the specific stage of growth.
Injury from low (or no) oxygen in the root zone can take several forms. Often the first sign of inadequate oxygen supply to the roots is wilting of the plant under warm conditions and high light levels. This however is not as a result of high water temps or low levels of DO. It is simply due to inadequate transpiration. This is most commonly due to an excessively high humidity in the growing area. Plants do not transpire if the air around them is at a high humidity level. Their stomata close and they quit transpiring and no water or nutrients are taken up by the roots so no oxygen is taken up. The closed stomata also causes respiration to stop. The solution for this is ventilation or preferably dehumidification, not higher DO or lower reservoir temperature or even lower growing temperatures.
Faster growth is achieved at higher temperatures as long as the humidity is not excessive, lighting is intense emough, CO2 levels are adequate and the nutrition delivery system is well designed and operated.
Insufficient oxygen reduces the permeability of the roots to water and there will be an accumulation of toxins, so that both water and minerals are not absorbed in sufficient amounts to support plant growth.
While it is possible to measure the levels of dissolved oxygen in a hydroponic nutrient solution, it is not carried out as often as EC/ppm or pH monitoring due to the cost of accurate DO meters. However, if an effective method of aeration is continually being used then good levels of oxygenation can be achieved without trouble.
A good aero system delivering a quality spray or properly sized water droplet size mist need not have an aeration system as long as a DO level of 2 ppm or so is present in its feed reservoir.
Most growers are familiar with the need to have some sort of aeration in their nutrient solution due to waters high surface tension – whether they are in a recirculating water-based or media-based system. However, the effect of temperature of the solution on the DO levels and on root respiration rates also needs to be taken into account. As the temperature of your nutrient solution increases, the ability of that solution to hold DO decreases. For example, the oxygen content of an aerated solution at 50 F (10 C) is about 13 ppm, but as the solution warms up to 68 F (20 C) the ability of the liquid to ‘hold’ oxygen drops to 9-10 ppm. By the time the solution has reached 86 F (30 C) it is only 7.5 ppm. While this may not seem like a huge drop in the amount of DO, we have to remember that as the temperature of the root system warms, the rate of respiration of the root tissue also increases and more oxygen is required by the plant. However, even this not not support the continula DO mhyths in mj growing forums and those posted by Hydro growing retal sites.
For example, the respiration rate of the roots will double for each 10 C rise in temperature up to 86 F (30 C). But we need consider the DO requirement is less than 2 ppm at even 76 F. So the situation can develop where the solution temperature increases from 68-86 F (20-30 C) during the day, with a mature crop, then the requirement for oxygen will double while the oxygen carrying capacity of the solution will drop by 25%. This means that the DO in solution will be much more rapidly depleted and then plants can suffer from oxygen starvation (root rot) for a period of time. But we must understand that this only applies to old style poorly designed and constructed growing systems all roots do not have frequent or constant (DWC) contact with water that is fully saturated. Old MYTHS are based upon old designs.
Lets look at new design systems.
A medium pressure aero, a high pressure aero or an air atomized aero in deep tubes or a deep chamber at say 37 degrees C. With water at 37 degrees C. First consider they reservoir is filled with chemical nutrients with a residual level of 0.5 ppm of chlorine to prevent bacteria/enzymes/pathogens, therefore DO levels in the reservior is not an issue. A finely atomized spray actually over saturates the nutrients water delivered to the plants roots. All the roots are in air so all receive at a minimum water that is fully saturated with DO. Now realize that even 2 ppm of DO is more than adequate at 78.6 degrees F We increase that temp to 98.6 F, so the DO requirement becomes 8 ppm and the DO is not delivered at a mere saturation level of 7 ppm but an over saturation level nearer 10 ppm.
So consider this: The real issue is can your system deliver water saturated with DO to “all the roots.” Most systems are poor designs that only supply adequate DO to a portion of the roots as all roots do not receive the same flow of fresh water over them but instead receive a flow of water where most of the DO was stripped by the roots previously in contact with the roots. When this is the case a larger percentage of the roots get inadequate oxygen at standard lower operating temps yet alone higher temps. IE it is s design problem rather that a DO problem.
Perhaps one of the commonest problems in hydroponic systems is the Pythium pathogen. What many growers do not realize is that Pythium, being an “opportunist” fungi, often takes advantage of plants which have been stressed/killed by oxygen starvation in the root zone. Pythium is usually described as a “secondary infection” meaning that the Pythium spores that are actually common in just about all hydroponic systems, don't actually attack the plant until it has been damaged in some way. Pythium is everywhere, so the best defense is a healthy plant. However Pythium can be eliminated from your systems water and kept from reestablishing in your system with use of chlorine. Pythoff sold by Flairform is merely dilute chlorine. Chlorine as a standard is used in the majority of commercial hydroponic green house systems at all times. Yes, Flairform sells a "commercial" Pythoff that use Chloroamine instead of just chlorine. Chloroamine is a mixture of ammonia and hydrochlorous acid from chlorine added to water. Chloroamine does not dissipate as quickly as chlorine.
What needs to be remembered is that adequate DO levels must be maintained for the plant roots use as well as the levels of bacteria you allow to grow in your system. Bacterial levels varies greatly depending on the temperature you maintain in your nutrient reservoir and throughout your whole growing system that has contact with the nutrient solution at any time. At high temps and high DO high levels of beneficial bacteria are present, along with their accompanying enzymes. At high temps and low DO high levels of non beneficial bacteria in great numbers are present. Chemical hydroponic nutrient systems containing no organics or organic supplements supplying nutrition to inert or no growing media have the advantage that no bacteria or enzymes needed be present in the nutrient water. This absence of non needed/undesirable bacterias/pathogens and enzymes and can readily be accomplished through use of Chlorox or hydrogen peroxide.
Adequate system solution DO can be very easily maintained and this is simply accomplished. A healthy plant is the best measure of protection against a disease outbreak. This is not an issue of water temps or reservoir DO at high levels but an issue of proper delivery of water with adequate DO to all roots at a level that root health is maintained. You can have a reservoir supersaturated with DO, but if the plants roots in their entirety are not always or frequently in contact with the water containing DO the plants will not receive adequate oxygen.
Oxygenation and Nutrient Uptake
Healthy roots supplied with sufficient oxygen are able to absorb nutrient ions selectively from the surrounding solution as required. The metabolic energy which is required to drive this nutrient uptake process is obtained from root respiration using oxygen. In fact there can be a net loss of nutrient ions from a plant’s root system when suffering from a lack of oxygen (anaerobic conditions). Without sufficient oxygen in the root zone, plants are unable to take up mineral nutrients in the concentrations required for maximum growth and development. Maintain maximum levels of dissolved oxygen boosts nutrient uptake by ensuring healthy roots have the energy required to rapidly take up and transport water and mineral ions.
Calcium is one important nutrient ion which has been shown to benefit from high levels of oxygenation in the hydroponic nutrient solution. Calcium, unlike the other major nutrients is absorbed mostly by the root growing tips (root apex). The root apex has a large energy requirement for new cell production and growth and is therefore vulnerable to oxygen stress. If root tips begin to suffer from a lack of oxygen, a shortage of calcium in the shoot will occur. This shortage of calcium makes the development of a calcium disorder such as tip burn more likely and severe under oxygen starvation conditions. High levels of oxygenation ensure healthy root tips are able to take the levels of calcium required for new tissue growth and development.
:fixed:
This write up is on chemical nutrients systems not organic nutrient systems or a hydro system using organic growing media.
Oxygen is an essential plant nutrient – plant root systems require oxygen for aerobic respiration, an essential plant process that releases energy for root growth and nutrient uptake. In many water-based hydroponic systems, (non medium pressure, or high pressure or air atomized aero) the oxygen supplied for plant root uptake is provided mostly as dissolved oxygen (DO) present in the nutrient solution.
Oxygen requirements for plants in flower tend to be more demanding in comparison to vegetative states. This is due to the size of the root system, temperature, and nutrient uptake rates, not the specific stage of growth.
Injury from low (or no) oxygen in the root zone can take several forms. Often the first sign of inadequate oxygen supply to the roots is wilting of the plant under warm conditions and high light levels. This however is not as a result of high water temps or low levels of DO. It is simply due to inadequate transpiration. This is most commonly due to an excessively high humidity in the growing area. Plants do not transpire if the air around them is at a high humidity level. Their stomata close and they quit transpiring and no water or nutrients are taken up by the roots so no oxygen is taken up. The closed stomata also causes respiration to stop. The solution for this is ventilation or preferably dehumidification, not higher DO or lower reservoir temperature or even lower growing temperatures.
Faster growth is achieved at higher temperatures as long as the humidity is not excessive, lighting is intense emough, CO2 levels are adequate and the nutrition delivery system is well designed and operated.
Insufficient oxygen reduces the permeability of the roots to water and there will be an accumulation of toxins, so that both water and minerals are not absorbed in sufficient amounts to support plant growth.
While it is possible to measure the levels of dissolved oxygen in a hydroponic nutrient solution, it is not carried out as often as EC/ppm or pH monitoring due to the cost of accurate DO meters. However, if an effective method of aeration is continually being used then good levels of oxygenation can be achieved without trouble.
A good aero system delivering a quality spray or properly sized water droplet size mist need not have an aeration system as long as a DO level of 2 ppm or so is present in its feed reservoir.
Most growers are familiar with the need to have some sort of aeration in their nutrient solution due to waters high surface tension – whether they are in a recirculating water-based or media-based system. However, the effect of temperature of the solution on the DO levels and on root respiration rates also needs to be taken into account. As the temperature of your nutrient solution increases, the ability of that solution to hold DO decreases. For example, the oxygen content of an aerated solution at 50 F (10 C) is about 13 ppm, but as the solution warms up to 68 F (20 C) the ability of the liquid to ‘hold’ oxygen drops to 9-10 ppm. By the time the solution has reached 86 F (30 C) it is only 7.5 ppm. While this may not seem like a huge drop in the amount of DO, we have to remember that as the temperature of the root system warms, the rate of respiration of the root tissue also increases and more oxygen is required by the plant. However, even this not not support the continula DO mhyths in mj growing forums and those posted by Hydro growing retal sites.
For example, the respiration rate of the roots will double for each 10 C rise in temperature up to 86 F (30 C). But we need consider the DO requirement is less than 2 ppm at even 76 F. So the situation can develop where the solution temperature increases from 68-86 F (20-30 C) during the day, with a mature crop, then the requirement for oxygen will double while the oxygen carrying capacity of the solution will drop by 25%. This means that the DO in solution will be much more rapidly depleted and then plants can suffer from oxygen starvation (root rot) for a period of time. But we must understand that this only applies to old style poorly designed and constructed growing systems all roots do not have frequent or constant (DWC) contact with water that is fully saturated. Old MYTHS are based upon old designs.
Lets look at new design systems.
A medium pressure aero, a high pressure aero or an air atomized aero in deep tubes or a deep chamber at say 37 degrees C. With water at 37 degrees C. First consider they reservoir is filled with chemical nutrients with a residual level of 0.5 ppm of chlorine to prevent bacteria/enzymes/pathogens, therefore DO levels in the reservior is not an issue. A finely atomized spray actually over saturates the nutrients water delivered to the plants roots. All the roots are in air so all receive at a minimum water that is fully saturated with DO. Now realize that even 2 ppm of DO is more than adequate at 78.6 degrees F We increase that temp to 98.6 F, so the DO requirement becomes 8 ppm and the DO is not delivered at a mere saturation level of 7 ppm but an over saturation level nearer 10 ppm.
So consider this: The real issue is can your system deliver water saturated with DO to “all the roots.” Most systems are poor designs that only supply adequate DO to a portion of the roots as all roots do not receive the same flow of fresh water over them but instead receive a flow of water where most of the DO was stripped by the roots previously in contact with the roots. When this is the case a larger percentage of the roots get inadequate oxygen at standard lower operating temps yet alone higher temps. IE it is s design problem rather that a DO problem.
Perhaps one of the commonest problems in hydroponic systems is the Pythium pathogen. What many growers do not realize is that Pythium, being an “opportunist” fungi, often takes advantage of plants which have been stressed/killed by oxygen starvation in the root zone. Pythium is usually described as a “secondary infection” meaning that the Pythium spores that are actually common in just about all hydroponic systems, don't actually attack the plant until it has been damaged in some way. Pythium is everywhere, so the best defense is a healthy plant. However Pythium can be eliminated from your systems water and kept from reestablishing in your system with use of chlorine. Pythoff sold by Flairform is merely dilute chlorine. Chlorine as a standard is used in the majority of commercial hydroponic green house systems at all times. Yes, Flairform sells a "commercial" Pythoff that use Chloroamine instead of just chlorine. Chloroamine is a mixture of ammonia and hydrochlorous acid from chlorine added to water. Chloroamine does not dissipate as quickly as chlorine.
What needs to be remembered is that adequate DO levels must be maintained for the plant roots use as well as the levels of bacteria you allow to grow in your system. Bacterial levels varies greatly depending on the temperature you maintain in your nutrient reservoir and throughout your whole growing system that has contact with the nutrient solution at any time. At high temps and high DO high levels of beneficial bacteria are present, along with their accompanying enzymes. At high temps and low DO high levels of non beneficial bacteria in great numbers are present. Chemical hydroponic nutrient systems containing no organics or organic supplements supplying nutrition to inert or no growing media have the advantage that no bacteria or enzymes needed be present in the nutrient water. This absence of non needed/undesirable bacterias/pathogens and enzymes and can readily be accomplished through use of Chlorox or hydrogen peroxide.
Adequate system solution DO can be very easily maintained and this is simply accomplished. A healthy plant is the best measure of protection against a disease outbreak. This is not an issue of water temps or reservoir DO at high levels but an issue of proper delivery of water with adequate DO to all roots at a level that root health is maintained. You can have a reservoir supersaturated with DO, but if the plants roots in their entirety are not always or frequently in contact with the water containing DO the plants will not receive adequate oxygen.
Oxygenation and Nutrient Uptake
Healthy roots supplied with sufficient oxygen are able to absorb nutrient ions selectively from the surrounding solution as required. The metabolic energy which is required to drive this nutrient uptake process is obtained from root respiration using oxygen. In fact there can be a net loss of nutrient ions from a plant’s root system when suffering from a lack of oxygen (anaerobic conditions). Without sufficient oxygen in the root zone, plants are unable to take up mineral nutrients in the concentrations required for maximum growth and development. Maintain maximum levels of dissolved oxygen boosts nutrient uptake by ensuring healthy roots have the energy required to rapidly take up and transport water and mineral ions.
Calcium is one important nutrient ion which has been shown to benefit from high levels of oxygenation in the hydroponic nutrient solution. Calcium, unlike the other major nutrients is absorbed mostly by the root growing tips (root apex). The root apex has a large energy requirement for new cell production and growth and is therefore vulnerable to oxygen stress. If root tips begin to suffer from a lack of oxygen, a shortage of calcium in the shoot will occur. This shortage of calcium makes the development of a calcium disorder such as tip burn more likely and severe under oxygen starvation conditions. High levels of oxygenation ensure healthy root tips are able to take the levels of calcium required for new tissue growth and development.
