Dr.Dutch
Well-known member
Ah, here you have a report, very nice.
You know my plants—3.5L (1 gallon) pots in coco/perlite. And even then, they’re only watered once, maybe twice a day during peak bloom.
It's bro-science that we need to water coco more frequently. It retains less "dead water" than peat, meaning more of the available water is accessible to the plants compared to peat. Drying down to about 30% or so isn’t an issue; the plants still have enough water.
I ditched high-frequency fertigation as nonsense over a year ago.
You can read about this kind of stuff, for example, on cocoforcannabis com (bullshit side).
Nutrients can be divided into three uptake categories: active, intermediate, and passive (Table 3). Nutrients with active uptake are rapidly removed from solution, and frequent replenishment can result in excessive uptake [48]. Nutrients with passive uptake are taken up at the same rate as water, and their concentrations remain close to their initial level [49]. Nutrients with intermediate uptake can be taken up faster than water but at lower rates than those with active uptake.
Table 3. Uptake strategies of essential plant nutrients.
An understanding of uptake rate is essential for interpreting the concentration of nutrients in solution [2]. Nutrients with active uptake are typically at extremely low levels, even with high concentrations in the refill solution. This indicates a healthy, actively growing crop. The appropriate nutrients are added with the refill solution.
Bugbee [2] appears to be the first to include Mn among the nutrients with active uptake, but its rapid uptake has not been widely reported. The active uptake of Mn is based on its rapid disappearance from solution and the resulting high concentration in leaf tissue. Castaings et al. [50] indicated that active Mn2+ uptake may be accomplished by the transporter IRT1. Mn uptake and acquisition were recently reviewed by Alejandro et al. [40].
Mn availability increases as pH decreases. The concentration of Mn must be maintained at low levels in the root zone to avoid toxic levels in the leaf tissue. Multiple studies have found Mn levels above 500 mg kg−1 (500 ppm) in leaf tissue [51,52], which is associated with necrotic lesions on the leaves. Maintaining a root-zone pH of 6 to 6.5 can minimize Mn toxicity.
Figure 3. pH over time in two systems. The system represented by the red line was controlled with a pH control solution containing only nitric acid. The system represented by the blue line was controlled by a solution containing a 2:1 ratio of nitric acid and ammonium sulfate (see Section 11.3). The ammonium was added in micromolar amounts with the nitric acid and did not exceed 10 µM in solution. Simultaneous uptake of nitrate and ammonium resulted in steady pH. Sharp pH dips are localized pH during acid injection and do not represent the pH of the bulk solution. Plant uptake of nitrogen is reduced during the night because of reduced root metabolism and there is minimal change in pH.
Excessive uptake of ammonium can inhibit the uptake of other cations. For this reason, maintaining ammonium at consistent low levels usually results in balanced nutrient uptake and optimal growth.
Excessive NH4+ in solution can decrease pH below 4 (Figure 4), which causes increased solubility of metals in soilless media, resulting in excessive uptake and potential toxicity. The pH typically increases due to predominance of NO3− uptake after the NH4+ has been absorbed. For most crops, including lettuce, tomato, wheat, and petunia, the NO3− to NH4+ ratio in the hydroponic solution must be at least 20:1 to avoid decreasing pH.
Figure 4. pH changes in lettuce grown with 100% nitrate (NO3−, red line) and ample NO3− but excess ammonium (about 0.1 mM ammonium, NH4+, blue line). The system with 100% NO3− did not increase above pH 5.8 because pH was automatically controlled to prevent increasing pH with nitric acid. Neither system had automated control to prevent decreasing pH. The pH in the high-ammonium system started to increase on day 17 after the NH4+ was depleted and uptake was all from NO3−.
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Yes, you can't overwater coco. But you can mess up the nutrient balance.watered to run off 3x per light cycle! My hopes are always to get them to 8x light cycle by week 5. There are a ton of variables that go into the COCO DTW small pots including all of my above faults that dictate if the plants will need 5 or want 10 waterings per day and only runs under your belt will teach you this. Not a podcast not a book not a fellow grower experience trumps everything you read, listen to, or watch!
Pro tip!
If you have read this far and understand that you cannot overwater small pots of coco once they are root bound and if you learn how to run salts properly you can unnecessarily water 10 extra times per day and besides the water waste the nutrient cost would not be 20 cents more per day!
You know my plants—3.5L (1 gallon) pots in coco/perlite. And even then, they’re only watered once, maybe twice a day during peak bloom.
It's bro-science that we need to water coco more frequently. It retains less "dead water" than peat, meaning more of the available water is accessible to the plants compared to peat. Drying down to about 30% or so isn’t an issue; the plants still have enough water.
I ditched high-frequency fertigation as nonsense over a year ago.
You can read about this kind of stuff, for example, on cocoforcannabis com (bullshit side).
3. Differential Rates of Nutrient Uptake
Frequent monitoring of individual nutrients in solution is often recommended, but the need for monitoring can be minimized by deriving a refill solution using the mass balance principles. Monitoring approaches usually attempt to maintain the concentration of each nutrient in solution. However, rapidly growing plants are hungry for nutrients with active uptake. They will continue absorbing nutrients with no sense of when to stop. If the nutrient concentration is maintained at initial levels, the plant will continue absorbing them, sometimes to toxic levels [45]. Loneragan et al. [46] found that excess phosphorus (P) can induce deficiencies in other nutrients, such as iron (Fe) and zinc (Zn). Parry and Bugbee [47] found excessive P in nutrient solutions can also precipitate Fe, even with ample Fe chelation.Nutrients can be divided into three uptake categories: active, intermediate, and passive (Table 3). Nutrients with active uptake are rapidly removed from solution, and frequent replenishment can result in excessive uptake [48]. Nutrients with passive uptake are taken up at the same rate as water, and their concentrations remain close to their initial level [49]. Nutrients with intermediate uptake can be taken up faster than water but at lower rates than those with active uptake.
Table 3. Uptake strategies of essential plant nutrients.

An understanding of uptake rate is essential for interpreting the concentration of nutrients in solution [2]. Nutrients with active uptake are typically at extremely low levels, even with high concentrations in the refill solution. This indicates a healthy, actively growing crop. The appropriate nutrients are added with the refill solution.
Bugbee [2] appears to be the first to include Mn among the nutrients with active uptake, but its rapid uptake has not been widely reported. The active uptake of Mn is based on its rapid disappearance from solution and the resulting high concentration in leaf tissue. Castaings et al. [50] indicated that active Mn2+ uptake may be accomplished by the transporter IRT1. Mn uptake and acquisition were recently reviewed by Alejandro et al. [40].
Mn availability increases as pH decreases. The concentration of Mn must be maintained at low levels in the root zone to avoid toxic levels in the leaf tissue. Multiple studies have found Mn levels above 500 mg kg−1 (500 ppm) in leaf tissue [51,52], which is associated with necrotic lesions on the leaves. Maintaining a root-zone pH of 6 to 6.5 can minimize Mn toxicity.
3.1. Uptake of Nitrate and Ammonium
N is taken up from solution faster than the sum of all other nutrients [53,54], and it is the only nutrient taken up as both a cation (ammonium, NH4+) and anion (nitrate, NO3−) [55]. The uptake of these two ions alters pH due to the principle of charge balance [33]. NO3− uptake causes hydroxide ions to be released (or protons to be absorbed), which raises the pH. NH4+ uptake releases protons, which lowers the pH. It is possible to stabilize pH by controlling the concentration of these two ions in solution (Figure 3), but NH4+ is taken up 100 to 1000 times faster than NO3− [56], and an elevated concentration of NH4+ thus causes a rapid pH decrease [57]. With most species, we have found that the NH4+ concentration must be maintained at micromolar concentrations with millimolar concentrations of NO3− to stabilize pH in systems without a solid substrate. NH4+ must be added in frequent small amounts in liquid hydroponic solutions that have low buffering capacity.
Figure 3. pH over time in two systems. The system represented by the red line was controlled with a pH control solution containing only nitric acid. The system represented by the blue line was controlled by a solution containing a 2:1 ratio of nitric acid and ammonium sulfate (see Section 11.3). The ammonium was added in micromolar amounts with the nitric acid and did not exceed 10 µM in solution. Simultaneous uptake of nitrate and ammonium resulted in steady pH. Sharp pH dips are localized pH during acid injection and do not represent the pH of the bulk solution. Plant uptake of nitrogen is reduced during the night because of reduced root metabolism and there is minimal change in pH.
Excessive uptake of ammonium can inhibit the uptake of other cations. For this reason, maintaining ammonium at consistent low levels usually results in balanced nutrient uptake and optimal growth.
Excessive NH4+ in solution can decrease pH below 4 (Figure 4), which causes increased solubility of metals in soilless media, resulting in excessive uptake and potential toxicity. The pH typically increases due to predominance of NO3− uptake after the NH4+ has been absorbed. For most crops, including lettuce, tomato, wheat, and petunia, the NO3− to NH4+ ratio in the hydroponic solution must be at least 20:1 to avoid decreasing pH.

Figure 4. pH changes in lettuce grown with 100% nitrate (NO3−, red line) and ample NO3− but excess ammonium (about 0.1 mM ammonium, NH4+, blue line). The system with 100% NO3− did not increase above pH 5.8 because pH was automatically controlled to prevent increasing pH with nitric acid. Neither system had automated control to prevent decreasing pH. The pH in the high-ammonium system started to increase on day 17 after the NH4+ was depleted and uptake was all from NO3−.

Principles of Nutrient and Water Management for Indoor Agriculture
Mass balance principles are a cornerstone of efficient fertilizer use and can be utilized to optimize plant nutrition without discarding or leaching solution. Here, we describe the maintenance of closed hydroponic and soilless substrate systems based on mass balance. Water removed by...
