Reviewed December 2023
A recurring sequence specializing in plant cultivation by college researchers.
All vegetation require sure macro- and micronutrients to develop correctly and full their lifecycles. If considered one of these components is missing or overapplied, plant development issues and tissue injury will happen, each above and under floor. When making use of these mandatory components, you will need to hit the “sweet spot”—the optimum stage for every nutrient. But wanting on the total nutrient ranges in your crop can also be necessary. This is the place electrical conductivity (EC) is available in.
As we defined within the article, “Optimizing Electrical Conductivity (EC) in Cannabis Cultivation,” in Cannabis Business Times’ April 2019 problem, “EC is the electrical charge that moves through a solution. The higher the salt concentration, the greater the electrical reading. The higher the concentration of fertilizer salts in the solution or in the substrate, the higher the EC reading will be.” That article detailed how one can monitor and handle EC. While that’s important, your vegetation also can let you know when EC ranges are too excessive, and figuring out the warning indicators may help you diagnose excessive EC.
How to Test EC Levels
Most water-soluble fertilizers are comprised of a cation (ions that carry a optimistic cost of their pure state) and an anion (negatively charged ions). These ions will dissolve and disassociate in water, so to measure the EC stage with an EC meter, {an electrical} cost from two diodes should go via an answer. Like drawing traces from dot to dot, {the electrical} cost will “connect” fertilizer ion to fertilizer ion till it reaches the opposite diode.
While an EC studying will let you know what number of dissolved ions are in answer, it doesn’t establish every particular person component or the focus of every. For all vegetation, together with hashish, excessively excessive EC will end in plant injury (extra on this later).
Additionally, fertilization and irrigation strategies can affect the distribution and accumulation of the utilized fertilizer ions (Fig. 1).
With overhead or top-down irrigation, water motion within the pot will circulation downward to the underside of the container because of gravity, root uptake and evaporation occurring on the intersection of the substrate and air via the drainage holes. These three elements will trigger salt accumulation on the backside of the container, given that is the place water is evaporating and being taken up in its best portions. Thus, the foundation injury will probably be best within the decrease portion of the substrate in top-down irrigation.
A easy visible inspection of the roots may help you identify the place the best root injury has occurred. Roots which might be clear or clear are wholesome, whereas roots that seem tan or brown could also be broken. This rule usually applies to hashish vegetation of their youthful and vegetative states. Larger hashish vegetation and a few cultivars have darker roots, and bigger roots will typically be tan or brown because of lignification, or a pure hardening of cell partitions that happens in older vegetation. Root rot may even end in discolored roots.
The identical applies when irrigating from the underside or with sub irrigation, as properly, however is inverted. In sub irrigation or flood irrigation, the underside of the containers are flooded with a small amount of water. This water is then absorbed up into the pot via adhesion, cohesion, root uptake, evaporation and capillary motion. Thus, fertilizer salts will accumulate within the higher third of the foundation ball or under the media floor.
When EC injury is suspected when utilizing sub or flood irrigation, look at the roots within the higher third of the pot for discoloration.
Visual Symptoms of High EC
Symptoms of toxicity differ relying on crops’ age. We have described signs typically noticed by age under.
Initial Symptoms. High EC injury signs will first seem within the decrease leaves and within the new and increasing rising suggestions (Fig. 2, prime of this web page). Damage begins there as a result of method vitamins transfer throughout the plant. The ions with the best portions in a high-EC answer are usually nitrogen (N), phosphorus (P), and potassium (Okay). As the plant takes up extra water, it additionally takes up extra ions, that are dissolved in that answer. This is a helpful course of when vitamins are in stability; nevertheless, if the EC is just too excessive (i.e., there are too many dissolved ions), extreme tissue demise, or necrosis, will happen because of extreme uptake.
Younger and Expanding Leaves. As famous earlier, signs of excessive EC will first develop and seem within the new and increasing leaves. These leaves are sometimes discovered on new development, whether or not on the information, facet shoots, or inside branches, and at any stage. These areas are present process fast cell division and are absorbing loads of water to completely develop and broaden. Hence, these areas would be the first to indicate excessive EC signs. Symptoms which will floor amongst new development embrace light-green coloration, and the margin (outer edges) of the increasing leaflets will flip brown (Figs. 2 & 3). This browning and leaf margin demise will proceed based mostly on the severity of the toxicity or focus of accrued fertilizer salts (excessive EC). If the EC could be very excessive, then these signs will probably be very extreme, and the whole leaf rising tip could flip brown and die.
Leaf Margin. The older and expanded leaves may even develop signs based mostly on excessive EC stress. These signs could seem together with the brand new and increasing leaves, or they could seem barely after. Much just like the symptomology within the new and increasing leaves described on p. 26, the preliminary signs of excessive EC burn will seem on the leaflet margins. Browning and tissue demise will first seem on the leaflet margins and can progress inward towards the center of the leaf (midrib) and down towards the leaf base (towards the petiole) (Figs. 3 & 4). Cannabis vegetation take up loads of water when actively rising. The older leaves are very photosynthetically lively and thus will use extra water assets and accumulate the ions within the excessive EC answer sooner.
Advanced Symptoms. If excessive EC options should not mitigated, then extra salts will accumulate within the plant, particularly within the older, decrease leaves (Figs. 5 & 6). As the leaves proceed to build up the ions, the leaflet margin will start to tackle a wilted look and can change into brittle and brown (necrotic). Eventually, the whole leaflet will die, and solely the center of the leaf alongside the midrib will probably be inexperienced. If circumstances should not corrected, the whole plant will die. Additionally, as a result of the plant isn’t taking on as a lot water, a layer of salt crusting could seem on the substrate floor because of evaporation with any irrigation technique (Fig. 7).
Correction and Prevention
The greatest method to make sure that excessive EC circumstances are averted is to arrange a monitoring program so you possibly can establish accumulating salts or fertility miscalculations early. Other articles we have now written for CBT tackle how one can arrange a monitoring program and how one can carry out an in-house check on substrate pH and EC, and can information you on this course of. (For extra on this, learn the beforehand talked about “Optimizing Electrical Conductivity (EC) in Cannabis Cultivation,” “Troubleshoot Cannabis Nutrient Problems Before They Occur,” and “New Research Results: Optimal pH for Cannabis.” Such assessments embrace the PourThru, 1:2 dilution, or saturated media extraction (SME). Checking the nutrient answer on the hose finish or drip emitter will assist decide if injector calibration is required, if injector failure has occurred, or if the fertilizer was miscalculated.
Submit Samples for Lab Testing
In-house monitoring of the EC gives a fast test of your crop’s nutrient standing. Another useful gizmo is lab testing. Consider submitting periodic fertilizer answer samples to a business testing lab to find out your fertilizer answer’s dietary composition. This is a good way to find out the nutrient ranges offered by an natural fertilizer. Periodic water assessments will present perception into your water high quality. Finally, periodic substrate samples will enable you to correlate your PourThru EC readings with the precise particular person component contribution of your fertilizer program.
Corrective Procedures for Modifying Substrate EC
When the EC drifts into undesirable territory (Table 1), changes should be made. Below are the usual corrective procedures used to change the substrate EC for greenhouse or indoor vegetation grown in soilless substrates and tailored for hashish.
1. High Substrate EC Correction. If the EC is rising over time, this means the fertilizer is accumulating within the pot and the speed is increased than the demand by the plant. The first step can be lowering the fertilizer price to reasonable the buildup of fertilizer salts. (This additionally may help lower your expenses by not losing fertilizer answer.)
The second choice is to irrigate the substrate twice with clear water to leach out the accrued fertilizer salts. This technique is used when EC ranges are extraordinarily excessive to assist keep away from plant burn. (It additionally flushes away your fertilizer funding.) Monitoring the crop throughout manufacturing will assist to keep away from these elevated ranges within the first place and enable you to lower your expenses.
2. Low Substrate EC Correction. On the alternative finish of the spectrum, if the degrees are decrease than the really helpful vary (Table 1), this means the nutrient demand of the plant is increased than what’s being provided. In this case, enhance the fertilizer price. One or two purposes of a better N price within the 250 to 400 ppm vary will increase the EC.
Conclusions
Excessively excessive EC ranges result in stunted development, leaf injury and finally plant demise. It is greatest to keep away from this case by implementing in-house monitoring of the EC in your normal working procedures (SOPs), thereby establishing an everyday fast test of the nutrient standing of your crop.
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