Symptoms of Cannabis Potassium Deficiency
Cannabis potassium deficiency symptoms typically appear in the flowering stage. They can include:
● Yellow or brown leaves, usually—but not always—starting with the tips of the oldest leaves, before extending further in the leaves and upwards to newer growth.
● Weak, easily bendable stems.
● Delayed bud formation.
● Reduced resistance to drought and extreme temperatures.
The first symptoms of potassium deficiency look similar to nutrient burn. But if the edges and insides of leaves increasingly turn yellow or brown, potassium deficiency is the likely culprit.
Cannabis and Potassium’s Role
Potassium fuels growth and stress resilience by enabling the movement of nutrients, water, and carbohydrates throughout plant tissue. It catalyzes cannabis growth and development by:
● Helping to synthesize the proteins and amino acids delivered by nitrogen.
● Improving resilience to both biotic and abiotic stresses, like pests, drought, and frost.
● Increasing the strength and resilience of plant tissue and root systems.
● Activating growth-promoting enzymes.
● Improving plant morphology, thus increasing the weight, volume, and density of cannabis buds.
Proper potassium levels also encourage the development of desirable aesthetic qualities in cannabis. Legal restrictions around the world have severely limited research on cannabis specifically, but potassium has long been identified as a “quality element” in food crops: it positively affects qualitative variables like fruit size, appearance, color, aroma, nutritional content, and shelf life.
Recent studies demonstrated that potassium has a similar effect on the qualitative variables of cannabis, including bud size, color, and aroma. However, oversupply of potassium may decrease concentrations of cannabinoids and terpenoids. Finding a balance between deficiency and excess is important.
Treating Potassium Deficiencies While Avoiding Excess Fertilization
Although prolonged potassium deficiency is a profound risk to crops, potassium excess is also an issue, especially for cannabis. Too little potassium, plant health suffers and yields drop. Too much, and cannabinoid and terpenoid levels may be negatively affected, potentially diminishing crop quality.
So, although added fertilization is sometimes necessary, it is helpful to understand the mechanisms of nutrient uptake before the addition of more potassium fertilizer to your growing medium.
Potassium is fixated in soils quite fast, but it is released—or made available to plants—slowly. As much as 90% of soil potassium may be unavailable to plants at any given time. Factors that can limit potassium availability include:
● Soil PH and chemical composition
● Extreme temperatures
● Excess magnesium
● Tillage systems
● Soil moisture and irrigation protocols
● The rhizosphere
A healthy rhizosphere, one replete with beneficial microbes, can moderate many of these variables to the plant’s benefit, increasing the bioavailability of potassium that would otherwise be “locked” in the soil.
Some soil bacteria and fungi are classified as potassium solubilizing microbes, or KSMs. They excrete organic acids that release potassium from minerals like illite, micas, and orthoclase. KSMs are the key to the potassium vault, unlocking it for plant uptake.
Most soils are rich in potassium. Expensive, environmentally damaging conventional fertilizers are often overapplied, and excess potassium can potentially even be detrimental to cannabis. In addition to appropriate fertilization programs, growers can treat deficiencies by leveraging the riches already in the soil—with the help of microbial inoculants and other plant biostimulants.
Treating Cannabis Potassium Deficiency with Plant Biostimulants
Microbial inoculants are classified as a plant biostimulant—any substance or product that stimulates biological processes to encourage plant growth and development. They are an easy way to introduce beneficial microbes to the rhizosphere. Other common biostimulants include amino acids, seaweed extracts, protein hydrolysates, and compost.
Microbial inoculants can be used in conjunction with any conventional fertilizer program to maximize plant uptake of potassium and other nutrients essential for cannabis plants, including nitrogen, phosphorus, calcium, magnesium, and sulfur.
Nutrient deficiencies are often treated by addressing the symptoms, not the cause. Causes can be multifaceted, defying a simple prognosis, but oversimplifying them risks long-term environmental and financial consequences.
Microbial inoculants help us approach the muti-faceted nature of complex horticultural problems more effectively. They provide growers with holistic solutions that simultaneously maximize yields, improve soil and plant health, and minimize environmental impacts by reducing fertilizer demand.
Microbial Inoculants for Cannabis Growers
Impello’s organic fertilizers and microbial inoculant amendments are designed to holistically address nutrient issues like cannabis potassium deficiency in all irrigation systems, media types, and growing environments.
Microbial inoculants, like our new Continuμm™ formulation, provide plant growth-promoting rhizobacteria (PGPR) that will improve nutrient availability while boosting root development, water uptake, and crop tolerance to abiotic stressors. Research focused specifically on beneficial microbes in cannabis production is still in its infancy, but early studies indicate that PGPR application can even positively impact CBD and THC content.
We’re passionate about making horticulture better, for growers and the planet. If you have any questions about microbial inoculants and biostimulants for cannabis production, we want to hear from you! For technical questions, please email us at firstname.lastname@example.org. For general questions or to place an order, email email@example.com.
For more on microbial inoculants and cannabis potassium deficiency, please see the references used to write this blog:
Bernstein, N., Gorelick, J., Zerahia, R., & Koch, S. (2019, June 17). Impact of N, P, K, and Humic Acid Supplementation on the Chemical Profile of Medical Cannabis (Cannabis sativaL). Frontiers in Plant Science, 10. https://doi.org/10.3389/fpls.2019.00736
Meena, V. S., Bahadur, I., Maurya, B. R., Kumar, A., Meena, R. K., Meena, S. K., & Verma, J. P. (2016). Potassium-Solubilizing Microorganism in Evergreen Agriculture: An Overview. Potassium Solubilizing Microorganisms for Sustainable Agriculture, 1–20. https://doi.org/10.1007/978-81-322-2776-2_1
Saloner, A., & Bernstein, N. (2022, May 23). Effect of Potassium (K) Supply on Cannabinoids, Terpenoids and Plant Function in Medical Cannabis. Agronomy, 12(5), 1242. https://doi.org/10.3390/agronomy12051242
Saloner, A., Sacks, M. M., & Bernstein, N. (2019, November 18). Response of Medical Cannabis (Cannabis sativa L.) Genotypes to K Supply Under Long Photoperiod. Frontiers in Plant Science, 10. https://doi.org/10.3389/fpls.2019.01369
Usherwood, N. R. (2015, November 2). The Role of Potassium in Crop Quality. Potassium in Agriculture, 489–513. https://doi.org/10.2134/1985.potassium.c21
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