Phosphate is one of the most important macronutrients for Cannabis farming. All forms of photosynthetic life utilize inorganic phosphates for energy storage, energy transfer, cell membrane construction and as a substrate for photosynthesis itself. Marijuana (Cannabis sativa/indica/ruderalis) requires ample and biologically available phosphorus in order to perform its many wonders. Industrial hemp cultivation requires large amounts of phosphate fertilizer to produce strong fibers. In medical/recreational Cannabis production, phosphates play a more nuanced role in the production of novel metabolites such as cannabinoids and terpenes. It is the cannabinoids (THC, THCA, D9THC, CBD, CBDA, CBG) which are responsible for the physiological and psychoactive properties of various Cannabis strains. Terpenes and other novel aromatic compounds define the strain’s specific smell, taste and coloration.
Producing crops of Cannabis sativa/indica with select cellulose/cannabinoid/terpene profiles is paramount to satisfying its intended use—controlling phosphorus levels is key to this goal. Plants have not evolved in a vacuum, and many species have formed symbiotic relationships with soil microbes which specialize in the solubilization of phosphorus. Microbial regulation through probiotics allows for the nuanced and efficient uptake of phosphorus and other elements into a plant’s anatomy. Thus, there is incredible value and interest in the development of Cannabis probiotics which facilitate the absorption of phosphorus, resulting in higher yields and lower fertilizer costs. The purple nonsulfur bacteria (PNSB) such as Rhodopseudomonas palustris are promising in this regard.
R. palustris is a broadly famous microbe due to its various powerful and novel abilities including diazotrophy, photosynthesis, antibiotic production, pigment production, etc. But it is arguably the ability of PNSB to solubilize and localize phosphorus that offers some of the most compelling potential for enhancing overall yield, disease resistance and other production characteristics of all industrial, medicinal and recreational Cannabis strains!
Phosphorus is a universally vital element to photosynthetic organisms. Chlorophytes and terrestrial plants in particular are ravenous consumers of the nutrient phosphate. Because of this, phosphorus has always been a tremendously important natural resource for Global Agriculture. Unlike nitrogen, which is fixed from the air via lightning or diazotrophy, phosphorus originates from subterranean rock. There is a relatively finite supply of natural phosphorus on the Earth. Unlike nitrogen–based fertilizers which can be made using the Haber-Bosch Process, there currently are no means to artificially synthesize phosphorus. And for this reason, phosphorus mines are the prized and coveted treasures of the nations/corporations/individuals who control them.
The large-scale extraction of subterranean phosphorus has allowed humanity to distribute phosphorus-based fertilizers worlds away from the soils which stored them. This has allowed for the intensification of agriculture in soils that would normally never produce such yields or sustain phosphate-hungry crops. However, the application of too much phosphorus too quickly can bear disastrous results. Excess application of artificial fertilizers eradicates decades of microbial community development, making the soil less and less naturally productive. Artificial fertilizers also leech through the soil and enter local streams, ponds, rivers, and estuaries; fluxes of phosphates into naive aquatic ecosystems can ignite harmful algae blooms that manifest as eutrophication, fishkills and other destructive episodes. Aside from these environmental concerns, there is also the pressing economic consideration that there is a finite supply of phosphorus that can be mined. Coupled with the issues of global supply chain distribution, it can be reasonably stated that the cost of mined phosphorus will only rise with time.
Phytic acid: A major source of insoluble phosphorus
There is, of course, an incredible amount of phosphorus in most naturally productive soils, but less than 0.01% of it is in a form which plants can access. Most naturally distributed phosphorus is trapped either in rock (calcium phosphate, aluminum phosphate, iron phosphate, etc.) or organic forms (phytate/phytic acid and other biomass). Plants cannot utilize the phosphorus in these latter compounds. They require ‘lighter’ compounds containing the delicious phosphate ion.
This is where Rhodopseudomonas palustris comes in!
PNSB are capable of Phosphate Solubilization. This is a process where the probiotic ‘mines’ large phosphate-containing compounds with enzymes and organic acids. These hydrolyze/break ester-phosphate bonds, releasing phosphate ions which either form into lighter, soluble compounds (hydrogen phosphate/dihydrogen phosphate) or are uptaken directly into a plant’s root cell. Phosphate solubilization is the natural mechanism for soil microbes to deliver bioavailable phosphorus to their host plants.
PNSB solubilize phosphates through a variety of mechanisms, but the release of gluconic acid is arguably the most ‘classic’ method. PNSB also secrete a variety of other substances (hydrogen ions, glucose dehydrogenase, pyrroloquinoline, EPS, phosphatase and phytase) in order to establish localized zones of acidity around insoluble phosphate sources.
Rhodopseudomonas is among the genera of symbiotic bacteria associated with wild Cannabis sativa/indica/ruderalis varieties. Inoculating production soil with this and perhaps many other PNSB allows for the Cannabis crop to recruit the probiotic into its roots, fostering greater growth for both organisms. This manifests in Cannabis crops with strong fibers, flavorful terpenes and concentrated cannabinoids!
Prabhu et al 2019
Phosphorus starvation in Cannabis plants manifests as olive-green spots, yellowing of the leaves and necrotic patches. This increases plant susceptibility to insect pests as well as fungal/bacterial disease. Phosphorous demand is highest during germination, seedling, cloning and flowering. This is why it is recommended to inoculate seeds directly with PNSB prior to planting so as to increase germination and early seedling survival rates. PNSB can also be applied to rooting solutions so as to assist in the rapid vegetative growth needed to root Cannabis cuttings. Populations of Rhodopseudomonas palustris will grow with the expanding Cannabis root systems, solubilizing and delivering phosphorus as it is needed. Phosphates are required for regular energy transfer, photosynthesis and DNA construction within the Cannabis plant.
However, plants arguably are most ravenous for phosphorus during flowering. Cannabis flower contains the highest concentrations of the cannabinoids important for its medicinal and recreational applications. Cockson et al 2020 demonstrated a positive relationship between phosphorus soil content and Cannabis sativa plant width, flower bud number and cannabinoid content produced per plant. Though Cannabis is a phosphorus-hungry crop, PO4 can be applied in excess through the use of synthetic fertilizers. For example, gregarious application of phosphate will deny plants access to other essential nutrients such as calcium, iron, zinc, copper and magnesium. PNSB supply phosphorus within the context of these other vital elements. This is why a ‘naturalized’ phosphate delivery system through microbes is more efficient and ultimately preferable. Simply put, associating a Cannabis production crop with a robust population of Rhodopseudomonas palustris ensures stable and ample phosphate delivery, decreased fertilizer costs and greater plant vigor, pest resiliency and overall yield!
Every cultivator has an inherent interest in the phosphorus dynamics of their soil. It is a precious, overtly finite resource which must be accessible when trapped in rock or organic matter. Fortunately, Rhodopseudomonas palustris and other microbes have evolved to acid-mine these inaccessible compounds so as to release a steady supply of essential phosphate ions. PNS is such an exciting product for Cannabis cultivation because it is the redeployment of millennia-old symbiosis between bacteria and plant. This reunion results in greater seedling survival couples with larger yields of strong hemp fibers as well as flavorful, potent buds. The cultivation of industrial, medicinal and recreational Cannabis strains presents an incredibly novel and lucrative opportunity for the 21st Century.
And for those who are watching and listening—with purple nonsulfur bacteria, more buds and more fibers can be grown with less fertilizer cost!
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