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Fertigation

Drip Tape Fertilization

Fertigation

A steady feed of nutrients through drip tape produces big plants, enhances pest and disease resistance, and increases the quality and quantity of the yield. As such, we’ve decided that in addition to spreading our own organic composted cow manure onto our fields this year, we’re going to experiment with “injecting” organic liquid fertilizer. Given that we are installing a drip irrigation system to ensure the plants get enough water, applying additional nutrients through the drip system just makes sense. This is called fertigation.

There are many advantages to using the drip system to apply nutrients. To start, it sure beats trying to get a granular fertilizer under the plastic “mulch”. Using the drip tape, nutrients get into the rows exactly where they need to be and there is no worrying over getting equipment into wet fields. With the addition of a metering device, the timing and rate of application are easily controlled.

Organic liquid fertilizers span the spectrum from products made using conventional GMO Round-Up ready corn to fertilizer derived from wild caught fish with metal and chemical testing showing they’re free of toxins. Naturally, we’ll be using a very clean fish hydrolysate from a local supplier here in the Great Lakes area. In addition to only applying fertilizer to some rows, we may also experiment with compost tea via the drip tape. By only applying nutrients to some rows through the tape, we’ll be able to do a cost versus benefit comparison along with finding out if there are issues with the tape plugging up.

Injectors

Dosatron Injector

While there are various types of “injectors” to meter the introduction of nutrients (venture bypass, positive displacement) into the lines along with various electronic components that further automate nutrient injection, our system is very basic. It will consist of a single Dosatron D14MZ2 Fertilizer Injector tied into the poly header pipe feeding the drip tape. This D14MZ2 injector has a 14 gpm maximum flow rate and this works out nicely with our 1” poly header piping – 1” piping has a maximum flow rate of about 13 gpm.

In particular, our plan is to the install the Dosatron just before the 50 psi well water is lowered by the pressure reducer to 10 psi. We’re keeping the injector on the high pressure side as we are concerned over the 3/4″ connectors on the Dosatron impeding the flow on the 10 psi side. It’s a bit surprising the injector has 3/4″ fittings with a 14 gpm flow rate as clearly this is the rate for 1” piping.

In any case, we like the Dosatron because it is a respected brand that works off of water pressure alone. The pressure causes a piston to move up and down drawing in nutrients at a metered rate through the pick-up line – like a big syringe. The pickup line from the Dosatron drops into a bucket filled with concentrated nutrients. We will install piping and valves such that our single injector can be used to feed each of our zones one at a time. Pipe unions and shutoffs will allow for the injector to be swapped from zone to zone. It’s a super simple setup, especially in comparison to large grow operations, but meets our needs.

Oxygen Loving Microbes

As noted, our basic plan is to introduce compost tea and an organic liquid fertilizer through our drip system. The organic compost tea and liquid fertilizer will either directly nurture our plants by providing bio-available nutrients, or indirectly help them grow by improving soil micro-biology. For example, the recipe for compost tea we’re brewing has been laboriously tested using a microscope to ensure it is teaming with the right kind of microbes. Namely, it’s loaded with oxygen loving aerobic microbes of all sorts – bacteria, fungi, flagellates, ciliates, and the like. Similarly, the liquid fish hydrolysate fertilizer we’ve selected not only contains Nitrogen (N), Phosphorous (P), and Potassium (K) for direct uptake, it also contains kelp extract, hummic acid, and fulvic carbon sources to promote healthy soil biology.

As an aside, we also looked into injecting mycorrhizal funji. These are hugely beneficial funji that extend the root system by many fold. These fungi don’t survive the tea brewing process but spores are available in powder form. So we were excited about the possibility of introducing mycorrhizal fungi spores right next to the roots using our drip system. Unfortunately, we were told the spore powder would plug up our tape. We’ll write more about mycorrhizal fungi in another article.

Before getting into the challenges of finding a deeply organic liquid fertilizer, it’s important to understand that farming that heals the land is so much more than simply top-dressing with fertilizer as in conventional farming practices. It even goes beyond the organic practices of applying well-composted manure along with good cover crop management. Sure, compost and cover crops make for stronger plants and better yields, but the deep and lasting story, when it comes to rejuvenating our soils and unleashing their full potential, is all about the tiny microscopic microbes that live in the soil.

By the way, there is a huge difference between well-composted manure and a pile of rotting poo. Well-composted manure is actively managed with the piles turned according to temperature. Turning mixes any dry matter added to the pile along with introducing oxygen. This promotes the growth of oxygen-loving (aerobic) microbes while killing off oxygen-hating (anaerobic) microbes. Piles are turned when the temperature dips below 130 degrees Fahrenheit or rises above 160 degrees – see How To Manage a Compost Pile Using Temperature.

To put this in context, we all know how important oxygen is to living beings including people. Plants grown in soil amended with compost containing oxygen loving microbes have the greatest benefit for people. It’s the oxygen-loving microbes that produce vibrant, nutrient rich plants.

The fact that oxygen-loving (aerobic) microbes are good for people and plants while oxygen-hating (anaerobic) microbes are problematic is made apparent by the fact that it is the anaerobic (oxygen-hating) bacterium that makes rotting manure smell bad – manure that sits stagnant in a heap. Everyone intuitively knows that anaerobic are to be avoided by using their noses. The by-products of anaerobic (oxygen hating) bacteria and their associated smells are dioxide (sulfur), butryic acid (sour milk), valeric acid (vomit), putrescine (decaying flesh) and so on. In contrast, well composted manure is fluffy and has a earthy tone.

Getting back to importance of improving soil biology, the work of Elaine Ingham B.A., M.S., Ph.D. from the Soil Food Web, makes it clear that very few additional nutrients are required in microbe rich soils. In other words, even though conventional soil testing may indicate lack in soil pH, phosphorus, potassium, and the like, when the soil is teaming with beneficial microbes, the nutrients will be unlocked from the soil on an as-needed basis. In healthy soil, the plant and the microbes live in a symbiotic relationship. The plant sends sugars down through its roots to feed the microbes and the microbes unlock otherwise inaccessible nutrients in the soil making them available for uptake by the roots.

Today, conventional farmers focus on the three major nutrients, Nitrogen (N), Phosphorous (P), Potassium (K), a handful of micro-nutrients like magnesium, along with soil pH. Soil tests tell the farmer how much of each of this limited number of nutrients needs to be spread onto the fields. If soil pH is off, it is adjusted by spreading lime or sulfur. It’s really a brute-force method that ignores the multitude of other micro-nutrients essential to healthy plants along with the microbial community that has evolved over thousands of years to live in harmony with plants.

In vibrant soil, the microbes extract the full range of nutrients required by the plant directly from the soil without any additional inputs. Said another way, regardless of what “deficiencies” soil testing my show and regardless of its type, all soil has thousands of years of all the nutrients plants would ever need. It’s just that from a conventional standpoint, these nutrients are locked up. They’re locked up because modern farming has killed off the microbial community through practices like constant tilling, leaving ground fallow, and applying chemicals. Working with dead soil, farmers have no choice but to pay chemical companies even more for fertilizer to make up for the lifeless soil the chemicals created; conventional farmers pay twice for benefits the microbes happily provide for free. By restoring the micro-biology, all the nutrients ever needed are available to plants.

One of the main edicts of organic farming is to restore soil health and we take this very seriously. By working to restore the microbial community in the soil, we unlock the virtually endless supply of nutrients in the existing soil without having to rely on the brute force, destructive, and expensive approach of trucking and spreading chemical fertilizers onto the soil. As we work to continually improve our soils, the amount of additional nutrients required becomes less and less, the plants are healthier, and the fruit/bud produced hold more and more of the full entourage effect.

Fertilizer for Flowering Plants

Before reviewing the various organic liquid fertilizer products that we researched, a brief overview of the relative amounts of Nitrogen (N), Phosphorous (P), and Potassium (K) makes sense. Knowing how of each of these three nutrients affect plant growth along with the relative levels required at the various stages of growth helps in evaluating the various liquid fertilizers on the market. These are the three ingredients listed in nearly all commercially available fertilizers.

N-P-K Benefits

  • Nitrogen (N): leaf growth
  • Phosphorus (P): strong root development in young plants, flowers, seeds, fruit
  • Potassium (K): larger diameter stems for bigger bud, water movement, promotion of flowering and fruiting, strong immune system to resist pests, strengthens metabolism, necessary for photosynthesis and the production of proteins

Vegetative Phase

N-P-K

Seedling: 1-2 Leaf Sets 2 – 1 – 2
Seedling: 5 Fan Leaves 4 – 2 – 3
Mid-Veggie Phase 10 – 5 – 7
Late Vegetative Phase 7 – 7 – 7

Flowering Phase

N-P-K

Early Flowering 5 – 10 – 7

or else
6 – 15 – 10
Final Flowering 4 – 10 – 7

In looking over the above, it should be noted that the N-P-K ratios are “ballpark” values. Every fertilizer will have slightly different ratios. In addition, it’s the relative ratio between N, P, and K that matter. For example, a person can use twice as much of a 2-1-2 fertilizer to equal a 4-2-3 fertilizer.

Above is an example of NPK ratios and timing of application for flowering crops. In the vegetative stage, nitrogen levels are increased. Later on as the plant approaches flowering, nitrogen is decrease while phosphorous and potassium are increased to promote flower production. About a week before harvest, all fertilization is stopped to “wash out” the plants.

Liquid Fertilizers

Looking over the OMRI certified products is enough to make a person’s head swoon. There are 80 pages with 3 columns on each page of suppliers. Even though they are divided up into categories, there is no category for liquid fertilizers that work in drip irrigation systems.

We spent quite a bit of time finding suppliers and researching their products. As anyone who looks into the organic scene today knows, the term “organic” doesn’t mean what it used to. Today CAFOs (concentrated animal feeding operations) and plants grown indoors without soil (hydroponics) are given “organic” status. In what “stretch of the imagination” do these types of operations have to do with nurturing the well-being of animals or the soil? We don’t know but there is a wide range of products when it comes to “organic” liquid fertilizers.

For direction on selecting larger scale suppliers, we relied on mentions in various online grower videos, as well as, the article Fertigation in Organic Vegetable Production Systems . The article has a table listing about 30 liquid fertilizer products along with their N-P-K ratios and cost per pound of nitrogen. We essentially researched the top 2/3rds of the list along with a handful of other manufacturers. We considered fertilizers that cost more than $25 per pound of nitrogen to be “boutique” products. What follows are more detailed notes on the three producers that we gave a call to along with a brief mention of a handful of others we looked into.

Dramm Drammatic

Drammatic

Per Dramm’s website, all six of their OMRI certified fertilizers are made ”… from fresh fish carefully processed at low temperatures to maintain the integrity of naturally occurring amino acids, vitamins, hormones and enzymes. The raw material is then stored in digestion tanks to liquefy the product. This method produces a product called a fish protein hydrolysate…”

Dramm Corporation
2000 North 18th Street
Manitowoc, WI 54221
(920) 684-0227

Dramm Notes

  • Produced in Algoma Wisconsin and available for pick-up in 55 gallon drums or 275 gallon totes.
  • Certified test results are available on request. In general, testing for heavy metals and chemicals comes back below detectable limits.
  • Apply the first one or two feedings at 1/2 the normal rate, then one or two feedings at 3/4 rate.
  • It’s OK to apply 2-3 gallons of Drammatic per 100 gallons of water during transplanting using a water wheel.
  • Use Drammatic One ($9.60/gal) during “veg” and switch to Drammatic E ($9.17/gal) for bloom.
  • Technically, Drammatic should not be used in drip tape but lots of grower do so without issue – make sure to flush lines for 20-30 minutes after fertigating.
  • Recommend Drammatic One and Drammatic E with kelp and fulvic acid.
  • Drammatic fish hydrolysate is filtered to 200 mesh.
  • Fish hydrolysate is superior to fish emulsion.
  • The fact that Dramm is local allows us to buy this higher priced fertilizer for less than those that have out-of-state freight charges. This in combination with testing that shows the fertilizer is toxin free made Dramm the choice for us.

Drammatic Recommendations

  • After transplanting or emergence, apply Drammatic “ONE” or “5N” 4-4-0.5 until flowering starts.
  • Tier 1: 5-10 gallons/acre every 7-10 days
  • Tier 2: 3-7 gallons/acre every 7-10 days
  • Tier 3: 2-5 gallons/acre every 10-14 days
  • Once flowering has begun, switch to Drammatic “K” or “E” 2-5-0.2 until harvest.
  • Tier 1: 5-10 gallons/acre every 7-10 days
  • Tier 2: 3-7 gallons/acre every 7-10 days
  • Tier 3: 2-5 gallons/acre every 10-14 days
  • Alternatively, begin Drammatic “K” or “E” 2-5-0.2 at flowering.
  • Tier 1: (not an option)
  • Tier 2: 7-10 gallons/acre every 7-10 days
  • Tier 3: 3-7 gallons/acre every 10-12 days
  • Fertilizer can be applied in the furrow, side dressed, or as a foliar spray.
  • Drammatic feeds soil microbes so applying less fertilizer more often is always better than more fertilizer less often.
  • Drammatic Fish Fertilizer Blends

BWF Banducci

BWF Banducci

Per BWF Banducci’s website, all of their OMRI certified products, ”Liquid Sunshine 5-1-1, Secure Organics 4-1-1, Secure Plus 4-6-1, Organique Exquis 3-1-1, Super 6-1-1 Plus Kelp, and Bandi Meal are manufactured under strict LGMA (Leafy Green Marketing Agreement) protocol guidelines at our facility in Mexico under BWF Banducci Inc. Our products are 100% naturally derived from “whole” ocean-going fish. BWF Banducci Inc. uses no animal by-products or manure in our formulation process; our products are strictly by-products of fish meal.”

BWF Banducci
P.O. Box 81506
Bakersfield, CA 93380-1506
661-328-9474

Banducci Notes

  • Available in drums, totes, and tanker loads.
  • Screened 3 times through 100 mesh filter so it is “tape ready”.
  • May want to use a Y-filter before the drip tape to further clean up the product.
  • It is recommended to lightly fertigate with 5-1-1 during the first two weeks after transplanting. Apply fertilizer every 2-3 weeks. At bloom, use 4-6-1 at 20 gallons per acre weekly. Alternatively and given our initial application of compost, wait for 3 weeks after transplanting and then apply 4-6-1 through the rest of the season.
  • As with all nutrients sent through drip tape, it is very important to run water for 30 minutes of longer to clean out the tape and emitters.
  • $5.90 per gallon plus up-charge for 55-gallon drums and shipping from Denver or California.
  • Except for shipping costs to the mid-west, Banducci looks like a good product.

Converted Organics

Converted Organics

Per Converted Organics website, their eight OMRI certified fertilizers with varying N-P-K ratios are derived from grain fermentation solubles, hydrolyzed soy protein, and fish… The High Temperature Liquid Composting (HTLC) process is an extremely efficient, state-of-the-art, in-vessel biological system which rapidly converts organic matter (including fish byproducts, vegetable and plant wastes, meat wastes, etc.) into high quality, manure free liquid organic fertilizer products.

Nature Based Technologies LLC
Converted Organics Distributor
7343 El Camino Real Suite #156
Atascadero, CA 93422
(800) 870-4012

Converted Organic Notes

  • A component of their fertilizer is made from corn steep water. In general, corn is steeped in large tanks filled with water containing sulfur dioxide so that the corn can be processed into constituents such as fiber, oil, carbohydrate, etc. The left-over steep water is then treated with enzymes and dried down somewhat to create liquid fertilizer. It is assumed that the corn is not organic – that it contains GMO and Round-Up.
  • Soil samples may be sent to an on-staff agronomist at Converted Organics for specific fertilizer recommendations.
  • In general, it is recommended to use 2-2-2 or 1-3-0 during vegetative stage and 2-2-4 during blooming to use about 1 tablespoon per gallon.
  • Their products are not recommended to be used in drip tape – apply as a drench. Note: Given what we’ve read, it would probably work fine in tape if the precautions below regarding flushing the lines are followed.
  • We now understand why this product is sold at a lower price. We would never use an “organic” fertilizer made from conventionally grown plant matter laden with DNA spliced material and life destroying chemicals – watch Dr. Davis – Wheat Belly and Dr. Seneff – GMO & Glyphosate (Round-Up).

Other Liquid Fertilizers

  • California Organic Fertilizers Phytamin – California based company sells a line of very soluble liquid fertilizers with higher levels of bio-available nitrogen.
  • Nutri Ag – Canadian based company at one time carried organic fertilizer but now only make three OMRI certified supplemental nutrients – Enviro Manganese, Enviro Calcium, and Enviro Potassium.
  • Botanicare – Washington based company sells Pure Blend Grow and Pure Blend Bloom Soil Formula for flowering plants (terrible website). Their products are not OMRI certified but reportedly exceed OMRI requirements – product view.
  • Hydroponic Research Veg + Bloom and Shine – California based company sells fertilizer for indoor hydroponic non-organic grow operations.

Flushing Drip Tape

Ever liquid supplier we spoke with all stressed the importance of flushing the drip tape after injecting fertilizer into the tape. Unlike chemical fertilizers, organic fertilizers are “alive” with microbes. If left to sit inside drip tape, the microbial community may flourish and plug up the tape. As such, it’s very important to flush out the lines. The general recommendation is to run water through the system for at least 20 minutes after. A much more thorough all method is described in Fertigation in Organic Vegetable Production Systems.

How to Flush Drip Tape

  1. Install a 200 mesh filter between the injector and the drip tape laterals.
  2. To ensure uniform distribution, wait until the entire system is pressurized before injecting.
  3. Using food dye, time how long it takes for water to reach the farthest emitter.
  4. Using food dye, time how long it takes for fertilizer to reach the farthest emitter.
  5. Time how long it takes to inject the fertilizer.
  6. Run water for 30 minutes longer than the sum of times from 3, 4, and 5.

Adding It All Up

Truly organic fertilization is at least as much about rebuilding soil biology as it is about providing readily available nutrients to the plant. When soil biology is restored, the microbes in the soil work in harmony with the plant. In exchange for sugars that the plant sends down through its roots, the microbes unlock nutrients in the soil making them available for uptake. Finding a deeply organic fertilizer requires research followed by lots of phone calls to determine the type and cleanliness of the materials used to create the fertilizer. Simply reading website selling points is not enough.

Note: Organic Entourage has no financial affiliation or otherwise with any products mentioned.

Heavy Metals

In this article, we discuss heavy metals. Heavy metal contamination has spread broadly over the globe and that there is a need to arrest this trend.

For farmers, chemical fertilizers, human sewage (BioSolids), and manure from animals given metal laden feed all contribute to the build up of heavy metals in our soils and the subsequent contamination of our crops. Furthermore, due to poor stewardship/naiveté, the soils in some areas of the country have been badly contaminated such that crops grown in these areas will likewise be contaminated. And finally, even organic farmers with relatively clean soil need to be careful about the materials they use as the case in New Zealand demonstrates wherein phosphate fertilizers were made using rock from the island of Nauru containing high amounts of the heavy metal cadmium

Heavy Metals in Food

Natural News Infographic

Heavy Metals in Chemical Fertilizers

In Screening Evaluation of Heavy Metals in Inorganic Fertilizers they write “the presence of heavy metals in inorganic (chemical) fertilizers is well established (US EPA 1999a; CDFA 2004; WSDA 2007)… Analytical testing of a wide range of fertilizer products shows that some phosphate and micronutrient fertilizers, and liming materials contain elevated levels of arsenic, cadmium, and lead compared to other fertilizer types (e.g., nitrogen, potash, gypsum)”. To get a sense for the level of heavy metal contamination in chemical fertilizers, on the Washington State Department of Agriculture (WSDA) website are the tabulated Metals Concentration in Fertilizer Sampled by WSDA. So OK, we know that chemical fertilizers contain heavy metals and we have some sense for the levels of these metals in fertilizers from the WSDA data. Let’s see if we can get a better sense for the degree of contamination.

Industry Safe Levels of Heavy Metals in Chemical Fertilizers

So the question at hand is to what degree heavy metal levels in chemical fertilizer end up in our soils. To answer this, we begin by looking at The Association of American Plant Food Control Officials (AAPFCO) agricultural industry standards. AAPFCO sets limits for heavy metals in inorganic (chemical) “fertilizers that contain guaranteed amounts of phosphates and/or micronutrients“. Their table and it’s use is shown below.

AAPFCO – The Heavy Metal Rule
Metals ppm per 1% P ppm per 1% Micronutrient
Arsenic 13 112
Cadmium 10 82
Cobalt 136 2,228
Lead 61 463
Mercury 1 6
Molybdenum 42 300
Nickel 250 1,900
Selenium 26 180
Zinc 420 2,900
http://www.aapfco.org
  1. Fertilizers with a phosphate guarantee; but, no micro-nutrient guarantee:
    Multiply the percent guaranteed P2O5 (phosphate) in the product by the values in the table to obtain the maximum allowable concentration of each metal. The minimum value for P2O5 utilized as a multiplier shall be six.
  2. Fertilizers with one or more micro-nutrient guarantees; but, no phosphate guarantee:
    Multiply the sum of the guaranteed percentages of all micro-nutrients in the product by the value in the appropriate column in the Table to obtain the maximum allowable concentration (ppm) of each metal. The minimum value for micro-nutrients utilized as a multiplier shall be one.
  3. Fertilizers with both a phosphate and a micro-nutrient guarantee:
    1. Multiply the guaranteed percent P2O5 (phosphate) by the value in the appropriate column. The minimum value for P2O5 utilized as a multiplier shall be 6. Then,
    2. Multiply the sum of the guaranteed percentages of the micro-nutrients by the value in the appropriate column. The minimum value for micro-nutrients utilized as a multiplier shall be one.
    3. Then, utilize the higher of the two resulting values as the maximum allowable concentration (ppm) of each metal.

For the sake of brevity, I’ll focus my attention on the heavy metal arsenic and leave it up to you to look at other metals. So what are the levels of heavy metals in chemical fertilizers? For that we can look at Metals Concentration in Fertilizer Sampled by WSDA. In the WSDA data related to arsenic, one of the more egregious fertilizers is KGRO Super Bloom with 136 mg/kg (ppm) of arsenic. Is this level “safe” per AAPFCO?

To answer this, we look up KGRO Super Bloom and find that this is a phosphate only 10-54-10 fertilizer. Knowing this, we can then use the table and rules above. Per AAPFCO, the allowable limit of arsenic for this particular fertilizer works out to be 54×13=702 ppm! So according to AAPFCO, it’s “safe” (136<702). But is it really? Let's look at arsenic from a different vantage point - in terms of natural background levels of heavy metals in soils.

Levels of Heavy Metals in Chemical Fertilizers Relative to Natural Soil Levels

Keeping up with our focus on arsenic, in Arsenic Cleanup Criteria for Soils in the US and Abroad, the range of natural “background” levels of arsenic in the soil is listed as being from 0.039mg/kg (ppm) in Wisconsin all the way up to 40mg/kg (ppm) for other states. All soil has some level of heavy metals in them and these are simply the natural, uncontaminated “background” levels for any given location. Using this information along with WSDA data in mg/kg (ppm), we can get a sense of the degree to which a given chemical fertilizers may lead to a build up of a given heavy metal in soils – in our case, arsenic. Note: Heavy Metals and Gardens has a table to help get a sense for safe levels of various heavy metals.

Before going any further, it’s worth noting that heavy metals do not go away over time – except when they’re taken up by plants or through targeted remediation. In other words, anytime a material like a chemical fertilizer, that has a higher level of a given heavy metal than the soil, is added to the soil, the concentration of the toxic metal builds up in the soil. So alright, let’s get back to the arsenic example.

To get a sense for how toxic a chemical fertilizer is, we need to compare the natural background level of a heavy metal in the soil to the chemical fertilizer in question. In Wisconsin, the background level of arsenic is really low, 0.039 mg/kg (ppm). However, in looking over the WSDA data, nearly all the chemical fertilizers listed have higher concentrations of arsenic. Fertilizers with a higher concentration would increase the level in the soil when added to the soil. Of course, the rate of build up would depend on the amount applied, the difference in concentrations, soil conditions, pH, and the like, but they would nonetheless build.

For examples, if Miracle-Gro Water Soluble Azalea with 0.2 mg/kg (ppm) of arsenic was applied, the build up would be relatively slow compared to KGRO Super Bloom with 136 mg/kg (ppm). Let’s try to get a better sense for the degree of build up. To do this, let’s assume that 1 ft3 of KGRO Super Bloom (weight of Super Bloom is 18.3 kg/ft3 based upon the box dimensions and listed weight) is worked into the top 8-inches of our loamy Wisconsin soil (weight of loamy soil is 36.5kg/ft3).

Let’s see over what area that amount of fertilizer would need to be applied in order to potentially double the level of arsenic to 0.078 mg/kg (ppm) in our Wisconsin soil. The math works out to about 140-foot by 140-foot area (19,600 ft3), or about 1/3rd of an acre. That’s a pretty large area of land. In other words, this chemical fertilizer would rapidly increase background levels of arsenic.

Now I would have ended the conversation here but my wife, who is an graduated with a degree in Agricultural Engineer, insisted I further quantify the application rate. In the USDA Data and Statistics for 2018 Vegetable Chemical Use in 2019 they list an average application rate for phosphate at 80 lbs/acre (36.3 kg/acre) per year for tomatoes. Tomatoes, you might ask? Well, there isn’t any data for cannabis and tomatoes are purported to be similar to cannabis in care – close enough for this discussion.

From above, we know that Super Bloom weighs 18.3 kg/ft3 and has an N-P-K ration of 10-54-10. In other words, it’s 54% phosphate by weight. To apply 80 lbs (36.3 kg) per acre, we need to use roughly ((36.3/18.3)/0.54)= 3.7 ft3 of this fertilizer per acre. Again from above, we know that applying 1 ft3 of Super Bloom over roughly 1/3rd of an acre potentially doubles the background levels of arsenic in Wisconsin. At 80 lbs/acre, we’re apply somewhat more than this amount. In other words, chemical fertilizers have the potential to increase heavy metals in the soil rather quickly – Super Bloom at this rate may very well double arsenic background levels in Wisconsin in less than a year.

OMRI Organic Safe Levels of Heavy Metals

A third way to approach getting a sense for the degree of potential harm heavy metals in chemical fertilizer pose is to look at the Organic Materials Review Institute (OMRI) safety guidelines. OMRI determines what materials may be used in certified organic production. The Rodale Institute states that, “OMRI requires heavy metals testing for many types of fertilizer products. If the test reveals that heavy metals exceed a certain concentration, the product may be either OMRI Listed with a ‘Caution’ statement, or potentially considered ineligible for OMRI listing. The following table provides an overview of the threshold levels“.

OMRI Heavy Metal Limits

Level 1 = level at which OMRI issues a ‘Caution’ statement for a given product based upon the potential for long-term contamination

Level 2 = level at which a product is ineligible for the OMRI Products List due to risk of soil contamination

Getting back to our arsenic analysis, OMRI says that compost with more than 10 mg/kg (ppm) is problematic. If you remember, Miracle-Gro Water Soluble Azalea has 0.2 mg/kg (ppm) of arsenic and KGRO Super Bloom has 136 mg/kg (ppm). Given that the average weight of compost is 24 kg/ft3 and knowing that Super Bloom weighs 18.3 kg/ft3, this means that the OMRI data equates to a safe level for chemical fertilizers of roughly (10×24/18.3)= 13 mg/kg (ppm). This is much lower than AAPFCO 702 mg/kg (ppm) and is consistent with certified organic standards being more conscientious.

Taking this all in, the agricultural industry limits for heavy metals appear to be very high. Depending on the background levels of the soil and level of contamination of the chemical fertilizer, less than a years worth of fertilizer could potentially double background levels. In addition, while OMRI levels are much more limiting, it’s essential that growers pay careful attention to heavy metal contamination.

Heavy Metals in Sewage Sludge

BioSolids

With savings of $200 per acre, it’s no wonder some farmers are using composted human waste (aka sewage sludge, BioSolids) instead of chemical fertilizers. Surprised? That’s right; farmers are putting human waste on their fields!

In it’s wisdom, the EPA approved BioSolids in 1993. In terms of heavy metals, the EPA regulated that BioSolids are to be tested for a paltry number of heavy metals – nine to be exact. To get a sense for the toxicity of BioSolids, understand that the EPA allows relatively high heavy metal concentrations in BioSolids and “according to Natural News, BioSolids are also loaded up with “appreciable concentrations of polybrominated diphenyl ether (PBDE) flame retardants, triclosan, an antibacterial agent, nonylphenol detergent breakdown components, and other things“. This is not nice stuff.

Thankfully and in spite of the EPA allowing BioSolids to be listed as “compost” on products, it is not allowed to be used on certified organic land. As such, folks that want to avoid the toxins in BioSolids can rest assured when they purchase certified organic cannabis. Note: For home gardeners, fertilizers labeled as containing “sewage sludge” are using composted human waste – BioSolids.

Heavy Metals in Feed Additives

Chickens Industrial

If you’re like me, you’ll be surprised to learn that heavy metals are intentionally put in livestock feed! In the case of arsenic, it is fed to chickens, turkeys, and pigs purportedly to prevent parasites. Copper is fed to pigs to fatten them up. In Accumulation of Copper and Zinc From Liquid Manure in Agricultural Soils and Crop Plants they write, “A comparison between the metal contents of liquid manure and normal heavy metal concentrations in soils demonstrates that the copper content in pig slurries is 10–40 times higher than in soil, whereas the zinc content in pig and calf slurries is 10–25 times higher”. In other words, heavy metals in feed additives end up in the manure at fairly high levels.

So what does this mean for cannabis? Well, we now know that manure from conventional farming is often contaminated with heavy metals. When this manure is applied to cannabis fields, depending on the soil, rate of application, and other factors, these heavy metals end up in the cannabis buds to varying levels. Furthermore, this is an issue for both conventional and organic farms. I say this because organic farmers are allowed to apply conventional animal waste to their land. I know; it makes no sense. The sad truth is that buying “certified organic” does not necessarily mean the heavy metal levels will be low.

Happily, at Organic Entourage, we do not bring in manure from other farms. The dairy compost we use comes from certified organic cows that are fed exclusively off of our certified organic land. Late spring through late fall, the cows graze on organic hay and alfalfa in the fields. During the colder months, they are fed the same from large bales set aside during harvest along with certified organic corn – they need the extra energy to keep warm.

In A Survey of Selected Heavy Metal Concentrations in Wisconsin Dairy Feeds they write, “Lowest heavy metal concentrations were found in homegrown alfalfa hay and haylage, and corn grain and silage. Highest metal concentrations were found in purchased feeds, particularly mineral supplements”. We’re doing everything we can to keep heavy metals low in our soil and in our cannabis.

Having said this, the unfortunate reality is that virtually all soil is contaminated to some degree with heavy metals. In today’s world, it is impossible to grow product without some level of contamination. We do everything we can, but all products have some level of contamination.

In addition to using only certified organic feed from our lands, the dairy makes an effort to properly compost their manure. This is done by adding carbon and aerating (turning) the piles in order to promote oxygen-loving microbial growth. These oxygen-loving (aerobic) micro-organisms are both beneficial to plants and people. The composting process is far from perfect at this point, but efforts are being made to construct a large roof soon. This will help keep the piles drier and promote better microbial growth.

Composting is not only important because it invigorates soil and plant life. In addition, organic matter in the compost often helps bind heavy metals in the soil. The graph below from Kansas University shows a notable reduction in lead contamination in Swiss chard, tomatoes, and carrots when grown in soils with higher amounts of organic matter. In our humble estimation, consumers concerned with heavy metals are best served by informed growers.

Compost Binds Lead Graph

Land Polluted with Heavy Metals

Los Angeles

While virtually all soil is contaminated with some level of heavy metals, parts of the country are so badly laden with heavy metals that they really shouldn’t be used for agriculture. For example, the lands around Los Angeles, Chicago, and New York City are loaded up with lead (Pb). This is a result of all of the traffic in these highly populated areas during the 70’s when leaded gasoline was allowed. Cannabis grown in these soils will have higher levels of lead. Is it any wonder that cannabis vaporizers are plagued with incidences of lead contamination?

Reading Heavy Metal Labs

Alright, we’ve finished the discussion on heavy metals. Let’s take a minute and look at the heavy metals report for our CBD hemp at Organic Entourage. What you’ll see is that, just like virtually all other food products, there are small amounts of heavy metals in our product. We’re not perfect. And yes, we know that any good marketer would tell us we’re nuts to disclose this information – especially since it’s well within limits. However, we fervently stand behind our commitment to transparency and believe in the intelligence of our customers.

Since our focus is on providing excellent product and nurturing the land, it was important for us to quantify our heavy metal results. Just how bad/good are they? To answer this requires looking at multiple guidelines for reference. There is no definitive source. Furthermore, it’s actually a complex question that really should take into consideration what other exposures a person is subject to, the food type the metal is in, the method of intake, and so on. At best, we can only get a sense for where we stand. Let’s look at some points of reference.

World Health Organization 2001
Maximum Heavy Metals Limits
Heavy Metal Soil (ppm) Veggies (ppm)
Arsenic 12.0 0.43
Cadmium 1.4 0.20
Chromium 64.0 2.30
Cobalt 40.0 n.a.
Lead 70.0 0.30
Mercury n.a. n.a.
Nickel 50.0 0.20
Copper n.a. n.a.
Iron n.a. n.a.
Manganese n.a. n.a.
Selenium n.a. n.a.
Zinc n.a. n.a.
 
World Health Organization 2014
Maximum Heavy Metals Limits
Heavy Metal Soil (ppm) Veggies (ppm)
Arsenic 20 n.a.
Cadmium 3 0.10
Chromium 100 n.a.
Cobalt 50 50.00
Lead 100 0.30
Mercury n.a. n.a.
Nickel 50 67.00
Copper 100 73.00
Iron 500 425.00
Manganese 2000 500.00
Selenium 10 n.a.
Zinc 300 100
https://www.researchgate.net
International Standards for Food 2011
Maximum Heavy Metals Limits
Heavy
Metal
Limit
(ppm)
Arsenic – solids not fish 1.4
Cadmium – cereal/veggie 0.1
Chromium – cereal/veggie 1
Cobalt n.a.
Lead – all solids 6
Mercury – all solids 0.5
Nickel n.a.
Copper n.a.
Iron n.a.
Manganese n.a.
Selenium n.a.
Zinc n.a.
https://www.govtlab.gov.hk

Currently, the U.S. Food and Drug Administration (FDA) has not established regulatory limits for heavy metals in finished food products other than bottled water. However, the data above gives us some sense for heavy metal limits.

New Standard in Consumer Safety
Verified A+++
Lead < 0.025 ppm
Cadmium < 0.1 ppm
Arsenic < 0.62 ppm
Mercury < 0.006 ppm
Verified A++
Lead < 0.05 ppm
Cadmium < 0.25 ppm
Arsenic < 1.25 ppm
Mercury < 0.012 ppm
 
Verified A+
Lead < 0.12 ppm
Cadmium < 0.5 ppm
Arsenic < 2.5 ppm
Mercury < 0.025 ppm
 
Verified A
Lead < 0.25 ppm
Cadmium < 1 ppm
Arsenic < 5 ppm
Mercury < 0.050 ppm
 
Verified B
Lead < 0.5 ppm
Cadmium < 2 ppm
Arsenic < 10.0 ppm
Mercury < 0.1 ppm
 
Verified C
Lead < 1 ppm
Cadmium < 4 ppm
Arsenic < 20.0 ppm
Mercury < 0.2 ppm
 
Verified D
Lead < 2 ppm
Cadmium < 8 ppm
Arsenic < 40.0 ppm
Mercury < 0.4 ppm
 
Verified F
Is anything worse than “D”
 
 
 
http://lowheavymetalsverified.org/

In addition, we have a heavy metal standard from the Consumer Wellness Center. Consumer Wellness Center is headed by Mike Adams. Setting Mr. Adam’s politics aside, this seems like a reasonable standard in light of the World Health Organization (WHO) data.