It is worth quickly discussing organics versus hydroponic nutritional regimes and methods of growing. There seems to be some confusion around this area with many organic enthusiasts claiming their product is invariably better –healthier, cleaner, “more natural” etc – than that of hydroponically grown produce.
Firstly, it is important to note that many attempts have been made to formulate the perfect organic hydroponic nutrient but so far nothing matches the purified mineral salts used in formulating hydroponic nutrient solutions.
Other than this, many hydroponic organic formulas sold through “hydro” stores under the “organic” banner are only part organic (kelp, fish by-product, guano, molasses etc) with the balance of these products being made up from standard fertiliser components. That is, nutrients that are, in many cases, passed off as organic would fail to get organic ratings/approval if put to the test. In addition, these fertilisers typically fail to perform as well as their “non organic” cousins and often suffer from pH fluctuations (among other things).
Don’t get me wrong – organic additives and stimulants certainly have a place in hydroponics (mineral/organic or hydro/organic combinations are a wonderful thing) and the use of some organics such as kelp based stimulants, in conjunction with a sound mineral nutritional regime, will ultimately result in healthier plants and potentially larger yields.
The Two Models – hydroponics and organics
In hydroponics minerals are provided to the plant in bio-available form, completely eliminating the need for soil and soil micro organisms. The result is a better optimised nutritional regime and higher growth rates and yields. In hydroponics all the elements can be controlled easily through pH adjustments (optimised pH for uptake), monitoring of EC (nutrient strength) and the provision of the right NPK ratios for every stage of the plants life cycle.
In the organic model, soil is enriched with compost, blood and bone, manures and other natural components. These components break down slowly in soil, through a microbial process, at a rate in harmony with the plant’s growth. This of course sounds nice but the level of control through the use of organics is greatly affected and to achieve optimum yields requires a high degree of expertise and soil testing (among other things) to ensure the right nutritional requirements for the crop are met.
The Science of Mineral Nutrition and Plants
Plants uptake mineral elements, when in bio-available form, and use them in a series of complex processes which ultimately ends in additional biomass (growth/size). Some minerals remain in the plant in bio-available form. This is a positive, as the human body requires these minerals for various physiological needs. It doesn’t matter whether these elements are derived from seaweed, fish by-product, compost or rocks. It is all the same to a plant and other living organisms (e.g. Humans).
It is important to note, that from a scientific/biochemical perspective an atom of nitrogen, whether it is derived from chook shit or synthetically derived from air (as is the case in the manufacture of most nitrogen fertilisers), is exactly the same thing to the plant. That is, potassium is potassium, nitrogen is nitrogen, phosphorous is phosphorous etc, etc, etc. As far as a plant is concerned there can be no distinction made between two atoms of the same chemical element. Put simply, synthetic (man made) fertilisers and organic fertilisers to a plant are the exact same thing and they are converted within the plant to the exact same thing (e.g… sugars and carbohydrates that are used in photosynthesis). For this reason, where the science is concerned, an organically grown plant is no different in its chemical makeup to a hydroponically grown plant.
Unfortunately, what organic enthusiasts have done is deny the science of mineral nutrition and plants, believing all that is natural is good and (therefore) all that is “unnatural” is bad; a post hoc ad hoc reasoning that seems to deny that many poisons (e.g. a Death Adders bite) and other toxins (e.g. heavy metals) are organic.
The Third Model – Soil Fertigation Growing
Soil fertigation growing involves using hydroponic like fertilisation techniques in soil. That is, it is possible to enhance plant growth (crop times and yields) using indoor hydroponic technologies in soil.
The material we have covered to date stresses that to achieve optimum yields it is necessary to provide an optimised environment along with an optimised nutritional regime. By using soil fertigation techniques the latter is very possible because food is delivered to the plant in much the same way as it is in hydroponics. I.e. we can effectively grow hydroponically in soil, providing the plant with readily bio-available nutrition and, hence, realise (hydroponic equivalent) optimum yields.
Soil Mix and Pots for Growing
A satellite run-to-waste system (as with coco growing) is best suited for the job.
Plant size will determine the size of the pots that are required for growing in. I.e. large plants will require plenty of room for large root systems, while smaller plants will need less room for their root systems. As a general rule, if growing to a finished height of 21/2 – 4 feet use 12 -20L pots, 4 -5 foot – 30 – 35L pots, and above 5 foot – 50 – 100L pots. As an absolute rule pots can never be too big; however, growing in undersized pots may inhibit adventurous root growth, resulting in the plants becoming root bound, which will adversely affect yields.
Line the base of the pots with clay balls (e.g. Hydroton) to facilitate adequate drainage.
Keep in mind that we have discussed the importance of air porosity in the growing media. Roots need oxygen for respiration and therefore a well aerated media is the ideal. In hydroponics the various media optimally contains 30% or more air porosity. We therefore want to mimic this in soil.
A mix that I like to work with and have found to be very effective is 20% perlite, 30% coco substrate and 50% potting mix. Use a medium to course grade coco substrate (as opposed to a fine powder substrate) to lighten the media and enhance air porosity. Place the perlite, coco and potting mix into a large bucket or tub and mix (integrate all components) well. If using an unbuffered coco substrate flush it well with water and ideally buffer it before mixing it with the potting mix (see buffer formula on page …….).
In many ways we are creating a hydroponic like medium with this mix. After some time the plants will deplete the potting mix of any available nutrition and, therefore, the medium becomes largely inert and the plants rely solely on their food through the delivery of nutrients as liquid mineral nutrition (i.e. hydroponics that isn’t quite hydroponics). Which brings us to our next point.
Soils for Hydro – Purchasing Options and pH Buffered Soils
There are numerous product options where potting mixes are concerned. Many companies produce mixes that include coco substrate, pumice, mulches, humis and organic and non-organic fertilisers. The best suited potting mix for soil fertigation growing will be a potting mix that:
- Contains sphagnum peat moss (sphagnum peat moss has high air porosity and is consistent so you know what to expect)
- Is fertiliser free (we add the fertilisers through fertigation and additional fertilisers in the potting mix will create a less than desirable/optimised nutrient regime)
- Is light and well aerated
- Doesn’t contain large amounts of sand
- Doesn’t contain compost (i.e. organic fertilisers)
Sand is widely used in some mixes, mainly because it’s cheap. It doesn’t hold water, it’s heavy, and, if it’s rounded and too fine-grained it can clog airspace and reduce drainage. Avoid the use of potting mixes that contain high degrees of sand. These products can too easily compact and, as a result, air porosity is reduced.
Many commercially available brands of potting soil have their pH fine-tuned with ground limestone (typically, dolomite lime), and some contain small amounts of fertiliser and slow-release nutrients. Lime breaks down into calcium and this will affect which nutrients are best suited for optimised soil fertigation growing (we’ll discuss more about this shortly and provide nutrient formulas for both lime treated and non treated potting mixes). Some bags list the ingredients while others don’t. Always purchase products where ingredients are fully listed. If in doubt speak to your supplier or source a product where ingredients are listed.
Standard potting mixes that are purchased through gardening centres can vary in pH dependent on what has been used, and at what levels, in manufacturing the potting mix. For instance, potting mixes that contain peat moss are acidic, usually with a pH of 4 (the optimum range for potting mixes is 5.5 to 6.5 dependent on crop type), so manufacturers add limestone (dolomite) to the soil to raise the pH.
Other than this, some potting mixes are made for different plant types and are buffered within different pH ranges. We require a soil fertigation media, for indoor growing, that has a pH of 6.0 (slightly acidic) to enable optimum nutrient uptake and, therefore, it is best to try to source a mix that caters to this.
Some “hydro” manufacturers supply pH buffered soils. These are buffered to the desired pH for indoor crops. Again, check whether lime has been used in buffering. Other than this, it is relatively simple to pH buffer a non-buffered potting mix.
Ph Adjustments in Soils
Raising pH in soils
Dolomite lime is typically used for raising pH in soils. Dolomite lime contains calcium and magnesium. The finer the particle size of lime the faster it will have an affect on soil pH. Particle size is indicated on the label as what percentage will pass through a given “mesh” size.
Be aware that where potting mixes contain lime (used for buffering pH) the lime breaks down into calcium over a period of time and for this reason nutrients containing calcium (or high levels of calcium) are best avoided where dolomite lime has been used for pH buffering. We cover a few nutrient formulations (options) in this section for this reason.
Lowering pH in soils
Sulfur containing products are typically used to reduce pH in soils.
Soil pH can also be lowered by using fertilizers containing ammonium-N (NH4 N). Ammonium sulfate is one of the best choices for acidifying potting mixes.
Other than this, aluminium sulfate or sulfur can be used to reduce pH. Aluminum sulfate will change the soil pH instantly because the aluminum produces the acidity as soon as it dissolves in the soil. Sulfur, however, requires some time for the conversion to sulfate and requires the aid of soil bacteria.
High levels of aluminium can be toxic to some species of plants (other than being linked to Alzheimer’s) and for this reason the use of ammonium sulfate for reducing soil pH is advised.
Measuring pH in Soils
Like coco, pH measurements should not be taken using run off. That is, the run off will not reflect the pH of the soil due to the preferential retention of cations.
Soil pH test kits are readily available through gardening centres. Test kits generally consist of a test tube, some pH testing solution and a colour chart. You put a sample of your soil in the tube, add a few drops of test solution, shake it up and leave it for an hour or so to settle. The solution in the tube changes colour according to the pH of your soil. Compare the colour of the soil sample with the colour chart that came with the kit.
Another method of testing is similar to measuring the pH of coco coir. Take 20 grams of soil (crush any clumps), and close it in a jar filled with 100ml of distilled water (1 part soil to 5 parts distilled water). After some vigorous shaking the sample should be left for 5 to 10 minutes to let soluble substances dissolve. Take a reading by immersing the pH electrode in the water above any settled soil. Make sure the electrodes are fully covered. Take care to minimize electrode contact with any soil at the bottom of the jar.
Ready to Go
Author’s note: In the past I have worked with citric acid (organic pH down) and potassium bicarbonate (organic pH up) and found this an efficient way of making subtle pH changes after buffering the potting mix with aluminium sulfate and/or dolomite lime, prior to use. During the course of the crop cycle I monitor pH through taking soil samples from around the root zones (about once weekly to fortnightly) and alter the pH when and if necessary through watering in a pH adjusted solution (for instance, if the pH is 6.3 I water in a solution at pH 5.6 to reduce overall pH to approx 6.1). Citric acid monohydrate (as powder) is generally available through food additive or veterinary suppliers (1-5kg) and potassium bicarbonate (as flake) is available through most agricultural suppliers. As you get used to working with these products it is easy to use a pH adjusted solution on feeds to adjust pH to 6.0 within the media. Other than this, a balanced nutritional program (i.e. a full spectrum hydroponic nutrient) helps to stabilise pH within the media, due to a cross section of cations, at balanced levels, being present in the feed (for instance the base cations Ca, Mg, and K increase pH while NO3 and S and, to some extent, ammonia (NH4) reduce pH). Organic pH up and down usage rates can be found on page …….
This is an area where differing approaches are espoused (and debated) via internet forums and literature. For instance, a few people recommend using premixed fertilisers such as Scotts Co. 20-20-20 or other agricultural fertilisers. By the way, under US standards of listing P as P2O5 and K as K20, NPK 20-20-20 is actually elemental NPK 20- 8.6- 16.6. That is, P as P2O5 is only 43% elemental P and K as K20 is only 83% elemental K. It’s something that you need to be aware of when looking at fertiliser numbers – in some cases the numbers are listed as elemental (UK, Australian standards) while in other cases they appear much higher (US standards). Other than this, we can do much better using a full spectrum hydroponic/soil fertigation formulation that is specifically developed for crop specific indoor growing. (There’s a catch to this, which we’ll discuss in a moment)
On this note, some years ago I worked closely with a Dutch multi-national and when discussing their soil nutrients it turned out that they were supplying a half strength coco nutrient for soil growing. This made some sense – after having used standard premixed agricultural fertilisers and organic combinations in soil and then having switched to standard (grow and bloom) hydroponic nutrients, along with organic additives, I found the latter performed somewhat better where plant health and yields were concerned. It hadn’t occurred to me to try a coco nutrient but after giving it a run the plants definitely seemed to appreciate it. One simply has to understand the principles of mineral nutrition.
Plants require a range of elements (the essential mineral elements – e.g. Ca, N, P, K, Mg, S) regardless of whether they are growing in soil or in hydroponics. By providing the full spectrum of these elements in readily bio-available form we are able to facilitate higher levels of mineral uptake and translocation within the plant. Other than this, different forms of elements are more readily bio-available than others. For instance, NO3 N (e.g. as calcium nitrate and potassium nitrate) is immediately available to the plant while NH4 N (ammonium nitrate) and Urea (CO(NH2)2) becomes available more slowly. Typically, agricultural grade fertilisers that are developed for outdoor crops such as tomatoes contain levels of urea due to its widespread use in agricultural outdoor growing. However, an idealised nutritional regime for indoor soil fertigation (and hydroponics) will ideally contain high levels of NO3 N, much lower levels of NH4 N and, arguably, no urea (although, some would disagree with the latter statement and who am I to argue?)
We have also touched on the fact that our soil medium (potting mix) will quickly become inert as the growing plants deplete it of its naturally present mineral nutrition. Typically, agricultural premixed soil fertilisers only contain some of the essential mineral elements (as NPK and micro elements) but lack on other elements such as magnesium and calcium. Particularly in this area, full spectrum hydroponic nutrients provide more rounded/optimised nutrition than their agricultural premixed (powder/solid) equivalents.
Friendly Bacteria (Biomass) in Soil
Soil and coco makes the ideal media in which to create a rich and diverse bio environment.
Friendly bacteria protect the plant from water born pathogens such as pythium and fusarium. Other than this, they help in nutrient uptake and produce plant growth promoting substances. They can also protect plant surfaces from attacks by pathogenic microbes through direct competitive effects and production of anti pathogenic compounds.
The Science of Friendly Bacteria
In nature non-harmful or beneficial organisms naturally combat harmful pathogens such as pythium and fusarium. Generally speaking non-harmful bacteria numbers explode at a faster rate than harmful bio organisms. As the non harmful bacteria numbers explode they form biomass around the rhizosphere of the plant. This biomass prevents harmful organisms entering the rhizosphere of the plant.
In addition to this, some bacteria are beneficial to plant growth. These bacteria are commonly known as plant growth stimulating bacteria (PGSB).
For instance, trichoderma Harzianum is particularly good at breaking down cellulose (dead root matter) and is the ideal product to use when recycling coco substrate etc. Other than this Trichoderma harzianum enhances plant growth due to its ability to produce beneficial enzyme complexes.
Trichoderma harzianum is a friendly mould that colonises the rhizosphere and competes with other organisms.
It is parasitic to other moulds such as pythium, fusarium and phytopthora. That is, Trichoderma protects the plants from these harmful organisms, all of which are capable of destroying your crop.
Trichoderma can also survive for long periods in a host, and needs only minimal carbon levels to ensure its subsistence. Trichoderma also stimulates root growth while breaking down cellulose (dead root matter etc).
Bacillus Subtillus, Pseudomonas and Azopirillum are all beneficial bacteria – they enhance nutrient uptake while protecting the plant from pathogenic microbes.
A pH level of approximately 6.5-7.5 is the optimum range preferred by most soil bacteria (e.g. bacillus strains are most effective at a pH of 7.0), although fungi, moulds, and anaerobic bacteria have a broader tolerance and tend to multiply at lower pH values.
The combination of trichoderma (mould) and bacillus (bacteria) strains is the ideal for hydroponic, soil fertigation and coco growing.
Sustaining ‘Biomass’ (Bacteria numbers)
The food source for friendly bacteria is sugars and carbons. Create an environment that is rich in these components and you will create a dynamic environment for friendly bacteria.
Where friendly bacteria are concerned humates (e.g. humic acid and fulvic acid) are an extremely effective food source. Humates are carbons – elements of ancient compost that formed over millions of years through the interaction of organic material and microbial action – and, therefore, their presence (along with other factors) in the growing system will ensure a rich environment in which friendly bacteria numbers will explode.
Fulvic acid is the most important humate bio-extract where hydroponics is concerned. It is water soluble and readily available for plant uptake.
Other than creating a dynamic environment for friendly bacteria, fulvic acid aids greatly in nutrient uptake and translocation within the plant. For this reason it should always be used in conjunction with a balanced nutritional program.
Fulvic Acid Benefits:
- Enhances cell growth
- Increases nutrient uptake
- Increases nutrient transportation
- Increases silica absorption
- Stimulates plant immune system
- Creates a dynamic environment for friendly bacteria
Humic acid is not suitable for hydroponic systems. However, humic acid is suitable for soil growing and its use in soils will prove beneficial for rhizosphere microbial interaction and nutrient uptake. Humic acid can be purchased via some agricultural suppliers and gardening centres and can be applied directly to the media (at the recommended rates that are advised for the product).
Other than humates (i.e. carbons) sugars are also the food source for friendly bacteria. Because of this, products containing molasses (e.g. some organic stimulants) and other sugars are beneficial in the growing system.
Thiamine (Vitamin B1)
Thiamine is a vitamin B1 complex that plays a role in the krebs cycle (tricarboxylic acid/citric acid cycle).
Thiamine also promotes beneficial rhizosphere bacteria which aid in nutrient uptake (among other things).
- Beneficial to photosynthesis
- Beneficial to growth and vigour
- Helps plants recover from stress
- Promotes beneficial rhizosphere bacteria
Cautions when using Friendly Bacteria
If you are adding friendlies to chlorinated water supplies (i.e. mains water), there is every chance (depending on the level of chlorine) that the chlorine is killing a good many of the beneficial microorganisms. Ideally you will have a secondary holding tank where you can leave your tap water exposed to air for 24 hours prior to it going into your system. This will ensure the water is chlorine free (the chlorine dissipates) by the time you introduce the friendlies.
On this note, sterilising agents (e.g. monochloramine or hydrogen peroxide) should never be used in conjunction with friendly bacteria.
Warning regarding mycorrhizae fungi in high phosphorous environments (i.e. hydroponics/soil fertigation)
At least one “hydro” company promotes the use of mycorrhizae fungi in hydroponic growing systems and sells products to this effect. However, it is important to note that mycorrhizae fungi cannot colonise and sustain biomass in high phosphorous (P) environments (i.e. hydroponic systems) and, therefore, their effectiveness and viability in hydroponics is questionable. That is, the mycorrhizae fungi cannot colonise and sustain biomass in a hydroponic growing system unless the nutrient has been formulated with low phosphorous levels to cater for colonisation of the fungi.
Mycorrhizae fungi are suitable for low phosphorous environments and are ideal for soil amendments where regular P fertilization isn’t taking place.
“In a second experiment, two nutrient media, modified Long Ashton and modified Knop plus Hoagland medium were compared for culturing G. mosseae on T. aestivum. A significantly higher root dry weight was found for the mycorrhizal versus the non-mycorrhizal wheat plants in modified Long Ashton nutrient medium, which contained 10 µM P and an organic buffer. Modified Knop plus Hoagland nutrient medium contained a high P concentration (0.9 mM) and did not produce viable cultures of mycorrhizal colonisation….. This report describes a system for the viable culture of G. mosseae with different plant species where a high mycorrhizal colonisation rate was produced under conditions of a short culture period using intermittent aeration, a low concentration of P supply and an organic buffer.” 1
1. H.-J. Hawkins and E. George (2004) Hydroponic culture of the mycorrhizal fungus Glomus mosseae with Linum usitatissimum L., Sorghum bicolor L. and Triticum aestivum L.
COMMERCIAL HYDROPONIC/FERTIGATION SOLUTION FOR PRODUCING ‘VAM’ (MYCORRHIZAE) FUNGI:
This is the working concentration used for growing host plants hydroponically for the multiplication of VAM propagules. (Edited out for purpose of website viewing)
Sciaridae (Shore Fly and Fungus Gnats) in Soil
Like coco substrate, potting mixes can attract sciaridae. Use yellow sticky traps as an early warning system (to alert you of the presence of fungus gnats) and if sciaridae are present in the growing environment treat the media with Coopex or another permethrin based product. Permethrin is non systemic (i.e. is not uptaken by the plant) and for this reason it is a highly effective and safe treatment option.
The product I typically work with is Coopex WP 250g/kg powder which comes in 25gram sachets. Coopex is manufactured by Bayer and is widely available in most countries. Mix one sachet to 10 litres, hand water (drench) the media and leave for an hour. After this, flush with pH adjusted nutrient and you are ready to go.
The Sum of It
Ok – so that’s the formula for success in soil fertigation growing; a well aerated (light) potting mix, coco, perlite combination in adequately sized pots. Then we have the nutritional regime – a coco nutrient used at half strength to three quarter strength in a non lime treated soil, or a soil formula (no calcium) where lime is present. Other than this use fulvic acid and/or humic acid, thiamine and organic additives that will aid growth and create a rich environment for beneficial bacteria. The beneficial bacteria can either be placed directly into the media or delivered via nutrition (feeds). They should ideally be bacillus strains and/or trichoderma Harzianum. It is also necessary to monitor and adjust pH to 6.0 in the media to ensure optimum nutrient availability. By following all these steps you will
- be providing the plants with all the essential mineral elements at optimised levels
- ensure that the plants are protected from root pathogens such as pythium and fusarium (prevention not cure)
- ensure high air porosity within the media
- ensure optimum uptake as the biomass explodes and facilitates nutrition/microbial interaction within the media and rhizosphere of the plants
Feed Regime (guide only)
All growers tend to have their own ideas about feed regimes (the best nutrients and what additives to use and when). In some cases nutrient manufacturers supply feed calendars with their product ranges that are generally very good. The material following is a guide only and experimentation, in all cases, is recommended when it comes to establishing the most suitable feed regime for your plants. I.e. The size of the plants and genetics, along with other factors, will determine the ideal nutritional regime for your crop.
Place struck clones (in clone blocks) directly into the soil mix. Use a nutrient at ¼ strength, in conjunction with a root stimulant, for the first 7-10 days.
Hand water once daily.
After 7 – 10 days remove the root stimulant from the equation and maintain nutrient at ¼ strength, hand watering once daily.
After 2 weeks go to 1/3 strength nutrient until the plants are beginning to grow vigorously and are shooting out laterals. After approximately 3-4 weeks go to ½ strength nutrient. The plants now have high uptake needs so hand water once to twice daily, allowing for 15 -20% run off (waste) on each feed.
Optional/Recommended: At week 3-4 introduce Psycho XLR8 at 0.25 – 0.35ml/L for 1 week. Working Concentrate Formula for Psycho XLR8 edited out for website viewing
When going to the 12/12 light cycle
Use a 1/3 to ½ strength root stimulant (e.g. rhizo product), along with nutrient (approx EC 1.2 – 1.4) until week 4 of flower.
Begin to introduce a PK product when the first signs of flowers begin to show. Initially use 1/4 the recommended dosage (e.g. if using a PK product with a recommended dilution rate of 1ml/L, use at 1ml per 4 litres) for 10 days before going over to half strength (1ml to 2L). If growing larger plants increase the nutrient strength to ¾ strength (EC should be approximately 1.4 – 1.6 if using RO water and 1.6 – 1.8 if using mains water). If using the higher EC watch for tip burn (signs of over feeding) and increase the waste to 30% to reduce nutrient salt build up in the media. The plants, at this point, should be getting 1- 2 feeds a day. Maximum EC of the nutrient throughout the bloom cycle should be 2.0EC or upto 3.0EC in the case of larger plants.
Use the netting system (tie the plants down) in the same way as coco growing.
Always Flush (water only) for the last 7 days or more prior to harvest to ensure a clean end product.
Technically speaking, “soil fertigation” refers to a nutrient drip feed system or automated feed system in soil. In this system, it is similar to RTW coco growing where a timer controls feeds and nutrient is delivered by a water pump through feed (dripper) lines. There are distinct advantages to this system – no more so than less hands on and, therefore (as with coco), lazy growing. If choosing to automate and provide multiples of smaller feeds maintain a 15-20% runoff regime in RO water/nutrient and 30% runoff if using tap/mains water.
Organic Tasting Produce
Recently I was speaking to a friend from Vancouver – a long time high-end commercial grower who has won several prizes for breeding and the quality of his product – about my views on organics (I.e. organic hydro nutrients versus hydroponic mineral nutrients). My friend agreed with everything I said but did make one important point. “Yeah, it’s true” he said. “Organics is a load of BS. Smaller yields, higher failure rates, harder to handle and I think more contaminants like mould may even be present… but you know what, the best tasting stuff I’ve ever had was the stuff I grew organically.”
I agreed with him and then explained that the same thing could be achieved in hydroponics using organic sugars and potash….
Some years ago I ran experiments which involved attempting to make “hydro” produce taste and look exactly like quality organic produce. What I discovered was that through using organic potash and organic sugars in the last two and a half weeks of flower my “hydro” produce looked and tasted very similar (if not exactly the same) to that of even the best organically grown produce.
The process was simple and here’s how I did it; 21/2 weeks (approx 20 – 21 days) before harvest I used molasses (at 0.5%w/v), and glucose (at 1%w/v) along with a ½ strength bloom nutrient (bloom nutrient at 1.0 EC in RO water – less if growing in soil) for 10 days.
After 10 days, I cut out the “hydro” fertilisers completely and used glucose and molasses for approximately five days. In the last 5-6 days, prior to harvest, I ran water only to ensure a good flush. I was also growing in coco substrate as run-to-waste (RTW) which enabled this process greatly (I hand fed/watered the plants the rather thick organic sugar and potash mix which may have otherwise blocked the feed/RTW drippers).
The result was an extremely sweet tasting and fantastic looking product, with only a marginal (approx 2-3%) loss in yield against a control crop I had growing in the same room using my standard fertiliser regime.
If you choose to use this method:
Let’s quickly have a look at a typical analysis of molasses.
Typical Analysis of Molasses
on an “As Fed” basis:
You’ll note that molasses contains 50%w/v sugars (35%w/v as sucrose). Other than this, it contains 5.19%w/v (51,900ppm) potassium. However, one of the key things here is that molasses feasibly contains 2.98%w/v chlorine, which equates to 29,800ppm of chlorine, so when molasses is used at 0.5%w/v you can theoretically have 149ppm of chlorine present in your feed. Chlorine at these levels is high so it’s important to premix the molasses at 0.5%w/v and store it in a secondary holding tank for several days to allow the chlorine to dissipate before feeding/use. Store the premix in an open topped and aerated holding tank to allow the chlorine to dissipate freely.
Usage Rates and Times
During the first part of the cycle (approx 10-11 days), while using a half strength bloom nutrient, add glucose at 10g/L (1.0%w/v) to the tank. Boil some water and mix/dissolve molasses into it. Add this to the desired levels of water in the nutrient tank (e.g. 50ltrs etc). Use raw molasses at approx 1L to 200L (0.5%w/v) of nutrient/water. Run a water pump at the base of the tank to continually circulate the ingredients and aerate. You’ll need to ‘burn off’ (dissipate) the chlorine from this mix for several days before use, so premix ahead of time.
For the next 4-5 days continue using glucose and molasses (no nutrient) at their 1%w/v (glucose) and 0.5%w/v (molasses) rates. In the last 5 days run water only to ensure a good “flush”.
Author’s note: It is important to note that British research recently proved traditionally grown agricultural produce was as nutritious as its organic equivalent. The research also found that organic produce contained higher levels of potassium and phosphorous while agricultural produce contained higher levels of nitrogen. Other than this, often potassium and phosphorous (potash) is used as a fertiliser by fruit growers (nectarines, peaches etc) just prior to harvest to raise natural sugar levels in the fruit. The use of P and K during flowering is highly recommended – not only will its use increase density and weight but increase natural sugars, leading to a sweeter tasting (more flavoursome) end product.
Ethical Growing Practices – pesticides and other residual toxins in hydro produce
“Organic food is no more healthy or nutritious than other food, watchdogs declared yesterday.
The Food Standards Agency’s ruling, which follows the world’s largest study into the subject, will be a huge blow to the booming organics business.” Daily Mail (http://www.dailymail.co.uk)
A claim made by organic growers in the past has been that organic produce is healthier, tastier and provides more nutrition than traditionally grown agricultural produce. Such claims were recently slated by British research that found that traditionally grown soil agricultural produce provided as much nutrition (was as healthy) and tasted the same as that of its organic equivalents.
Of course, organic advocates were quick to protest, pointing out, that among other things, the research failed to test for pesticides and other potential toxins. On this point I must agree – the research was too narrow and to be absolutely credible would require both crop types to be tested for heavy metal concentrations and pesticide residues. I.e. there is little point in eating/consuming nutritious food if it is laden in pesticides and other potential toxins.
The basic objectives of organic agriculture include:
- Avoidance of the use of chemical pesticides through the use of natural pest controls (also applied by many hydroponic growers)
- Caring for soil by recording nutrients and composting
- Moderation of nutrient application with the reliance on the buffer action of humus derived from compost
These are environmentally sound objectives comparatively to traditional agricultural practices where pesticides are often used and mineral fertilisation treatments (e.g. heavy use of urea) can result in leaching and, hence, soil and ground water (river etc) contamination. However, these organic objectives can also be met using hydroponic growing technologies. That is, hydroponics allows us to A) separate minerals from the environment (no leaching into water tables and rivers) and B) use organic pest control agents.
What Causes Toxicity in Hydro Produce?
Quite simply, the very same thing that causes toxicity in soil grown produce! That is, toxins which remain on the surface of or residual in the plant.
Hydroponics, however, allows us to control exactly what the plant consumes (unlike soil which could contain toxins that we can do nothing about). For this reason ethical growing practices are a must.
Scientists have known since the 1920s that organic fertilisers (composted animal manure, rock phosphates, fish emulsions, guano, and wood ashes etc) contaminate topsoil with varying concentrations of heavy metals. Organic advocates, who rely exclusively on these fertilisers, are well aware of the problem, although they rarely publicise the point.
Rules for Producing a Clean Product
- Avoid using systemic products (e.g. systemic chemical pesticides and systemic fungicides – a formula for an organic fungicide can be found on page ……)
- If you do need to use a systemic product, note the clearing time and double it
- Never use a systemic product past the midway point of the flowering cycle. There are less harmful ways of dealing with pests (e.g. botanical and biological control agents)
- If you do need to use pesticides that are potentially toxic, never spray within 4 weeks of harvest.
- Avoid the use of questionable products (e.g. PGR flowering products/additive – c formulas on page …. – , chemical pesticides and some hormone products – e.g. NAA)
- If purchasing additives, attempt to find out what the actives of any given product are. If the product is suspect exercise your right to pass (for instance, any product that has a profound effect on plants likely contains actives that are problematic. E.g. A product that ceases vertical growth, induces early flowerset and heavy flower formation – contrary to claims – is unlikely to be organic and safe).
- Avoid purchasing under the counter (not displayed) or unlabeled products. It stands to reason that anything sold from under the counter and/or is unlabelled has dubious origins (the reason its under the counter is because it, in all probability, fails to meet agricultural codes)
- Always flush for a minimum of five days (ideally 7 or more). This will help convert the residual elements into biomass and ensure a very clean end product, provided that other growing practices are in check.
THE IMPORTANCE OF THE “FLUSH”
There’s been some controversy in California of late around “chemically tasting” med marijuana being sold through State licensed medical (215) outlets. For this reason, it’s important to address (reiterate the importance of) the “flush”. Put simply, the “flush” is the key to producing a clean (non chemically tasting) end product, provided that other growing practices are in check (e.g. systemic products with long withholding periods aren’t used during flowerset). That is, the flush is imperative (an ethical must) when growing with hydroponic fertilisers.
Put simply, plants accumulate fertiliser elements in the leaf and stem tissue. The more fertilisers that are fed to the plant and the higher the bioavailability of these fertilisers the more fertiliser elements that can accumulate in the leaf and stem tissue. By using water only (no nutrients) in the last 5 or more days (ideally, 7 – 10 days) of the flowering cycle, the plant is forced to use up residual fertiliser elements and convert them to sugars and carbohydrates for photosynthesis (i.e. convert the residual elements into biomass). Put more simply, the flush ensures a “chemical” free end product. Put even more simply… Flush! Flush! Flush!
Outdoor Sustainable (Earth Friendly) Growing Practices (for up on the hill)
One of the issues that some/many outdoor growers consider is leaching and the use of “chemical” fertilisers in the outdoor environment. Leaching is relatively easy to circumvent using run-to-waste (drain-to-waste) growing methods and catching runoff before it enters the surrounding environment.
What you can do is dig growing trenches and line these with thick plastic (e.g. Panda Plastic/film) before refilling the trenches with soil (or, preferably, a light pH buffered soil/potting mix, perlite, coco substrate mix). Dig the trench on a slight downhill angle and make a deep hole at the end where a catchment reservoir can be placed. The waste can then be emptied into a larger reservoir that has an open top (exposed to air), allowing for evaporation of water (whereby the raw minerals in the fertilisers can be trapped/contained and disposed of safely away from the environment and water tables and waterways).
Alternatively, outdoor RTW (DTW) growing can be facilitated by using 44-gallon (200 litre) drums that are cut in half and either placed above ground or below ground (buried) and interconnected using pipes and/or hoses. Line the base of the drums with expanded clay (or scoria etc) to ensure adequate drainage. Run perforated PVC piping through the drums. Again, collect the waste and dispose of it away from the environment. Using half 44gallon drums (22gal – 100L) means that you can often grow two plants per drum. If growing two plants per drum, bend the plants away from each other during grow and bloom.
Another option is to use large (50 -100L) pots as a satellite system (a pot in a pot – similar to coco RTW growing) either above ground or placed below ground. The key, whatever system you use, is to separate nutrient runoff from the environment. (See illustrations)
Outdoor soil fertigation has distinct advantages over organic growing methods. You are able to provide optimised nutrition via the hydro organic fertigation process (e.g. a drip system can be used) in an optimised, pH buffered, bio-rich (biodiverse) soil (i.e. environmentally friendly, outdoor hydro growing).