Dr. Richard Freeman
This guide provides instructions to formulate a high-production, biologically-intensive horticultural container media using sustainable resources. The intended audience includes urban horticultural operations seeking to maximize production of sun-grown crops in limited space using sustainable practices. The practitioner can easily improvise using this framework as a reference for smaller operations without conducting rigorous tests. Larger operations should conduct testing to assure maximum benefit over the long term. Please see the author’s note at the end of this guide.
Urban horticulture generally lacks the benefits of a clean agricultural field soil with well-developed soil profiles, natural buffering systems and soil biodiversity that support plant productivity and corresponding functions. Thus, formulating and creating artificial soils, or horticulture container media (HCM) must fill this requirement. A sustainable urban horticulture requires that the substrates composing these HCMs be produced sustainably, as well. However, substrates vary widely from region to region due to uneven availability and variation in substrate properties from region to region. Thus, the HCM formulator must create high-functioning HCMs with available resource, requiring an analytical framework for formulation. With an understanding of the background science underlying formulating a high-quality HCM using sustainably-produced substrates, the operator can create these HCMs to suit specific management objectives.
This guide provides a framework for formulating an HCM with substrates sourced from agricultural and lawn wastes that are currently readily available in the western United States. Some of these substrates are sourced internationally (coir) and some are sourced regionally (biochar, composted pine bark). The HCM formulation process follows a functional logic that begins with defining project goals and objectives, and proceeds by translating those goals and objectives into a specific HCM blend.
Each section describes a part of the process for formulating the HCM. Section 1 explains the goals and objectives this HCM will meet. Section 2 outlines the process of identifying physical, chemical and biological properties and target values for HCM properties. Section 3 identifies some common bulk substrates that will combine to meet the HCM properties and that are commonly available at a feasible price or can easily be made. Section 4 describes a basic process for formulating the HCM. Section 5 outlines some procedures for testing the HCMs effectiveness.
Section 1. Horticultural goals and objectives for the HCM
Goals and objectives are fundamentally important to assuring that an HCM is formulated to meet the needs of the horticultural operation for the long-term. Formulation requires time and investment and once the operation has established an effective HCM, it can depend on it for years.
1.1. Goal statements
The main goal or goals state the desired, general aim of the formulation in a brief, one- or two-sentence statement. For the example, a goal statement is “Formulate a premium HCM that is suitable for professional horticulture or home-scale growing and meets these sub-goals.”
Sub-goal statements clarify what the formulator wants to accomplish in more specific terms without delving into how the goals will be accomplished. For the example, sub-goal statements follow:
1.1.a. The HCM grows large, vigorous, nutrient-demanding annual plant species and strains.
1.1.b. It creates a substantial biologically beneficial rhizosphere and container environment, substantially contributing to nutrient pathways.
1.1.c. It works well with a biologically robust fertilization regime.
1.1.d. It relies on the most sustainably-sourced substrates available at feasible cost.
1.1.e. It is made from bulk substrates that are biodegradable and/or contribute to beneficial soil organic matter (SOM) so that used media constitute a valuable field soil amendment or compost substrate.
1.1.f. It is mixed from bulk substrates that sequester carbon as recalcitrant SOM.
1.2. Objective statements
These management objectives are general directions on how to accomplish the main goal. For the reference example, objectives include those listed below. For clarity, sub-objective statements offer more information to the formulator:
1.2.a. Identify substrates with properties that promote a beneficial root biology (Goals a, b, c, d, and g). Thus the HCM substrates in blended form must minimize prolonged anaerobic and septic conditions. Likewise, it must be easy to correct and adjust.
1.2.b. Identify substrates that blend well to create a good environment for effectively managing high-biology fertilization. (Goals a, b, c and d) Again, the HCM must minimize prolonged anaerobic and septic conditions and be easy to correct and adjust.
1.2.c. Find a source for stable and mature composted substrates (specifically, composted pine bark, green waste compost and vermicompost). (Goals a, b, c and d) HCM substrates must be able to withstand a high-biology environment with minimal decomposition and degradation.
1.2.d. Favor substrates that will enhance field soil when used as a conditioner, with an emphasis on recalcitrant SOM. (Goals f and g). All organic substrates will meet this objective with varying degrees of effectiveness.
1.2.e. Favor substrates with higher sustainability index ratings.
1.2.f. Assure that substrates that will be reliably available (steady supply and stable cost), favoring regional availability as a component of reliability (Goals a and e) Availability will vary by region, requiring flexibility in formulation.
1.2.g. Favor substrates that minimize operational costs. (Goal a) Worker safety issues are significant and costly, hazardous dust be a primary concern along with exposure to toxins and pathogens.
1.2.h. Pre-load maximum possible nutrient base into the HCM using composts, plant-based meals (alfalfa, soybean oil cake) bone meal as nutrient sources when possible, supplementing with the most basic mineral salts (specifically some use of gypsum, dolomite and epsom salts).
Constraints limit objectives and often reflect cultural and political values. Also, they often reflect operational conflict between objectives.
1.3.1. Avoid bulk substrates that require mining or unsustainable harvest.
1.3.2. Avoid bulk substrates that vary in uniformity and quality.
Section 2. Defining target HCM properties
This section gives an overview of the process of defining target values for physical, chemical and biological properties.
2.1. Physical properties
Formulating an HCM mixture for objectives 1 and 2, which emphasize promoting and maintaining a robust beneficial biology, requires an HCM that meet these criteria:
2.1.a. It has effective hydraulic conductivity.
2.1.b. It has excellent gas and oxygen diffusivity.
2.1.c. It holds a sufficient quantity of available water in the context of water management practices.
Generally, particles that maximize hydraulic conductivity and diffusivity are coarser than particles maximizing available water holding, though some overlap exists. Thus, formulating a balance that favors diffusivity will sacrifice some readily-available water-holding capacity. While this aerated mixture will lose some available water-holding capacity in order to gain maximize aeration and hydraulic conductivity, it will still maintain a large reservoir, overall. However, under extreme drying conditions, the aerated mix will require more frequent irrigation than will a mix with less aeration.
2.1.2. Targeted particle size range
The particle size range for the HCM should reflect the formulator’s desired functions and properties for the HCM. For the reference example formulation, the ideal overall target is 100% particles evenly distributed between 0.1-3.0 mm diameter, with less than 10% total particles under 0.2 mm and 5% total particles over 3 mm.
However, a target for each type of substrate based on particle shape will be useful, because the functional properties that particles confer depend upon their geometry. In the reference example,
The HCM will include at least two distinct particle types with different shapes and corresponding water and air relations. Fibrous particles, like coco coir or peat moss, can maintain available water-holding capacity and aeration while maintaining high gas and oxygen diffusion with comparatively larger particles than can angular, quasi-disk-shaped particles, like biochar, composted pine bark or perlite, and somewhat like parboiled rice hulls. Thus, a target for each type of substrate based on particle shape will be useful. Once the threshold levels are empirically established, this distinction will make lend more opportunity to adjust mixtures.
For this formulation, the ideal target for fibrous substrate particle-diameter is an even distribution of particles sized between 0.25-3.0 mm with an allowable error of 10-15% for smaller particles and 5% for larger particles. Less than 2% should be under 0.1 mm and all particles should be less than 4 mm. For disc-shaped particles, the ideal target is ranges evenly between 0.2-2.5 mm with an allowable error of 10% for smaller particles and 5% for larger particles.
To note, due to blending dynamics and the threshold effect, the particle-size target will likely change as the formulator tests mixtures.
2.2. Chemical properties
Formulating an HCM mixture in reference to pre-loading a generous nutrient reserve and promoting and maintaining a robust beneficial biology for pest suppression and nutrient cycling suggests several criteria in respect to chemical properties:
2.2.a. It has a high total exchangeable cations index.
2.2.b. It has a neutral pH in reference to container environments (less than 6.5).
2.2.c. It has acceptable EC values.
2.2.d. It sequesters reserve quantities of nutrients biologically that will become available through the growing cycle in forms that minimize leaching.
2.3. Biological properties
Formulating an HCM mixture in reference to pre-loading a generous nutrient reserve and promoting and maintaining a robust beneficial biology suggests several criteria in respect to biological properties:
2.3.a. It has a high microbial diversity with adequate representation of soil fungi.
2.3.b. It has generous representation of substrates known to stimulate beneficial biology.
2.3.c. It lacks a substantial population of pathogenic microbes.
Section 3. Obtaining and processing available substrates
This project will consider coconut coir for a substrate with fibrous particles, screened biochar and screened and composted pine bark (CPB) for coarse, granular and disc-shaped particles, and green waste compost and vermicompost for fine-particle, high-biology bulk substrates.
3.1. Coconut coir (Coco)
Coco is the pith and residual fiber that is the by-product of coconut long-fiber production. Coco offers several properties that support formulation objectives, and by itself makes an excellent germination medium.
3.1.1. Physical properties
Coir functions, generally, as a fibrous substrate. Given the specified particle-size distribution, coir presents a good balance of aeration and readily available water holding capacity. In addition, due to its fibrous structure, coir will distribute water horizontally within a short distance, especially as a function of water application rate.
3.1.2. Chemical properties
High-quality coir generally presents a neutral pH, a modest EC and a fairly low CEC (roughly half the CEC of peat). It does contribute substantial available potassium.
3.1.3. Biological properties
Coir confers no significant biological supplement, affinity or hazard.
3.1.4. Operational qualities
In terms of operational properties, coir is stable under operational conditions, readily available, cost-effective, and has low-bulk density. However, coir requires specialized equipment, specifically machinery for decompressing highly-compressed coir bales without breaking fibers. At the small-scale, decompressing without equipment is simple but labor-intensive. At a larger, commercial scale this process requires specialized equipment that will preserve fiber particles.
Coir is readily available in all parts of the United States as an imported substrate. The coir for this formulation is sourced from Sri Lanka, though future work will test Mexican coir. (Long-term goals include developing other plant-based substrates with fibrous particles.)
Biochar is the product of pyrolizing woody (ligno-cellulosic) materials — or super-heating them in the absence of oxygen. This guide refers to biochar made from pyrolizing pine in a kon-tiki open kiln at highest heating temperatures of 650–750°C (c. 1,200–1.380°F). Biochar has several properties that support formulation objectives.
3.2.1. Physical properties
Biochar is a disk-like or modified granular substrate. Within a given the specified size class, biochar presents a good balance of aeration and readily available water holding capacity. However, these properties are more dependent on particle size than fibers. In addition to holding water between particles, biochar holds water in material pores that is available to microbes and to limited root access.
3.2.2. Chemical properties
Biochar has several chemical properties that support formulation objectives. In raw form, it has a high pH due to ash content (especially calcium carbonates). However, if biochar is correctly inoculated with microbes or charged with nutrients (especially high-H and high-P), pH is typically neutral.
In addition, biochar has high cation and anion exchange functionality and exhibits surface electrical conductivity, independent of its salinity, due to its unique physical and chemical properties.
3.2.3. Biological properties
Biochar provides a robust environment for the biofilm accumulation of beneficial bacteria and fungi due to its water-holding capacity, complex porous structure, CEC and Anion EC. Further, due to a combination of factors biochar supports systemic resistance properties.
3.2.4. Operational properties
In terms of operational properties, biochar is stable under growing conditions, but it is somewhat susceptible to size degradation during shipping and handling.
The performance of the HCM, however, proves worth the effort on high-production, high-value plants, especially high-value plants.Currently, biochar is not widely available in the United States, though it is available from a few sources in the western U.S. Screen-graded biochar is not yet available anywhere in the U.S. However, though biochar has not reached distribution in proportion to its value as a substrate, it can be made inexpensively anywhere with clean woody material to pyrolize using primitive screening technology and composting technology for charging the raw biochar. At a small scale, screen-grading is easily accomplished but labor intensive. For larger-scale production, dry-screening equipment will be necessary. Screening removes most fines, within an accepted margin of error; screening costs show diminishing returns, % removal of fines is not cost-feasible. Shredding coarse biochar for screening produces rounded, granular particles compared to screening directly.
3.3. Composted Pine Bark (CPB)
Composted pine bark offers several properties supporting formulation objectives, especially if it is screened to specification.
3.3.1. Physical properties
CBP is as a disk-like substrate that offers several beneficial physical properties. Given that the particle-size distribution is within a specified size range, CPB presents a good balance of aeration and readily available water holding capacity. Particle size is especially important, as performance declines significantly outside specific ranges compared to fibers.
3.3.2. Chemical properties
CPB has several chemical properties that support formulation objectives. CPB has good cation exchange, low EC and slightly low pH, which is advantageous to all objectives and can offset the high pH of raw biochar.
3.3.3. Biological properties
CPB holds water in material pores that is available to microbes and its chemical properties make it attractive to microbes. Generally, horticulturists manage CPB as a sterile medium, though it does have suppressive characteristics, including suppression of Phytophthora root rot. It can also take inoculation of bacteria and fungi that enhance suppression of root pathogens.
3.3.4. Operational properties
CPB is generally available in regions with timber production. However, screen-graded CPB is not yet available, so the blender or blending facility will need to screen this product. At a small scale, screening is easily accomplished but labor intensive. For larger-scale production, dry-screening equipment will be necessary.
3.4. Green waste compost (GWC)
Green waste compost has several properties that support HCM formulation objectives.
3.4.1. Physical properties
GWC contains a variety of particle types, ranging from fibrous to disk-like and granular. Given the specified size class, compost presents an acceptable balance of aeration and readily available water holding capacity. However, compost contains a large proportion of particles finer than the target size-distribution for this formulation.
3.4.2. Chemical properties
In terms of chemistry, high-quality green waste compost generally presents a high pH, a modest EC and a substantial contribution of macro- and micronutrients.
3.4.3. Biological properties
GWC is a product of thermophilic composting and if prepared carefully performs well in a container environment. In addition, high-quality compost contains a robust microbial diversity beneficial to nutrient cycling and pest suppression.
3.4.4. Operational properties
In terms of operational properties, high-quality compost is stable under operational conditions, readily available and cost-effective, though bulk density is higher than with non-compost substrates. High-quality green waste compost is available in all parts of the U.S., but formulators must source carefully because most green waste compost on the market is sub-standard.
3.5. Vermicompost (VC)
Vermicompost is a product of worm composting and if prepared carefully performs well in a container environment — in SMALL amounts.
3.5.1. Physical properties
VC contains a variety of particle types, ranging from fibrous to disk-like and granular. It is the finest of all the substrates and can contribute a substantial volume of particles smaller than target distribution. VC offers poor aeration but substantial readily available water holding capacity.
3.5.2. Chemical properties
High-quality VC generally has a high pH, a modest EC and contributes a substantial contribution of macro- and micronutrients. VC is generally lower in nitrogen than green waste compost but higher in phosphorus and potassium and comparable in micronutrients.
3.5.3. Biological Properties
VC is the product of slow decomposition and does not reach high temperatures. Thus, it is suitable for containers ONLY in relatively small proportion. However, given judicious use, high-quality VC contains a robust microbial diversity beneficial to nutrient cycling and pest suppression.
3.5.4. Operational properties
High-quality VC is stable under operational conditions, readily available and cost-effective, though bulk density is higher than with non-compost substrates. High-quality VC is available in all parts of the U.S., but formulators must source carefully because much of the VC on the market is sub-standard.
Section 4. Formulating the HCM
Having obtained the substrates, formulating the mixture requires several steps, described below.
4.1. Formulate size distribution targets
Choose an acceptable distribution of particle-sizes in each substrate. For each size class within each substrate, choose targeted percentage values. For examples, see the percentages below.
For fibrous substrates, use the following breakdown of particle-size classes.
|Recommended Particle Size Classes||Example Target Percentages|
|< 0.25 mm||5%|
|0.25 — 1.0 mm||30%|
|1.0 — 2.0 mm||30%|
|2.0 — 3.0 mm||30%|
For cubical, granular or “disc-like” particles, use this breakdown of particle-size classes.
|Recommended Particle Size Classes||Example Target Percentages|
|< 0.25 mm||10%|
|0.25 — 1.0 mm||20%|
|1.0 — 3.0 mm||35%|
|3.0 — 5.0 mm||35%|
4.2. Measuring substrate particle size distribution
Screen samples from each substrate using screens that correspond to the size classes. Record the volumes and weights of substrate in each size class into a written table or spreadsheet. Calculate particle size distribution by percentage. Also, record the time period (in minutes) that you screened each substrate for each screen size.
4.3. Determining which substrates to screen before blending HCM
Based on screening efficiency, choose which substrates (if any) you will screen before blending into an HCM. Screening efficiency is inverse to the time required, per screening, to attain the target distribution within acceptable error. Generally, screening fibrous substrates will be more difficult and less exact than screening disc-like particles. For this example, only biochar and CWB should be screened.
4.4. Screening substrates
Screen a cubic foot each of the chosen substrates with two screen sizes — one slightly larger in opening than the smallest test screen and one equal to the largest test screen. In reference to disc-like particles, the smallest test screen size is 0.25 mm and the largest is 5.0 mm. For screening the substrates to blend. I would recommend 1-2 mm screen and a 5 mm screen. (I use a 1/8″ and a 1/4″ screen.)
The objective is to meet the size class volume targets within acceptable margins of error (in reference to the target) within a reasonable time frame. Roughly speaking, when screening fines on the maximum end (1/4″), when the amount of substrate falling through the screen decreases to roughly 10 percent of initial of volume, I stop screening it. Likewise, when screening fines on the minimum end (1/8″). Particles over 1/4″ and under 1/8″ go to perennial HCMs or raised beds.
4.5. Re-Measuring substrate particle size distribution
Re-screen samples from each screened substrate to determine whether or not you have achieved size class distribution targets. Record the volumes and weights of substrate in each size class into a written table or spreadsheet. Calculate particle size distribution by percentage. If the particle-size distribution varies too much from the targets, re-screen the substrates, reassess the screen efficiencies of substrates that do not screen well, and/or widen acceptable errors.
Record and compile the data in tabular form. This step is highly important because it will form the basis for later calculations.
Differences and trends in size-class distribution between weight and volume provide insight into packing characteristics. With data from the properties of blended HCMs, these particle-size data will be useful to guide future formulations.
4.6. Establishing a rule set for formulating HCMs
Establish a rule set for combining substrates. For example, the following rules can guide a formulation:
4.6.a. The ratio of green waste compost to vermicompost will remain at 6:1 for any mixture. Examples will refer to this blend as the compost blend.
4.6.b. The ratio of biochar to compost blend will always be greater than 1:1.
4.6.c. The highest contribution for biochar to the HCM is 20%.
4.6.d. The highest contribution for vermicompost to any HCM will be 3 percent.
4.6.e. The lowest contribution for compost blend will be 10%. (A 10% compost blend breaks down to 8.4% GWC with 1.4% vermicompost.)
4.6.f. Coarse, disc-like particles (biochar and CWB) will constitute at least 30% of the HCM.
4.6.g. CWB will fill the remaining volume percentage for coarse, disc-like particles.
4.6.h. Coco coir will constitute at least 35% of the HCM.
4.6.i. CWB will constitute at least 5% of the HCM.
4.7. Formulating test blends
Follow these steps to formulate six test mixtures:
4.7.a. Choose a fixed percentage of fibrous substrate (coco coir) near the minimum volume, for example, 40%.
4.7.b. Choose two combinations of biochar/compost blend, for example, 15% biochar and 15% compost blend or 25% biochar and 20% compost blend.
4.7.c. Fill the remaining volume percentage with CWB. So, for example, the HCM blend might include, consistent with the above example, 40% coco coir, 25% biochar, 20% compost blend and 15% CWB.
4.7.d. Choose a larger fixed percentage of coco coir near the middle of the acceptable range, for example, 50%.
4.7.e. Repeat steps b. and c. See the below table for examples.
4.7.f. Repeat 5.7.d. with a larger percentage of coco coir at the upper end of the acceptable range, for example, 60%.
4.7.g. Repeat steps b. and c. See the below table for examples.
4.8. Blending the HCM mixtures
Carefully measure and blend 1-1/2 gallons of each candidate HCM mixture. Thorough blending is highly important, because achieving false results will cause failure further into the development process. Be sure to label each mixture.
4.9. Bench testing substrate samples
Perform bench tests to determine which substrate combinations in varied combinations exhibit the threshold effect, when total porosity begins to decrease with addition of a substrate to a polydisperse medium (blended substrates).
Given the ease of the tests and the value of the resulting data, the sample bench tests are worth the cost of being thorough.
Record data in a written table or spreadsheet.
4.10. Calculating particle-size breakdowns
Calculate the total particle size class distribution of each of the HCMs, given the known size-class distributions and the percentage volume of each substrate in the HCM.
4.11. Calculating particle size distribution deviation from target
Calculate the differences in percentage volume that each substrate will contribute to each particle size class in the initial HCM from the target values (step 1).
4.12. Evaluating particle size distribution
Determine whether or not the differences between target and empirical values are acceptable. Factor in results from bench tests. If not, adjust proportions of substrates until differences are acceptable. If differences are too high, choose another mixture from the test mixtures.
4.13. Choosing one or two candidate HCM blends
Based on determinations from the last step and on bench tests, determine which blend you prefer.
4.14. Lab testing candidate HCM blends
Conduct laboratory tests to determine the level of target physical, chemical and biological properties. Specifically ask the lab to determine water volumes as a percent of container capacity for levels of water available at tensions of 5 kPa, 10 kPa, 16 kPa and 30 kPa.
4.15. Making adjustments
If necessary, assess another HCM blend and re-conduct lab tests.
4.16. Adding supplements
Thoroughly moistening the HCM, add all supplements, and thoroughly blend the mixture. Allow the mixture to rest for 7 days in a warm, dry space in a ventilated container.
4.17. Final Lab test
Conduct laboratory tests for all properties and make adjustments as necessary. Test and adjust until the mixture meets the target properties.
Section 5. Testing and Adjusting the HCM
Field-testing the candidate blend is the final step in formulating an HCM. Running a variety of distinct tests will identify problems. I recommend at least three types of tests: worm tests, germination tests and cultivation tests.
5.1. Worm tests
Worm testing an HCM is an easy technique to determine basic toxicity. The basic concept involves determining whether worms are attracted or repelled by the HCM. This technique in various forms is well-documented and widely-used. (For example, International Organization for Standardization (ISO) guideline no. 17512-1.)
One can devise a simplified version for product development. The basic steps include:
5.1.a. Blend 1-1/2 gallons of the candidate HCM mixture. Blend thoroughly. Moisten and blend again.
5.1.b. Procure 1-1/2 gallons of popular commercial HCM with compost (“potting soil”). Moisten the HCM.
5.1.c. Build a rectangular container or box that will hold 3 gallons of HCM. With a barrier that will permit free passage of worms, divide the box evenly so each half will contain 1-1/2 gallons. Make a loose-fitting lid for the container.
5.1.d. Fill one half with the candidate HCM and the other with an established equivalent HCM.
5.1.e. Put 20 worms in each half and cover the container.
5.1.f. Place the box in a warm place (60-70°F) and leave it for 48 hours.
5.1.g. After 48 hours, empty the HCM from each half into separate containers, and count the worms.
5.1.h. If the candidate HCM has more worms, continue to other tests. If the candidate has fewer worms, analyze the HCM contents and make necessary adjustments.
5.2. Germination Tests
Germination tests provide another basic test for any HCM, with an important proviso: biologically-intensive HCMs are not meant for germination. For horticultural operations, a sterile media is preferable for germination, for example, a peat-lite mixture or coco coir.
Germination tests are basic and simple. The basic steps include:
5.2.a. Blend 1-1/2 gallons of the candidate HCM mixture. Blend thoroughly. Moisten and blend again.
5.2.b. Procure 1-1/2 gallons of popular commercial HCM with compost (“potting soil”). Moisten the HCM.
5.2.c. Fill half the cells in a 128-cell plug tray with the candidate HCM and the other half with the commercial potting soil.
5.2.d. Choose a plant species to germinate and sew one seed into each cell in the plug-tray.
5.2.e. Thoroughly moisturize the plug tray and place it under LED light or in a window. Keep temperatures between between 70-75 F.
5.2.f. Maintain moisture by ONLY spraying the surface of the plug trays as the media shows signs of drying.
5.2.g. Record the number of newly emerged seedlings 4 times a day.
5.2.h. Observe and record the health of all seedlings.
5.2.i. When germination of new seeds has stopped, compile and analyze the data and assess the effectiveness of the HCM.
5.3. Plant Tests
Plant tests will demonstrate the efficacy of the candidate HCM over an expended period of time (4-6 weeks) without fertilization.
5.3.a. Blend 2 gallons of the candidate HCM mixture. Blend thoroughly. Moisten and blend again.
5.3.b. Procure 2 gallons of popular commercial HCM with compost (“potting soil”). Moisten the HCM.
5.3.c. Fill 30 small containers (3-1/2″ x 3-1/2″) with the candidate HCM and 30 more with the commercial potting soil.
5.3.d. In a separate plug-flat, germinate 60 plants in a sterile medium per instructions in above section 6.2 Germination Tests.
5.3.e. Transplant the seedlings into the the small containers and grow the plants for 4-6 weeks.
5.3.f. Observe and record standard morphological and yield characteristics, pest problems, nutrient problems,water use, nutrient use and deficiencies, and other operational behaviors.
5.3.g. Compile and analyze data to determine efficacy of the HCM.
This guide is in draft form. It includes no foot notes or references and it contains significant omissions. Anyone interested in republishing using the content in this guide should first contact me, the author, Richard Freeman, to gain permission.
I am interested in co-authoring a final version of this guide.
The information I present is for educational purposes and I am not liable or responsible for anyone’s use or misuse of this information.
I will periodically post updates to this blog by adding a detailed example and providing specific values for chemical and physical properties.