Sustainability is a growing theme made more urgent by climate changes, population growth, and limited natural resources. The search for more effective ways of producing healthy food continues. A 2014 study estimated that 40 million cubic meters (1.412 trillion cubic feet) of peat is used annually worldwide in horticultural production, destroying wetlands.
Both peat moss and coconut coir are inert growth mediums. You can use pure coconut coir in an analogous non-organic system where nutrients are highly available. Peat moss is unsuitable as a long-term medium on its own.
Peat moss is anaerobic biomass accumulated in peat bogs over millennia as layers of grass, reeds, and vegetable matter not fully decomposed. Coconut coir is the outer husks of coconuts and is an agricultural by-product. There are pros and cons to each medium, so let’s look at these two in some detail.
The Bioponic Media Debate
It’s worth noting that the Merriam-Webster definition of hydroponics, as mentioned above, equates soil to an inert substrate in a system where plants’ nutrient needs are met through liquid feeding. We acknowledge that in a soil-based cropping system, where the earth meets the plants’ nutrient requirements, the soil is not inert but actively supplies and cycles nutrients.
However, any rooting medium, including soil, will not provide an appropriate or long-term source of fertility for growing plants unless managed.
Coconut coir is a typical rooting material used in hydroponic container cultivation. Coir is resistant to microbial degradation, and therefore it will keep its structure and water-holding capacity in the container for longer than other roofing materials.
Coir, according to proponents of hydroponics, is not inert. However, after much research, the NOP included “coconut husk” in a list of instances of an “inert medium” in the Organic Integrity Quarterly in May 2014 (page 13).
Coconut coir is an excellent rooting media for hydroponic production since it is refractory and has a high air and water retention capacity. The cation exchange capacity of coir pith is 20-30 meq/100g.
Coir pith has a nitrogen level of less than 1%. Because coir pith has a C: N ratio of 100:1, the small quantity of nitrogen in it will not function as a nitrogen source for developing plants, which means that in a hydroponic system with coir as the rooting medium, all of the plants’ nitrogen demands will have to be met through liquid feeding.
The final verdict came at a meeting held on August 29, 2017, by the National Organic Standards Board, where the following two-thirds-majority votes regarding “Hydroponics and Container-Growing,” were cast. An extract of the two motions follow:
Subcommittee vote, container production:
Motion that for container production to be certified organic, a limit of 20% of the plants’ nitrogen requirement can be supplied by liquid feeding. A limit of 50% of the plants’ nitrogen requirement can be added to the container after planting the crop. For perennials, the nitrogen feeding limit is calculated on an annual basis. Transplants, ornamentals, herbs, sprouts, fodder, and aquatic plants are exempted from these requirements.
Yes: 6 No: 3 Abstain: 0 Absent: 0 Recuse: 0
Subcommittee vote, hydroponics:
Motion that any container production system that does not meet the standard of a limit of 20% of the plants’ nitrogen requirement being supplied by liquid feeding, and a limit of 50% of the plants’ nitrogen requirement being added to the container after the crop has been planted is defined as hydroponic and should not be allowed to be certified organic.
For perennials, the nitrogen feeding limit is calculated on an annual basis. Transplants, ornamentals, herbs, sprouts, fodder, and aquatic plants are exempted from these requirements.
Yes: 6 No: 3 Abstain: 0 Absent: 0 Recuse: 0
Comparative Study – Peat vs. Coir
A 2017 study, “Comparison of Coconut Coir, Rockwool, and Peat Cultivations for Tomato Production: Nutrient Balance, Plant Growth and Fruit Quality,” compared the three mediums in the production of tomatoes. We summarise the outcomes of the study in respect of coconut coir and a peat-vermiculite mix here:
Composition and Properties
|EC (dS m-1)||0.1||1.1|
|N (mg kg-1)||44||64|
|P (mg kg-1)||38||42|
|K (mg kg-1)||1560||246|
|Ca (mg kg-1)||58||1668|
|Mg (mg kg-1)||55||636|
|S (mg kg-1)||405||645|
|Water porosity (%)||80||64|
|Air porosity (%)||5.6||2|
|Bulk density (g cm-3)||0.2||0.4|
Although there was no significant variation in fertilizer input between different substrate cultivations, there were substantial changes in nutrient uptake by crops and nutrient residual in substrates, resulting in noticeable nutrient balance disparities. Coconut coir cultivation showed the highest nutrient uptake by crops, particularly for P, K, and S. In addition, coconut coir production had the most significant P residue in the substrate.
However, peat-vermiculite cultivation had the highest residues of other nutrients (e.g., Ca, Mg, and S) in the substrate. Because of these variances, coconut coir had the lowest uncredited nutrient levels (the lower, the better), particularly for N, P, and K. Furthermore, the peat-vermiculite cultivation yielded the lowest uncredited Ca.
|Uptake by Crops||Coconut Coir||18.70||6.00||41.20||9.50||3.70||6.10|
|Residue in Substrate||Coconut Coir||7.80||1.20||17.20||18.30||3.10||8.00|
|Uncredited Nutrient||Coconut Coir||29.60||4.90||26.50||7.10||0.10||1.80|
Coconut coir was a possible substrate for tomato production that may be widely employed. Coconut coir had higher K and S uptake by crops, photosynthesis, individual fruit weight, and total fruit output than Rockwool and lower uncredited nutrient levels (the lower, the better). Coconut coir had more P and K uptake by crops and total fruit yield than peat-vermiculite, as well as lesser unaccounted P and K.
In comparison to Rockwool or peat-vermiculite, coconut coir does not affect blossom-end rot. Furthermore, the impacts of substrates on fruit quality were not always clear.
Peat moss, generated over thousands of years when a lack of oxygen disrupts natural decay processes, is a non-renewable resource. Peat bogs form over ages and ages, but our consumption rate far outstrips any possible replenishment of this resource.
Wetlands, which often serve as bird sanctuaries, are drained to mine peat. These wetlands are carbon basins, absorbing tons of carbon from the air. But once the bogs are exposed, they become methane pits. Pound for pound, the comparative impact of methane is 25 times greater than carbon dioxide over 100 years.
In horticulture, mixing perlite and vermiculite into peat moss increases its usability. Unmixed, it is unsuitable for some hydroponic systems. Perlite functions as an aerator, allowing water to escape the soil. Vermiculite acts like a sponge, allowing the soil to retain moisture. Together they provide your soil with a proper drainage and water retention balance. Without the addition, decomposing peat moss tends to strangle your plants’ roots, cutting the air supply off.
As a result, a high-quality peat replacement that is always available and meets increased environmental concerns would be a “natural” on the market. The study above clearly shows that coconut coir is a competitive replacement for peat moss.
These systems use solid fertilizers incorporated into the growing media and liquid fertilizers given through irrigation systems to grow crops in containers and provide nutrients. Containerized production requires sufficient biology to transform natural fertilizers into a form that plants can use.
Growers are discovering further water-saving and land-conservation benefits from growing in containers to produce vegetables like tomatoes, peppers, cucumbers, and small berries like blueberries and raspberries.
Because containerized production is complex and capital-intensive, it only lends itself to the production of higher-value specialty crops like fruits and vegetables. It is unlikely to see widespread adoption of containerized production to grow crops that require large acreage, such as grains.
However, when producers confront increasing constraints such as water and labor shortage, land scarcity, and a growing urban population, these creative production techniques may address some of these issues.
As these systems prove successful, there is growing adoption of containerized production in urban settings. Urban agriculture has the potential to address food sovereignty issues for densely populated areas. The Urban Agriculture Act of 2018 aims to create new economic opportunities and increase access to healthy foods. These include:
- Community gardens and farms located in urban areas, suburbs, and urban clusters;
- Rooftop farms, outdoor vertical production, and green walls;
- Indoor farms, greenhouses, and high-tech vertical technology farms;
- Hydroponic, aeroponic, and aquaponic farm facilities; and
- Other innovations in agricultural production, as determined by the Secretary.
For most of these, the use of coconut coir is a growing option as a proven substrate. When the funding allocated to this Federal initiative becomes available, real opportunities for localized production will increase.
While peat moss will have a continued uptake as a soil additive to influence soil pH levels, especially for lawn grasses, it is reasonable to predict that coconut coir will increasingly be the medium of choice for hydroponic-type installations. In answer to the question in the title of this article, “Is Coconut Coir a Natural Alternative to Peat Moss?” the answer has to be “yes,” in most cases.
This article did not include a look at the combined usage of peat moss and coconut coir. In container production, this is a real option as peat moss’s distinct advantages are its superior surface area and thus water retention. Because of its fibrous texture and porosity, its use continues as a plant-growth medium in several horticultural and agricultural applications.
Its fibrous structure and porosity promote a mix of water retention and drainage. Potting soils, lawn and garden soil additions, and golf course turf management are examples of commercial usage. In industry, peat is primarily employed as a filtration medium to remove toxic compounds from process waste streams, pathogens from sewage effluents, and deleterious items floating in storm-drain water.
We trust that this article was informative. We have included multiple links for you to explore a diverse source of research topics on peat moss and the up-and-coming champion, coconut coir. The Hydroponic and Aquaponic Task Force Team Report has loads of relevant information, including extensive information on both topics and more. Drafted in 2016, it may not be fully up-to-date in an ever-evolving landscape, so keep visiting us regularly for updates on various issues.
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