Coconut substrate: what it is and how it is made
March 16, 2021
Coco coir substrate basics
December 6, 2021
Overview
Coconut coir substrates are taking the soilless market by storm, but they are still relatively novel compared to other growing media alternatives like rockwool and peat moss. Let’s compare the three and see which substrate is most suitable for each purpose.
First, we are going to briefly explain what each growing media is and how it is made.
- Peat moss, or sphagnum peat, is created when mosses and other organic material very slowly decompose in acidic and anaerobic conditions (without the presence of air). This kind of decomposition gives it its fibrous properties, acidity, and good water retention. Peat is formed in bogs and it takes thousands of years for it to form, making it a non-renewable resource.
- Rockwool is an inorganic man-made growing media that is mainly manufactured by melting diabase and limestone at high temperatures (between 1000-2000 ◦C), creating thin fine fibers. These fibers are then spun into a fiber-glass-like material and shaped in the form of a block or slab.
- Coconut coir substrate is made from coconut coir, a middle fibrous layer between the shell and the outer coating of coconut. After being separated from the husk, the coir is dried out and separated into pith, fiber, and chips. Each of these components has different properties and mixing them allows achieving a great variety of growing media.
Making a choice in this variety seems hard, as there are many variables for each crop. We are going to look at the existing scientific research in this field to find the most optimal solution for each property.
Nutrient uptake, yield, and fruit weight
The performance of these three growing media was compared in a study published by researchers from China Agricultural University and Beijing Academy of Agriculture and Forestry Sciences. Their research discovered the effects of each substrate on EC, pH, mineral ions in root-zone, nutrient uptake, nutrient balance, plant growth, and fruit quality in tomato plants.
We have summarized some of their findings in the table below:
| Coconut coir | Peat moss with Vermiculite | Rockwool | |
|---|---|---|---|
| Total fruit yield | Significantly higher | Higher | Significantly lower |
| Individual fruit weight | High, similar to peat vermiculite | High, similar to coco coir | Lower |
| Nutrient uptake | Highest nutrient uptake, especially P, K, and S | Comparable to coco coir uptake of Mg, better uptake of N, Ca, and S than rockwool | Comparable to coco coir uptake of Mg, better uptake of P, K, and Mg than peat vermiculite |
| Plant biomass | Significantly higher | Lower, but comparable to rockwool | Lowest, but comparable to peat moss |
| Accumulation of N, P, K, and S nutrients | Highest | Medium | Lowest |
| Blossom-end rot occurrence | Medium throughout most harvests | Lowest throughout most harvests | Highest throughout most harvests |
Advantages and disadvantages based on other properties
| Coconut coir | Peat moss with Vermiculite | Rockwool | |
|---|---|---|---|
| Advantages | - Comes in compressed form: easy and cheap transportation and handling - Sterile, doesn't contain any harmful chemicals and pathogens - Slow breakdown, can be used for many years - Great water retention, drainage, and aeration - Close to neutral pH - Antifungal properties - Easily rewetted, very hydrophilic - Does not compact over time - Renewable and eco-friendly | - Sterile, doesn't contain any harmful chemicals and pathogens - Great water retention and highly absorbent - Does not compact for a long time - Contains a bit of nutrients - Light and porous - Completely organic | - Comes in blocks and bales, making handling and transportation easier - Completely sterile, doesn't contain any harmful for plants chemicals and pathogens - Does not break down over time - Great water holding capacity and aeration - Do not influence EC, pH or composition of the applied nutrient solution |
| Disadvantages | - Can have high EC and salt content, so washing and buffering is necessary for most crops - Contains extremely small amount of nutrients, so good fertilization is required - Can hold on to magnesium and calcium, so fertilisation regime has to be adjusted | - Extraction of peat moss is very harmful to environment - Acidic pH, so not ideal for alkaline-loving plants - Contains very small amount of nutrients, so good fertilization is required - Supplied only in loose form in bags so transportation and handling are expensive - Difficult to rewet | - Disposal is a big problem, does not break down over time - Bulky to transport and store - Contains no nutrients, so good fertilization is required |
In the next article, we are going to dive deeper into the effect of each of these growing media on the environment. Stay tuned!
Sources
Xiong, Jing, Yongqiang Tian, Jingguo Wang, Wei Liu, and Qing Chen. “Comparison of Coconut Coir, Rockwool, and Peat Cultivations for Tomato Production: Nutrient Balance, Plant Growth and Fruit Quality.” Frontiers in Plant Science 8 (2017). doi:10.3389/fpls.2017.01327.
QUANTIS. Comparative Life Cycle Assessment of Horticultural Growing Media Based on Peat andOther Growing Media Constituents 2012. Available online: http://epagma.eu/evidence-based.
Gruda, Nazim. “Increasing Sustainability of Growing Media Constituents and Stand-Alone Substrates in Soilless Culture Systems.” Agronomy 9, no. 6 (2019): 298. doi:10.3390/agronomy9060298.
