Organic Soil Materials
Inorganic materials may provide structure and drainage for your growing media but you still need to breathe life into the soil for your plants to thrive! Organic materials do just that, not only do they provide nutrients, but they also cultivate a rich and complex soil microfauna that is necessary for healthy plant growth. Typically, these organic materials are used as mulch and soil amendments to improve water retention, nutrient level and biological activity. In this article we’ll talk about commonly available organic soil materials and how to use them.
First up, you have compost. This seems to be the darling of gardeners everywhere and rightly so. Compost is made up of decayed organic matter typically made from plant matter such as wood or horticultural clippings. On top of being packed with all the nutrients needed, it hosts a vast range of bacteria, fungi and other microorganisms that help your plant get what it needs! If you’re looking for compost, we happen to carry some in our online store. Typically in a soil mix, the primary carrier for nutrients is the compost which is usually mixed with other inorganic or organic components to improve drainage and aeration of the mix. Additionally, compost can be used as a mulch for planting beds or trees, simply add the compost on top of the soil or ring the base of a tree with compost. While you get the best benefit from working the compost into the top 10-15cm of soil, simply adding on top of the soil can bring about great benefits! When storing compost, take care to store in a cool and dry location as wet compost creates an anaerobic environment, forcing the compost microfauna to undergo anaerobic respiration and increasing the acidity of the compost. In this case, while the compost may still provide nutrients to plants, the decreased pH can stunt or kill your plants and the smell of wet rotting compost is extremely foul. On the other hand, observing mould on your compost is a sign that your compost is rich in microfauna and has plenty of nutrients. If you do observe mould you might want to hold off on compost application as the fungi growth can temporarily reduce the bioavailability of nutrients. Don’t fret over this too much as when the fungi dies down, these nutrients are returned to the compost in a more easy to absorb state. For more information on this, look out for our article explaining nutrient bioavailability and the composting process!
Our next organic material that we’ll talk about is a bit contentious when it comes to sourcing. We’re talking of course about peat moss which is derived from digging up partially decaying vegetative matter from swamps, bogs and peatlands. When extracted, this material is then dried and packed into large bales before being shipped out. However, when peat moss is extracted, large quantities of carbon dioxide are released due to the mechanical disturbance to the natural environment. The extraction of peat moss exposes carbon that has been sequestered in the bog to an aerobic environment. Furthermore, peat moss mining requires that larger pieces of vegetation are removed, thereby exposing the sequestered carbon to the sun which provides the activation energy for the oxidation of the sequestered carbon. While peat moss is advertised as a renewable resource given the fact that it is a plant based material, this is quite contentious as peat bogs tend to regenerate slowly. The horticultural value of peat moss lies not in its nutrient level or biology but in its physical properties. It has a high water retention and high cation exchange capacity, making it an excellent addition to mixes for aroids or other water loving plants. Additionally, its spongy structure reduces compaction and thereby helps to facilitate aeration of the roots. Despite these properties, there are a few things to be aware of when using peat moss. Firstly, despite the number of sources that claim that peat moss does not easily decompose, there are many environmental factors to take note of such as heat, humidity and soil microfauna. From personal experience, environments such as those in tropical Singapore or in a closed terrarium can make peat moss decompose in a matter of months. If the peat moss remains soaked during this duration, it will likely undergo anaerobic respiration and become more acidic than it normally is. Given the downsides both from the horticultural and environmental perspectives, consider using alternatives to peat moss to improve water and nutrient retention such as cocopeat.
Coco coir, also known as coco fibre is one of the two big horticultural products that come from the humble coconut. Not to be confused with its cousin coco peat, coco coir refers to the aggregated fibrous strands of the coconut husk while coco peat refers to the spongy material that inhabits the spaces between the strands. Outside of some specialist orchid and aroid mixes, coco coir is not typically used in soil and is more commonly used for grow poles for aerial roots to latch onto. This is because it’s non compact structure allows for good aeration whilst providing a porous surface for aerial roots to grow into. When mixed with soil, coco coir is used to improve drainage but is seldom used for mulching as the airy structure and poor water retention of coco coir means that it is easily carried away by the wind. coco coir is not typically used in soil mixes either as coco coir tends to clump together. Therefore, more effort is needed to separate the fibres into smaller chunks to more evenly distribute the coco coir throughout the soil mix. Outside of horticultural uses, coco coir is also sometimes used as stuffing for pillows and cushions due to its spongy qualities.
Coco peat is the bigger brother to coco coir in terms of horticultural usage as it is more commonly used in mixes, soil amendments and mulch. While both coco peat and coco coir are both sourced from the same coconut husk, they are two distinct materials. Coco peat refers to the spongy material between coco coir strands which make up the bulk of the mass of coconut husk. Typically, coco peat is sold in solid bricks that need to be soaked in water for several hours before usage. During this process, the tight mass of coco peat loosens, making it easier to break up the brick of coco peat to be used. Typically, coco peat is used as a base for most conventional soilless mixes to make up volume and aid in water retention. Mixes with coco peat can go through wild weight variations that come from its amazing water capacity which causes these fluctuations. It also has a good level of CEC which ensures that coco peat is able to hold onto nutrients well. While coco peat is relatively cheap, don’t skimp on other ingredients of your mix as coco peat does not carry much nutrients despite its organic origin and its high water retention. As with all other organic ingredients, balance water retention against drainage as water logged organic materials will cause the microfauna to undergo anaerobic respiration, reducing the soil oxygen content and increasing soil acidity.
Sphagnum moss are the dried and dead mosses harvested from swamps. Unlike peat mosses, sphagnum moss is significantly less decomposed and is thus, more sustainable as it has a much shorter regeneration time. Much like peat moss, sphagnum moss contains little nutrients and has a good water retention ability. Sphagnum moss tends to hold its shape much better than other organic materials, allowing it to be shaped and be used in crafts such as moss balls and Kokedamas. Due to its relative difficulty in sourcing, sphagnum moss might be the most expensive material in this article. Hence, it’s typically used for very specific mixes or purposes such as for exotic aroids or carnivorous plants.
On the opposite end of the price spectrum from sphagnum moss, we have horticultural waste which as the name implies, refers to the trimmings and ends of other plants. Typically, these are used to make up volume in large containers to reduce the amount of top soil or other more expensive ingredients in a mix. Horticultural waste isn’t typically used as an ingredient in mixes but is added to either the bottom of a container to make up volume or to the top of a planting surface as a mulch. While it can add nutrients to the soil, depending on the state of decay of the waste it can temporarily reduce the bioavailability of certain nutrients. This is because the soil microfauna will cannibalise the horticultural waste and in doing so, take up some of the soil’s nutrients. However, once the waste has decomposed completely, all the nutrients (including those added in horticultural waste) are returned to the soil in a bioavailable state. When using horticultural waste in gardening, take note to remove any parts that look obviously diseased with fungi or insects as these can cause plant diseases to spread.
If you’ve enjoyed this article, let us know what else you’d like us to write about! Stay tuned for our next article on how to create your soil mixes!