Potting soil, also called potting mix, is here meant to refer to a material or a mixture of materials which is used to fill pots or containers for the growing of plants. Perforated pots made of different materials in various colors, designs and sizes, including hanging baskets and wall planters, are common in urban agriculture particularly in home gardening.
These plant containers are especially desired for indoor houseplants as well as for outdoor ornamental plants and vegetables which are placed somewhere without permanence. At any time these containers may have to be moved from one spot to another.
Generally, potting soils for these plants should be light in weight for ease in mobility. To produce one such growing medium, the use of soil as an ingredient is therefore avoided or at least limited to a minimal amount. Being fine, soil tends to make the growing medium compact and heavy.
Despite the redundancy, soilless potting soil is a commonly used term. The term also connotes that the inclusion of soil as an ingredient in any potting mix is not excluded outright.
We prefer to use pure garden soil (loam soil) for commercial production of tree seedlings including those of fruit trees in plastic bags. These seedlings are allowed to grow bigger in the nursery for several months.
Upon disposal, the seedlings would have developed extensive root system within the plastic bag. The soil would also have compacted.
During hauling it is customary to hold the potted seedlings by the stem. This technique enables an individual to carry as many as either hand could grasp. Otherwise, if the potting medium is loose, seedlings are easily uprooted.
We make our own potting soil mainly for foliage ornamental plants that we raise at home. Eventually, we increased the volume of production to accomodate consistent requests from customers at our Barj Hortorium garden supplies store.
Here’s how we make a general-purpose potting soil:
1. Partially decomposed coconut coir dust - Also known as coconut peat or cocopeat, it is an agricultural waste from the processing of coconut husk to produce a fiber called coir. It consists of fine particles and short strands of fiber from coconut husk. It is brownish when fresh but progressively darkens with age.
2. Rice hull - Also called rice husk, it is the hard, protective covering of the grain of rice. It is removed from the grain in the milling process which produces the rice staple. Voluminous amounts of rice hulls become waste in rice mills.
3. Topsoil - Garden soil that consists of loam soil is preferred.
Mixing ratio: 6:1:1 by volume.
This means that the potting soil consists of 75% coir dust, 12.5% rice hull and 12.5% topsoil by volume. This formula, however, is good only for one kind of coir dust with a level of decomposition which we determine visually.
For ease where only one person does the work, we mix 6 sacks of coir dust, 1 sack of rice hull, and 1 sack of topsoil for a total of 8 sacks of ingredients in one batch. These ingredients are mixed as thoroughly as can be on the ground with the use of a shovel. Immediately, the potting soils are placed in plastic sacks.
But where only a minimal amount of potting soil is needed, such as when repotting a few plants, we use a different container to measure volume. Still following the same ratio of 6:1:1 or its multiple (for example 12:2:2), a dipper or a used tin can or a pot can be a convenient measuring tool.
We have not undertaken any quantified assessment of the properties of our home-made potting mix. Nevertheless, there is regular demand from customer-gardeners and no complaint has ever been received.
The product is light, comparatively so much lighter in weight than milled rice and pure topsoil at the same volume.
It is loose rather than compact but has a good water retention ability. Water poured on the medium easily drains downward. Apparently the medium is well aerated, a condition that is important in root respiration.
It is not sterilized but weeds rarely grow. Perhaps the few weeds that grow, most commonly the purple nutsedge or Cyperus rotundus, come from the part of the soil close to the ground surface. Anyway, the potting soil being coarse permits easy uprooting by hand.
Further, it’s what we use mainly for ornamental plants in the nursery at home. These plants include aglaonema, dieffenbachia, foxtail palm, philodendron and zingiber, as well as artemisia, coleus, oregano and other plants which are used as medicinal herbs. We also used the same potting medium to propagate foxtail fern in medium-sized containers serving as seedbeds.
- Ben G. Bareja July 13, 2019