Potting Mix II: Compost & Vermicast


Good morning, fellow gardeners!

Thank goodness the haze situation seems to be getting better and the PSI levels have dropped; fresher air for everyone and for our plants too! Continuing from last week’s post on potting mix, this week we touch on compost and worm castings (vermicast) two very important components that provide our plants with the nutrients they need in order to fruit or grow better.


Compost is the single most important supplement which is made up of decayed organic matter that you can give your garden soil. Using compost improves soil structure, texture, and aeration and increases the soil’s water-holding capacity. Specifically, compost loosens clay soils and helps sandy soils retain water. Adding compost improves soil fertility and stimulates healthy root development in plants. The organic matter provided in compost provides food for microorganisms, which keeps the soil in a healthy, balanced condition. Nitrogen, potassium, and phosphorus will be produced naturally by the feeding of microorganisms, so few if any soil amendments will need to be added.

One may choose to buy bagged compost for your garden soil but making your own compost is not difficult at all. Furthermore, it is free AND good for the environment as you reduce food waste and turn them into something very useful instead. Thus, composting is an alternative method of dealing with waste and this helps conserve landfill space, especially in land tight Singapore.

Here is a video you can watch to know more about composting:

For many of us here who live in HDBs and cannot compost directly on soil, refer to this video instead for a useful guide on creating your own compost bin along your corridor:

Here’s also a useful table on the kinds of materials that can go into your compost:




 table scraps


 add with dry carbon items

 fruit & vegetable scraps


 add with dry carbon items



 best when crushed



 leaves break down faster when shredded

 grass clippings


 add in thin layers so they don't mat into clumps

 garden plants


 use disease-free plants only

 lawn & garden weeds


 only use weeds which have not gone to seed

 shrub prunings


 woody prunings are slow to break down

 straw or hay


 straw is best; hay (with seeds) is less ideal

 green comfrey leaves


 excellent compost 'activator'

 pine needles


 acidic; use in moderate amounts

 flowers, cuttings


 chop up any long woody stems

 seaweed and kelp


 apply in thin layers; good source for trace minerals

 wood ash


 only use ash from clean materials; sprinkle lightly

 chicken manure


 excellent compost 'activator'

 coffee grounds


 filters may also be included

 tea leaves


 loose or in bags



 avoid using glossy paper and colored inks

 shredded paper


 avoid using glossy paper and colored inks



 shred material to avoid matting

 corn cobs, stalks


 slow to decompose; best if chopped up

 dryer lint


 best if from natural fibers

 sawdust pellets


 high carbon levels; add in layers to avoid clumping

 wood chips / pellets


 high carbon levels; use sparingly

Difference Between Compost and Fertilizer

The simplest way to distinguish between compost and fertilizer is this: Compost feeds the soil while fertilizer feeds the plants.

Fertilizer adds to the soil’s nutrient supply, but instead of feeding the soil food web, the ingredients in fertilizers are intended to meet the needs of fast-growing plants. However, soil that is regularly amended (i.e., improved) with compost becomes wonderfully dark and crumbly and often requires much less fertilizer compared to soil that has not yet benefited from regular helpings of compost.


Worm Castings/Vermicast

Worm castings are an organic form of fertilizer produced from earthworms. Also known as vermicast, worm castings manure is essentially earthworm waste, otherwise known as worm poo. As these creatures eat through compost, their waste creates an optimal soil enricher. Worm castings resemble football-shaped particles that improve soil aeration and drainage, as well as increase water retention in the soil.

Difference Between Compost and Worm Castings
The main difference between compost and worm castings is that compost has higher NPK (Nitrogen, Phosphorus & Potassium) values BUT worm castings have a huge positive effect on plant growth.  When up to 20% of the soil consists of worm castings, plants germinate better, grow faster, and produce higher yields. This is because worm castings have much higher percentages of humus than either soil or compost, which helps the castings hold more water and stay aerated, while also providing binding sites for micronutrients that would otherwise wash out of soil. The castings are also chock full of plant growth promoters like cytokinins and auxins, along with increased levels of micronutrients like calcium, magnesium, and sulfur.  Worm castings also host ten to twenty times as much microorganism activity as plain soil. 

If you are interested in creating your own worm bin, this video may be useful:

Other useful articles:




Tl;dr? Just click on the embedded videos! Till next week, Happy Gardening :)


Leave a comment

Please note, comments must be approved before they are published