Updated: Jul 4, 2022
by Insect Feed Technologies
When was the last time you fertilised your plants?
In the tropics, including Singapore, the soil is generally acidic and low in essential nutrients necessary for our plants’ growth. This tends to be due to excessive rainfall, causing nutrients to be lost rapidly. Even if we start with great garden soil, our plants grow and absorb these nutrients, eventually leaving the soil less fertile. By using plant fertiliser, we help to replenish lost nutrients and ensure that they have the food they need to flourish!
What is N–P–K?
Walking through the aisles of our garden centres, we observe that fertilisers are usually distinguished by the series of three numbers on their packaging labels, like 3-3-3 or 6-2-4. These three numbers represent the value of the Nitrogen (N), Phosphorus (P) and Potassium (K) ratio of each pack respectively, in which the higher the number, the more concentration of nutrients in the fertiliser.
N, P and K are macronutrients that our plants in relatively large amounts require. To better understand the individuals’ purpose, here is a visual representation.
Image Credit: Illustration of the Purpose of N-P-K
When should I use fertiliser with NPK?
The table below breaks down the benefits of NPK to help you make a more informed decision when it comes to your plants.
Starting your Vegetable Garden
A general vegetable fertiliser with balanced N-P-K is adequate. Phosphorus is needed for root development and growth, and potassium strengthens plants’ resistance to diseases. When starting your vegetable garden, nitrogen is the least important macronutrient. Hence, the first number in the N-P-K formula can be lower.
A good representation of this reason are leafy and lush tomato plants without flowers or fruits due to too much nitrogen in the soil. That does not mean your plants do not need nitrogen, vegetable crops would require most of their nitrogen only after they have made considerable growth or have already begun to fruit.
To understand better the timing to fertilise your plants, here are some tips:
Cabbage, cauliflower and broccoli – 3 weeks after transplanting
Peas, beans, cucumbers, and muskmelons – After blossoming begins
Peppers and eggplants – After the first fruit sets
Tomatoes – After the first fruit sets, more about 2 weeks after picking your first tomato, and then again a month later
Sweet corn – When plants are 8-10 inches tall and then 1 week after tassels appear
Spinach, kale, mustard, and turnip greens – When plants are about ⅓ grown
Nitrogen should NOT be added to: sweet potatoes, watermelons, carrots, beets, turnips, parsnips, and lettuce
Flowering plants are a little different from vegetable crops. In fact, nitrogen is their best friend. Overly high phosphorous values in fertilisers are not needed for flowers to bloom and fertilisers for flowers need to be high in nitrogen.
An example of a good benchmark for N-P-K values for flowering plants is 12-4-8. Nitrogen promotes the growth of leaves on the plant and it is needed for photosynthesis, green leaf development, and fruiting and seed development.
Types of Fertilisers
Fertilisers with NPK are considered complete fertilisers and usually come in the form of granules or pellets, while incomplete fertilisers supply only one or two of these primary nutrients and often come in the form of soluble crystals.
The most important question is, how do you identify what fertilisers do your plants need?
Inorganic vs Organic Fertilisers
Plants do care where they get their nutrients because organic and inorganic fertilisers provide nutrients in different ways.
1. Inorganic / Synthetic Fertilisers
They are manufactured artificially and come from sources other than animals or plants. They usually contain mineral and chemical products. These fertilisers are quick-release in a water-soluble form to deliver nutrients quickly to our plants, which can be useful in some situations. However, because of this, synthetic fertilisers can “burn” our foliage and damage our plants. Synthetic fertilisers give our plants a quick boost but do little to improve soil texture, stimulate soil life, or improve your soil's long-term fertility.
Another concern due to its high water solubility; they can also leach into our streams and ponds, affecting our environment and ecosystem. These synthetic fertilisers are often used in colder countries in temperate zones when the soil is cold and soil microbes are inactive in colder seasons.
2. Organic Fertilisers
Organic fertilisers are made from naturally occurring mineral deposits that are derived from plants or animals, such as, frass, leaves and compost. Generally, most organic fertilisers will be darker coloured and in the form of granules and powders.
The nutrients in organic fertilisers are usually not water-soluble and are released to the plants slowly over a period of months or even years. This actually allows organic fertilisers to invigorate beneficial soil microorganisms and improve the structure of the soil. Microbes in our soil play an essential role in converting organic fertilisers into soluble nutrients that our plants can absorb.
Why Organic Fertilisers?
Organic fertiliser may be more costly compared to their synthetic alternative, but they do offer more long-term benefits. For the long-term health of your garden, feeding your plants with organic fertilisers and compost is best. Organic fertiliser will not only replenish lost nutrients, but it will also give you soil that is rich in organic matter, teeming with microbial life.
Types of Organic Fertilisers
The most common types of organic fertilisers include insect frass, manure, bone meal, vermicompost and rock phosphate.
Insect Frass Insect frass is the excrement that is left behind by any type of insect. The completely organic material offers a good dose of potassium, nitrogen, and phosphorus for soil, with an added bonus of chitin, which can be converted to chitosan. The market benchmark for insect frass N-P-K values is 3-2-3. Insect Feed Technologies' frass has a N-P-K ratio of 3-3-5 which works perfectly to start your vegetable garden and your flower garden.
Manure Manure is made from animal excrement like cow dung and goat droppings. Cattle Manure is a good source of nitrogen and organic carbon while goat manure is rich in nitrogen and potassium.
Bone Meal Bone Meal is a mix of ground slaughterhouse waste products like animal bones. It is a very good source of phosphorous and amino acids.
Vermicompost Vermicompost is a product of organic material degradation using various species of worms to create a heterogeneous mixture of decomposing food waste. This waste is used to help improve the drainage, aeration of the soil, and water retention.
Rock Phosphate Rock Phosphate are sedimentary rocks that contain high amounts of phosphate minerals. It is used naturally to fix phosphate levels of soil.
We are spoilt for choice when it comes to deciding the types of organic fertilisers our plants may need. Here is why frass stands out among the 5 common types of organic fertilisers.
Insect frass contains chitin, which is found in the exoskeletons of insects. Chitin’s benefits to plants include improving their immune system and supporting the defence from pests and diseases.
Insect frass also offers a good dose of phosphorous, nitrogen, and potassium for soil and your crops. Chitin’s natural pH level is three, which is beneficial to our soil’s pH level as most plants thrive in slightly acidic soil because that pH affords them good access to all nutrients.
Frass is, therefore, a natural solution for your plants if you are looking for a sustainable and organic solution without any additives. If you are looking to purchase organic insect frass, you can check our Insect Feed Technologies fertiliser on Shopee and Lazada.