A guide to fertilising your plants

A guide to fertilising your plants

Understand the basics of fertilising your plants is important in taking good care of your plants.  Plants need the presence of air, water, and light to produce food. More than that, plants require a wide range of other nutrients to sustain healthy growth.

Essential plant nutrition

Plants take in carbon, oxygen, and hydrogen from the air, water, and light. These elements are abundant in nature. Their source for other nutrients relies on the soil. 14 more nutrients must be available in the soil for the roots. The missing or the lack of these nutrients can lead to stunted growth, slow growth, weak plants, or cell death. They are categories as:

Fertilising young seedlingslush leafy vegetables

  1. Primary macronutrients: They are nutrients that plants need in huge quantities.
  •       Nitrogen: responsible for the growth of leaves
  •       Phosphorus: promotes root growth, flowering, fruiting and increases plant stem strength
  •       Potassium: also known as the "quality" nutrient, it strengthens the overall functions of the plant. Hence, it  also affects the quality the flower or fruits produced, including size and colour.

2. Secondary macronutrients: The intake of secondary macronutrients is lower compare to primary macronutrients. Namely, they are sulphur, calcium, and magnesium.

3. Micronutrients: They are trace or minor elements that plants require in minimum quantities. They are namely Copper, manganese, zinc, iron, boron, and molybdenum.

Types of fertilisers

There are 2 types of fertilisers - organic and chemical.

  1. Organic fertilisers

Organic fertilisers are usually derived from plant waste, animal waste or powdered minerals. They are natural matters, neither extracted nor refined.

In terms of properties, organic fertiliser is slow-release. The moisture and soil organisms take time to decompose the fertiliser. Hence, organic fertilisers are not instant fix for plant nutrient deficiency. Be diligent in fertilising regulary. Examples of different types of organic fertiliser are:

  • Plant-based fertiliser: Kelp seaweed and alfafa meal
  • Animal-based fertiliser: Manure, fish emulsion, bone meal, and blood meal
  • Mineral-based fertiliser: Calcium and Epsom salt

2.  Inorganic fertilisers

On the other hand, chemical fertiliser comes from synthetic chemicals. For instance, synthetic nitrogen is usually made from petroleum or natural gas. Phosphorus, potassium, and other trace elements are often mined from the earth.

Unlike organics, chemical fertilisers are plant nutrients in their concentrated forms.  They dissolve and release the nutrients readily to the plants.

Why Organic fertilisers

Given the efficiency of chemical fertilisers, why a lot of fellow home gardeners still prefer organic fertilisers? There are three main reasons.

  1. Organic fertiliser improves soil quality over time. As it breaks down, the organic matters are added to the soul. These matters enhance the soil structure for better moisture and nutrients retention.  At the same time, organic fertiliser feeds the soil microbes, promoting resistance against fungal and bacterial diseases.  These soil properties greatly improves soil fertility and thus plant health. In contrast, chemical fertilisers do nothing to improve the soil. In the worse case of excess salt or chemical build-ups in the soil, they could be harmful not only to the plants but also our health as we consume these affected crops.
  2. The application of organic fertiliser reduces the risk of fertiliser burn. Fertiliser burn happens when there is an nutrient overdose. Over applying or insufficiently diluted fertilisers are reason for fertiliser burn. Fertilisers contain salt which draws moisture out of the plants. Burn symptoms include yellowing and withering plants or white streaks on the leaves due to fertiliser being sprayed on.
  3. Lastly, the use of organic fertilisers is environmental-friendly. Organic fertilisers are renewable and biodegradable.

Choosing fertilisers for your edibles

Our bodies needs to receive a variety of nutrients to maintain life and health. Similarly for plants, a thriving garden needs to be supplied with all essential nutrients.

Soil test involves determining soil PH and nutrient content. Soil PH test kit is widely available for purchase. However, soil nutrient test is done in labs and costly. In Singapore, per nutrient type analysis cost is $28.35. Such analysis could be more practical in a commercial setting.

For hobbyists, choosing the fertiliser means to understand NPK ratio on packaging labels and how it suits your plants.  NPK stands for the 3 primary macronutrients that plants require - nitrogen (N), phosphorus (P), and potassium(K). The higher the percentage number, the higher the concentration of the nutrients present in the fertiliser.

The NPK ratio on our organic  fertiliser is listed as 8-8-8.  It is a general fertiliser suitable for all types of plants. If you are growing leafy vegetables, look for fertilizer that is high in nitrogen content to encourage lush foliage. However, if you are growing fruiting plants, a fertiliser with NPK ratio 2-5-8 is much better. Higher phosphorus encourages fuller blooms and fruits.

Baba fruit trees fertiliser

When to fertilise your plants

showing true leaves of seedlings

Start fertilising your seedlings once their true leaves appear. Feed them according to the suggested frequency on your fertiliser label to maintain their growth vigor. As a guideline, if you are using organic fertiliser, apply once every 2 weeks for leafy vegetables. For herbs, apply fertiliser once every 4 weeks. For fast release fertilise, you have to fertiliser more frequently.

It is best to fertilise during the coolest time of the day. For plant spike or dry pellet formula, apply when you are also going to water the plants. In this way, the nutrients can start to break down immediately and get to the roots.

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