How to Apply Fertilizer

In our previous section we discussed the different types of fertilizers. We now turn our attention to applying the different types of fertilize, but first there is the issue of when is the best time to apply the specific type of fertilizer that you require. In the case of bulky organic manures and other organic fertilizer, you would serve your garden well if you apply the fertilizer well ahead of sowing time. The reason would be that the preliminary decomposition can then take place prior to the seeds germinating. However, if you neglected to fertilize prior to sowing or time is against you, then you may apply bulky organic fertilizer any time after the seedlings have established themselves. (TIP: In such a case it is best to user fertilizer in the powder form.) Further good gardening practice would be to make sure there is a sufficient supply of moisture in the soil.

When you want to make use of inorganic fertilizer and fertilizer types that include the Potassic and Phosphatic fertilizers, then it is best to apply the fertilizer before sowing or transplanting the seedlings. In the case of Nitrogenous fertilizers, you can feel free to apply the fertilizer at planting and even slightly after planting time. In many cases split application of nitrogenous fertilizers is advantageous in heavy rainfall areas.

Despite all the different types of fertilizers that are available from local nurseries and garden centers it is easy to work out which fertilizer is best for which types of plants by simply reading the container. If you are in doubt regarding the suitability of the fertilizer for your garden then make use of the NPK ratio rhyme.

Leaves and shoots
Stems and roots
Flowers and fruit

The NPK ratio is then read as follows: – leaves and shoots : stems and roots : flowers and fruits. Make use of this ratio rhyme and make your own assessment.

Fertilizers bags and containers also provide ample instructions on the best ways in which to apply the particular fertilizer. Nonetheless, the following is a general guide on the application of different types of chemical or inorganic fertilizer.

Applying Liquid Fertilizer

Liquid fertilizer is usually concentrated. They need to be mixed or dissolved in water before application to the intended plants. When properly diluted you also negate the chances of fertilizer burn. Properly diluted liquid fertilizer is ideal for use of soft, sensitive and young plants. Fertilizer for indoor plants, specialized food for seedlings, bonsai fertilizer, and orchid fertilizer are all water soluble.

Mixing and application of liquid fertilizer

Liquid fertilizer is easy to apply – simply mix the required amount into a watering can or bucket filled with water. (TIP: Add the fertilizer concentrate to the water.) Water the plant with the mixture and do remember that the fertilizer will be more easily absorbed if the soil is moist. You can also use some of the liquid fertilizer as foliar spray. This liquid fertilizer is then sprayed on the leaves since the fertilizer will be absorbed through the leaves. In this case you pour the fertilizer and water mixture into a spray bottle and apply to the leaves. (TIP: Only foliar feed if the instructions on the container indicate so and use the recommended rate.)

Applying Granular Fertilizer

Granular fertilizer can be used in its dry form sprinkled on the soil around the intended plants. After application these types of fertilizer should be watered in immediately to avoid the plants burning. Using granular fertilizer is a trifle more complicated than using liquid fertilizer. In many cases gardeners would just scatter a handful or so around each plant and hope that it will suffice. This brings on problems like burnt plants and even overfed plants, or alternatively not applying enough fertilizer for the size of the plant.

Mixing and application of granular fertilizer

The instruction that you will find on the fertilizer container or bag will indicate the amount (in grams or ounce) that should be applied to a square meter. It sounds easy enough, but it can be difficult to apply this dosage in a garden. Say for instance the recommended dosage is 60g per m2. First you need a 60g measuring cup. No problem. Take a cap, say the plastic cap of an empty aerosol spray (a deodorant cap will do fine) and place it on a kitchen scale. Fill it with fertilizer until it weighs 60g. Shake the cap to level the fertilizer in the cap. Then take a marker and mark the level. Empty the fertilizer back into the fertilizer container. Now take a strong pair of scissors and cut along the line that you marked. Voila – now you have your 60g measuring cup. (TIP: Write on the cup the name of the type of fertilizer and the gram measurement for next time.) You will also find that each type of fertilizer has its own dose rate and weight. You will thus need a measuring cup for each of the different types of fertilizer.

When actually applying the granular fertilizer you need to gauge an approximate square meter either by pacing or by cutting a thin stick or bamboo stake to 1 meter in length. Then sprinkle the full measuring cup evenly over the whole area that you gauged as 1 square meter. When fertilizing trees or large shrubs you need to sprinkle the fertilizer over the whole drip area even if it happens to be over the grass. The roots of plants grow away from the trunk; and the fine hair root are usually those furthest away from the base of the tree or shrub. These fine hair roots are the ones responsible for feeding the tree or shrub. Heavy handfuls of fertilizer near the base of the tree or shrub can damage the root system by burning it. (TIP: Use the measuring cup and stake method to apply lawn fertilizer as well.)

General tips for applying fertilizer

  1. All fertilizers should preferably be applied before sowing.
  2. Fertilizer should preferably be broadcast uniformly and harrowed in.
  3. All fertilizers that contain soluble phosphates should preferably be applied in wide bands of between 2.5 and 5 cm on each side of thee rows of seeds at a depth of 10 to 15 cm.
  4. The superphosphate fertilizer should preferably be mixed with farmyard manure (in particular organic manure from dairy farms works excellent.)
  5. Fertilizer types that include sulphate of ammonia can be used as a top dressing, but do not apply this type of fertilizer when the leaves of the plants are wet.
  6. The application of fertilizer should preferably be followed by watering when applied to irrigated crops.
  7. When fertilizing fruit trees, the fertilizer should preferably be applied to the soil under the crown. The crown is the area about a few meters away from the trunk. As the tree grows this crown area expands and then fertilizer should also be applied as per the crown of the fruit tree.