Fertilizing the Garden: When and How to Fertilize your Garden Plants

When would you say that you have successfully fertilized your plants? Well, successful fertilizing of garden plants goes beyond the type of fertilizer you use; when and how you fertilize are equally important factors.

For example, most vegetable plants are high feeders; as they grow, they deplete soil nutrients. Therefore, you will need to fertilize these plants frequently for them to reach their full potential regardless of how fertile your soil was initially.

With that in mind, let’s see the big keys helpful in fertilizing the garden.

In simple terms, fertilizers are nutritional supplements crucial for the healthy growth of plants. For example, tomatoes thrive in soils rich in calcium.

On that note, if you just harvested your garden produce, you will need to apply additional fertilizer in the garden before planting again. This is because the previous crops used up the former application.

What is Fertilizer Made Of?

Fertilizers are made up of different ingredients, which include the main three macro elements, secondary macro elements, trace elements, fillers, and time-release ingredients. Let’s see each of these ingredients in detail:

Main ingredients

Fertilizers contain three main ingredients required by plants in large quantities, namely:

Nitrogen (N) – Nitrogen ensures plants have a leafy top growth. Without this nutrient, your plants can either wither or fail to produce a harvest.

Phosphorus (P) – Phosphorus aids in photosynthesis which is important for root growth and fruit production.

Potassium (K) – This nutrient helps protect your plants from diseases and strengthens them against cold.

The above trio of macroelements is often written as “N-P-K.” So, if you see your fertilizer labeled 10-15-10, 10% of its content is nitrogen, 15% is phosphorus, and 10% is potassium.

If you add the above percentages, you will see that they don’t add up to 100%; the sum is 35%. So, what makes the remaining 65%? The 65% here includes other ingredients, e.g., secondary macro elements, trace elements, fillers, and time-release ingredients.

Let’s see these additional ingredients in detail:

Secondary macro elements

These include calcium, magnesium, and sulfur. Also, the secondary macro elements are either sufficiently included in the fertilizer or in other elements, e.g., lime.

Trace elements

While your soil might not require a lot of trace elements, it still needs some small amounts. These trace elements include copper, zinc, manganese, and magnesium.

One more thing to note here is that synthetic fertilizers are pure chemicals, most of which do not contain trace chemicals, unlike organic fertilizers.

Therefore, to ensure your soil gets all the desired plant food, including the trace elements, you can include other organic matter in your soil, e.g., manure, compost, mulch, etc.

Fillers

Fillers help keep your garden fertilizer from drying and crumping. Also, the fillers allow a more even spread to lower the chances of spreading a concentrated amount in an area.

These fillers often contain ingredients like ground corn cobs, lime, sand, etc.

Time-release ingredients

When you apply fertilizer in your garden, you want it to stay longer in the soil. Now, time-release ingredients ensure the fertilizer is not absorbed all at once but is slowly absorbed for an extended period.

Fertilizers and PH

PH is a crucial factor to have in mind when gardening. But what is PH? PH is the degree of acidity or alkalinity in the soil.

The PH levels of your soil dictate the availability of nutrients. At a very high PH, some nutrients become completely or partially unavailable to the plants even if the nutrients are in the soil.

For example, if your soil test shows a PH of around 8.0, manganese, phosphate, and iron become less available. On the other hand, if the soil test shows a PH below 4.5, calcium, phosphorus, and magnesium become less available for your plants.

Additionally, at extreme PH levels, toxic elements like aluminum become readily available, and such can harm your plants.

The best PH level for most vegetables is between 6.0 and 7.0.

You can add lime to your garden soil to increase the PH if it is low. On the other hand, you can add sulphuric acid, elemental sulfur, or aluminum sulfite if you would like to lower a high PH.

However, it will be good to note here that whatever element you use to make your soil PH desirable doesn’t replace the need for fertilizer.

Symptoms of Nutrient Deficiencies in Plants

Hereunder are the general symptoms you will notice on your plants when they are missing the nutrients we discussed earlier:

Table 1: Nutrient deficiencies and their symptoms

Nutrient	Deficiency Symptoms
Nitrogen	● Symptoms are first seen on the older leaves ● Yellowing of leaves resulting from lack of chlorophyll ● Slow or poor plant growth ● Fewer leaves, lower protein, and early maturity ● In corn, you will notice yellowing on the leaf tip and the midribs ● Less tillering in grasses ● Lower produce
Phosphorus	● Symptoms often develop on older leaves first ● Overall stunting ● Purple or reddish ● Low tillering in small grains ● Low produce
Potassium	● Symptoms begin to develop on older leaves ● Scorching or yellowing along leaf margins ● A poorly developed root system and poor growth ● Weak stalks ● Lower disease resistance ● Small and wrinkled fruit or grain ● Low produce

Source: USDA

Types of Fertilizers

There are different types of fertilizers used on crops; let’s see each of them in detail:

Organic fertilizers

The nutrients in organic fertilizer are derived from organisms that once lived. Some good examples of organic fertilizers include all manures, cotton seed meal, bone meal, blood meal, and hoof & horn meal.

If you buy packaged organic fertilizer, you can check its nutritional content on the label.

Additionally, most of the organic fertilizers you will come across are high in one of the main nutrients we discussed earlier and low on the others.

Other organic fertilizers will be low on the three main nutrients, while others will be fortified for better yields.

One key feature of organic fertilizers is that they slowly release plant food into the soil. This feature can be beneficial to some plants and not useful to others, especially where plants require immediate nutrient absorption.

Another key benefit of organic fertilizers is that they improve the soil structure, making plants access nutrients easily.

For example, “clay soil seems baked or looks like hard concrete on sunny days” – Big B., Orchid lecturer. Here, an organic fertilizer will help loosen the clay soil making nutrients readily available to plant roots.

However, a common challenge with organic fertilizer is that it only releases nutrients properly when the soil is moist and warm.

Synthetic fertilizers

Generally, synthetic fertilizers release nutrients faster than organic fertilizers.

However, this doesn’t mean you do away with organic fertilizer. Organic fertilizer will improve your soil structure while adding nutrients.

On the other hand, synthetic fertilizer will only add nutrients to the soil but won’t improve your soil structure.

One best thing about general-purpose synthetic fertilizers is that they are readily available to gardeners and are relatively inexpensive.

However, you will need to be cautious when applying synthetic fertilizer since an incorrect application of this fertilizer can be harmful to earthworms. So, ensure you observe the instructions on the label when using this fertilizer in your garden.

Complete vs. incomplete fertilizers

A complete fertilizer will have all three main nutrients: nitrogen, phosphorus and potassium. Some examples of complete fertilizers include 10-10-10, 5-30-5, and 5-10-10.

On the other hand, an incomplete fertilizer will be missing one or two of the main nutrients. Some examples of incomplete fertilizers include:

Ammonium nitrate (33.5-0-0)
Triple super phosphate (0-46-0)
Potassium nitrate (13-0-44)

You can use an incomplete fertilizer when your soil tests show that the soil is high in some main nutrients and low in others. For example, you can use ammonium nitrate(33.5-0-0) if the soil has low nitrogen content but is high in phosphorus and potassium.

Fertilizer Formulations

Fertilizers come in different shapes and sizes, with each kind targeting a particular need. That said, some of the formulations you will come across include granular solids, liquids, water-soluble powders, tablets, and slow-release spikes.

As I have mentioned above, each formulation targets a particular need. So, every gardener can choose from the above formulations depending on their needs. For example, a vegetable gardener will go with granulated and liquid fertilizers.

Lets now see the two common formulations we just mentioned in detail:

Granular fertilizer

Also known as dry fertilizer, granular fertilizer is the most common in gardening. This fertilizer features large evenly-sized grains that are sometimes coated to keep them from absorbing moisture.

Examples of dry fertilizer include 10-10-10, 5-10-10, and 5-10-5.

Liquid fertilizers

Liquid fertilizers come in different forms, including complete and incomplete, where all are meant to be diluted with water.

So, you will buy your liquid fertilizer in the form of pellets, powder, or concentrated liquid and dilute it for yourself with water before use.

When to use liquid fertilizer:

You can use liquid fertilizer on transplants for immediate nutrient provision, faster root growth, and plant development.
On the foliage to allow nutrients to be absorbed quickly from the leaf surface

How to Apply Fertilizer

There are different ways of applying fertilizer which include: broadcasting, banding, liquid solutions, side-dressing, and foliar feeding. Choosing between these fertilization ways will depend on the fertilizer formulation and plant needs.

Let’s look at these techniques in detail.

Broadcasting

In broadcasting, you spread your fertilizer on the soil surface and then use a spade, hoe, or rototiller to incorporate the fertilizer into the soil.

This method is usually used over a large piece of garden. Also, this technique is used when labor or time is limited.

Banding

This method is popular in tomato farming though you can use it with other crops.

Unlike broadcasting, where you spread your fertilizer in a whole planting area, banding involves creating a band of fertilizer and running it alongside your plants.

The bands should be 2 to 3 inches from the seeds you are planting and 1 to 2 inches deeper than your seeds or plants. Creating the bands too close can burn the plant roots.

Remember to cover the bands after spreading the fertilizer in them.

Starter solutions

Starter solutions involve using liquid fertilizers to provide phosphorus nutrients to transplants. Remember to observe the instructions on the label when using these solutions in your garden.

Side-dressing

Side-dressing refers to the use of dry fertilizer on plants that are up and growing. Here, you will spread fertilizer 6 to 8 inches from the plants on both sides of a row.

Then you can rake the soil to mix it well with fertilizer and then water thoroughly.

Foliar feeding

You can use foliar feeding in either of the following situations:

If you didn’t use enough fertilizer when you were planting
When micronutrients like zinc or iron are locked in the soil, making them not accessible to the plants
When you want quick growth
When the soil is too cold making the plants unable to use the fertilizer already in the soil

The key benefit of foliar feeding is that plants instantly absorb the applied nutrients. However, foliar feeding is not a substitute since plants require more nutrients than can be absorbed through leaves.

Remember that too much foliar feeding can burn your foliage. So ensure you follow the instructions carefully when applying this fertilizer or other synthetic fertilizers.

Timing of Fertilizer Application

Here are the factors that will dictate how often you’ll use fertilizer:

Type of soil

sandy soil needs more frequent fertilizer applications than clay soil.

Type of crops

Some crops are heavy feeders
Root and fruit crops like potatoes and tomatoes respectively need lesser nitrogen fertilizer applications than leafy crops
Sweet corn feeds more on nitrogen and thus may require nitrogen fertilizer application every four weeks.

The desired crop productivity
Amount and frequency of watering
Type of fertilizer used and the rate at which it is released to the plants

Remember that when and how you fertilize your plants can determine their growth and character. For example, if you apply too much nitrogen fertilizer to tomatoes, especially when fruits want to develop, you might end up with too much vine and no fruits.

Before You Go

One major contributor to healthy plants and great produce is fertilizing the garden in the right way, at the right time, and using the right fertilizer.

The other key factor to successful gardening is soil-drainage capability. Most plants prefer well-draining soils.

If your soil holds water for extended periods, it can lead to root rot. But don’t worry; you can improve that soil using some readily available additives. You can add perlite or sand to your soil to boost drainage; here is an article on this: Perlite Vs Sand: Everything You Need To Know For Gardening

Resources

Robert Silver

Robert Silver is a writer, speaker and certified master gardener who has been sharing his landscaping experiences through personal blogs. Taking it to the next level, Robert Silver has come up with this progardeningblog.com to shine a light on new planters and experts, discussing plants, landscape projects and much more. He has published numerous research articles on horticulture that have helped many people attain fruitful outcomes.