How to Fertilize Plants: Nutrients and Techniques

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Plants and other flora make significant aesthetic improvements to any yard, home or office. Those that bear food–fruits and vegetables–further add value by saving money and learning the fine techniques of cultivation and harvest. In fact, it is difficult to imagine a world worth living in that lacks flowers, shrubs and greenery.

That said, plants are not self-generating and self-sufficient. To grow, live and reproduce, they need food, i.e. nutrition. Those that grow in the wild find their sustenance in the soil or neighboring media. Gardeners, on the other hand, must learn the nurturing art of how to fertilize plants.


The three primary elements in most plant food are nitrogen, potassium and phosphorus. These are each present–in differing proportions–in most fertilizers. Other ingredients, like calcium, magnesium and sulfur appear in lesser amounts depending on the plants they feed.


Those wondering how to fertilize plants should know what nitrogen (N) is doing in their plant food mix. Garden soil is often times of a sandy texture. This type of earth is short on the nitrogen needed for plants to grow adequately. Those organisms that lack sufficient nitrogen grow poorly, with yellowing leaves and meager foliage. Many plant residues contain nitrogen, as does animal manure and synthetic fertilizer.

nitrogen fertilizer


Potassium (K) facilitates the movement of water, nutrients and carbohydrates through the very tissue of a plant. It also serves as a catalyst to regulate the process of photosynthesis. Moreover, potassium gets credit for fortifying a plant against drought; improving its moisture retention; boosting the protein content; and fortifying immunity against disease. Sodium is present in most soils but not necessarily in usable form for flora. Hence, supplemental fertilization is sometimes necessary.


Phosphorus (P) aids in the process of cell division. It also spurs the production of flowers and fruit. When its presence is low, poor flowering (and fruit bearing) will be the result. The problem is that phosphorus is only taken up by plant roots when thoroughly dissolved. Since so much undissolved P has remained in the ground over the years, it contaminates the groundwater and produces large amounts of algae in nearby rivers or tributaries. Consequently, governments regulate the phosphorus content in most commercial fertilizers.

Other Nutrients

The component issue of how to fertilize plants does not end with N, P and K. Just as different species of animal require different diets, so plant varieties need specific nutrients in varying quantities. Most of these contribute to development in smaller portions than N, P or K but they are no less necessary.

Iron, for instance, is essential to the production of chlorophyll. Boron stabilizes and strengthens cell membranes. Copper fosters vitamin A production and stimulates protein synthesis. Meanwhile, zinc is a crucial party to high yields. For proper energy reactions at the cellular level, chlorine must be present, as well. Although indispensable, all of these can do their jobs in very small amounts.

Organic or Synthetic?

Organic vs Synthetic

Gardeners are sometimes vexed over the choice between plant food from natural sources–e.g. compost or manure–or from chemical synthesis. The fear that chemical fertilizers pollute the groundwater and nearby streams is not unfounded. At the same time, the basic chemical elements are present in both natural and synthetic nutrients. The key is to carefully steward the land with an eye to your surroundings. Many successful gardeners employ both kinds of fertilizer.


Knowing what is in their food helps when learning how to fertilize plants. Another helpful bit of wisdom is when to apply the fertilizer. A slew of gardening magazines advise one annual treatment in the early spring of the year. This, they assert, is the best way to produce leaves, then flowers, then fruit on an orderly basis.

This strategy is not without hazard, particularly in northern climes. Should the garden suffer a late freeze or–worse–snow, the benefits of fertilizer may be nullified. Cold climate gardeners do well to record final frost dates from previous years to determine the best time to put down plant food.

Still, some plants are hungrier than others, and do better with adjusted feeding schedules. For those growing vegetables like sweet corn, monthly administrations heavy in nitrogen often prove beneficial. Of course, time-release fertilizers are a way of reducing the frequency of applications. Consultation with a cooperative extension officer or, alternatively, a garden center employee assists gardeners with any timing judgment calls.


The means and manner of fertilizer spreading are as diverse as the plants and soils they cover. The size of the garden bed, species of flora and density of seedlings have much to do with selecting the optimal application medium.

  • Broadcasting serves best when the area is large and time is short. The fertilizer is spread consistently over the entire plot, and worked in with a spade or rototiller.
  • Side-Dressing involves sprinkling the plant food on each side of a row–about six to eight inches from the plants–after the crop emerges. A rake and water are sufficient to integrate the fertilizer with the soil.
  • Similar to side-dressing, banding places the nutrients closer to the plants, i.e. around three inches. Since phosphorus is difficult for plants to absorb from soil, this method allows for a greater uptake.
  • Foliar feeding is a reactive measure when the initial fertilizing proved insufficient or when the soil is too cold. As its name indicates, the plant food is applied directly to the foliage by means of liquid spray.
  • Starter solutions are often high in phosphorus, and applied to soil at the time of seedling transplant.

Summing Up

For one question, how to fertilize plants has many answers. From plant food composition to application frequency to the manner of treatment, gardeners must match their fertilizing to the size, scope and character of the growing beds. Independent research, good advice, as well as simple trial and error, effectively teach how to fertilize plants.

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Jonathan E. Bass

Graduated from Middle Tennessee State University. I am currently a gardener. I have a small garden behind my house. I love it.

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