Fertilizer has been used for virtually as long as humans have been growing food crops. In the “new world”, Native Americans taught the colonists how to use fish heads as fertilizer to supplement their corn and other food crops. The fish heads were dried out and then ground up to effectively create the first powdered fertilizer; in this form it could be used anywhere and stored easily. In fact, a derivative called fish meal remains one of the main ingredients found in many fertilizers to this day.
In this modern world, a wealth of manufactured and organic fertilizers are available to choose from. However, different types of plants need different types of nutrients for optimum growth and productivity. This guide only provides the most basic of information so for a more in-depth understanding of fertilizer, contact a certified horticulturist, a home and garden specialist, or an agriculture expert at your local university.
Fertilizer Ingredients
Virtually every fertilizer is classified by the three basic ingredients needed for healthy plant growth. These are nitrogen, potassium and phosphorus, or known as N-P-K numbers.
“N” is for nitrogen.
Nitrogen is one of the basic building blocks in every plant. It affects the health and growing cycle of a plant cells and is naturally derived from organic decomposition. The more nitrogen added to the soil, the taller and more vigorous a plant will grow. Since nitrogen allows a plant to produce more chlorophyll, plants with an abundance of nitrogen will also be a darker green than those that don’t grow in nitrogen rich soil.
“P” is for Phosphorus.
Phosphorus promotes root growth and blooming. This naturally occurring substance comes from both the weathering of rocks and minerals into the ground. The uptake of these minerals occurs from organisms which eat decaying plant matter and then excrete the phosphorus back into the soil.
“K” is for Potassium
Potassium is like a medicine plants need to remain healthy. This compound makes a plant more drought resistant, improves root development, and it makes a plants photosynthesis, (the process that uses sunlight to synthesize food from carbon dioxide and water) more efficient.
Other Ingredients
Although the N-P-K numbers are only used to show the nitrogen, phosphorus, and potassium content, there are generally other nutrients added. These “micro-nutrients” are comprised of such ingredients as iron, manganese, molybdenum, zinc, and copper, among others. Much like people who take a multi-vitamin to ensure they get all of their nutritional needs, adding in these micro-nutrients (plus trace elements like sulfur, calcium, and magnesium) gives plants their own full multi-vitamin nutritional needs.
Fertilizer Types
Synthetic
Manufactured fertilizer is generally inexpensive and will promote stellar plant growth with an abundance of flowers and fruit. It’s usually high in nitrogen and phosphorous which contributes to rapid green plant growth while also promoting flowering and larger fruit yields.
Ammonia and nitric acid are combined to achieve high nitrogen levels in the form of ammonium nitrate. Phosphorus is manufactured by dissolving mineral laden rocks in sulfuric acid, while potassium is made by treating potassium hydroxide with hydrochloric acid. Micro-nutrients and trace elements can then be added to this mix for a more complete fertilizer, such as ground up animal bones for calcium and powdered molybdenum and zinc metals, among others.
Organic
Organic fertilizers are made from all natural ingredients with the largest source of organic fertilizers coming from manure, compost, blood meal, and seaweed. For example, manure and blood meal produce both nitrogen and phosphorus while seaweed, compost, and wood ash are great sources of potassium. While micro nutrients and trace elements can be added to these fertilizers, most of the essentials are already present since the plant and animal compounds already contain them naturally.
Synthetic vs. Organic
There’s an ongoing debate about which type of fertilizer is healthier to use for you and your plants. The most comprehensive study to date from the Newcastle University in London, England, has proven that organic foods are healthier and provide more base nutrients and anti-oxidants than commercially grown food.
In general, manufactured fertilizers can be engineered to last longer and require less fertilizing than their organic counterparts. Very high N-P-K numbers can be achieved with manufactured fertilizers, because you can concentrate the ingredients through artificial means. By adding a coating to the fertilizer granules, these types can be made to dissolve slowly over the course of weeks or months. You may only have to feed your plants 2 or 3 times throughout the year to maintain healthy and productive growth.
On the other hand, organic fertilizers break down quickly once spread. They have lower N-P-K numbers and because of this you'll need to fertilize more often, sometimes weekly if your plants are heavy feeders. They are more time consuming to use and require more work to use utilize correctly. However, if you're concerned about chemicals showing up in your edible plants, organic fertilizers are the way to go.
What's Best for You
Lawns, Trees, Shrubs, and Houseplants
These plants are all ornamental for which any good high nitrogen fertilizer will work. Remember, the nitrogen makes plants green and ornamental plants such as lawns and shrubs look the best when they have a vibrant, dark green hue. A high nitrogen content is the most valued fertilizer for these types of plants, but in southern climes or where the weather can be dry over long periods of time, a fertilizer which contains a higher potassium count will help promote deeper root growth.
Flowering Plants and Trees
The most valuable fertilizer for these plants are those with a higher phosphorus content. Certainly, both nitrogen and phosphorus are needed, but a flower garden or ornamental flowering trees will produce a greater amount of larger, longer-lasting flowers if the fertilizer has a higher phosphorus content.
Edible Plants
Fertilizers with a lower nitrogen content with higher phosphorus and potassium contents are the best fertilizers for edible plant gardens. Plants bearing edible fruits and vegetables need to produce more flowers and buds, and this also goes for fruit trees as well. They also need to be hardy and disease free, so both the phosphorus and potassium ingredients should be more prominent for edible plant gardens. In doing so, you'll reap the rewards in the form of more fruit on healthier plants.