As long as there has been agriculture there has been interest in understanding plant nutrition. As agriculture developed special attention was paid to what plants needed to survive and thrive. This information was either noted mentally, to pass that knowledge on to the next generation, or, in more recent years, physically written down to be further studied. This knowledge has now spilled into the world of the home gardener. Hydroponic retailers, nurseries, and even the local home repair store all now carry an overwhelming amount of plant specific fertilizers. Although these products do differ greatly in the quality of ingredients, they are all trying to accomplish the same thing: supply your plant with the essential elements needed to grow.
To survive plants must absorb mineral elements from the soil or hydroponic solution. These essential mineral elements are further classified as either macro or micronutrients. Macronutrients are the nutrients used in higher concentrations relative to micronutrients which are absorbed in smaller amounts.
The six essential elements classified as macronutrients are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
(N) – Nitrogen is a basic component of chlorophyll and is associated with the green color of a plant’s leaves. Nitrogen is the main nutrient responsible for vigorous growth, hence its higher concentration in “grow” base fertilizers. Nitrogen makes up a large percentage of our atmosphere; however, plants are unable to absorb nitrogen in that form. Instead, plants rely on microbes in the soil to “fix” nitrogen into a form capable of root absorption.
(P) – Phosphorus stimulates root growth and, in turn, helps young plants or transplants establish more quickly. Phosphorus also plays a key part in initiating flowering, fruiting, ripening and respiration.
(K) – Potassium helps with the movement of sugars and other nutrients (via osmosis). Potassium is directly linked to a plant’s structural integrity and increases the overall resistance to cold, drought, and pathogens. Much like phosphorus, potassium plays an intricate role in initiating the fruiting/blooming process.
(Ca) – Calcium is vital to plant structure and it helps build, and becomes part of, the cell walls. Calcium has been shown to promote growth of young shoots and roots. Calcium is also needed for fruit ripening and seed production.
(Mg) – Magnesium helps reinforce cell walls and is an important component of chlorophyll. Magnesium encourages the absorption of phosphorus, nitrogen, and sulfur. Like calcium, magnesium plays a vital role in the ripening of fruit and the germination of seeds.
(S) – Sulfur aides chlorophyll production and is a necessary component of several proteins, enzymes, and vitamins. Sulfur also contributes to a plant’s absorption of potassium, calcium, and magnesium.
Although micronutrients are absorbed in lower amounts than macronutrients, they play an equally important role in overall plant health. The eight essential elements classified as micronutrients are iron, manganese, chlorine, boron, zinc, copper, molybdenum, and nickel.
(Fe) – Iron assists in biochemical processes including the manufacturing of chlorophyll. Iron also aids in the formation of some enzymes and amino acids.
(Mn) – Manganese plays an essential role in chlorophyll production, nitrogen assimilation and the formation of proteins. Manganese stimulates seed germination and has been linked to the speed at which a plant matures.
(Cl) – Chlorine is involved in the stimulation of photosynthesis.
(B) – Boron is essential for tissue growth within the plant. Boron helps to promote the absorption of water and regulate a plant’s metabolism. Boron also assists in the formation of fruit.
(Zn) – Zinc helps with the development of enzymes and growth hormones.
(Cu) – Copper helps activate various enzymes and plays a role in chlorophyll production.
(Mo) – Molybdenum is needed to produce nitrogen-based proteins. Molybdenum is, in a way, linked to nitrogen and is essential for nitrogen assimilation by plants.
(Ni) – Nickel regulates mineral metabolism, enzyme activity and other metabolic processes in plants.
Other Useful Elements
Scientists also note another set of mineral elements used by plants and refer to them as beneficial elements. These elements are not required for plant functions but have been found to exhibit various beneficial characteristics.
(Si) – Silicon is thought to strengthen a plant’s cell walls and heighten resistance to pathogens.
(Na) – Sodium helps to maintain turgor within the plant stem. Sodium also helps with osmosis.
(Co) – Cobalt is an essential component of many enzymes and a stimulator of beneficial bacteria.
(Se) – Selenium plays a role in a plant’s metabolism by its involvement in anti-oxidative processes.
Don’t get overwhelmed by all the scientific, chemistry mumbo-jumbo. It’s nice to use as a reference but this knowledge is not necessary to find the appropriate fertilizer regiment for your garden. A basic understanding of these elements may aid you in determining the subtle differences between two fertilizers designed for the same crop or which additives would work better with which fertilizers. Today’s fertilizer manufacturers make finding a good fertilizer easy.
Plant fertilizer is any organic or synthetic substance that provides the plant with any of the essential elements. Most soils contain some form of fertilizer in either organic or synthetic form. Fertilizers can come in liquid, powder, or granular forms. Federal and State standards require that every fertilizer must exhibit the N-P-K value on its packaging. A closer look at the label will usually reveal the percentages of every essential element contained within. Fertilizers can be broken into two sub-categories: base fertilizers and supplemental fertilizers.
A base fertilizer is a fertilizer that acts as the foundation of any feeding regiment and contains a majority, if not all, of the essential elements. Many general base fertilizers contain all the essential elements in almost equal amounts relative to one another. Other liquid fertilizer manufacturers separate the base nutrients into “grow” and “bloom” formulations. This is because the nutritional requirements for most annual plants change throughout the growing season. Throughout the first part of the growing season an annual plant’s energy is focused on growth. This is commonly referred to as the vegetative or growth stage. Specific “grow” fertilizers contain a ratio of the essential elements geared toward promoting vigorous growth.
During the later stages of the growing season the nutritional needs of annual plants change. Once a plant’s fruiting or flowering hormones have been triggered it will begin to absorb the essential elements in a different ratio than during its vegetative growth. Fertilizers designed specifically for blooming provide a better ratio of essential elements specific to the fruiting/flowering stage of growth. Although a base fertilizer is all that is required for basic plant health, many horticulturists use them in conjunction with supplemental fertilizers to better tailor the feeding regiment to their plants or crop.
Supplemental fertilizers are fertilizers that contain one or a few of the essential elements. Supplemental fertilizers can be used to correct deficiencies or supply specific nutrients to plants that may prefer higher amounts of those nutrients. As with base fertilizers there are stage specific supplemental fertilizers that heighten performance in either the growth or blooming stage. Calcium and magnesium formulas, phosphorus and potassium formulas and micronutrient formulas are all common examples of supplemental fertilizers. Many tomato growers have dealt with blossom rot due to insufficient calcium. A calcium and magnesium supplement will easily rectify this problem if it is implemented early enough. Read this article to learn more about the causes and cures for blossom rot.
Phosphorus and potassium supplements are generally used as blooming stimulators. Increased amounts of these essential elements will trigger flowering hormones and result in more prolific blooms. New shoots on a plant showing signs of deformation or discoloration are probably a result of a micronutrient deficiency. Micronutrient supplemental fertilizers will often correct these deficiencies soon after they are introduced.
Non-fertilizer additives are liquid or granular additives that are beneficial to plants but contain negligible amounts of actual essential elements. These formulations usually stimulate microorganisms or hormones within the plant which, in turn, help boost the uptake of the essential elements. Vitamins, plant hormones, enzymes, and supplemental beneficial microbes are all examples of commonly used non-fertilizer additives.
When trying to select a fertilizer for their garden, a gardener may be overwhelmed by the sheer number of choices. For most gardeners a good general base fertilizer is all that is necessary for decent results. If your garden contains a wide variety of annual plants, it would probably be advantageous to invest in both “grow” and “bloom” base fertilizers. Serious gowers or commercial greenhouse vegetable gardeners will combine their “grow” and “bloom” base fertilizers with an array of supplemental fertilizers and additives.
Experimentation is the best method to determine the optimal diet for your garden. Be patient as this process may take a while, especially if a wide variety of plants are being grown. Start out by purchasing the smallest size container of any given fertilizer on your quest to find optimal nutrition. This way you can try more fertilizers and you are not stuck with a surplus of fertilizers that didn’t meet your needs. Through experimentation and careful note taking any gardener can build an effective fertilizer regiment that will make every member of his or her plant family thrive.
Eric Hopper resides in Michigan’s beautiful Upper Peninsula where he enjoys gardening and pursuing sustainability.