Plant Nutrients Explained

Primary, Secondary & Micro Plant Nutrients

Plant Nutrients
Sixteen chemical elements are known to be important to plant growth and survival. The sixteen chemical elements are divided into two main groups: non-mineral and mineral.  The non-mineral nutrients are hydrogen (H), oxygen (O), & carbon (C).
These nutrients are found in the air and water.
In a complex process known as photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 – carbon and oxygen) and water (H2O- hydrogen and oxygen) into starches and sugars. These starches and sugars are then utilized by plants as food.

In their natural environment, plants obtain carbon, hydrogen, and oxygen from the surrounding air and water.  So it follows that when managing an indoor hydroponic garden, among other environmental conditions, one must carefully control the lighting, water and ventilation systems to provide adequate amounts of these essential materials which are otherwise lacking in such artificial environmental conditions.

Mineral Nutrients
The 13 mineral nutrients which come from the soil are readily dissolved in water and absorbed through a plant’s roots.  Depending upon soil composition, there are not always enough of these nutrients available in the root zone to facilitate healthy plant growth.  This is why plants generally respond so well when nutrient fertilizers are added to the soil.
The 13 mineral nutrients are divided into two separate groups: Macro-nutrients and Micro-nutrients.

Macronutrients themselves are further divided into two separate groups: NPK, or primary nutrients, and secondary nutrients which are required in smaller amounts, but are no less important to plant function and development.

The primary nutrients are nitrogen (N), phosphorus (P), and potassium (K).  The percentage of NPK amounts found in chemical and organic fertilizers are usually displayed with three bold numbers on the product label.  These three mineral nutrients are required in large quantities and benefit plants in the following ways:

Nitrogen
· Necessary for formation of amino acids, the building blocks of protein
· Essential for plant cell division, vital for plant growth
· Aids in production and use of carbohydrates
· Directly involved in photosynthesis
· Necessary component of vitamins
· Increases foliage and plant vigor
· Affects plant energy reactions

Phosphorus
· Facilitates photosynthesis, respiration, energy storage and transfer, cell division
and enlargement
· Improves quality of fruits, vegetables, and grains
· Helps plants survive harsh winter conditions
· Promotes early root formation and growth
· Increases water-use efficiency
· Stimulates plant metabolism
· Vital to seed formation
· Hastens maturity

Potassium
· Carbohydrate metabolism and the break down and translocation of starches
· Activates enzymes and controls their reaction rates
· Increases disease and cold resistance
· Improves quality of seeds and fruit
· Essential to flower development
· Increases water-use efficiency
· Essential to protein synthesis
· Important in fruit formation
· Improves winter hardiness
· Increases photosynthesis

The secondary nutrients are calcium (Ca), magnesium (Mg), and sulfur (S).

Calcium
· Increases fruit set
· Regulates plant respiration
· Stimulates microbial activity
· Involved in nitrogen metabolism
· Essential for nut development in peanuts
· Utilized for Continuous cell division and formation
· Aids translocation of photosynthesis from leaves to fruiting organs

Magnesium
· Improves utilization and mobility of phosphorus
· Activator and component of many plant enzymes
· Influences earliness and uniformity of maturity
· Key element of chlorophyll production
· Increases iron utilization in plants
· Aids in seed germination

Sulfur
· Aids in seed production
· Integral part of amino acids
· Helps develop enzymes and vitamins
· Promotes overall growth and maturity
· Promotes nodule formation on some plants
· Necessary in chlorophyll formation (though not a constituent)

Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities.  These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America.

The micronutrients are: boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).

And even though plants require micronutrients in far lesser quantities than macronutrients, they are just as important for plant development, overall health, and crop yields.  Most of the micro nutrients serve as plant activators and as such are critical to many plant functions.

The following is a brief summary of the functions which micro nutrients perform:

Boron
· Essential for germination of pollen grains and growth of pollen tubes
· Essential for seed and cell wall formation
· Affects nitrogen and carbohydrates
· Necessary for sugar translocation
· Promotes plant maturity

Chlorine
· Interferes with phosphorus uptake
· Controls water loss and moisture stress
· Enhances maturity of small grains on some soils

Copper
· Intensifies color
· Increases sugar content
· Catalyzes several plant processes
· Major function in photosynthesis
· Major function in reproductive stages
· Indirect role in chlorophyll production
· Improves flavor of fruits and vegetables

Iron
· Acts as an oxygen carrier
· Promotes formation of chlorophyll
· Reactions involving cell division and growth
· Activator for enzymes that control respiration

Manganese
· Essential in phosphorous and magnesium uptake
· Functions as a part of certain enzyme systems
· Increases the availability of P and Ca
· Aids in the utilization of nitrogen
· Aids in chlorophyll synthesis

Molybdenum
· Aids in the formation of legume nodules
· Needed to convert inorganic phosphates to organic forms in the plant
· Required to form the enzyme “nitrate reductas” which reduces nitrates to ammonium in plants

Zinc
· Essential for protein and growth hormone synthesis
· Necessary for chlorophyll production
· Necessary for carbohydrate formation
· Necessary for starch formation
· Increases leaf and fruit size
· Aids plant enzyme system
· Aids in seed formation

In addition to the 13 nutrients listed above, plants require carbon, hydrogen, and oxygen, which are extracted from air and water to make up the bulk of plant weight.

Organic Versus Chemical Fertilizers
Although organic and natural fertilizers usually have a lower NPK number, they are nevertheless valuable soil amendments that work slowly over time to improve soil quality, and thus effectively empower plant growth.  Natural fertilizers do not induce the fast growth and flowering provided by chemical fertilizers that can actually weaken plants. Therefore, big NPK numbers don’t necessarily mean a better fertilizer.

Organic composts and composted manure are excellent sources of all nutrients plants require for healthy growth, including NPK.  Professional gardeners often use a combination of  both chemical and organic / natural fertilizers in order to utilize the advantages of each.  And many professional gardeners agree that using compost is among the best methods of providing a well-balanced supply of nutrients.

Other excellent sources of natural plant nutrients are humic acid, sea weed, fish meal, bone meal, alfalfa meal, bat guano and earthworm castings.