WHAT'S WITH THE ELEMENTS?!
This is the first post in a series of articles explaining the foundations of fertilizing plants.
We’ll start with the basic question:
What are the nutrients? What defines an element as a plant nutrient?
Well, in 1939 Stout and Arnon (2 scientists) defined 3 criteria:
1. An element that a plant can’t accomplish a full life cycle (Seed to plant through all it’s stages, to producing seeds again) if it lacks this element.
2. This element can not be replaced by any other.
3. The element is part of an essential metabolite or part of an enzyme.
With time, scientists have found 16 of this nutrients. 16 elements that are crucial for plants’ life cycle, and with out one of them – the plant won’t be able to fulfill it’s destiny.
On the next articles we’ll dedicate each article to discuss each one of them, but for now, we’ll just list them all:
C – Carbon.
H – Hydrogen.
O – Oxygen.
N – Nitrogen.
P – Phosphorus.
K – Potassium.
Ca – Calcium.
Mg – Magnesium.
S – Sulfur.
Fe – Iron.
Mn – Manganese.
Zn – Zinc.
Cu – Copper.
Mo – Molybdenum.
B – Boron.
Cl – Chlorine.
Ni – Nickel (The newest one on the list!)
These fellows are divided into 2 groups, separated by the amount the plant needs from them:
Group 1# are elements 1-9 which are called “Macro-Nutrients”. Because the plants need a (relatively) large amount of them, measured by percentage of the plants dry weight.
In most approaches, 3 of them are a semi-group, needed in smaller amounts in the plant:
Calcium (Ca), Magnesium (Mg), and Sulfur (S).
Group 2# are elements 10-17 called the “Micro-Nutrients”. These are needed in smaller amounts, measured by PPM = Parts-Per-Million (=A milligram for kilogram.)
AVAILABILITY:
C,H and O are elements the plant gets from the air and the water it is watered by.
All others it gets naturally from the soil, or more accurate from the soil solution - the water in the soil (or the water in the hydroponic/aeroponic system..).
Now, the availability of the elements is affected by these 3 factors:
1. EC - The salinity the plant meets. This effects the plant by the sheer chemical principal that solubles will transfer from a solution with high concentration to the solution with low concentration.
So, if the EC of the soil solution is too high, the chemicals that are in high concentration in that solution will force themselves into the plant root cells. In many cases, those elements will be Chloride and sodium (Na) which can harm plants in those concentrations.
The tolerance that plants have for high EC differs in different species.
2. pH - Each element has a slightly different optimal pH where it's most available for plants absortion, as seen in the table.
