& PLANT NUTRIENTS
Some gardening knowledge is
gained by doing. Other knowledge is gained by studying.
Fertilizers fall into that second category. But once you understand the
basics of fertilizer it will become rather simple. Therefore, this
webpage is to share my knowledge (both remembered and already * forgotten
-- see my note below) about
* I had to reference some old
university notebooks from my agronomy and horticulture classes to compile this plant nutrient information
Here's to vigorous plants through proper fertilization!
N, P, K
Secondary Nutrients -
Ca, Mg, S
Essential Elements -
C, H, O
C, H, O + N, P, K +
Ca, Mg, S
Minor Elements -
Fe, B, Mn, Cu, Cl,
Remembering it all -
C. Hopkins, Cafe
does fertilizer "analysis" mean?
fertilizers have three numbers on the label which indicate the fertilizer
analysis, or "percentage by weight" of nitrogen, phosphorus and
potassium, in that order.
Therefore, a 50 pound bag of fertilizer labeled 20-10-5 would contain 20%
nitrogen (10 pounds), 10% available phosphates (5 pounds), and 5% soluble potash
(2.5 pounds). See the calculations below:
pound bag of 20-10-5 fertilizer
nitrogen .20 x 50 lbs = 10 lbs
10% available phosphates .10 x 50 lbs = 5 lbs
5% water soluble potash .05 x 50 lbs = 2.5 lbs
this product would be considered a "complete" fertilizer, since all
three nutrients are present.
An "incomplete" fertilizer would
have a label like 0-0-60 or 46-0-0, since it would only have one of the three
major nutrients present. Another example of an incomplete fertilizer would be
0-20-20, since one of the three nutrients is missing.
also have "ratios" which indicate the relative amounts of
nutrients to each other. For example, a 10-10-10 fertilizer is a 1-1-1 ratio,
and a 20-10-5 fertilizer is a 4-2-1 ratio.
Ratios can be helpful when looking for the "right mix" for a certain
type of plant or situation. For example, vegetable gardens often call for
a 1-2-1 ratio, which would translate into a 5-10-5 or 10-20-10 fertilizer.
Most trees like a 2-1-1 ratio, which would be a fertilizer product such as
10-5-5 or 20-10-10. Lawns prefer a 3-1-2 ratio fertilizer, so a fertilizer
product with 30-10-20 on the label would be a good ratio match.
analysis fertilizers (those with larger numbers on the label) would be applied
at a lower rate to yield the same results. In other words, 5 lbs of a
20-20-20 fertilizer would yield the same amount of actual nutrients as 10 lbs of
a 10-10-10 fertilizer.
READ AND FOLLOW
What do the 3 numbers on the fertilizer
Answer: N - P - K
These are the "major nutrients"
Nitrogen - Phosphorus -
(N) - the Nitrogen percentage is the first number on
Nitrogen is a primary nutrient that really makes plants "grow."
When you put fertilizer on your lawn, most of the "green-up and grow" comes from
'quick release' and 'slow release' forms of nitrogen. Slow release forms are more
expensive but remain effective for a longer period of time. Organic fertilizers are
slow release, and have less potential to "burn" plants.
produces vegetative growth in plants, but too much nitrogen can cause problems. One
problem is succulent growth, which makes a plant more susceptible to certain diseases.
our atmosphere is nitrogen, and rain and snow account for 2 to 12 pounds of actual
nitrogen per acre (43,560 square feet), per year. "Lightning charged rain"
is high in NH4 and NO3. Snow has been called "poor man's manure". . . now
you know why!
the Legume family "fix" atmospheric nitrogen into the soil. Peas, beans, clover,
and alfalfa are legumes, as well as Black Locust trees.
PHOSPHORUS (P) - the Phosphorus
percentage is the middle number on the label
Phosphorus is a
primary nutrient that encourages rooting, blooming and fruit production in plants.
gardeners have typically been told to apply 5-10-5 since the higher middle number (P)
helps vegetable production.
is important for root-growth and blooming in plants, and is the main ingredient in
"starter fertilizers" as well as liquid fertilizer "bloom boosters".
is lacking in most Southwestern Pennsylvania soils we have tested since 1979.
Applications of super-phosphate (0-20-0), triple super-phosphate (0-46-0), or bone meal
(organic source) can be used to correct deficiencies.
phosphorus moves very slowly through the soil, it should be incorporated into the soil
prior to, or during planting. In existing lawns, we recommend core-aeration prior to
2015 Update: Many states have
now banned the use of phosphorus in fertilizers due to concerns for
POTASSIUM (K) - the Potassium percentage is last on the label
Potassium helps plants
resist disease and aids in winter hardiness.("K" is the symbol for
"kalium" or potash, and is commonly used to represent potassium)
'winterizer' fertilizers used on lawns in late fall are high in Potassium, since it
promotes winter hardiness in turfgrasses.
fertilizers have a high "salt index" and should be used with caution, since they
can "burn" plant foliage.
"complete" fertilizers contain potassium since it is fairly mobile, and readily
leaches out of the soil profile.
nutrients also play an important role in plant growth. The 3 secondary nutrients are
Calcium (Ca), Magnesium (Mg) and Sulfur (S).
essential elements are basic to plant growth, and need to be mentioned here, even though
they aren't commercially available fertilizers. The 3 essential elements are Carbon (C), Hydrogen (H) and Oxygen (O).
Plants obtain these elements from carbon dioxide (CO2) and water (H2O).
When you group the
essential elements with the major nutrients and secondary nutrients, you end up with the 9
macronutrients: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Potassium, Calcium,
Magnesium, and Sulfur: C, H, O N, P,
K Ca, Mg, S
Nutrients needed by
plants in lesser amounts are known as the minor elements. These include Iron
(Mo), and Zinc
Remembering it all
How can you possibly remember everything?
Simple . . . start with the name of a famous restaurant manager in the table
Hopkins, Cafe Mgr.
But mother's cooking is more zestful
C - Carbon
H - Hydrogen
P - Phosphorus
K - Potassium
I - (nothing)
N - Nitrogen
S - Sulfur
Ca - Calcium
but - Boron
mother's - Manganese
is more - Molybdenum