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Fertilizer Basics
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Bulletin #TP2600 |
Horticultural Observations for Healthier Landscapes |
There is not a lot of clarity regarding which fertizer is needed for which plants. Add to this
the timing of fertilizer application varies not only with plant type but also
with the current climate in the particular region where the plant is installed.
This Bulletin will attempt to provide some basic information to help simplify this
very important aspect of keeping our landscapes and gardens healthy.
The primary nutrients (by volume required) for plant growth are nitrogen, phosphorus and potassium
often referred to as macronutrients or the "NPK" listed on the package. When you purchase a
packaged fertilizer, the numbers listed on the bag like 5-10-5 or 16-6-8 indicate
the total percentages of nitrogen, phosphorus and potassium respectively.
These are known as the primary or macro "nutrients".
Calcium, sulfur and magnesium are also required by plants in larger quantites and so
are technically classified as "macro-nutrients". As these are not included within
the "NPK" statement, a popularly used category is "major-nutrients,
and therefore one needs to look at the micro-nutrient listing to find out
what percentage of these nutrients are contained in the particular fertilzer.
This grouping of several macro with the micro nutrients adds greatly to the confusion of understanding fertilizers,
and a reason I felt this bulleting on fertilizer basics was needed.
Minerals used in very small amounts, but very important to plants, are known as micro nutrients.
These include iron, molybdenum, boron, copper, zinc, and manganese.
◊ Nitrogen
◊ VARIOUS FERTILIZERS AND THEIR USES
Ammonium Phosphate (16-20-0)
Sulfate of Ammonia (21-0-0)
Calcium Nitrate (27-0-0)
Those fertilizers with equal N-P-K listings
Those fertilizers that provide the complete array of nutrients needed.
The nutrient formulla does not need to be balanced, but can be
Fertilizers that combine pesticides with nutrients
Please read the discussion to understand this complex subject!
Where the nutrient formula is designed for specific plant types
The nutrient formula is designed for certain applications
◊
Time or continuous-release fertilizers
Phosphorus
is a vital nutrient for root development, fruit and flower production.
It is necessary for photosynthesis and provides a mechanism for energy transfer within the plant.
Native soils in drought prone areas typically have small amounts of absorbable phosphorus available to plants.
Potassium for
fertilizer comes primarily from Potash. Potassium helps produce a strong plant
structure and increases resistance to stress and disease.
VARIOUS
FERTILIZERS AND THEIR USES:
Let's take a look at some fertilizers
and groups of fertilizers that you're likely to encounter. When a particular
fertilizer lacks one or more of the macro nutrients, it is classified as
incomplete. This group of fertilizers is aimed to specifically to perform a
specific benefit for the plant. If trying to "green up" a lawn) lots of nitrogen is provided.
Incomplete fertilizers should not be used as the only source of nutrients for
any plants as they lack the other vital elements. Ammonium Phosphate
(16-20-0) is perhaps the most
widely used chemical fertilizer in drought prone areas. Though used for other reasons, it
is best used as a pre-plant soil amendment for new lawns, flower and vegetable
beds. It should be combined and mixed with the soil as it lacks solubility when applied
on the surface. Apply spring or fall, not summer.
Sulfate of Ammonia
(21-0-0) is a popular nitrogen
fertilizer for leafy vegetable crops, grapes, spring lawns and trees and
shrubs. Better if not used in summer heat. Should be alternated with a
complete fertilizer or used with a mineral supplement.
Apply spring or fall, not summer. This refers to a group of
fertilizers that contain equal amounts of macro nutrients (N-P-K). Like a 8-8-8, 15-15-15
or 20-20-20 which have equal percentages of nitrogen, phosphorus and
potassium are suitable for large-scale or general fertilizing. Most do not
contain the needed micronutrients and should be routinely augmented with a
supplemental mineral fertilizer.
This refers to those fertilizers that provide all the macro, major and micro nutrients
that a particular plant would need. To do this, the manufacturer will encouter
the expense of adding each of these to the end product. Due to cost, few complete fertilizers are found on the market today.
This refers to products
like Weed & Feed . These kill existing broad leaf weeds while fertilizing the
lawn at the same time. Temperature and watering restrictions often apply so be
sure to read the label completely before broadcasting. These products work best
when applied during the early spring or fall when weeds are actively
growing and temperatures are between 70 and 80˚ F.
There are also combinations of fertilzer and disease or insect control. Reducing
the time needed to be spent applying nutrients and pest control can be helpful.
As these products must be more general in design (fertilizer formula, or pesticide
utilized) they may not be the best choice for your plant when the specific issues are
analyzed.
Are packaged formulations
designed to meet the needs of special groups of plants or fill specific
planting functions. A quick example: Palm Trees need a nutrient formula meant for them. Boron, which
is not desired by most plants is a requirement in Palms in micro amounts.
These are liquid fertilizers
formulated to be absorbed through the leaf stomata and epithelial cells. These
types of nutrient will get into the plant quicker than any other and very beneficial when a
malnourished plant has stressed or damaged roots.
Vital nutrients, used in
very small amounts, these address specific problems caused by our tough, arid
soils. Soil sulfur & Ammonium Sulfate neutralize alkaline soils and makes trace elements
readily available to plants. Adding Iron is helpful in correcting chlorosis, if the soil pH is not too high.
Chelated iron will correct chlorosis in alkaline soil, as the chelation helps the plant to uptake the iron.
When applying fertilizer to
the soil always remember to: 1) Water the entire area under the plant canopy. 2) Apply the Fertilizer. 3) Water again deeply. Avoid high nitrogen
fertilizer during summer months (Palms are OK for summer nitrogen!). When applying foliar
fertilizer, apply during the late afternoon so there is no chance of sun
scorch. Always read the label carefully! If fungus is suspected, do not
fertilize until the fungus is treated.
NOTE: there are several types of nitrogen. How quickly they get into the plant
ranges from overnight to over the course of many weeks. Nitrate is the fastest - 12 to 24 hours.
Ammoniacal nitrogen is quick - about 7 days. Then Urea nitrogen - about 30 days.
Water insoluable nitrogen usually takes 8 to 10 weeks.
Work high-phosphorus fertilizer lightly into the soil around your plants and water
well. Most organic phosphorous products like bone meal and fish meal provide a source of phosphorus that can be used
by plants only if applied directly in the root zone at time of planting. This is because
these move very slowly through the soil. Sometimes around an inch per year. There are
sythesized phosphorous products that move more rapidly. Ammonium phosphate is an example.
Routine tests of soils in the California's high desert and southern Nevada typically indicate potassium levels of around 45 ppm.
This is very low. Therefore this supplement is important and beneficial for adding to your
fertilizing plan.
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(top)Calcium
Nitrate (15.5-0-0) is now used in place of "Ammonium Nitrate (34-0-0)".
Ammonium Nitrate was commonly used for greening lawns in the fall due to it's high concentration of
fast acting - nitrate nitrogen, and it's low cost. It became a popular choice for terrorist
activity and was removed from commercial sale.
Calcium Nitrate is a safe alternative provides all the fast-acting nitrogen required by winter lawns
to keep them lush and green. It provides 19% of plant available calcium to
the product to make it stable, and better for the plants.
Much of the calcium to be found in drought prone soil is not plant availabe as a nutrient. So, adding
a good quality calcium is a beneficial idea.
If it is not known that a plant has a sensitvity to one of this group, or
fertilizer is being used to facilitate all around growth (not just fruiting or blooming),
then a balanced fertilizer is a good idea. Apply this type of fertilizer
in spring or fall.
A fertilizer becomes better, not because it has superior marketing or exposure,
but because it has a more complete formula of nutrients for the plants to be fed.
A landscaper or gardener is not likely to pay for a more expensive fertilizer
if they don't understand why it's better. Unfortunately many garden shoppers
repeatedly ask for highly advertized fertilizers.
The purpose of this bulletin is to assist in seeing that the garden nutrient
shopper, has the know-how to select fertilizers that give the reward of
healthier and more beautiful and bountiful plants.
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Seeking the advice of a trained plant and nutrient specialist (who is not employed
on a comission basis) may be a good option. A qualified specialist will be
able to answer why any of the specific nutrients are needed, and if the
quantity listed is sufficient.
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The term "organic" is used for marketing purposes in nearly every part of our economy.
The Chemical definition of an organic molecule requires that it includes carbon. Water itself,
and all of the micro nutrients are "natural", but not organic.
Lets take the confusion out of this term.
Rainwater contains nitrogen that is organic. Only after being "fixed" by soil bacteria does
this nitrogen become available to plants. Plants don't utilize organic nutrients directly,
they require the nutrient to be processed within the soil. Organic nutrients actually feed the soil;
not the plant directly. Once the soil bacteria and fungi get to work they convert
these nutrients into a salt form so that the plant can use them.
Organic nutrients are safer to apply to plants as the nutrients get into the plant in a gradual manner.
Having soil with a healthy and active bio-structure, is very important because of this. Soil biology is
mostly inactive during the cold season. The best time for applying organic nutrients is in
March and April.
Some common Organic nurtients are Bone or Blood Meal, Chicken & Steer Manure, Fish Emusion,
Cottonseed Meal and Compost. Greensand is a source for micro nutrients and is derived from
marine sediment beds. AS you can see all of these come from some part of living creatures.
Malorganite is not really an organic nutrient but is primarily derived from what we send
from our homes to treatment plants.
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When installing a new plant the formula required needs to be very light in nitrogen and
stronger in Phosphorous. These are called "Starter Fertilizers". Flowering plants
are looking for a similar recipe. However, if you have a flowering plant that also needs to grow
to a much larger size - you want more nitrogen; here a balanced formula would work. When this plant
approaches its mature size, change back to a flower formula.
The are specialty formulas for starting turf seed, feeding cactus, citrus, vegetables
as well as Fruit and Nut trees. And don't forget those beautiful Plumeria Trees!
n many cases the forumula is only customized around the Macro nutrients. Seldom
but notably formulas are specialized around certain micro nutrients.
Fruiting vegetables require a good portion of calcium. Blossom end rot
is a conseqence when not provided. An available form of calcium is often found in soil
(and often not!), but is rarely found in raised bed soil. So, in this case
a specialty formula adding this major nutrient is appropriate.
Often we wind up with umpteen "specialty fertilizers"
and a confusing and messy garden shed.
Garden Galaxy's Tip! Using your cell phone get a couple good photos of
the specialy formula you need instructions on. Put these photos into a folder for
your garden advice.
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is caused by over watering!
The Myth of Gypsum Magic
{Linda Chalker-Scott, Ph.D., Extension Horticulturist and Associate Professor,
Washington State University} can add some depth of understanding.
Gypsum has benefits, but should really only be used in the appropriate situations.
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Usually beginning 2 to 3 times the trunk width, fiberous roots begin.
Editing and Updating by Garden Galaxy
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