INTRODUCTION
Fertilizer is a substance added
to soil to improve plants' growth and yield. First used by ancient farmers,
fertilizer technology developed significantly as the chemical needs of growing
plants were discovered. Modern synthetic fertilizers are composed mainly of
nitrogen, phosphorous, and potassium compounds with secondary nutrients added.
The use of synthetic fertilizers has significantly improved the quality and
quantity of the food available today, although their long-term use is debated
by environmentalists.
Like all living organisms,
plants are made up of cells. Within these cells occur numerous metabolic
chemical reactions that are responsible for growth and reproduction. Since
plants do not eat food like animals, they depend on nutrients in the soil to
provide the basic chemicals for these metabolic reactions. The supply of these
components in soil is limited, however, and as plants are harvested, it
dwindles, causing a reduction in the quality and yield of plants.
Fertilizers replace the chemical
components that are taken from the soil by growing plants. However, they are
also designed to improve the growing potential of soil, and fertilizers can
create a better growing environment than natural soil. They can also be
tailored to suit the type of crop that is being grown. Typically, fertilizers
are composed of nitrogen, phosphorus, and potassium compounds. They also
contain trace elements that improve the growth of plants.
The primary components in
fertilizers are nutrients which are vital for plant growth. Plants use nitrogen
in the synthesis of proteins, nucleic acids, and hormones. When plants are
nitrogen deficient, they are marked by reduced growth and yellowing of leaves.
Plants also need phosphorus, a component of nucleic acids, phospholipids, and
several proteins. It is also necessary to provide the energy to drive metabolic
chemical reactions. Without enough phosphorus, plant growth is reduced.
Potassium is another major substance that plants get from the soil. It is used
in protein synthesis and other key plant processes. Yellowing, spots of dead
tissue, and weak stems and roots are all indicative of plants that lack enough
potassium.
Calcium, magnesium, and sulfur
are also important materials in plant growth. They are only included in
fertilizers in small amounts, however, since most soils naturally contain
enough of these components. Other materials are needed in relatively small
amounts for plant growth. These micronutrients include iron, chlorine, copper,
manganese, zinc, molybdenum, and boron, which primarily function as cofactors
in enzymatic reactions. While they may be present in small amounts, these
compounds are no less important to growth, and without them plants can die.
Many different substances are
used to provide the essential nutrients needed for an effective fertilizer.
These compounds can be mined or isolated from naturally occurring sources.
Examples include sodium nitrate, seaweed, bones, guano, potash, and phosphate
rock. Compounds can also be chemically synthesized from basic raw materials.
These would include such things as ammonia, urea, nitric acid, and ammonium
phosphate. Since these compounds exist in a number of physical states,
fertilizers can be sold as solids, liquids, or slurries.
HISTORY
The process of adding substances
to soil to improve its growing capacity was developed in the early days of
agriculture. Ancient farmers knew that the first yields on a plot of land were
much better than those of subsequent years. This caused them to move to new,
uncultivated areas, which again showed the same pattern of reduced yields over
time. Eventually it was discovered that plant growth on a plot of land could be
improved by spreading animal manure throughout the soil.
Over time, fertilizer technology
became more refined. New substances that improved the growth of plants were
discovered. The Egyptians are known to have added ashes from burned weeds to
soil. Ancient Greek and Roman writings indicate that various animal excrements
were used, depending on the type of soil or plant grown. It was also known by
this time that growing leguminous plants on plots prior to growing wheat was
beneficial. Other types of materials added include sea-shells, clay, vegetable
waste, waste from different manufacturing processes, and other assorted trash.
Organized research into
fertilizer technology began in the early seventeenth century. Early scientists
such as Francis Bacon and Johann Glauber describe the beneficial effects of the
addition of saltpeter to soil. Glauber developed the first complete mineral
fertilizer, which was a mixture of saltpeter, lime, phosphoric acid, nitrogen,
and potash. As scientific chemical theories developed, the chemical needs of
plants were discovered, which led to improved fertilizer compositions. Organic
chemist Justus von Liebig demonstrated that plants need mineral elements such
as nitrogen and phosphorous in order to grow. The chemical fertilizer industry
could be said to have its beginnings with a patent issued to Sir John Lawes,
which outlined a method for producing a form of phosphate that was an effective
fertilizer. The synthetic fertilizer industry experienced significant growth
after the First World War, when facilities that had produced ammonia and
synthetic nitrates for explosives were converted to the production of
nitrogen-based fertilizers.
TYPES OF CHEMICAL FERTILIZERS
The
different types of chemical fertilizers are usually classified according to the
three principal elements, namely Nitrogen (N), Phosphorous (P)
and Potassium (K), and may, therefore, be included in more than one
group.
Nitrogenous Fertilizer Types
This type of fertilizer is divided into different groups according to the manner
in which the Nitrogen combines with other elements. These groups are:
Ammonium Sulphate
This
fertilizer type comes in a white crystalline salt form, containing 20
to 21% ammonia cal nitrogen. This fertilizer type is soluble in water; its
nitrogen is not readily lost in drainage, because the ammonium ion is retained
by the soil particles. A note of caution: Ammonium sulphate may have an acid
effect on garden soil. Over time, the long-continued use of this type of
fertilizer will increase soil acidity and thus lower the yield. The application
of Ammonium sulphate fertilizer can be done before sowing, at sowing time, or
even as a top-dressing to the growing crop.
Ammonium Nitrate
This
fertilizer type also comes in white crystalline salts. Ammonium Nitrate salts
contains 33 to 35% nitrogen, of which half is nitrate nitrogen and the
other half in the ammonium form. As part of the ammonium form, this type of
fertilizer cannot be easily leached from the soil. This fertilizer is
quick-acting, but highly hygroscopic thus making it unfit for storage. On a
note of caution: Ammonium Nitrate also has an acid effect on the soil.
Ammonium Sulphate
Nitrate
This fertilizer type is
available as a mixture of ammonium nitrate and ammonium sulphate
and is recognizable as a white crystal or as dirty-white granules. Ammonium Sulphate Nitrate is non-explosive,
readily soluble in water and is very quick-acting. Because this type of
fertilizer keeps well, it is very useful for all crops. Though it can also
render garden soil acidic, the acidifying effects is only one-half of that of
ammonium sulphate on garden soil. Application of this fertilizer type can be
done before sowing, at sowing time or as a top-dressing, but it should not be
applied along the seed.
Urea
This
type of fertilizer usually is available to the public in a white, crystalline,
organic form. It is a highly concentrated nitrogenous fertilizer and
fairly hygroscopic. Urea is also produced in granular or pellet forms and is
coated with a non-hygroscopic inert material. It is highly soluble in water and
therefore, subject to rapid leaching. It is, however, quick-acting and produces
quick results. When applied to the soil, its nitrogen is rapidly changed into
ammonia. Application of Urea as fertilizer can be done at sowing time or as a
top-dressing, but should not be allowed to come into contact with the seed.
Ammonia
This
fertilizer type is a gas that is made up of about 80% of nitrogen and
comes in a liquid form Ammonia can be applied by introducing it into irrigation
water, or directly into the soil from special containers. Use of ammonia as a
fertilizer is very expensive.
Phosphate Fertilizer Types
The
Phosphate fertilizers are categorized as natural phosphates, either treated or
processed, and also by products of phosphates and chemical phosphates.
Rock Phosphate
As a type
of fertilizer, rock phosphate occurs as natural deposits in some
countries. Powdered phosphate fertilizer is an excellent remedy for soils that
are acidic and has a phosphorous deficiency and requires soil amendments. However,
the disadvantage is that although phosphate fertilizer such as rock phosphate
contains 25 to 35% phosphoric acid, the phosphorous is insoluble in
water. It has to be pulverized to be used as a type of fertilizer before
rendering satisfactory results in garden soil.
Super phosphate
Super phosphate is a fertilizer
type that most gardeners are familiar with. As a fertilizer type one can get super
phosphate in three different grades, depending on the manufacturing
process. The following is a short description of the different super phosphate
fertilizer grades:
·
Single super phosphate containing 16 to
20% phosphoric acid;
- Dicalcium phosphate
containing 35 to 38% phosphoric acid; and
- Triple super phosphate
containing 44 to 49% phosphoric acid.
Triple super
phosphate is used mostly in the manufacture of concentrated mixed fertilizer
types. All garden soil types can benefit from the application of Super
phosphate as a fertilizer. Used in conjunction with an organic fertilizer, it
should be applied at sowing or transplant time.
Bone-meal
Bone-meal is used as a phosphate fertilizer
type and is available in two types: raw and steamed. The raw bone-meal
contains 4% organic Nitrogen that is slow acting, and 20 to 25%
phosphoric acid that is not soluble in water. The steamed bone-meal on
the other hand has all the fats, greases, nitrogen and glue-making substances
removed as a result of high pressure steaming. But it is more brittle and can
be ground into a powder form. In powder form this fertilizer is of great
advantage to the gardener in that the rate of availability of the phosphoric
acid depends on its pulverization. This fertilizer is particularly suitable as
a soil amendment for acid soil and should be applied either at sowing time or
even a few days prior to sowing.
Potassium fertilizer types
Chemical Potassium fertilizer
should only be added when there is absolute certainty that there is a Potassium deficiency in your garden
soil. Potassium fertilizers also work well in sandy garden soil that responds
to their application. Crops such as chilies, potato and fruit trees all benefit
from this type of fertilizer since it improves the quality and appearance of
the produce. There are basically two different types of potassium fertilizers:
- Muriate of potash
(Potassium chloride) and
- Sulphate
of potash (Potassium sulphate).
Muriate of Potash
Muriate
of potash is a gray crystal type of fertilizer that consists of 50 to
60% potash. All the potash in this fertilizer type is readily available to
plants because it is highly soluble in water. Even so, it does not leach away
deep into the soil since the potash is absorbed on the colloidal surfaces.
Sulphate of Potash
Sulphate of potash is a
fertilizer type manufactured when potassium chloride is treated with magnesium
sulphate. It dissolves readily in water and can be applied to the garden
soil at any time up to sowing. Some gardeners prefer using sulphate of potash
over muriate of potash.
Organic fertilizers ('natural' fertilizer)
Naturally
occurring organic fertilizers include manure, worm castings, peat moss, seaweed, sewage and guano. Sewage sludge use in organic agricultural
operations in the U.S.
has been extremely limited and rare due to USDA prohibition of the practice
(due to toxic metal accumulation, among other factors)
Cover crops may are also grown to enrich soil as
a green manure through nitrogen fixation from the atmosphere by
bacterial nodules on roots); as well as phosphorus (through nutrient
mobilization) content of soils.
Processed
organic fertilizers from natural sources include compost (from green waste), blood meal and bone meal(from organic meat production
facilities), and seaweed extracts (alginates and others).
Mixed definitions of 'organic'
There
can be confusion as to the veracity of the term 'organic' when applied to
agricultural systems and fertilizer. The problem is one of confusion of
terminology between agricultural and chemical disciplines.
Minerals
such as mined rock phosphate, sulfate of potash and limestone are also considered organic fertilizers, although they
contain no organic (carbon) molecules. Some ambiguity in the usage of the term organic exists; however, it is simple
to differentiate with a separation between the scientific and colloquial uses
Synthetic
fertilizers, such as urea and urea formaldehyde, are organic in the sense of
the organic chemistry
definition of organic, can be supplied organically
(agriculturally), but when manufactured as a pure chemical is not organic under organic certification
standards.
Naturally
mined powdered limestone, mined rock phosphate and sodium nitrate, are inorganic (in a chemical sense) in that they contain no carbon
molecules, and are energetically-intensive to harvest, but are approved for organic agriculture in minimal amounts.
Benefits of organic fertilizer
However,
by their nature, organic fertilizers provide increased physical and biological
storage mechanisms to soils, mitigating risks of over-fertilization. Organic
fertilizer nutrient content, solubility, and nutrient release rates are
typically much lower than mineral (inorganic) fertilizers. One study found that
over a 140-day period,
- Organic fertilizers had released between 25% and 60%
of their nitrogen content
- Controlled release fertilizers(CRFs) had a relatively
constant rate of release
- Soluble fertilizer released most of its nitrogen
content at the first leaching
Disadvantages of organic fertilizer
It is
difficult to chemically distinguish between urea of biological origin and those
produced synthetically. It is possible to over-apply organic fertilizers.
ENVIRONMENTAL IMPACTS OF FERTILIZERS
Fertilizers
contribute to the variety, abundance, and low cost of food stuffs available to
the public. However, fertilizer misuse can lower air, soil, and water quality.
Impacts of Intensive Farming on Soil and Water Resources:
Damage to Soil:
Soil erosion from farmland
threatens the productivity of agricultural fields and causes a number of
problems elsewhere in the environment. Agricultural topsoil takes up to 300
years for 1 inch to form, soil that is lost is essentially irreplaceable. The
amount of erosion varies considerably from one field to another, depending on
soil type, slope of the field, drainage patterns, and crop management
practices; and the effects of the erosion vary also. Areas with deep organic
loams are better able to sustain erosion without loss of productivity than are
areas where topsoils are shallower.
·
Erosion affects productivity because it removes the
surface soils, containing most of the organic matter, plant nutrients, and fine
soil particles, which help to retain water and nutrients in the root zone where
they are available to plants.
·
The effects of erosion are also felt elsewhere
in the environment. A recent study estimated the off-site cost of cropland
erosion in the United States
to be in the range of a billion dollars per year (Clark, Haverkamp, and Chapman
1985).
·
The eroded soils contain nutrients and other
chemicals that are beneficial on farm fields, but can impair water quality when
carried away by erosion. As a result, drinking water supplies may contain
nitrate or organic chemicals in concentrations that exceed public health
standards or surface waters may become clogged with excessive plant growth from
the added nutrients.
·
Even when soil erosion is not excessive,
intensive agriculture can impair soil quality by depleting the natural supplies
of trace elements and organic matter.
Contamination of Water:
·
Farming is one potential source of such
contamination. Surface runoff carries manure, fertilizers, and pesticides into
streams, lakes, and reservoirs, in some cases causing unacceptable levels of
bacteria, nutrients, or synthetic organic compounds.
·
Similarly, water percolating downward through
farm fields carries with it dissolved chemicals, which can include nitrate
fertilizers and soluble pesticides. In sufficient quantities these can
contaminate groundwater supplies.
·
Eroded soil clogs streams, rivers, lakes, and
reservoirs, resulting in increased flooding, decreased reservoir capacity, and
destruction of habitats for many species of fish and other aquatic life.
·
Nutrients are lost from agricultural fields
through runoff, drainage, or attachment to eroded soil particles. The amounts lost
depend on the soil type and organic matter content, the climate, slope of the
land, and depth to groundwater, as well as on the amount and type of fertilizer
and irrigation used.
·
Leaching of nitrate from agricultural fields can
elevate concentrations in underlying groundwater to levels unacceptable for
drinking water quality. In the Suffolk County area of Long Island, for example,
almost 10 percent of private wells tested for nitrate exceed the 10 mg/l
drinking water standard.
·
Phosphorus is carried with eroded soil into
surface water bodies where it may cause excessive growth of aquatic plants. If
this process precedes far enough, lakes and reservoirs become choked with
decaying mats of algae, which have offensive odors and can cause fish kills
from the resulting lack of dissolved oxygen.
Eutrophication:
The most complete global study of eutrophication was the Organization
for Economic Cooperation and Development (OECD) Cooperative Programme on
Eutrophication carried out in the 1970s.Although both nitrogen and phosphorus
contributes to eutrophication. The symptoms and impacts of eutrophication are:
- Increase in production and biomass of phytoplankton, attached algae, and macrophytes.
·
Production of toxins by certain algae.
·
Increasing operating expenses of public water
supplies, including taste and odour problems, especially during periods of
algal blooms.
·
Deoxygenation of water, especially after
collapse of algal blooms, usually resulting in fish kills.
·
Infilling and clogging of irrigation canals with
aquatic weeds.
·
Economic loss due to change in fish species,
fish kills, etc.
Problems with Organic fertilizers
Major problems are associated
with organic fertilizers. Manure produced by cattle, pigs and poultry are used
as organic fertilizer the world over. Intensive livestock production has
produced major problems of environmental degradation in the Eastern and
Southern parts of the Netherlands .
·
Surface waters and the groundwater are being contaminated by heavy metals. High
concentrations of these substances pose a threat to the health of man and
animals. To a certain extent these heavy metals accumulate in the soil, from
which they are taken up by crops. For example, pig manure contains significant
quantities of copper.
·
Acidification as a result of ammonia emission (volatilization) from livestock
accommodation, manure storage facilities, and manure being spread on the land.
Ammonia constitutes a major contribution to the acidification of the
environment, especially in areas with considerable intensive livestock farming.
Environmental Implications of Fertilizer
Mismanagement:
When
nutrients and other pollutants associated with animal manures and commercial
fertilizers are not managed properly, they can affect plant and animal life
(including humans) negatively. Some of these impacts include algae blooms
causing the depletion of oxygen in surface waters, pathogens and nitrates in
drinking water, and the emission of odors and gases into the air.
Oxygen depletion:
When
manure or commercial fertilizers enter surface water, the nutrients they
release stimulate microorganism growth. The growth and reproduction of these
microorganisms will reduce the dissolved oxygen content of the water body.
Without
sufficient dissolved oxygen in surface water, fish and other aquatic species
suffocate. The resulting dead fish degrade the water quality and cause
unpleasant odors.
Weed growth and algae blooms:
The
number of plants and algae in a lake, pond or other water body increase with an
increased supply of nutrients, particularly nitrogen (N) and phosphorus (P).
The nutrient present in the least amount for growth will limit the production
in the aquatic system. However, increased production of aquatic plants and
algae is not healthy for water resources. For example, 1 extra pound of P in a
lake can produce hundreds of pounds of weeds and algae that compete with other
aquatics for oxygen. Eutrophication is the term used to describe the natural or
human accelerated process whereby a water body becomes abundant in aquatic
plants and low in oxygen content.
Health effects:
In
addition to oxygen depletion, there is potential that the algae can be toxic.
Blue-green algae (cyano-bacteria) can cause rashes, nausea and respiratory
problems in humans and has been documented to kill livestock that drink from
affected water storage.
Ammonia toxicity:
Ammonia-contaminated runoff from
fresh manure application sites is toxic to aquatic life. At high enough levels,
ammonia in surface water will kill fish. Fish are relatively sensitive to
ammonia in water. Concentrations as low as 0.02 parts per million (ppm) may be
lethal.
Fecal organisms:
The
fresh manure from warm-blooded animals has countless microorganisms, including bacteria,
viruses, parasites and fungi. Some of the organisms are pathogenic (disease
causing).If manure applications are mismanaged near wells, the risk of
bacterial contamination of the groundwater via the well is greatly increased.
Therefore, avoid surface application of manure where it can come into direct
contact with a well or other drinking water supply.
Nitrates in drinking water:
High
levels of nitrates in drinking water are known to cause methemoglobinemia
(blue-baby syndrome) in human infants and other warm-blooded animals. In human
infants, the nitrate is ingested, usually in water used to mix formula, and
nitrate-reducing bacteria in the upper gastrointestinal system convert it to
nitrite. The nitrite, in turn, interferes with the uptake and movement of
oxygen throughout the body. The pale, bluish color of the infant's skin is the
result of oxygen deprivation.
Odors and gases:
Manure
odors can be a nuisance for nearby neighbors and communities. Constant nuisance
odors can degrade the "quality of life" for anyone.
Gases are emitted from
facilities throughout the year, but are released at the highest rates during
agitation, pumping and application of liquid manure systems or during cleanout
and application of solid manure systems. Volatilization of ammonia to the
atmosphere may become a water quality problem near animal production facilities
when it is returned to the earth dissolved in rainfall. (http://www.ag.ndsu.edu/pubs)
Global Ethical Issues
The
growth of the world's population to its current figure has only
been possible through intensification of agriculture
associated with the use of fertilizers. There is an impact on the sustainable consumption of other global resources as a consequence.
The
use of fertilizers on a global scale emits significant quantities
of greenhouse
gas into the atmosphere. Emissions come about through the use of:
·
animal manures and urea, which release methane, nitrous
oxide, ammonia,
and carbon
dioxide in varying quantities depending on their form (solid or liquid) and
management (collection, storage, spreading)
·
fertilizers that use nitric acid
or ammonium bicarbonate, the production and
application of which results in emissions of nitrogen
oxides, nitrous oxide, ammonia and carbon
dioxide into the atmosphere.
By
changing processes and procedures, it is possible to mitigate some, but not
all, of these effects on anthropogenic climate change.
The
nitrogen-rich
compounds found in fertilizer run-off are the primary cause of a serious
depletion of oxygen in many parts of the ocean, especially in coastal zones;
the resulting lack of dissolved oxygen is greatly reducing the ability of these
areas to sustain oceanic fauna.
Fertilizing Alternatives
Fertilizers contain nitrogen,
phosphorous, potassium, and other elements that help build strong roots and
plants. But as the saying goes, too much of a good thing can be
bad.
Many of us unknowingly waste
time and money by putting too much of the wrong kind of fertilizer on our
landscapes, often at the wrong times. This is partially because our soil
is not properly balanced (that is, it’s too acidic or alkaline) to allow plants
to absorb the nutrients they need in the first place. Not only does your
lawn and wallet suffer, but so does the environment.
Generally speaking, lawns need
much less fertilizer than is advertised. Fertilizers that are not
immediately absorbed by plants in our landscapes end up polluting our water
through storm water runoff. These excess nutrients either leach through
the soil to the groundwater or they are washed by rain into storm drains that lead
to the nearest water body. These nutrients can contaminate our drinking
water and cause rapid alga growth in ponds and bays. Alga blooms not only
make swimming and boating unpleasant, but also block sunlight and deplete
oxygen, killing fish and other animals.
Save time and money by following
these helpful guidelines to provide your lawn with all the nutrients it needs
to be healthy, beautiful, and easy to maintain.
Add lime if your soil is
acidic:
Soil’s pH should be between 6.0
and 7.0 for a healthy lawn. Most landowners will find that their soil’s
pH is below 7, which means it is acidic. Acidic soil is more hospitable
to weeds than grass because it prevents nutrient absorption. Adding lime
will remedy this problem. To raise your soil’s pH one point, use a mechanical
spreader to evenly broadcast 40 pounds of palletized lime per 1000 square feet
of grass.
Leave grass clippings on
the lawn:
Mulching mowers create fine
grass clippings that will break down and add nitrogen and organic matter to the
soil. Leaving grass clippings on the lawn over the season provides the
equivalent of one regular fertilizer application, and will not cause
thatch. Take advantage of this free natural fertilizer and let nature do
the work!
Top dress with compost:
If soil analysis shows that lawn
needs nutrients, a thin layer of compost (1/4” or less) will provide most of
what your soil needs. Compost also adds organic materials that help the
soil retain moisture. The best time to treat your lawn with compost is in the
spring, by using a wheelbarrow, shovel and lawn rake.
If necessary, use
organic fertilizers. For this, be sure to: (1) use an organic,
slow-release, water-insoluble fertilizer at the recommended dose; (2) don’t
spread the fertilizer if heavy rain is predicted; and (3) evenly distribute the
fertilizer using a mechanical spreader at the lowest setting, going over the
area two or three times.
Organic fertilizers and
synthetic fertilizers are not the same.
Organic fertilizers are less
concentrated, but have longer lasting benefits because they gradually release
nutrients. Synthetic fertilizers are more concentrated which makes it is
easier to over fertilize, burning the plant, and potentially harming soil
organisms. Synthetic fertilizers also tend to be more water-soluble,
leaching out of the soil faster and potentially polluting our water resources.
Organic fertilizers offer an additional benefit of recycling waste that would
otherwise contribute to pollution.
Alternative Fertilizer Choices Including Organic Options
Conventional
fertilizer is made mainly from phosphorus, a natural element already found in
most soils. Though, phosphorous is natural and already in soil, adding
additional phosphorus to soil is usually unnecessary and sometimes even harmful
to the environment. In many cases, people put far too much fertilizer on their
lawns. The excess phosphorous disrupts their garden’s natural ecosystem
balance. Causing certain plants to swell and dominate unnaturally just like
plants on steroids.
Organic lawn
care compared to contemporary intensive lawn care is much healthier for the
yard the environment and in many cases to one’s family. There are almost an
infinite number of fertilizer variations that can be used to supply the
nutrients recommended by your soil test.
The following information will help to fine tune fertilizer program or
make substitutions.
Alternatives
for 10:10:10 (N/P/K):
1 lb. of
10-10-10
Equals 5 lbs. of dried,
aged chicken manure
Equals 10 lbs. of
composted cow manure
Equals 30-40 lbs. of
fresh horse and cow manure
Equals
2 lbs. of
fishmeal
Nitrogen
alternatives
3 lbs. of
ammonium nitrate OR
2 lbs. of urea
OR
5 lbs. of
ammonium sulfate
Equals
8 lbs. of blood meal
Equals
13 lbs. of soybean extract
Potash
alternatives
1 lb. of,
muriate of potash
Equals
2 lbs. of potassium sulfate
Equals
7 lbs. of green compost
Phosphate
alternatives
1 lb. of super
treble phosphate
Equals
4 lbs. of steamed bone meal
Equals
2 lbs. of rock phosphate
Natural
organic materials are variable in nutrient content from different samples, therefore,
the quantities listed above are approximate.
References:
- (http://www.landscape-and-garden.com/Garden-Soil/fertilizer-types.aspx)
- (http://www.climateethics.org/fertilizerimpacts)
- (http://organicgardens.suite101.com)
- (http://www.greencapes.org/)
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