Fertigation Man'iniuut for the
Wholesale Container Nursery
Thomas H. Yeager
Florida Cooperative Extension Service Institure of Food and Agricultural Sciences
University of Florida / John T. Woeste, Dean
Mention of a tradename or a proprietary product does not constitute a guarantee or warranty of the product
by the University of Florida and does not imply its approval to the exclusion of other products that also may be
Fertigation Management for the Wholesale Container Nursery
Thomas H. Yeager
Table of Contents
Introduction .................................................................. ..........
Fertigation Management: Concentration Basis
Collection of M edia Sam ples ........... .....................................................
Media Test Results and Interpretation .....................................................
Injection Calculations ......................................................................
Irrigation Water Monitoring .................................................................
Fertigation Management: Area Basis ....................... ...................................
Properties of Fertilizers ......................................................................
Fall Fertilization ............ .............................................................
M marketing ............. ..................................................................
Glossary of Fertilizer Terms ................ ....................... .............................
References .............. ....................................................................
Thomas H. Yeager is an Extension Ornamental Horticulturist, Ornamental Horticulture Department,
Institute of Food and Agricultural Sciences, University of Florida.
Fertilizers applied in irrigation water (fertigation)
may be purchased dry, as suspensions, or as solu-
tions. Suspension fertilizers contain undissolved
constituents, whereas the constituents of solution
fertilizers are completely dissolved. Dry or suspen-
sion fertilizers are mixed with enough irrigation wa-
ter prior to application that the fertilizer material
dissolves completely and forms a solution (no undis-
Fertilizers purchased as solutions, not suspen-
sions, are presently used mostly in agronomic crop
production, yet interest in the use of these fertilizers
for woody ornamental production has increased re-
cently. This interest is probably related to the
smaller labor requirement necessary for the applica-
tion of fertilizer solutions compared with that needed
for dissolving dry fertilizers or fertilizing individual
containers with dry fertilizer materials. Many nur-
sery operations with more than 12 to 15 acres (5 to 6
ha) are currently purchasing fertilizers as solutions.
However, these fertilizers can be used just as effi-
ciently and economically with drip irrigation sys-
tems on smaller acreages. The practice will probably
become more widely used because fertilizers pur-
chased as solutions are generally less expensive per
pound of nutrient than nursery fertilizers purchased
dry. At present, solution fertilizers are not used ex-
tensively in the ornamental industry because special
equipment is needed to inject the fertilizer into the
irrigation water and because more intense manage-
ment is required for fertigation systems.
This publication will provide basic guidelines for
management of fertigation systems for producing
container-grown woody ornamentals. You may refer
to computer software available through the Coopera-
tive Extension Service for cost comparisons of solu-
tion fertilization systems as well as cost comparisons
of solution and dry fertilization systems.
Solution fertilizers may be purchased containing
various ratios of nitrogen, phosphorus pentoxide and
potassium oxide (N-P205-K20), although a 3-1-2 or
4-1-2 (Dickey et al., 1978) ratio is recommended.
Urea is often the ammoniacal nitrogen carrier
although ammonium nitrate or ammonium thiosul-
fate is also used. Sulfur is supplied by ammonium
thiosulfate while nitrate nitrogen is supplied by
ammonium nitrate and potassium nitrate. Potas-
sium nitrate and potassium chloride (muriate of
potash) are the primary potassium carriers. Potas-
sium sulfate is also used as a potassium carrier if
additional sulfur is needed. Ammonium polyphos-
phate is used to supply ammoniacal nitrogen and
phosphorus, while phosphoric acid is used to supply
Nursery operators could purchase concentrated
suspension fertilizers or the common fertilizer car-
riers such as ammonium nitrate, potassium chloride
and magnesium sulfate as dry formulations and dis-
solve either with water prior to injection. How-
ever, dissolving fertilizer at the nursery is a time-
consuming laborious task and is not recommended
unless a specific plant nutrient problem exists, such
as severe magnesium deficiency. If the nursery oper-
ator could not purchase magnesium as a concen-
trated solution, magnesium sulfate or chelate could
be dissolved and then injected into the irrigation
water. A consideration when dissolving fertilizers is
the salt index or the relative degree to which a fertil-
izer compound will contribute to the growing
medium-soluble salts compared to an equal weight of
sodium nitrate (Table 1). For example, similar
amounts of monoammonium phosphate and calcium
nitrate are required to supply an equivalent amount
of nitrogen, yet calcium nitrate would contribute
more to the growing medium-soluble salts than
Fertilizers purchased as solutions may contain
magnesium, usually as magnesium sulfate or che-
late, while many formulations do not contain calcium
because calcium often forms insoluble compounds
with phosphorus. Calcium and magnesium are
usually provided to plants by adding dolomitic lime-
stone to the potting media. The irrigation water in
some areas of the state contains concentrations of
calcium and magnesium (30 40 ppm) adequate for
plant growth (Starr and Wright, 1984); thus, addi-
tional calcium and/or magnesium may not be re-
Solution fertilizers may be purchased that contain
macronutrients and/or micronutrients. If the micro-
nutrients needed for plant growth are supplied by
amending the potting media, then micronutrients
are not usually supplied by fertigation unless a cor-
rective nutrient application is needed. For example,
iron chelate may be applied to correct iron deficiency.
Sulfate and citrate and/or chelate forms of the micro-
nutrients manganese, iron, copper and zinc are used
in solution fertilizers and under most growing condi-
tions these forms are acceptable. Molybdenum and
boron are usually supplied as sodium molybdate and
sodium borate, although other carriers such as
molybdic acid and boric acid may be used.
Nitrogen (N), phosphorus (P) and potassium (K)
are the most common plant nutrients applied with
fertigation systems when producing woody ornamen-
tals. Other essential plant nutrients are usually sup-
plied as preplant container medium amendments.
Consequently, the following discussion will deal with
the management of a fertigation system that is used
to supply N, P and/or K to container-grown woody
One approach to management of fertigation is to
maintain the desired concentration of nutrients in
the growing medium solution. For example, a nur-
sery operator may want to maintain 60 to 90 parts
per million (ppm) N, 10 to 15 ppm P and 25 to 40 ppm
K (Wright, 1983b) in the container medium as deter-
mined by a saturated paste extraction method. Using
a 15-5-10 that contains 1.5, 0.2 and 0.8 pounds (681,
91 and 363 g) of N, P and K, respectively, per gallon
(3.8 liters) of fertilizer or 179,739 ppm N, 25,763 ppm
P and 99,456 ppm K; 1 gallon of concentrated fertil-
izer should be diluted with 2499 gallons (9460 liters)
of water so 72, 10 and 40 ppm N, P and K, respec-
tively, would be applied. Regardless if 1 inch (2.5 cm)
or one-half inch of irrigation water were applied per
application, the approximate concentration of N, P
and K that is to be maintained in the media solution
should be applied at each watering. However, this
does not ensure that these levels will be maintained,
and media nutritional levels must be monitored.
Collection of Media Samples
Diagram the nursery growing beds and divide the
nursery into blocks or groups of beds according to
those plants that are treated similarly and grown
under similar conditions. For example, plants of the
same genera or species growing in the same media
and irrigated similarly may comprise one block,
while plants of the same species and receiving less
irrigation water or growing in a different medium or
container size would comprise another block. The
idea is to separate blocks of plants that would result
in different media test results.
The number of growing beds per block will vary but
for discussion assume 6 beds for each of 4 blocks
(Figure 1). One of the beds of plants in a block, for
example bed 1, should be sampled each sampling
time. This is a check or reference bed so that future
test results from plants of bed 1 can be compared with
previous test results of bed 1 to detect errors in sam-
pling or the extraction procedure. One core of media
is removed with a soil probe (see front cover) from
Table 1. Salt indices and solubilities of common fertilizer compounds*
Fertilizer compound Chemical formula Salt index (oz/gal) (g/100 ml)
Ammonium chloride NH4CI 26% N 66% Cl 52 39
Ammonium nitrate NH4NO3 34% N 105 157 118
Ammonium sulfate (NH4)2SO4 21% N 24% S 69 93 70
Borax Na2B407 10H20 11% B 4 3
Calcium carbonate CaCO3 40% Ca 5 0.003 0.002
Calcium nitrate Ca(N03)2 4H20 12% N 17% Ca 53 178 134
Calcium sulfate CaSO4 2H20 23% Ca 19% S 8 0.3 0.2
Copper sulfate CuS04 26% Cu 13% S 42 32
Diammonium phosphate (NH4)2HPO4 21% N 23% P 34 33 25
Iron sulfate FeSO4 20% Fe 12% S 20 15
Magnesium nitrate Mg(N03)2 6H20 10% Mg 11% N 56 42
Magnesium sulfate MgS04 7H20 10% Mg 13% S 44 113 85
Manganese sulfate MnS04 4H20 25% Mn 14% S 140 105
Monoammonium phosphate NH4H2PO4 12% N 27% P 30 57 43
Potassium chloride KCI 52% K 47% Cl 114 37 28
Potassium diphosphate K2HPO4 45% K 18% P 222 167
Potassium monophosphate KH2PO4 29% K 23% P 8 44 33
Potassium nitrate KNO3 14% N 39% K 74 17 13
Potassium sulfate K2SO4 45% K 18% S 46 10 8
Sodium molybdate Na2MoO4 2H20 40% Mo 74 56
Sodium nitrate NaNO3 17% N 100 97 73
Urea CO(NH2)2 47% N 75 89 67
Zinc sulfate ZnSO4 6H20 24% Zn 12% S 93 70
*Solubility varies with temperature and ionic composition of water. Data taken from Berg (1980), Bunt (1976) and Hanan et al.
1 2 3 1 2 3
I I I I I I
I I I I I I
I I I I I I
4 5 6 4 5 6
I I I I I I
I I I I I I
I I I I I I
I I I I I I
Fig. 1. Four blocks of container plants in which each
block contains 6 beds or groups of plants.
each of 5 to 20 containers of bed 1 in order to obtain a
1-pint (473 cm3) sample of media. At each sampling
time, also remove media from 5 to 20 containers from
each of 2 or 3 other growing beds in the block and at
the next sampling time, sample the check bed and 2
or 3 beds not sampled last time.
Media Test Results and Interpretation
Once media samples are obtained, the saturated
paste or 2:1 dilution procedure may be used to obtain
the liquid extract needed for analysis (see Commer-
cial Circular 556 for extraction details). If the reason
for sampling was to obtain growing medium-soluble
salts levels, then it is recommended that the extrac-
tion procedure be performed at the nursery since
extract-soluble salts can be determined rapidly, in-
dicating the relative fertility status of the container
medium needed for quick management decisions.
Optimum growing medium-soluble salts levels for
most plants excluding azaleas and salt-sensitive
plants range from 1000 to 1200 ppm for the saturated
paste extraction and 600 to 700 ppm for the 2:1 dilu-
tion procedure (Smith, 1983). Optimum soluble salts
for azaleas and salt-sensitive plants are about 400 to
600 ppm for the saturated paste and 250 to 350 for the
2:1 dilution (Smith, 1983).
A soluble salts level below optimum indicates that
the concentration of fertilizer in the irrigation water
should be increased. The magnitude of increase and
number of irrigations with water of increased nutri-
ent concentrations needed to increase soluble salts
levels of the growing medium to optimum levels
varies; therefore, soluble salts should be monitored
at least weekly during the growing season.
Many N fertilizers contain urea and are hydro-
lyzed to ammonium carbonate by the enzyme urease.
Urea does not increase soluble salts (conductivity)
until hydrolyzed, so soluble salts levels of media fer-
tilized with urea could be less than that of media
fertilized with the same N concentration from ammo-
nium nitrate. Urease is commonly found in the en-
vironment and hydrolysis of urea occurs naturally.
Recent research (Wright, 1983a) indicated that
about 70% of urea is hydrolyzed in 24 hours in a pine
bark growing medium.
Soluble salts levels represent the electrical con-
ductance of ions in solution and do not indicate a
deficiency or excess of a nutrient or ion in the growing
medium. Thus, N, P and K of the growing medium
should be monitored at least monthly to ensure that
desired levels are maintained. Sample the container
medium as described previously and send media
samples to the University of Florida Extension Soil
Testing Laboratory or a private laboratory for analy-
ses and interpretations. Detailed nutritional records
should be maintained so future nutritional manage-
ment decisions can be based on past experience.
A low growing medium concentration of N, P and/
or K may be corrected by a supplemental applica-
tion(s) of the deficient elementss. For example, a low
growing medium N level may be corrected by a cou-
ple of irrigations in which only N is injected into
irrigation water. The medium should be sampled
again in 1 to 2 days to ensure the desired N level.
The nursery operator may wish to apply a correc-
tive applications) of 150 ppm N by dissolving ammo-
nium nitrate (34% N) in irrigation water. Based on
the fact that 1 ounce (28 g) of any pure dry substance
dissolved to a volume of 100 gallons (379 liters)
equals 75 ppm, the following formula can be used to
calculate the ounces of dry fertilizer material to dis-
solve with water to a volume of 100 gallons to achieve
the desired ppm.
ppm desired 100 (constant)
75 (constant) % N in fertilizer
= ounces of fertilizer to dissolve to 100 gallons*
*No liability is assumed by the author or the University of Florida
for the use of formulas in this publication.
Substituting in the desired values:
150 x100 = 5.9 ounces
which indicates that 5.9 ounces (165 g) of ammonium
nitrate would be dissolved with water to a volume of
100 gallons to obtain a 150-ppm N solution. The same
formula could be used for P and K but we must re-
member the percentages of P and K given on the bag
are as oxides, P205 and K20, respectively. Therefore,
when using the P205 and K20 percentages on the bag
and substituting in the above formulas, the ounces
obtained for P205 should be multiplied by 2.3 and the
ounces obtained for K20 multiplied by 1.2.
For example, if potassium diphosphate (54% K20)
is the potassium carrier the following substitutions
are made in the formula.
x 1-- = 3.7 x 1.2 = 4.4 ounces
Thus, 4.4 ounces (126 g) of potassium diphosphate
dissolved to the 100-gallon volume results in a 150-
ppm K solution.
If the nursery operator is to inject the K solution
into the irrigation water with an injector that has a
1:500 dilution ratio, 499 gallons (1886 liters) of
irrigation water are mixed with each gallon of fertil-
izer solution. Therefore, 500 times 4.4 ounces or 138
pounds (62 kg) of potassium diphosphate are dis-
solved with irrigation water to a volume of 100 gal-
4.4 ounces x 500 dilution ratio = 2200 ounces
2200 ounces 16 ounces/pound = 138 pounds
This 100 gallons of concentrated solution will be
mixed during injection with 49,900 gallons (188,622
liters) of irrigation water for a total volume of 50,000
gallons (189,000 liters) of irrigation water with 150
ppm K. If the nursery operator was irrigating an acre
with 0.5 inch (1.27 cm) or 13,500 gallons (51,030
liters), then 3.7 acres (1.5 ha) could be irrigated with
the 50,000 gallons of irrigation water or 100 gallons
of concentrated K solution.
50,000 gallons of irrigation water
= 3.7 acres
The nursery operator may not want to spend the
extra time involved in dissolving dry fertilizers and
may choose to purchase solution fertilizer. For exam-
ple, a 34% N solution could be purchased and injected
instead of dissolving and injecting ammonium ni-
trate. The concentration of N in the solution fertilizer
should be obtained from the manufacturer or calcu-
lated from the weight of 1 gallon of fertilizer. Assume
the fertilizer weighs 10 pounds (4.5 kg) per gallon.
Thus, each gallon contains 3.4 pounds or 1,542,214
mg of N. Divide this by 3.8 since 1 gallon is approx-
imately 3.8 liters which converts to 405,846 mg of N
per liter of fertilizer or 405,846 ppm N.
10 pounds/gallon x -- = 3.4 pounds N/gallon
3.4 pounds N/gallon x 453,592.4 mg/pound
= 1,542,214 mg N/gallon
1,542,214 mg N/gallon = 405,846 mg N/liter
= 405,846 ppm N
If the nursery operator injects this fertilizer and is
using a 1:500 injector, the irrigation water would
contain 812 ppm N which is about 5.4 times the 150
ppm N desired.
405,846 ppm N
= 812 ppm N
500 dilution ratio
812 ppm N
150 ppm N desired
Thus, each gallon of concentrated fertilizer must be
diluted 5.4 times before injection. An alternative is to
use an injection system that will dilute the concen-
trated fertilizer 2706 times, which also results in
irrigation water with 150 ppm N.
405,846 ppm N
150 ppm N desired
= 2706 dilution ratio
Refer to Circulars 693 and 694 for computational
assistance when dissolving fertilizers for injection.
Irrigation Water Monitoring
The elemental content of the irrigation water be-
fore and during injection should be determined
monthly or as changes are made in the concentration
of fertilizer applied. Checking the nutrient concen-
tration of the irrigation water during injection en-
sures that proper elemental concentrations are being
disseminated. The irrigation water may inherently
contain fertilizer elements, especially if runoff water
is used. Thus, the injected concentration of an ele-
ment should be reduced to compensate for the indige-
nous concentration of the element in the irrigation
A correlation between the elemental content of the
irrigation water and soluble salts of the irrigation
water can be established so that future soluble salts
levels of the irrigation water containing injected
plant nutrients. could serve as an indication that
appropriate concentrations of elements are dissemi-
nated. However, this is only a guideline since the
soluble salts value represents the total conductivity
of the water and excludes nonhydrolyzed urea.
Another approach to fertigation is to use the water
as a means of distributing a certain amount of fertil-
izer on a given area rather than approaching fertil-
ization from the standpoint of maintaining desired
nutritional levels in the growing medium. The water
is a carrier of the fertilizer or is a means of broadcast-
ing the fertilizer. Consequently, the total amount of
water per unit of fertilizer applied is of little impor-
tance, other than that ample water is used to effec-
tively disseminate the fertilizer. The following dis-
cussion considers this approach for a fertilizer pur-
chased as a solution.
Solution fertilizers are purchased by the ton (907
kg) and for many solution fertilizers this is approx-
imately 200 gallons (760 liters) of concentrated fertil-
izer. Thus, 1 ton of 15-5-10 solution fertilizer would
contain 300 pounds (136 kg) of N, 43 pounds (19.5 kg)
of P and 166 pounds (75 kg) of K.
2000 pounds/ton x = 300 pounds N/ton
2000 pounds/ton x --2 = 100 pounds P205/ton
100 pounds P2zO/ton x 43 pounds P/100 pounds P205
= 43 pounds P/ton
2000 pounds/ton x K20 = 200 pounds K20/ton
200 pounds K20/ton x 83 pounds K/100 pounds K20
= 166 pounds K/ton
If a nursery operator is to apply 1500 pounds of N
(680.4 kg) per acre per year, then 5 tons (4536 kg) or
1000 gallons (3800 liters) of solution fertilizer (15-5-
10) should be applied per acre per year. The nursery
operator must manage the fertilizer applications and
may decide to apply fertilizer 3 times a week during
the 10 warmest months of the year. Based on 4 weeks
per month (120 applications), the nursery operator
would apply about 8.3 gallons (32 liters) of fertilizer
or 12.5 pounds (5.7 kg) of N per acre per application.
1000 galln = 8.3 gallons/application
8.3 gallons/application x 1.5 pounds N/gallon
= 12.5 pounds N/application
The 12.5 pounds of N would be injected into the
irrigation water at a rate necessary to facilitate N
dissemination during irrigation. Consequently, the
concentration of N disseminated by the irrigation
water varies with the gallons of water applied. If
one-half inch of water or 13,500 gallons are applied to
irrigate 1 acre, the water would contain 110 ppm N
and if 1 inch of water were used to disseminate 12.5
pounds of N, then 55 ppm N would be applied.
The previous example involved disseminating fer-
tilizer by irrigation water on an acre basis. However,
when using irrigation systems in which the water is
delivered to individual containers, the fertilizer ap-
plications are based on container surface area. For
example, the surface area of a 20-gallon container is
approximately 1.8 square feet (0.16 m2) which is a
fraction of the 43,560 square feet (4047 m2) in an
acre. Thus when applying 1500 pounds of N per acre
per year, each 20-gallon container receives 0.06
pound (27 g) of N per year. Assuming 120 applica-
tions per year, 0.0005 pound (0.23 g) of N would be
applied to each container per application.
1.8 square feet/container
x- 1500 pounds N/acre/year
43,560 square feet/acre
= 0.06 pound N/container/year
0.06 pound N/container/year
= 0.0005 pound N/container/application
The nursery operator must manage application of
the 15-5-10 solution fertilizer so that 0.0005 pound of
N is applied per application to each container. This is
easily facilitated by injecting the concentrated fertil-
izer into the irrigation water so that 1 gallon of con-
centrated fertilizer (1.5 pounds or 680 g of N) is di-
luted with 2999 gallons (11,396 liters) of irrigation
1.5 pounds N
3000 gallons (fertilizer + water)
= 0.0005 pound N/gallon of irrigation water
Note: 1 gallon of water on the surface of an 18-inch-
diameter container is approximately 1 inch of water.
If 1 gallon or 1 inch of irrigation water is applied
per container, this results in 0.0005 pound of N ap-
plied to each container. Even though the concentra-
tion of fertilizer applied to the container plant is not a
major consideration when fertilizer is applied on an
area basis, soluble salts and nutritional levels of the
media and irrigation water should be monitored, as
discussed previously, to prevent toxicities and to
maintain the proper balance of nutrients. Regardless
of the approach taken when disseminating fertilizer
in the irrigation water, it is Florida law that injection
systems contain antisyphon devices to protect the
water supply from contamination. Information on
antisyphon devices and backflow regulations can be
obtained from the County Extension Office.
Properties of Fertilizers
The physical and chemical properties of fertilizers
vary depending upon their composition. For exam-
ple, fertilizers purchased dry have varying solubili-
ties depending upon elemental carriers (Table 1).
The quantity of fertilizer that will dissolve in irriga-
tion water also varies due to natural concentrations
of nutrients in irrigation water. Some fertilizers have
an extremely low pH and should not be broadcast on
plant foliage but may be ideal where irrigation water
contains excessive carbonates. The nursery operator
should be aware of the length of time fertilizers can
be stored and the effects of cold weather. Many solu-
tion fertilizers will salt out or precipitants will form
at low temperatures, thus altering nutrient concen-
trations. For example, a urea-ammonium nitrate
solution (35% N) will salt out at about 590F (15C)
(Tennessee Valley Authority, 1979b). Check with
manufacturers or distributors about these and other
properties that may influence the desirability offer-
tilizers for use in your nursery.
Fertilizing woody ornamentals in the fall is impor-
tant in northern and central Florida so the plant can
accumulate nutrients for spring growth. The objec-
tive of the fall fertilization program is for the plant to
accumulate nutrients to the point where elonga-
tion would occur if it were not for the onset of cold
weather. This is easily accomplished with fertigation
systems by reducing the concentration of applied fer-
tilizer in the fall and, consequently, the rate of nu-
trient accumulation slows. Thus, the plant does not
exhibit a shoot flush in late fall that would be dam-
aged by cold, yet accumulates nutrients used for the
spring growth flush.
Solution fertilizers may be applied during the win-
ter if additional elemental accumulation is needed
for maximum spring growth. However, in areas
where drainage is inadequate, granular slow release
fertilizer should be considered to prevent applying
Plants removed from fertigation will usually ex-
hibit one or two shoot flushes. Thus, plants that will
not be fertilized again for several months after being
sold should be fertilized with a slow release fertilizer
prior to shipping. The slow release fertilizer will re-
sult in the maintenance of foliage color and plant
quality until plants are established in the landscape.
Glossary of Fertilizer Terms
Ammoniacal nitrogen: chemical complex of nitrogen
and hydrogen. May exist as NH3 or ammonium
Analysis (see also Grade): the percentage composi-
tion of a fertilizer as found by chemical analysis.
Methods of analysis are specified by laws and rules
of individual states. Although analysis and grade
are sometimes used synonymously, the term grade
applies only to the guaranteed minimum quanti-
ties of N, P205 and K20.
Carrier: chemical compound containing a desired
Chelate: fertilizer element in unique chemical com-
bination with organic constituents such that plant
availability is often increased.
Citrate: chemical reaction product of citric acid.
Clear liquid: a fertilizer composed of materials that
are totally dissolved. A true solution.
Enzyme: proteins or molecular constituents re-
sponsible for many biological reactions.
Essential nutrient: a nutrient required for plant
growth and development.
Fertigation: application or dissemination of fertilizer
through the irrigation water.
Fertilizer: "any material, organic or inorganic, natu-
ral or synthetic, that furnishes to plants one or
more of the chemical elements necessary for nor-
mal growth" (Tennessee Valley Authority, 1979a).
Fluid fertilizer: "a general term including fertilizers
wholly or partially in solution that can be handled
as a liquid. This includes clear liquids, liquids con-
taining solids in suspension, and (usually) anhy-
drous ammonia" (Tennessee Valley Authority,
Formula: a statement of how various ingredients are
combined to make a fertilizer. A recipe.
Grade (see also Analysis): "the grade of a fertilizer is
the nutrient content expressed in weight percent-
ages of N, P205 and K20 in that order. For exam-
ple, a grade of 10-15-18 indicates a fertilizer con-
taining 10% N, 15% P205 and 18% K20 as found by
prescribed.analytical procedures" (Tennessee Val-
ley Authority, 1979a).
Hydrolysis: reaction with water.
Macronutrients: essential plant nutrients used in
large quantities by plants. Nitrogen, phosphorus,
potassium, calcium, magnesium, and sulfur are
Micronutrient: the essential plant nutrients iron,
manganese, molybdenum, chlorine, boron, copper
and zinc required by plants in small quantities.
Nitrate nitrogen: chemical complex of nitrogen with
Nutrient: "any of the elements classified as essential
to plant growth including N, P, and K (primary or
major nutrients); Ca, Mg, and S (secondary nutri-
ents); and Fe, Cu, Zn, Mn, B, Mo, and Cl (micro-
nutrients)" (Tennessee Valley Authori ', 1979a).
Parts per million: a means of expressing concentrra
tions of nutrients. For example, 9 art- :.:r million
of nitrogen in water means 9 pounds of nitrogen
per million pounds of water.
Salt index: relative degree to which a fertilizer com-
pound will contribute to the soluble salts, com-
pared to an equal weight of sodium nitrate. Useful
only in comparing one fertilizer to another.
Salt out: to precipitate; not to remain dissolved; to
crystallize from solution.
Soluble salts: an estimation of the total dissolved
minerals in a solution. Determined by measuring
the electrical conductivity of a solution with a spe-
cial meter and multiplying by an empirically de-
termined factor. Some ions conduct much better
Solution fertilizer: "aqueous liquid fertilizer free
from solids" (Tennessee Valley Authority, 1979a).
Stock solution: the solution from which other solu-
tions are made; parent solution.
Sulfate: chemical complex of sulfur with oxygen
Suspension fertilizer: "a liquid (fluid) fertilizer con-
taining solids held in suspension, for example, by
the addition of a small amount of clay. The solids
may be water-soluble materials in a saturated
solution, or they may be insoluble or both" (Ten-
nessee Valley Authority, 1979a).
True liquid: a liquid fertilizer in which the constit-
uents are totally dissolved; a solution.
Unit: a unit of plant nutrient is 20 pounds or 1% of a
ton. For example, a ton of 15-8-17 would contain 15
units of nitrogen, or 300 pounds of nitrogen.
MARSTON SCIENCE LIBRARY
Urease: enzyme responsible for the breakdown of
Berg, G. L. (ed). 1980. Farm Chemicals Handbook.
Meister Publishing Co., Willoughby, OH.
Bunt, A. C. 1976. Modern Potting Compost. The
Pennsylvania State University Press, University
Dickey, R. D., E. W. McElwee, C. A. Conover, and
J. N. Joiner. 1978. Container Growing of Woody
Ornamental Nursery Plants in Florida. University
of Florida Extension Bulletin 793, Gainesville, FL.
Hanan, J. J., W. D. Holley, and K. L. Goldsberry.
1978. Greenhouse Management. Springer-Verlag,
Smith, G. 1983. An easy method of determining when
to fertilize container plants. Georgia Nursery
Notes, July-August, University of Georgia,
Starr, K. D. and R. D. Wright. 1984. Calcium and
magnesium requirements of Ilex crenata 'Helleri'.
J. Am. Soc. Hort. Sci. 109:857-860.
Tennessee Valley Authority. 1979a. General con-
cepts and definitions. In: Fertilizer Manual, IFDC-
R-l, pp. 32-35. International Fertilizer Develop-
ment Center, Muscle Shoals, AL.
Tennessee Valley Authority. 1979b. Production,
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This publication was produced at a cost of $1237.60, or 28 cents per copy, to inform nursery owners
about economical and efficient fertigation management practices. 7-4.5M-86
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