homework #3
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PLSC 210 Horticulture Science
Name____________________________
Fall Semester, 2010
Homework #3
(Total 25 points, due November 12, show calculations for full credit)
1.
You have a 50 lb bag of 20-20-20 commercial analysis (general purpose) fertilizer.
a.
Indicate the amounts of each fertilizer (in oxide form) contained in the 50 lb bag. (
2 points
)
Answer: N = _______ lb,
P
2
O
5
= _______ lb,
K
2
O =_______ lb
Calculations
:
b.
What is the elemental analysis of this fertilizer?
(
2 points
)
Answer:
Elemental analysis ______ - _______ - _______
N - P - K.
Calculations
:
c.
How many lb of each fertilizer element (elemental analysis) is contained in the 50 lb bag? (
2 points
)
Answer:
N =_______ lb,
P =_______ lb,
K =_______ lb
Calculations
:
2.
You would like to fertilize your potted plants with a nutrient solution containing 200 ppm nitrogen (N),100
ppm phosphorus (P
2
O
5
) and 250 ppm potassium (K
2
O) using a 100-gallon stock tank which is installed
with a 1:200 proportion injector. Your fertilizers are ammonium nitrate (NH
4
NO
3
), potassium mono-
phosphate (KH
2
PO
4
) and potassium chloride (KCl).
Commercial analysis (N-P
2
O
5
-K
2
O):
NH
4
NO
3
(33.5-0-0), KH
2
PO
4
(0-53-34), KCl (0-0-62) (see Table 1)
Conversion factors:
P/ P
2
O
5
= 0.44, K/K
2
O = 0.83
a.
How many lb of each fertilizer should you use for the 100-gallon stock tank?
(
3 points
)
Answer: NH
4
NO
3
=________ lb,
KH
2
PO
4
=_________ lb,
KCl=_________ lb
Calculations
:
b.
What are the concentrations of elemental nitrogen (N), phosphorus (P) and potassium (K) of your stock
solution and the final fertilizer solution being applied?
(
3 points
)
Answer:
1) Final fertilizer solution:
N =__________ ppm, P =___________ ppm, K =___________ ppm
2) Stock solution:
N =__________ ppm, P =___________ ppm, K= ___________ ppm
Calculations
:
c.
You have 5,000 pots of chrysanthemums in your greenhouse and each pot requires 0.5 gallon of
fertilizer solution per day.
How many days would the stock tank (100 gallon) last after it has been
filled once with your fertilizer stock?
(
2 points
)
Answer:
1) Total volume of final solution:_____________ gallon
2) Total number of days:
_____________ days
Calculations
:
d.
Using Table 1, calculate the cost of fertilizer needed to fill your stock tank and feed your crop. (
3
points
)
Answer:
1) Cost of fertilizers
$_____________/100-gallon stock tank
2) Cost of fertilizers
$_____________/5,000 pots per month
3) Cost of fertilizers
$_____________/pot per month
Calculations
:
Costs of chemical fertilizers:
Commercial
Cost per
Fertilizer
Formula
analysis
50- lb bag
Ammonium nitrate
NH
4
NO
3
33.5-0-0
$20.50
Potassium mono-phosphate
KH
2
PO
4
0-53-34
$22.30
Potassium chloride
KCl
0-0-62
$15.50
3.
You would like to prepare 100 liter of 200 ppm nitrogen (N) using magnesium nitrate [Mg(NO
3
)
2
6H
2
O].
How many grams of this fertilizer should be used in 100 liter?
(
4 points
)
Answer:
Magnesium nitrate needed:
_________________ g/100 liter.
This solution will contain:
_________________ ppm Mg.
Calculations
:
4.
How many ounce (oz) of a 20-20-20 commercial fertilizer or potassium nitrate (KNO
3
) should be
dissolved in 100 gallon of water to make a 200 ppm nitrogen (N) solution? (
4 points
)
(Note: 1 oz/100 gallon = 75 ppm)
Answer:
20-20-20 fertilizer:
________________ oz/100 gallon.
KNO
3
:
________________ oz/100 gallon.
Calculations
:
Note
1 gallon=3.8 liter, 1 kg=2.2 lb, 1 oz=29 g
1 kg=1,000 g=1,000,000 mg
Atomic weights:
N=14.01, P=30.98, K=39.1, Mg=24.32, S=32.07, Ca=40.08
H=1.01, C=12.01, O=16.0
Molecular weights:
KNO
3
=101.11
Mg(NO
3
)
2
6H
2
O=256.4
Commercial analysis:
Mg(NO
3
)
2
6H
2
O=11-0-0
KNO
3
=13-0-44
2
Table 1. Common fertilizers supplying macronutrients required by plants.
____________________________________________________________________________________________________________
Effect
Molec.
Equiv.
on
Solubility
c
Other
Compound
Formula
a
Analysis
b
weight
weight
acidity
g/100 ml
lbs/100 gal
materials
____________________________________________________________________________________________________________
Ammonium chloride
NH
4
Cl
25-0-0
53.5
53.5
acid
39.7
248
---
Amdmonium nitrate
NH
4
NO
3
33.5-0-0
80.05
80.05
acid
118.3
991
---
Monoammonium
NH
4
H
2
PO
4
11-48-0
115.04
115.04
acid
22.7
190
1.4% Ca
phosphate
2.6% S
Diammonium phosphate
(NH
4
)
2
HPO
4
21-53-0
132.07
66.0
acid
42.9
359
---
Ammonium sulfate
(NH
4
)
2
SO
4
20-0-0
132.15
66.1
very acid
70.6
591
24% S
Aluminum sulfate
Al
2
(SO
4
)
3
.
18H
2
O
0-0-0
666.45
222.15
very acid
soluble
soluble
14% S
Calcium sulfate
CaSO
4
.
2H
2
O
0-0-0
172.18
86.09
neutral
0.2
1.7
23% Ca. 19% S
(gypsum)
Calcium nitrate
Ca(NO
3
)
2
.
4H
2
O
15-0-0
236.16
118.1
basic
102.0
854
17% Ca
Sodium nitrate
NaNO
3
16-0-0
85.01
85.01
basic
73.0
611
27% Na
Urea
CO(NH
2
)
2
45-0-0
60.06
30.03
acid
78.0
653
---
Superphosphate
CaH
4
(PO
4
)
2
0-20-0
---
---
neutral
1.8
15
18% Ca, 12% S
Treble superphosphate
CaH
4
(PO
4
)
2
0-46-0
---
---
neutral
1.8
15
12% Ca
Phosphoric acid
H
3
PO
4
0-52-0
98.0
98.0
very acid
548
4,600
---
Potassium chloride
(muriate of potash)
KCl
0-0-62
74.55
74.55
neutral
34.7
291
---
Potassium nitrate
(saltpeter)
KNO
3
13-0-44
101.1
101.1
basic
13.3
111
---
Potassium sulfate
K
2
SO
4
0-0-53
174.26
87.13
neutral
6.9
58
18% S
Magnesium sulfate
MgSO
4
.
7H
2
O
0-0-0
246.5
123.25
neutral
71
595
10% Mg, 13% S
(epsom salts)
Magnesium nitrate
Mg(NO
3
)
2
.
6H
2
O
11-0-0
256.4
128.2
neutral
42.3
354
10% Mg
Calcium carbonate
(limestone)
CaCO
3
0-0-0
100.1
50.1
basic
0.002
0.01
40% Ca
Calcium hydroxide
(hydrated lime)
Ca(OH)
2
0-0-0
74.1
37.1
basic
0.19
1.6
60-80% Ca
Potassium mono-
phosphate
KH
2
PO
4
0-53-34
120.1
120.1
basic
33
276
---
Potassium diphosphate
K
2
HPO
4
0-41-54
174.2
87.1
basic
167
1,400
---
Calcium cyanamide
CaCN
2
20-0-0
80.11
---
basic
decomposes
---
Sulfur
S
0-0-0
32.1
---
acid
insoluble
---
Dolomite
MgCO
3
.
CaCO
3
0-0-0
---
---
basic
---
---
22% Ca, 13% Mg
(dolomitic limestone)
Basic slag
CaO
.
P
2
O
5
.
SiO
2
0-17-0
---
---
basic
---
---
33% Ca, 10% Fe
____________________________________________________________________________________________________________
a
Formula may differ due to addition of water molecules; or source of material as the case of limestone, superphosphates, etc.
b
Percentage N, P
2
O
5
, and K
2
O will differ between sources, depending upon manufacturing process.
Molecular and equivalent weights
are for the formulas as given.
c
Solubility of materials in water, usually 0
o
C.
3
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Table 2.
Parts per million (ppm) and milliequivalents per liter (meq/
) supplied when one pound or kg of
material is dissolved in 1000 gal or 10 m
3
(
10,000
) of water.
Analysis
a
ppm
meq/
b
Compound
(N-P
2
O
5
-K
2
O)
lb/1000 gal
kg/10 m
3
lb/1000 gal
kg/10 m
3
NH
4
NO
3
33.5-0-0
40
N
34
1.5
NH
4
+
1.3
1.5
NO
3
-
1.3
NH
4
Cl
25-0-0
30
N
25
2.2
NH
4
+
1.9
79
Cl
66
2.2
Cl
-
1.9
(NH
4
)
2
SO
4
20-0-0
24
N
20
1.8
NH
4
+
1.5
29
S
24
1.8
SO
4
-
1.5
Ca(NO
3
)
2
4H
2
O
15-0-0
18
N
15
1.0
NO
3
-
0.8
44
Ca
37
1.0
Ca
2+
0.8
NaNO
3
16-0-0
19
N
16
1.4
NO
3
-
1.2
32
Na
27
1.4
Na
+
1.2
H
3
PO
4
0-80-0
c
80
P
64
1.2
H
2
PO
4
-
1.0
KNO
3
13-0-44
16
N
13
1.2
K
+
1.0
53
K
2
O
53
1.2
NO
3
-
1.0
KCl
0-0-62
74
K
2
O
62
1.6
K
+
1.3
57
Cl
48
1.6
Cl
-
1.3
(NH
4
)
2
HPO
4
21-53-0
25
N
21
1.8
NH
4
+
1.5
63
P
2
O
5
53
1.8
HPO
4
2-
1.5
K
2
SO
4
0-0-53
63
K
2
O
53
1.4
K
+
1.1
21
S
18
1.4
SO
4
2-
1.1
NH
4
H
2
PO
4
11-18-0
13
N
11
1.0
NH
4
+
0.9
57
P
2
O
5
48
1.0
H
2
PO
4
-
0.9
MgSO
4
-
24
Mg
20
2.0
Mg
2+
1.7
32
S
27
2.0
SO
4
2-
1.7
Mg(NO
3
)
2
6H
2
O
11-0-0
13
N
11
0.9
Mg
2+
0.8
11
Mg
10
0.9
NO
3
-
0.8
HNO
3
(pure)
18-0-0
21
N
18
1.9
NO
3
-
1.6
K
2
HPO
4
0-11-54
49
P
2
O
5
41
1.4
K
+
1.1
64
K
2
O
54
1.4
HPO
4
2-
1.1
KH
2
PO
4
0-53-34
61
P
2
O
5
53
1.0
K
+
0.8
41
K
2
O
34
1.0
H
2
PO
4
-
0.8
a
Analyses in percentage N, P
2
O
5
, and K
2
O.
b
Milliequivalents are calculated on the basis of equivalent weight.
c
Percentage of H
2
PO
4
in liquid.
4