Table 18.1
Composition of Various Common Amendments and Commercial Fertilizers (%)
N
P2O5
K2O
ca
Mg
S
cl
N Materials
Anhydrous ammonia
82
Aqua ammonia
20
Ammonium nitrate
34
Ammonium sulfate
21
24
Calcium nitrate
16
19
1
Urea
46
UAN solutions (urea + ammonium nitrate)
28–32
P and N+P Materials
Superphosphate (ordinary)
20
20
12
Triple superphosphate
46
14
1
Diammonium phosphate (DAP)
18
46
Monoammonium phosphate (MAP)
11–13
48–52
K Materials
Potassium chloride (muriate of potash)
60
47
Potassium–magnesium sulfate (“sul-po-mag”)
22
11
23
2
Potassium sulfate
50
1
18
2
Other Materials
Gypsum
23
18
Limestone, calcitic
25–40
0.5–3
Limestone, dolomitic
19–22
6–13
1
Magnesium sulfate
2
11
14
Potassium nitrate
13
44
Sulfur
30–99
Wood ashes
2
6
23
2
to meet nutrient needs in specific fields and provide
fertilizers account for 25% to 30% of the energy that
predictable effects. Their behavior in soils and the ready
goes into growing a corn crop. Also, the high nutrient
availability of the nutrients are well established. The
solubility can result in salt damage to seedlings when
timing, rate, and uniformity of nutrient application
excess fertilizer is applied close to seeds or plants.
are easy to control when using commercial fertilizers.
Because nutrients in commercial fertilizers are readily
However, there also are drawbacks to using commercial
available, under some circumstances more may leach to
fertilizers. All of the commonly used N materials (those
groundwater than when using organic nutrient sources
containing urea, ammonia, and ammonium) are acid
when both are used properly. For example, high rainfall
forming, and their use in humid regions, where native
events on a sandy soil soon after ammonium nitrate fer-
lime has been weathered out, requires more frequent
tilizer application will probably cause more nitrate loss
lime additions. The production of nitrogen fertilizers
than if compost had been applied. (On the other hand,
is also very energy intensive—it’s estimated that N
high rainfall events on a recently plowed-down alfalfa
208
Building SoilS for Better CropS: SuStainaBle Soil ManageMent