Agriculture Reference
In-Depth Information
Table 3.1
Macro- and Micronutrients, their Chemical Symbols, and Common Ionic
Forms in Soil
Macronutrient
(>1000 mg/kg)
a
Common ionic forms
in soil
Micronutrient(<1000
mg/kg)
a
Common ionic forms
in soil
Carbon (C)
HCO
3
−
, CO
3
2−
Iron (Fe)
Fe
3+
(sometimes Fe
2+
)
Hydrogen (H)
H
+
Manganese(Mn)
Mn
4+
(sometimes
Mn
2+
)
Oxygen (O)
H
2
O and many ions,
(e.g., OH
−
, NO
3
−
,
SO
4
2−
)
Zinc (Zn)
Zn
2+
Nitrogen (N)
NH
4
+
, NO
3
−
Copper (Cu)
Cu
2+
Phosphorus (P)
H
2
PO
4
−
, HPO
4
2−
Boron (B)
H
3
BO
3
, B(OH)
4
−
Sulfur (S)
SO
4
2−
Molybdenum(Mo)
MoO
4
2−
Calcium (Ca)
Ca
2+
Magnesium(Mg)
Mg
2+
Potassium (K)
K
+
Chlorine (Cl)
Cl
−
a
See box 3.1 for units of measurement.
Box 3.1 Units for Nutrient Concentrations and Amounts
Concentration (symbol
C
)
a
is the amount of a substance per unit volume or unit
weightofsoil,plantmaterial,orliquid.Forexample,theconcentration
C
of the
element nitrogen (N) can be expressed as micrograms (μg) of N per gram of soil
b
,
noting that
1
g N/g
µ
=
1
mg N/kg
=
1
part per million (ppm N)
(B3.1.1)
An amount is the product of concentration and weight. For example, the
total amount of N of concentration
C
(measured in μg/g) in a soil sample of 100
g is
µ
(B3.1.2)
100
C
g or
01
.
C
mg
Because all soil and plant materials contain some water, analyses are best
expressed in terms of oven-dry (o.d.) weights. The o.d. weight of a soil sample is
obtained by drying it to a constant weight at 105ºC; for plant material the drying
temperature is 70ºC.
The amount of a nutrient is often expressed per hectare (ha) of vineyard. In
this case, we need to calculate the weight of soil in 1 ha to a chosen depth, usually
0.15 m (15 cm). Unless it is measured directly, assume the bulk density for the top
0.15msoiltobe1.33megagram(Mg)perm
3
, so that the weight of dry soil per
hais1995Mgorapproximately2000Mg(2,000,000kg).hustheconversion
(continued)
