Environmental Engineering Reference
In-Depth Information
Urea (NH
2
)
2
CO
Carbon diox
ide
(CO
2
)
Nitric acid
(HNO
3
)
Sulphuric ac
id
(NH
3
)
Phosphoric
acid
(H
3
PO
4
)
Ammonium nitrate
NH
4
NO
3
Ammonium
sulphate (NH
4
)
2
SO
4
Ammonium
phosphates
NH
x
H
y
PO
4
Atmospheric
nitrogen (N
2
)
Methane
(CH
4
)
Ammonia
(NH
3
)
+
+
+
Fig. 5.4. Synthesis of nitrogen fertilizers.
they quickly dissolve. Ammonium ions (NH
4
) are held in the soil by the
negatively charged clay particles and by organic matter. They can be
taken up by the turf either immediately or at a later time. Dissolved
nitrate ions (NO
3
) become available immediately for uptake but are not
held in the soil. Any that are not taken up at once are subject to loss by
leaching.
Inorganic nitrogen carriers are the least expensive, but they are also
the most unsafe to apply. Application of these fertilizers in the powder
form can cause profound damage to the turf. They are all hygroscopic
(i.e. they absorb moisture from the air), and when they come in contact
with the leaves they burn them severely. Granular forms are safer be-
cause much less of the leaf area is in contact with the granules, so less
burning takes place. Light watering immediately after fertilizer applica-
tion is helpful and highly recommended.
Organic nitrogen carriers
Organic nitrogen carriers can be divided into two major categories:
natural and synthetic. In natural organic fertilizers, nitrogen originates
from plant or animal sources. Composts, sewage sludge and similar types
of products belong to this group. In synthetic organics, the nitrogen
originates from atmospheric air, and fertilizers are mass-produced in
the process of organic synthesis. Urea is the most important fertilizer in
this group.
Natural organic sources have gained increasing popularity, espe-
cially in the home-lawn industry. Much of the public worldwide con-
siders natural products better than synthetic ones and less damaging to
the natural environment. In general, natural fertilizers are excellent
sources of nitrogen, as well as other nutrients, needed by turf-grass plants
and assure their healthy growth. They usually contain less than 10%
of slow-release nitrogen and cause very little burning. Sewage-based
