Agriculture Reference
In-Depth Information
Table 3.9 Forms of Soluble Nitrogen Fertilizer Suitable for Vineyards
Nitrogen
content
(%)
Compound
Chemical formula
Comments
Potassium nitrate
KNO 3
13
KNO 3 and Ca(NO 3 ) 2 are very
soluble; suitable for fertigation but
more expensive per kilogram N
than other forms
Calcium nitrate
Ca(NO 3 ) 2
15.5
Ammonium sulfate
(NH 4 ) 2 SO 4
21
Supplies N and S in soluble forms;
oxidation of the NH 4 + ions
acidifies the soil
Ammonium nitrate
(Nitram)
NH 4 NO 3
34
NO 3 is immediately available; NH 4 +
is adsorbed in the soil and oxidized
to NO 3
Monoammonium
phosphate(MAP)
NH 4 H 2 PO 4
11
Water soluble; also supplies P;
acidifying
Diammonium
phosphate (DAP)
(NH 4 ) 2 HPO 4
18
As for monoammonium phosphate
Urea
(NH 2 ) 2 CO
46
Verysoluble,pronetovolatilizeifnot
washed into the soil; acidifying;
can be used as a foliar spray
Urea ammonium
nitrate solution
(NH 2 ) 2 CO,
NH 4 NO 3 in
water
30-32
Has the advantages and
disadvantages of urea and
NH 4 NO 3
fertilizer Horticulture Special has a composition of 10-3-10, meaning 10% N,
3% P, and 10% K. 4
Water-soluble N fertilizers are supplied as solids or liquids. Fertigation
involves applying water-soluble N fertilizers in solution, usually by drip irrigation.
herearealsoliquidorganicproducts,suchasseaweedandishextracts,which
have low N concentrations (1%-2% N) but are promoted primarily on the ben-
efits of their organic constituents. Because of the variety of compounds claimed to
be present, often in unspecified concentrations, any of these benefits are difficult
to confirm scientifically. Although the products are usually applied as foliar sprays,
some are also recommended as a soil drench. Because of their low macronutrient
concentrations, incomplete absorption through the leaves, and spray drift, it is
advocated by vendors of these products that they be applied several times during
a growing season, which adds to the cost of their use. Losses may also occur when
more concentrated fertilizers are applied directly to the soil as solids or by fertiga-
tion, as discussed in the next section.
4 Inthefertilizertrade,analysesareoftenquotedastheratioofNtoP 2 O 5 to K 2 O, but for simplicity
all analyses are given as elemental percentages in this topic.
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