Agriculture Reference
In-Depth Information
Leaf fall,
prunings
Compost
Organic P
Fertilizer P
(inorganic)
Mineralization,
immobilization
Soil solution
P
Uptake
Labile P
Fast
Mycorrhizas
(organic and
inorganic P)
Adsorbed P
Slow
Strongly sorbed P and
P in insoluble compounds
Nonlabile P
Figure 3.14
The phosphorus (P) cycle in a vineyard. (White, 2003)
Table 3.11 shows the main forms of P fertilizer for use in vineyards. Rock phos-
phates are of special interest because, being a natural product, they are acceptable
in organic viticulture. A commercial rock phosphate should be “soft” rather than
“hard,” finely ground, and used only on soils of pH(CaCl
2
) of 5.5 or less (see box 3.6)
to maximize its effectiveness. Because they are slow-release fertilizers, rock phosphates
are most effective if mixed into the soil by plowing or ripping at vineyard establish-
ment. Phosphate ions are very immobile in all but sandy soils low in Fe and Al oxides,
so even water-soluble fertilizers such as superphosphate are more effective if mixed
into the soil by cultivation. Alternatively, soluble P can be supplied by fertigation.
Other Macronutrient Fertilizers for Vineyards
Calcium,Magnesium,andPotassium
Calcium is supplied in fertilizers such as Ca(NO
3
)
2
, single superphosphate, tri-
ple superphosphate, and rock phosphate, as well as in various liming materials
(see table B3.6.1). Gypsum also supplies Ca and, because it is more soluble than
