FERTILISER GUIDELINES FOR THE WINE INDUSTRY

TABLE 12: Norms for phosphate content of vineyard soils with pH (KCl) 5.0-5.9.

Phosphate norm (mg.kg -1 )

Clay content (%)

Bray I* 2

Olsen *3

Citric acid

Bray II* 1

0-6

25

20 25 30

15 20 25

12 14 16

6-15

30 35

>15

* 1 Stronger acid & ammonium fluoride mixture for strong Pfeeders and acidic soil. Citric acid is comparable with this. * 2 Weaker acid & ammonium fluoride mixture for weak Pnourishers and acidic soils. * 3 Sodium bicarbonate for high pH soils.

Leaf norms (Table 13) can be used in a supplementary manner, although the same restrictions apply as already indicated for N. TABLE 13: Norms for the phosphate contents (%) of leaf blades and petioles of grape vines.

Fruit set

Leaf blade

Petiole

Minimum

Maximum

Minimum

Maximum

5

0.15

0.55

0.13

0.62

Veraison

Leaf blade

Petiole

Minimum

Maximum

Minimum

Maximum

0.13

0.45

0.12

0.64

Local experience indicate that appoximately 0.7 kg/ha -1 P is required annually by the grapevine for 1 ton/ha -1 production, and that there are two peaks of uptake, i.e. after bud break and after harvest. Due to the immobility of P in the soil, the risk of losses are negligible, with the exception of bleached sands or peat soils. Consequently, as a rule, P is only applied once per year, according to soil analyses by broadcasting it before soil preparation or deep placement in a band, in existing vineyards.

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