FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 5

TABLE 9: Annual uptake of macro-nutrients by the different organs of table grapes, based on a production of 30 ton per hectare.

Annual uptake of macro-elements (kg)

Organ

N

P

K

Ca

Mg

Bunches

43.2 43.2 14.4 16.8

8.4

61.8 19.4

5.2

2.7

Leaves Shoots

7.8

60.3 11.0

13.0

2.6 2.2

6.4 8.8

2.3 5.0

Permanent structure

6.6

Total

117.6

21.0

96.4

83.1

23.0

Seasonal uptake patterns Each element should be applied according to the grapevine’s seasonal requirement for that specific element, implying that the seasonal uptake pattern should be known. In Table 10 these values are shown for N, P, K, Ca and Mg. For fertilisation during the different growth stages, the aspects to be considered are the following:

TABLE 10: Seasonal uptake of N, P, K, Ca and Mg by table grapes (uptake for each growth stage is expressed as a percentage of the annual uptake).

N

P

K

Ca

Mg

Growth stage

Percentage (%) of annual uptake

Bud break to fruit set

25 41 34

35 40 25

40 45 15

30 47 23

30 55 15

Fruit set to harvest

After harvest

From bud break to fruit set from 25% (N) to 40% (K) of the annual requirement is absorbed. Little root growth occurs during the first month after bud break (Van Zyl, 1984), because the soil is usually still cold at that stage. Consequently the nutrient requirement of the new growth (leaves , shoots and bunches) exceeds the quantity absorbed from soil at the start of this period (Conradie, 1980, 1981 & 1986; Williams 1991), thus implying that the vine depends initially on remobilisation from the permanent structure (roots, perennial wood). From fruit set to harvest between 40% and 47% of the annual requirement for N, P, K and Ca is absorbed, while the slightly higher figure for Mg (55%) is in accordance with the fact that Mg deficiency symptoms occur readily at the start of this period, where the Mg supply is insufficient.

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