FERTILISER GUIDELINES FOR THE WINE INDUSTRY

ROOTSTOCK MOTHER BLOCKS The work that Conradie (2005) conducted on rootstock mother blocks, indicated that the uptake of fertiliser elements is indeed influenced by rootstock cultivar and soil type to an extent, but the average uptake per vine was comparable in all the experimental blocks. This means that the amount of nutritional elements that is taken up per hectare, is largely determined by planting width. Average seasonal uptake of macro-elements (with the presumption of a typical planting width of 2.7 x 1.2 m; c. 3000 vines per hectare), are indicated in Table 24.

TABLE 24: Average seasonal uptake of fertiliser elements by wine grape rootstocks.

ELEMENT

N

P

K

Ca

Mg 4.7

Ave. per vine (g)

17.6

2.6

11.5 13.3

Ave. per hectare (kg)

53

8

35

40

14

Conradie’s (2005) guideline recommendation of 100 kg/ha -1 N therefore, at this planting width, leaves room for ineffectiveness. This amount of N can be applied in 3-5 increments from September to January. Excessive N-application can negatively affect the quality of grafting material. If the P-content of the soil is < 30 mg.kg 1 , it can be corrected with a single application during soil preparation, or with localised deep placing between the tractor track and vine row in existing vineyards. As alternative a seasonal maintenance programme of approximately 10 kg/ha 1 P can be followed, which for the sake of convenience can be broadcast in a single increment at the end of the season (February-March), so it can also be utilised by the cover crop and transported to the deeper soil layers. Potassium fertilisation is required if the K-content of the soil is < 80 mg kg -1 or constitutes less than 4% of the CEC of the soil. Like with P, it can corrected with a single application or deep placing in soils containing more than 10% clay. Potassium is assimilated proportionally to P at the same amounts as for wine grapes and as alternative a seasonal guideline amount of K of approximately 45 kg ha -1 can be applied, especially in sandy soil. Uptake of Ca by rootstocks is proportionally significantly higher than for wine grapes, but no Ca-fertilisation is recommended if the soil pH (KCl) is 5.5 or higher. If the Ca-content is low (Table 3), application of approximately 1 ton ha -1 gypsum every 5 years should be sufficient to meet the Caneeds of rootstocks, which would then also serve as source of sulphur (S).

8

95