FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 8

8 FERTILISATION OF ROOTSTOCK MOTHER BLOCKS AND NURSERIES ROOTSTOCK MOTHER BLOCKS The work that W.J. Conradie (Conradie, 2005 b) conducted on rootstock mother blocks indicated that the uptake of nutrients is indeed influenced, to some extent, by rootstock cultivar and soil type, but the average uptake per vine was comparable in all the experimental blocks. This means that quantities of nutrients assimilated 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. 3 000 vines per hectare), is indicated in Table 31. DAWI D SAAYMAN

TABLE 31: Average seasonal uptake of fertiliser elements by grapevine rootstocks.

Element

N

P

K

Ca

Mg

Ave. per vine (g)

17.6

2.6

11.5

13.3

4.7

Ave. per hectare (kg)

53

8

35

40

14

At this planting width, the recommended guideline (Conradie, 2005 b) of 100 kg N ha –1 N, therefore, provides ample provision for ineffective applications. This amount of N can be applied in 3 – 5 increments from September to January. Excessive N application can affect the quality of grafting material negatively. If the P content of the soil is < 30 mg kg –1 , it can be corrected with a single application during soil preparation, or in existing vineyards with localised deep placements between the tractor track and vine row. As alternative a seasonal maintenance programme of

FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY | 105