FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

NUTR I ENTS REQU I RED BY GRAPEVI NES It is accepted that the following macro-elements are required:

Carbon (C), hydrogen (H) and oxygen (O), are derived from air and water, while nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S) are obtained from the soil. Additionally, the following micro-elements are required: Iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo) and chlorine (Cl). Before the approach for each for each element is discussed in detail, note must be taken of the following three aspects that are of importance for all nutrients: Quantities that are absorbed annually The quantities of the different nutrients which are absorbed annually, have been quantified in in various experiments in South Africa, while comparable studies, sometimes aimed at N only, have also been carried out in other countries (Löhnertz, 1988; Williams & Biscay, 1991; Hanson & Howell, 1995). Despite climatic and cultivar differences, comparable results were obtained for the Coastal region (Conradie, 1980, 1981 & 2001) and the Lower Orange River region (Conradie, 2005a; Conradie & Raath, 2002; Raath, 2005). The results are summarised in Table 8. On account of S, Mo and Cl not having received the same attention as the other nutrients, these three elements are not included in the table, but guidelines will be supplied later. The values in in Table 8 are specifically valid for table grapes , and not necessarily for wine grapes . Due to different cultivation practices, there may be minor differences between the values for wine and table grapes, in some cases.

TABLE 8: Nutrient quantities absorbed annually by table grapes, based on a production of 30 ton per hectare.

N P K Ca Mg Mn Zn Cu B Fe (kg ha –1 ) (g ha –1 )

Element

Uptake per hectare 118 21 96 83 23 180 300 60 240 760 Uptake per ton produced 3.93 0.70 3.20 2.77 0.77 6 10 2 8 25

Distribution of elements between different organs: The quantities in Table 8 depict the annual uptake of the different nutrients and should not be seen as the amounts that should be applied annually. It must be taken into consideration that nutrients that are assimilated in leaves and shoots, are recycled to the soil at leaf fall and during pruning. As indicated for macro-elements in Table 9, the quantities that are removed annually by the bunches, may vary from 61.8 kg ha –1 for K to only 2.7 kg ha –1 for Mg, while the quantity that lands on the soil during leaf fall, may vary from 60.3 kg ha –1 for Ca, to 7.8 kg ha –1 for P.

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