FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

In Europe and the USA, P and K concentrations are expressed as P 2 O 5 and K 2 O respectively. In order to convert this notation to the singular elements, the following factors must be used: P = 0.436 x P 2 O 5 K = 0.83 x K 2 O Because drip systems are not effective for washing granular products into the soil, the increased use of drip irrigation has led to a decline in the use of granular fertilisers. For these systems, water soluble or liquid fertilisers are preferred. Micro-sprinklers offer the advantage that they are effective for washing fertilisers of any form into the soil. However, where cover crops are established in the vine rows, granular fertiliser is still the primary product for fertilisation. Examples of inorganic products that are generally used are shown in Table 28.

TABLE 28: Chemical composition (%) of some inorganic fertilisers that are generally used.

Product

N P K S Ca Product

N P K S Ca

Potassium chloride KCl

50

UAN 32

32

Potassium sulphate K 2 SO 4 Ammonium sul- phate (NH 4 ) 2 SO 4

40 16

AN 21

21

Calcium nitrate Ca(NO 3 ) 2 Potassium nitrate KNO 3 Double superphos- phate (20) Calfos 14 Rock phosphate

21

24

15.5

19-21

MAP(33) NH 4 H 2 PO 4 Urea(46) (NH 2 ) 2 CO

11 22

13

37

20

46

LAN(28) NH 4 NO 3

28

14

35

Water-soluble products – water soluble fertilisers often have the same chemical composition as granular fertilisers. However, the use thereof is increasing, due to the following reasons: • Easy application through irrigation systems • High concentrations, i.e. saving on transport costs • Placement of nutrients in the root/drip zone • The availability of a variety of mixtures to address certain needs and therefore making management easier.

86 | PRACTICAL GUIDELINES FOR IMPLEMENTATION OF THE FERTILISATION PROGRAMME