FERTILISER GUIDELINES FOR THE WINE INDUSTRY

WATER SOLUBLE PRODUCTS Often water soluble fertilisers has the same chemical composition as granular fertilisers. Commonly used water soluble products (Table 21) include KNO 3 , Ca(NO 3 ) 2 , MKP (Mono-potassium phosphate), MAP (Mono-ammonium phos phate) and mixtures like e.g. 6-1-3(42). The use of water soluble products are becoming increasingly popular due to the following reasons: (i) easy application through irrigation systems, (ii) high concentrations, i.e. a saving on transport costs, (iii) placing of nutrients in the root/drip zone, and (iv) the availability of a variety of mixtures to address certain needs and therefore making manage ment easier. TABLE 21: Forms of water soluble nitrogen fertilisers suitable for vineyards.

Chemical formula

Nitrogen content % Remarks

Composition

Both compositions are very soluble, suitable for use with irrigation Supplies both N and S; oxidation of the ammonium acidifies the soil Nitrate is immediately available; ammonium first has to be oxidised to nitrate Both forms are water soluble; also supply P; acidifying effect

K NO 3 Ca(NO 3 ) 2

13 15.5

Potassium nitrate & Calcium nitrate

Ammonium sulphate

(NH 4 ) 2 SO 4

21

Ammonium nitrate

NH 4 NO 3

34

Monoammonium phosphate (MAP) & Diammonium phosphate (DAP)

6

NH 4 H 2 PO 4 (NH 4 ) 2 HPO 4

11 18

Highly soluble; volatile if not washed into soil; acidifying; can be used as foliar nutrition

Urea

(NH 2 ) 2 CO

46

Has the benefits and disadvantages of urea and ammonium nitrate

(NH 2 ) 2 CO, NH 4 NO 3

Urea ammonium nitrate solution

30-32

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