FERTILISER GUIDELINES FOR THE WINE INDUSTRY

is known beforehand to ensure that the required product is delivered from the correct source. Lime reacts with the soil to increase the hydroxyl (OH - ) ions in the soil solution, and therefore reduce the soil acidification (H + ) and achieve an increase in soil pH. The most common product is agricultural lime or calcitic lime – CaCO 3 , which contains about 40% Ca and consequently its application will also increase the calcium levels in the soil. If the magnesium levels in the soil are < 40 mg/kg, dolomitic lime – CaMg(CO 3 ) 2 , is recommended. This product contains approximately 12% magnesium and 20% calcium. When lime is ordered, it is important to take the distance between the lime source and the producer’s farm into consideration as transport costs can be very high. It is equally important, however, to also take note of the neutralisation ability of lime products. In order to compare products, the neutralisation ability of pure CaCO 3 is defined as 100%. The neutralisation value (CCE = calcium carbonate equivalent values) of calcium oxide (CaO) and calcium hydroxide [Ca(OH) 2 ], for example, is considerably higher than that of calcium carbonate (CaCO 3 ). The oxides and hydroxides of magnesium also have considerably higher neutralisation values than magnesium carbonate. It is therefore possible that the CCE of an agricultural lime can be more than 100%. The CCE values of different wellknown products are indicated in Table 7:

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TABLE 7: Different lime products, their composition and neutralisation abilities.

Chemical composition in pure form

Neutralisation ability (CCE)

PRODUCT

Calcitic lime/ agricultural lime

CaCO 3 ( 40% Ca)

50-85

CaMg(CO 3 ) 2 (20% Ca and 12% Mg)

95-110

Dolomitic lime

Ca (OH) 3 (54% Ca)

120-135

Slaked lime

31