FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 6

After harvest – this is an extremely important phase, because the nutrients that are assimilated during this period are stored in the grapevine as reserves, for utilisation during the next season. The compelled difference in nutrient management between early and late cultivars, during this phase, is discussed in Chapter 5. Apart from the grapevine’s uptake pattern for nutrients, environmental factors like soil temperature play a major role as well. Active root growth, and thus nutrient uptake, only commence at soil temperatures above 13 – 15 °C. Fertilisation through the irrigation system in this early stage is therefore not desirable. On sandy soils there is also the risk of leaching and on clayey soils it leads to a raised concentration of salts in the root zone that may impede the new root growth. FERTI LI SATI ON PRODUCTS Products for plant nutrition can be grouped as: • Inorganic fertiliser : four types are found, namely granular products, water soluble products, liquid fertilisers and enriched organic fertilisers. • Organic fertilisers : examples include chicken manure, cattle manure and compost. • Enriched organic products: balanced combinations of the above mentioned and may also contain lime and gypsum in their formulations. Granular products – because these products are easy to handle (and often also the cheapest), it can be applied by hand or using fertiliser spreaders. A large variety of products is available. These include singular products like Urea (N), LAN (N), Double superphosphate (P), Potassium chloride (K), Potassium sulphate (K) and mixtures like 3-1-5(37) and 1-0-1(44). The elemental concentrations of fertiliser mixtures are generally indicated according to a specific “notation”. An example, indicating the way to interpret this notation, is shown below: Fertiliser 3-1-5(37) In the 3-1-5 notation the N-P-K-concentrations are indicated as ratios. This means that there is three times more N than P in the product, and 5 times more K than P. The (37) the total concentration of nutrients (N+P+K) in the product, expressed as a percentage. The N, P and K concentrations may be calculated individually as follows: N = 3/(3+1+5) x 37 = 12.3% P = 1/(3+1+5) x 37 = 4.1% K = 5/(3+1+5) x 37 = 20.6% To check whether the calculation is correct: 12.3% (N) + 4.1% (P) + 20.6% (K) = 37%

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