w w w. s o p i b. c o m Sulphate of Potash and Wine Grapes

Transcription

1 w w w. s o p i b. c o m Sulphate of Potash and Wine Grapes

2 Managing the equilibrium The fertilization of vines is a delicate agronomic operation that has a decisive effect on the quality of the grapes and the resulting wine. The fertilization programme must successfully complement the supply of plant nutrients available in the soil in order to allow the vines to express the land's full potential. The fertilization of perennial plants, such as vines, consists primarily of managing the equilibrium of the mineral elements present in the soil. An excess will increase plant vigour to the detriment of grape quality, whereas a deficiency will compromise production as well as the long term quality of the vine. In winemaking, the element potassium is essential for obtaining a good quality must. A potassium deficiency (corresponding to less than 0.5% potassium in the leaf dry matter) will lead to a reduction in the alcoholic level of the wine and will also weaken the plant. A production of 60 hl/ha requires from 50 to 80 kg K 2 O/ha. Availability is most important from mid-june until the end of August in Europe. Absorption of potassium by vines (g K 2 O/ha/day) Potassium deficiency in vines The form of potassium The supply of nitrogen should therefore be limited to the replacement of that removed, typically units per year in the case of vines that are not very sturdy. Demand for phosphorus is low and vines should only require around 30 units per year. Magnesium should be monitored on a case-by-case basis. Potassium, delivered in the form of sulphate of potash (SOP) is always preferable, notably because of its beneficial role in the formation of sugars and organoleptic constituents, the contents of which will determine the quality of the wine. In highly calcareous soils, the calcium has a tendency to block the availability of iron to the vine. The sulphate anion helps acidify the soil, liberating both iron and also phosphorus, which would otherwise be rendered insoluble by the excess calcium. This helps improve the supply of iron and phosphorus to the plant. In addition, sulphate of potash increases frost resistance and encourages growth of fruitbearing branches. The grapes are also firmer and less sensitive to parasites. Below are some examples of the effect of the form

3 (MOP or SOP) and dose (100 or 150 g/plant) of potassium from an experiment carried out by the University of Shandong in 2004/2005 (Cl = potassium chloride; S = potassium sulphate). Effect on Italian Riesling % Sugar ( Brix) SOP is also preferable in regions where there is a risk of salinity, such as in the Mediterranean, where vines are widespread. Of all the potassium fertilizers, sulphate of potash is the form that has the lowest salinity index. Effect on Chardonay % Sugar ( Brix) Effect on Cabernet Excess chloride in vines Potassium sulphate and wine quality % Sugar ( Brix) In wine production, there are three important components at the beginning of fermentation: sugar, malic acid and tartaric acid. Potassium is essential for the biosynthesis and transport of sugars from the leaves to the grapes. It also reacts with the various acids, influencing the ph of the must.

4 A long term experiment conducted in the Bordeaux region of France has demonstrated that a well balanced fertilization programme, based around potassium sulphate, improves production by maintaining the ph of the must between 3.2 et 4, permitting good transformation of acids during fermentation. This study also demonstrated the positive effect of potassium sulphate on the sugar levels in the fruit and, consequently, the level of alcohol in the wine as well as its quality. Sulphate of potash reduces the formation of tartaric acid and the subsequent formation of sediment. The colour of the wine is improved and blind tests confirm the improvement in the taste and character of the wine. Wine benefits from all grades of SOP Notations made by wine experts concerning the aroma and other taste characteristics show the positive effect of potassium in the sulphate form compared to a control. The dose of potassium is also important, particularly on the power, structure and harmony of wine. Results of wine tasting from plots receiving 0, 120 or 240 kg K 2 O/ha in the form of SOP SoluPotasse, the soluble grade of SOP from Tessenderlo Group for fertigation, can be used on grapes grown under drip irrigation. In many parts of the world, such as South Africa, India, Australia and Latin America, it is the ideal fertilizer for late season application when potassium is required but when nitrogen would be detrimental for high quality production. K-Leaf TM, Tessenderlo Group s new fastdissolving SOP, can be used as a foliar spray to supplement the soil application. Three to five applications of K-Leaf TM at 5-10 kg/ha/application help to provide the required level of potassium in the leaves. Nose (before agitation) Nose (after agitation) Spice aroma Dry fruit aroma Fresh fruit aroma Suppleness Aromatic qualities Power Finish Structure Harmony Control 120 kg K 2O 240 kg K 2O

5 A recent experiment carried out in the southeast of France found that the combination of soil and foliar application of SOP is the best solution to combat a strong potassium deficiency. View of the plot with soil and foliar application (T5) View of the control (T1) The different treatments covered the control (T1), soil application of MOP (T2) and SOP (T3), foliar application of SOP (T4), and soil and foliar application of SOP (T5). Doses were 200 kg K 2 O/ha for soil application and four sprays at 2% concentration in 300 l/ha of water for foliar application. One of the many additional benefits of sulphate of potash is the supply of sulphur in a form that is readily available to the vine. Finally, potassium delivered in the sulphate form does not add chloride, which can perturb the transpiration of the plants and affect their growth. With SOP, the supply of water is better regulated, minimising the effects of dry periods. Foliar application alone provides the plant with a better physical aspect, while soil and foliar application allows for a better recovery and, consequently, better grape production and quality. Effect of potash form and application method on grapes Alcohol

6 Different forms of SOP available from Tessenderlo Group Standard: for direct application or for use in the manufacture of compound fertilizers. GranuPotasse : a granular grade ideal for bulk blending or for direct application with an even distribution on the soil. SoluPotasse : K-Leaf TM : a highly soluble grade for fertigation. a new fast-dissolving grade specially developed for foliar application Imported and distributed by: Tessenderlo Group Fertilizers giving nature a helping hand w w w. s o p i b. c o m Tessenderlo Group Rue du Trône 130 B-1050 Brussels, Belgium Tel: Fax: fertilizers@tessenderlo.com GranuPotasse and SoluPotasse are registered trademarks of Tessenderlo Chemie NV/SA. K-Leaf TM is a trademark of Tessenderlo Chemie NV/SA.