Using foliar applications of magnesium and potassium to improve yields and some qualitative parameters of vine grapes (Vitis vinifera L.)

Abstract

Grapevine (Vitis vinifera) is a productive drought stress-adapted plant and one of the most economically important fruit crops (Zörb et al. 2014). Production of quality grapes suitable for winemaking depends on numerous factors (Gerendás and Führs 2013). Moretti (2002) stated that among intrinsic (degree of wood maturation, content of nutritive and nitrogenous compounds) and external factors (temperature, rain distribution, soil parameters) the quality of wine produced is also modulated by fertilization to a central degree.Magnesium (Mg) is an important macronutrient with a number of physiological functions in the plant. The importance of magnesium in the plant Using foliar applications of magnesium and potassium to improve yields and some qualitative parameters of vine grapes (Vitis vinifera L.) T ABSTRACTIn a three-year field experiment (2011)(2012)(2013) we assessed the effect of magnesium (MgSO 4 ) and potassium (K 2 SO 4 ) applied as foliar applications both separately (3.86 kg Mg/ha or 12.44 kg K/ha) and in combination (1.93 kg Mg/ha + 6.22 kg K/ha) on yields of grapes of cv. Zweigelt and some qualitative parameters of the grapes. The applications were repeated 4 times in stages BBCH 15-19; 55; 75 and 83. The experiment was carried out on soil well supplied with Mg and K in the subsoil layer. In terms of average 3-year results the grape yields were by 11.2% (MgSO 4 ), 13.9% (K 2 SO 4 ) and 6.6% (MgSO 4 + K 2 SO 4 ) significantly higher than the untreated control. The sugar content of grapes (sum of glucose and fructose) was lower (mostly insignificantly) by 0.5-4.3% in all the fertilized treatments than in the untreated control. Fertilization had no significant impact on the pH of must (juice) and ranged between 3.02 and 3.25. The content of titratable acids in the must ranged insignificantly between 8.73 and 10.86 g/L, and average values were the highest in the untreated control. On the basis of these results it is evident that separate applications of Mg and K have a positive effect, in particular in that they stimulate grape yields, and at the same time the effect of the year is significant. Keywords 451Plant Soil Environ. Vol. 61, 2015, No. 10: 451-457 doi: 10.17221/437/2015-PSE is in many ways connected with photosynthesis. It is the central atom of chlorophyll and it activates enzymatic processes. Magnesium also favourably influences assimilation (Mengel and Kirkby 2001). Magnesium deficiency reduces the content of chlorophyll in the leaves and changes the chlorophyll a:b ratio in favour of chlorophyll b. Visually it is seen as chlorosis of leaves, especially older ones and causes premature abscission. Chlorosis is caused either by Mg deficiency, high content of soil Ca (calcareous soils) or a combination of these factors (Marschner 2002, Ksouri et al. 2005, Gluhić et al. 2009). Magnesium uptake by the plant is also affected by the antagonistic effect of Ca and K and as was confirmed by Garcia et al. (1999) who discovered a marked reduction of Mg in grape berries on soils with high supply of Ca...

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