GRAPEVINE FE-CHLOROSIS ON PODUNAVLJE VINEGROWING AREA

The characteristic of Podunavlje vinegrowing area in the far east of the Republic of Croatia is carbonate soil with loess as a parent substrate. Chlorosis is common on this soil and it is often caused by excess concentrations of calcium and magnesium and deficiency of iron and zinc. It can also be resulted by inactivation, if it is transformed so that a plant can not use it. The lack of iron in grape vine is resulted in leaf vein, first in younger leaves where the venation remains green, and then marginal necrosis and defoliation are developed. The results of the study include the data based on the field researches of Podunavlje vinegrowing subregion and exact research of fertilization field trial. Field research of Podunavlje vinegrowing subregion, vineyards of Srijem, Erdut and Baranya were conducted in July 2007. The field research consisted of locating plantations, measuring plantations chlorosis, determining their general condition and measuring total concentration of chloroplast pigments by an indirect method (chlorophyll meter) on the chlorotic and nonchlorotic plants of a grapevine. The intensity of a relative chlorosis was calculated from data measured by a chlorophyll meter. Field research was located on the production area of a company Agro-Ilok ltd. in Ilok, locality Radoš, and carried out during the period 2008 and 2009. It included cultivar Welsh Riesling, grapevine stock Kober 5BB, the most important white cultivar and grapevine stock in the vinegrowing region Continental Croatia. The experiment was set up according to a split plot method at 5x3 levels. The main factor A consisted of different chemical treatments in a basic fertilization: : A1 = 0 control without fertilization; A2 = 150 kg P2O5 + 300 K2O kg ha-1 (KCl); A3 = 150 kg P2O5 + 300 K2O kg ha-1 (K2SO4); A4 = 150 kg P2O5 + 300 K2O kg ha-1 (KCl) + 25 kg ha-1 Fe - FeSO4x7H2O; A5 = 150 kg P2O5 + 300 K2O kg ha-1 (K2SO4) + 25 kg ha-1 Fe - FeSO4x7H2O. Factor B had got three levels: B1 = without foliar treatment; B2 = two foliar treatments (once before and once after the flowering with 2.5 kg Fe ha-1); B3 = four foliar treatments (twice before and twice after the flowering with s 5.0 kg Fe ha-1). Potassium fertilization has significantly increased yield by P=0.01% in both years of the research considering the control treatment. Fertilization with different source of potassium with FeSO4x7H2O supplement in the main fertilization hasn’t affected the sugar content in must in any year. The fertilization treatments in the main fertilization like the foliar treatments, haven’t reached a significant effect on the total acidy of the must in any year. The percentage of phosphorus in leaf dry matter hasn’t changed as a result of different sources of potassium, iron supplement in soil or foliar treatment. The amount of potassium in leaf was increased by potassium fertilization, compared to the cases where this element hasn’t been used. The amount of iron in the leaf was increased by potassium chloride and sulphate with 25 kg ha-1 of iron in the main fertilization, or even without the iron. Foliar fertilization with iron had a significant effect on the increase of iron in leaves in both years, except for 2009 in the flowering stage. There were no visual symptoms of Fe-chlorosis on leaves in both growth stages in any of the research year. Manganese concentration hasn’t changed as a result of potassium fertilization with different sources, potassium and iron fertilization in the main fertilization or foliar treatment during the vegetation. Zinc amount in leaf dry matter hasn’t significantly changed due to fertilization of different sources of potassium or potassium with iron in the main fertilization. Foliar treatment has made even a smaller effect on the change of zinc in leaves in the flowering stage. The amount of copper has slightly changed during the potassium fertilization, yet foliar fertilization hasn’t affected the change of copper in any of the research year. Correlation analysis laid down a negative correlation between the potassium content and the K/Ca ratio in the leaf dry matter. There is a very positive correlation between the amount of potassium in the leaf dry matter and the sum of cations K+Ca+Mg. On the grounds of these results it can be concluded that Fe-chlorosis of the vine in a wide area of the Podunavlje vinegrowing subregion represents a considerable problem in the grape and vine production. Expected effects of the fertilization variants concerning the chlorosis and the phenomena associated to this physiological defect have failed. These results are obtained in significantly changed climate conditions with the tendency of drought in vegetation and a mild winter. That is why the research requires the continuity in order to obtain even more data in the new climate conditions