| Abstract | 'Malvazija istarska' (Vitis vinifera L.) jedna je od najznačajnijih bijelih sorata u Hrvatskoj. Njezina kvaliteta prepoznata je kako u Hrvatskoj, tako i šire, stoga se domaći proizvođači sve češće odlučuju za ovu sortu. Razvojem tehnologije i sve većom potražnjom tržišta za pjenušavim vinima, raste i interes lokalnih proizvođača za proizvodnjom pjenušca od 'Malvazije istarske'. Mošt za proizvodnju baznoga vina za pjenušce po svom sastavu treba zadovoljavati svojstva kao što su niža pH vrijednost i koncentracija šećera, te viša ukupna kiselost s većim udjelom vinske kiseline, naspram jabučne. S obzirom na to da se 'Malvazija istarska' uzgaja pretežito u Istri, gdje je klima mediteranska, a najzastupljenije tlo crvenica, teško je zadovoljiti sva navedena svojstva potrebna za proizvodnju baznoga vina, posebice u suhim i vrućim godinama. Poznato je da sastav i dostupnost minerala iz tla ima značajan utjecaj na kemijski sastav mošta. Posebno je to važno za dostupnost kalija, za koji je dokazano da utječe na porast pH vrijednosti mošta i smanjuje koncentraciju ukupne kiselosti što ima nepovoljan utjecaj na kakvoću baznog vina. Također višak kalija često blokira usvajanje magnezija, te dolazi do njihovog nepovoljnog međuodnosa. Kako nedostatak vode tijekom vegetacije može usporiti i smanjiti dostupnost minerala, posebice magnezija bitnog za proces fotosinteze, a time i utjecati na kvalitetu baznoga vina, folijarna gnojidba jedan je od načina da se taj nedostata nadoknadi. Unatoč ovim važnim saznanjima mali broj autora se bavio istraživanjima utjecaja folijarne gnojidbe na sastav i kvalitetu baznoga vina u proizvodnji pjenušca. Stoga je cilj ovog istraživanja bio utvrditi utjecaj folijarne gnojidbe na količinu biogenih elemenata i suhu tvar u lišću vinove loze, te na svojstva mošta (ukupnu kiselost, organske kiseline, pH vrijednost, koncentraciju šećera) i baznoga vina (alkohol, ukupni suhi ekstrakt, pepeo, pH vrijednost, ukupnu kiselost, hlapljivu kiselost). Istraživanje je uključivalo četiri gnojidbena tretmana (T1, T2, T3 i T4) u tri repeticije. Pokus je bio postavljen po slučajnom bloknom rasporedu (RCBD) na sorti 'Malvazija istarska', podloga SO4, kroz dvije godine (2013. i 2014.). Tretmani su bili: T1 - NPK, T2 - NPK + Agromag (6 % MgO), T3 - NPK + Agromag + Fosforo (30 % P205) i T4 - NPK + Agromag + Fosforo + Bio Prot). Dobiveni rezultati ukazuju na postojanje značajnog utjecaja gnojidbenih tretmana na količinu kalija, kalcija, magnezija, željeza, cinka i bakra u lišću 2013., te kalija 2014. godine. Najveći utjecaj na smanjenje kalija u obje godine istraživanja imao je tretman T2 odnosno tretman magnezijem. Pozitivan utjecaj folijarnih tretmana na koncentraciju šećera, pH vrijednost i ukupnu kiselost mošta zabilježen je u 2013. godini, te na pH vrijednost i koncentraciju šećere u 2014. godini. Viši udio vinske kiseline i najniži udio jabučne kiseline imali su tretmani T3 i T4 u obje godine. Istraživanjem je utvrđena pozitivna korelacija između suhe tvari s pH vrijednosti i prinosom, te kalija i kalcija s ukupnom kiselosti u sušnoj 2013. godini. U vlažnoj 2014. godini utvrđena je pozitivna korelacija ukupne kiselosti i kalija, te negativna ukupne kiselosti i magnezija, što dodatno upućuje da je međuodnos kalija i magnezija za vinovu lozu bitniji od njihovih apsolutnih količina. Iako nije utvrđen značajan utjecaj tretmana na kemijski sastav baznoga vina, iz dobivenih rezultata vidljiv je trend opadanja pH vrijednosti i rasta ukupne kiselosti 2013. godine, te trend rasta ukupnog suhog ekstrakta u obje godine. Iz dobivenih rezultata vidljivo je da postoji povoljan utjecaj gnojidbenih tretmana na svojstva mošta i baznoga vina, a kako su se u istraživanju koristile minimalne doze preporučene od proizvođača za pojedina folijarna gnojiva, ostaje mogućnost daljnjih istraživanja. Dobiveni rezultati mogli bi biti znanstveni temelj pri dizajniranju folijarnih gnojidbenih tretmana u vinogradima sličnih agroekoloških karakteristika, gdje se grožđe ciljano koristi za proizvodnju pjenušavog vina. |
| Abstract (english) | 'Istrian Malvasia' (Vitis vinifera L.) is one of the most important white cultivars in Croatia. Its quality is recognized both in Croatia and throughout the world, which is the reason why domestic producers are increasingly opting for this cultivar. With the development of technology and an increase in the market demand for sparkling wines, there is also a growing interest of local producers in the production of sparkling wines from 'Istrian Malvasia'. In 2018., sparkling wine production accounts for an average of 7 % of global wine production and the volume of global exports accounted for 9 % of the total wine exported worldwide, representing 20 % of the total value of exported wine. That indicate sparkling wines are was increasingly produced in warmer and drier regions of the world, so it is difficult to achieve satisfactory parameters in the chemical composition of the base wine, which limits their production despite the adaptation of agricultural techniques and earlier harvest dates. The composition of must for the production of base wine for sparkling wine should satisfy components such as a lower pH value and sugar concentration, as well a higher content of total acidity with a higher proportion of tartaric acid, compared to malic acid. A high pH in the must is not desirable because it directly affects the wine by reducing the quality and stability of the color, negatively affecting the freshness and aging potential, and giving the wines an inharmonious taste. These negative effects are undesirable in the pro-duction of base wines for sparkling wine, because sparkling wines need freshness and a long aging potential. Preferably, base wines have a pH between 2,90 and 3,10. In base wine, a total acidity of 6,00 – 8,00 g/L is desirable, and this level is reduced by the precipitation of potassium bitartrates during must vinification. Since a high alcohol content in base wines is not desirable and an addi-tional 1,3 – 1,5 % vol. alcohol is formed during secondary fermentation, it is important that the sugar content in the must is not too high. The preferred alcohol content in the base wine is up to 11,5 %. vol. Given that 'Istrian Malvasia' is grown mainly in Istria, where the climate is Mediterranean, and the most common soil is red, it is difficult to satisfy all the mentioned components required for the production of base wine, especially during dry and hot years. It is known that the composition and availability of minerals from the soil have a significant influence on the chemical composition of the must. This is especially important for the availability of potassium, which has been proven to increase the pH value of the must and reduce the concentration of total acidity, which are unfavorable components for base wine. The idea of the possible positive effect of foliar fertilization with magnesium, phosphorus and amino acid-based biostimulants on the potassium decrease of leaves and, consequently, on the chemical composition of must arose from the knowledge of the strong antagonistic effect of potassium and magnesium. Potassium blocks the uptake and especially the translocation of magnesium in the plant much more than vice versa. Therefore, in soils with excess potassium or excessive application of potassium fertilizers, magnesium deficiency often occurs due to their antagonistic relationship and large K/Mg ratio. Foliar application of magnesium decreases the K/Mg ratio. Since the lack of water during growing season can slow down and reduce the availability of minerals, especially magnesium, which is essential for the photosynthesis process, and thus affect the quality of the base wine, foliar fertilization is one of the possibilities which can compensate for this lack. Also, foliar application of magnesium decreases the K/Mg ratio. Despite this important knowledge, a small number of authors have done research on the influence of foliar fertilization on the composition and quality of the base wine in the production of sparkling wines. Therefore, the aim of this research was to determine the influence of foliar treatments on the amount of plant nutrients and dry matter in the leaves, as well as on the properties of the must (total acidity, organic acids, pH value, sugar concentration) and base wine (alcohol, total dry extract, ash, pH
value, total acidity, volatile acidity). The research included four fertilization treatments (T1, T2, T3 and T4) in three repetitions. The experiment was set up according to a randomized block arrangement (RCBD) on the cultivar 'Istrian Malvasia', rootstock SO4, for the duration of two years (2013 and 2014). The treatments were as follows: T1 - NPK, T2 - NPK + Agromag (6 % MgO), T3 - NPK + Agromag + Fosforo (30 % P205) and T4 - NPK + Agromag + Fosforo + Bio Prot). The obtained results indicate that there is a significant influence of fertilization treatments on the amount of potassium, calcium, magnesium, iron, zinc and copper in the leaves in 2013, and potassium in 2014. Treatment T2, treatment with magnesium, had the greatest influence on the decrease of potassium in both years. A positive influence of foliar treatments on the sugar concentration, pH value and total acidity of must was recorded in 2013, and on pH value and sugars concentration in 2014. Treatments T3 and T4 had a highest proportion of tartaric acid and the lowest proportion of malic acid in both years. A positive correlation between dry matter with pH value and yield was established by this research, and potassium and calcium with total acidity in the dry year of 2013. In the wet year of 2014, a positive correlation of total acidity and potassium, and a negative correlation of total acidity and magnesium was determined, which additionally indicates that the relationship between potassium and magnesium is more important for grapevine than their absolute amounts. Although no significant influence of the treatment on the chemical composition of the base wine was determined, the obtained results show a trend of a decrease in pH values and an increase of total acidity in 2013, as well as a trend of growth of total dry extract in both years. From the obtained results, it is evident that there is a certain favorable influence of fertilization treatments on the components of the must and the base wine, and as minimum dosages recommended by the manufacturer for individual foliar fertilizers were used in the research, this leaves room for additional research. This approach to the application of foliar fertiliza-tion aimed at correcting the chemical composition of the must could reduce the need for corrective measures in the must and wine during the production process. The obtained results could be a scientific foundation for designing foliar fertilization treatments in vineyards with similar agroecological characteristics, where grapes are targeted for the production of sparkling wines. |
