The effect of partial defoliation on the uvometric and mechanical values of Merlot and Cabernet sauvignon grapes

Defolijacija je jedan od zahvata zelene rezidbe. To je postupak prorjeđivanja ili potpunog uklanjanja listova u zoni grožđa. Vrijeme izvođenja zahvata djelomične defolijacije još uvijek je tema brojnih istraživanja. Ukoliko se provodi u periodu cvatnje, smatra se ranom, a između oplodnje i šare, smatra se kasnom defolijacijom. Cilj ovog rada bio je istražiti utjecaj djelomične defolijacije provedene u četiri različita termina (prije cvatnje i oplodnje, neposredno nakon cvatnje i oplodnje, fazi zatvaranja grozdova te razdoblju šare) na uvometrijske vrijednosti te mehanički sastav grozda sorata Merlot i Cabernet sauvignon u uvjetima Zagrebačkog vinogorja, podregije Prigorje-Bilogora. Rana defolijacija prije cvatnje i oplodnje imala je niže prinose i broj grozdova po trsu, koji je povezan sa boljom kvalitetom samog grožđa kod obje sorte. Defolijacija u fazi zatvaranja grozdova imala je najpovoljniji utjecaj na postotak mesa bobice i grozda, rezultirajući dobrom iskoristivošću grožđa kod obje sorte. Djelomična defolijacija u razdoblju šare bilježila je visoke prinose i broj grozdova po trsu što se odrazilo na smanjenu kvalitetu grožđa.Defoliation is one of the canopy menagment treatment. It is a process of thinning or completely removing leaves of canopy grape zone. Perfect time to preform defoliation is still a topic of numerous researches. If it si carried out in the period of flowering, it is considered early, and in between fertilization and veraison, it is considered as late defoliation. The aim of this study was to investigate the influence of partial defoliation carried out in four different terms (before flowering and fertilization, immediately after flowering and fertilization, in the faze of berry set and in the period of veraison) on the uvometric values and the mehanical composition of grapes Merlot and Cabernet sauvignon in the condition of Zagreb vineyard, subregion Prigorje-Bilogora. Early defoliation before flowering and fertilization had lower yields and the number of grape clusters per vine, wich was correlated with higher quality of grapes in both varieties. It was established that defoliation in the stage of berry set had optimal effect on the percentage of meat in a cluster and berries, which resulted in good grape utilization of both varieties. The partial defoliation in the period of veraison recorded high yields and number of grape clusters per vine, wich reflected on reduced quality of grapes