Commentary for Berakhot 69:5
ולמאן דתני כרם רבעי הניחא אי יליף ג"ש דתניא ר' אומר נאמר כאן (ויקרא יט, כה) להוסיף לכם תבואתו ונאמר להלן (דברים כב, ט) ותבואת הכרם מה להלן כרם אף כאן כרם אייתר ליה חד הלול לברכה
According to him who teaches "the vineyard of the fourth year" it is quite right if he argues by analogy of expression ; for there is a teaching : Rabbi says : It is stated here, "That it may yield unto you more richly the increase thereof" (Lev. xix. 25), and it is stated elsewhere, "the increase of the vineyard" (Deut. xxii. 9) — as in the latter passage "increase" refers to the vineyard, so also in the former passage it refers to the vineyard ; and there thus remains over one hillul to be interpreted as meaning that a benediction is required [when partaking of fruits].
Tosafot on Berakhot
What do we do with vineyards of the fourth year? And the fruit of the vineyard of the fourth year nowadays, we transfer the sanctity to the amount of a p’rutah,1The rule is that when one transfers sanctity from an item that is worth one hundred dollars to a coin worth a penny, the transfer is effective. One is initially not allowed to do this, because he is cheating the Temple Treasury fund, but if he did do it is valid. Nowadays when there is nothing one can possibly do with the fourth year fruits, it is permissible to initially transfer the sanctity to a very small coin. a very small coin, and one grinds it and throws it into a river, so that nobody should accidentally violate its sanctity. And so is it clearly stated in the Sh’iltos of Rav Achai (Parshas K’doshim Simon 100).