If a crop for which ‘ushr has been paid is not disposed of but kept in storage, and a year passes over it, is zakat and…

Crops for which ‘ushr has been paid are not subject to ‘ushr again, no matter how long they remain in storage as produce, unless they are converted into cash by the owner. (Ibn Abidin, Radd al-Muhtar, 2/268, 298) However, if a crop for which ‘ushr has been paid is sold and converted into cash, this money is evaluated together with other zakatable assets of cash type.

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu