Is Zakat obligatory on the two inherited plots of land, which were sold years after the father's death, knowing that no Zakat had been paid on them previously, and no money was available to pay it?

Land and عرض (commercial goods) are not subject to zakat unless they have been sold and a full year has passed on their price. Zakat is then obligatory for whoever's share reaches the nisab (minimum threshold) or completes the nisab for them. This is because their physical essence is not subject to zakat unless intended for trade, as the Messenger of Allah, peace and blessings be upon him, said: "There is no sadaqah (zakat) on a Muslim's horse or slave."

If the land was inherited and its price was sold and spent before a full year passed on it, then there is no zakat on it. However, if it was sold and its price distributed among the heirs, zakat becomes obligatory on whoever's share reaches the nisab and a full year has passed on it.