Is zakat obligatory on a piece of land that I inherited and deposited its value in a usurious bank, then bought it with my siblings with the intention of preserving the money and selling it in the future when needed, or when money becomes available, or when a large sum is offered?

If the land is a partnership between you and your siblings, with the intention of selling it, then it is considered a trade commodity. Each partner must pay Zakat on their share if it reaches the Nisab (minimum threshold) and a hawl (lunar year) has passed over it. As for whoever's share is less than the Nisab, there is no Zakat due on them. The intention to sell the land out of necessity does not obligate Zakat; rather, the intention to sell must be clear at the time of purchase.