Is zakat obligatory on the value of leased land, or on its rent, if it is not for commercial purposes? And are rent and farming costs deducted before paying zakat on crops?

Zakat is obligatory on the surplus amount used to purchase land if it reached the nisab and a full year passed over it before the purchase. Zakat is not waived by purchasing the land.

As for after purchasing the land, Zakat is not obligatory on the value of the land if it was not bought with the intention of trade. Rather, it becomes obligatory on the rent if it reaches the nisab and a full year passes over it.

Regarding the tenant, Zakat is obligatory on the entire crop without deducting the rent value. Zakat is due from the tenant of the land, not its owner.