What is the ruling if a tree owner breaches an agreement concerning the roots' growth?

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If an agreement is made that the growth from the tree roots belongs to the landowner or a portion of it, and after a period, the tree owner refuses to deliver the growth to the landowner, the tree owner must pay the fair rental value (Ujrat al-Mithl). This is because the landowner permitted the roots' presence in his land for that consideration, and withholding the agreed-upon growth necessitates payment of the fair rental value, analogous to a situation where an item is offered for a price but not delivered.