[Ruling on one who neglected the cultivation of a waqf]

Answer—and Allah is the One who grants success: What is binding upon the guardian of the waqf is to plant (cultivate) the endowed property and maintain it, exactly as farmers do; he is not permitted to be remiss or neglectful. If he does not do so, he must hand it over to one who will cultivate and maintain it.
Thereafter he must monitor the new partner, reckon with him, take the waqf’s share from him, and then deliver it to the designated beneficiaries, and so on—and after that, nothing else is binding upon him. If he had previously fallen short and neglected the cultivation of the endowed property, then no compensation is binding upon him to the beneficiaries; rather, on him is the sin of negligence and neglect—so he should seek forgiveness and repent to Allah.
This is how the jurists of the madhhab have determined the matter, as in the Commentary and its marginalia; and this is so long as he has not prevented others from cultivating it—if he prevented others, then he is a usurper in possession.
Yes: If the guardian of the waqf wishes to lease out the property, he may do so; however, he should not lease it for a long period that might jeopardize the waqf due to its length. Rather, he should lease it for a year or two; when the term ends, he leases it again for a year or two, and so on. If the guardian of the waqf does none of what we have mentioned—neither cultivation, nor partnership, nor leasing—then it is binding upon the judge to remove it from his hands and place it with one who will undertake its cultivation and maintenance.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2