How do rice farmers pay zakat on their harvest after selling it entirely to the harvesting company and before it is harvested and dried? Is it obligatory to buy rice of the same type and give zakat from it, or can it be given as a cash amount?

Zakat on grains becomes obligatory when they are fully formed, but the obligation is not finalized until they are placed in a threshing floor or similar location. If they are destroyed before that without negligence, then there is no Zakat due on them. The amount of the nisab (minimum threshold) is calculated after they are purified. If rice is stored with its husk, its nisab is ten awsuq with the husk; otherwise, it is five awsuq. If the crop is sold after Zakat becomes due on it, the seller must pay what corresponds to one-tenth or one-half of one-tenth of the crop, or its value.