What invalidates sharecropping (musāqāh or muzāra'ah) agreements regarding the known share of each party?

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Agreements become invalid if they lead to ambiguity concerning the share of each party. This includes stipulating an unknown share for one party, a fixed amount of currency (dirhams), specific quantities (aqfiza), or conditional shares based on the method of irrigation (e.g., receiving a certain amount if watered by runoff ('sayh') versus receiving another amount if watered with effort/cost ('kulfah')). Such conditions invalidate the contract because they lead to ambiguity regarding the subject matter of the contract, similar to a sale with an unknown price or a partnership (mudārabah) with an unknown share for one partner.