בראשית מז:כד פירוש: רש״י, ספורנו, אור החיים ורד״ק

לזרע השדה FOR SEED OF THE FIELD — for sowing every year),

את האדמה, which is his, והיה בתבואות When it come to the crops, which are his,

חמישית לפרעה, one fifth for Pharaoh, etc. Joseph was astute enough to say that Pharaoh would collect the first 20% of any seed. Even if, as a result, the remaining 80% would be only sufficient for the farmer to plant and to break even, Pharaoh would not agree to collect less than his 20%. On the other hand, the farmers would be at liberty to collect the overage whether there be a lot or a little.