Sforno on Deuteronomy 33:13/ספורנו על דברים ל״ג:י״ג

1מבורכת ה' ארצו, Moses explains that the lands given to the tribe of Joseph are naturally fertile, blessed by G’d.

2ממגד שמים מטל, He now prays that in addition to this “natural” fertility, G’d should also endow Joseph’s portion with the attributes provided only by Divine assistance, such as regular dew from the skies so that it will not have to depend on rain, and on the underground springs, all of which will help to produce bountiful crops.