[senortumnus]

Slightly informed guess is that the highly productive but water-constrained farmland of the nile valley is better used for value crops, like fresh fruits and vegetable, than a staple such as wheat which is more cheaply grown elsewhere.

Edit: there’s a great writeup about “hoop” style greenhouse farming there and how productive and water efficient it is… but the article escapes me presently

Edit2: ah! Here: https://www.nytimes.com/2019/07/30/dining/norwich-meadows-fa...