Go search "Heinlein" and "Food shortages" and you will find a number of readers who agree with me.
You may think it is not there but a good number of other people do. And the author himself has stated it and also stated that he got it wrong.
You really need to read that part of "Expanding Universe".
My point, Teddy, is that pessiistic "food shortages" were not a recurring theme running throughout, or even in any but one or two (if that), his fiction works. Population pressure was commented on in any book about colonization... and even in Farmer in the Sky, the colonization intent was never to ship food back to Earth but to find additional living room and for the colonists to achieve self-sufficiency.
You certainly won't find it in The Door Into Summer, Beyond This Horizon, Double Star, Red Planet, The Star Beast, Sixth Column, Methusalah's Children, If This Goes On, Rocket Ship Galileo, Starman Jones, The Rolling Stones, Tunnel In the Sky, Tme for the Stars, Citizen of the Galaxy, or Starship Troopers which comprise the bulk of his early works.