The world's population should be at most 50 million.

[Alan V]

The method I just presented to you is site independent.   You can set it up in an abandoned walmart parking lot.  You can service the people who used to come to the walmart, without the need for biofuel shipping...which is still a pollutant and still a problem at some level.  It also saves water.  Unlike no till, there's nothing -to- til, and no tractor dragging a drum.  The mechanical work is in the form of air lift - easily handled by solar (whereas tillage obviously isn't).  The chemical work is nonexistent, preventative management is relied on, instead.

Why would the population need to come down if we can produce more food in less space, locally, with less pollution and greater conservation of water..while providing higher wages for the producers?  

Really try to work that one out.  See if it's more than an ideological sticking point, pessimistic malthusianism that's a holdover from the 19th century intellectual tradition, long demonstrated to be wrong before innovation outstripped the concern if it were right.

Let me put it to you a different way.  If we assume that theres a carrying capacity for earth, we make that assumption based on current patterns of use.  Alt ag and alt energy can produce much more food and free up nearly two times over again the amount of freshwater available to us.  So, if a person tells me that 10bil is earths limit...I'mma contend that it's closer to 30, at least - and that's ignoring future innovation and improvements to existing infrastructure.  That's just what we know now.

You seem to be saying we all just need to eat salads all the time and live as simply as possible. Then, poof, our population problems will disappear.

Well, yes and no. Yes, that would help a lot. But no, that won't work. People won't do it.