From: alain245@videotron.ca   
      
   On Mar/3/2021 at 09:19, David Spain wrote :   
   > IMHO one of the biggest blows to the concept was went it was discovered   
   > that the chemical composition of Martian soil sampled at one of the   
   > lander sites (I forget which) showed that the soil contains poisonous   
   > compounds that would either prevent plant growth or cause grown plants   
   > to become inedible. Therefore either soils will have to be transported   
   > from Earth or food grown hydroponically. I suppose one could hold up   
   > hope that with an extensive surface exploration program, maybe one might   
   > find a spot on Mars that is otherwise. Seems unlikely from where we   
   > stand today.   
      
   I'm not sure what you're talking about up there with the chemical   
   composition of Martian soil. I've heard that the soil is too salty. If   
   you have a cite for some information I don't have please provide it.   
   Soil that is too salty isn't a show stopper, just a hassle.   
      
   Here is how you would start a greenhouse operation on Mars. First you   
   plant a few rugged plant, let's call them weeds, that can survive in   
   harsh conditions. If the soil is really too difficult for plants, you   
   can bring from Earth a little soil to start; you mix that Earth soil   
   with some Martian soil. Once your weeds have grown, you cut them and put   
   them in the compost pile (really a bio-digester instead of a compost   
   pile, you don't want to wait years for your compost). Your weeds have   
   extracted some nutrients from the Martian soil, so you can get more   
   fertile soil from your compost than what you brought from Earth. The   
   nutrient depleted Martian soil can be discarded. You start again with   
   another batch of Martian soil. Because you had more fertile soil to mix   
   with Martian soil than the first time, you can harvest more weeds than   
   the first time. Repeat... Once you have enough compost you can start   
   growing tomatoes or what not. You still continue to grow weeds because   
   you want to increase your amount of fertile soil in order to increase   
   the produce crop sizes. For a fixed amount of produce you shouldn't have   
   to add new soil from the weeds, the nutrients for the next generations   
   of produce can come from the compost from the unused parts of the plants   
   and the ... ugh ... manure the colonist make.   
      
      
   Alain Fournier   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)