<font color="yellow">"we don't have to ship up huge amounts of dirt to the Moon to use in greenhouses, just a concentrated form of it as a seed that brings life to the desolate soil of the Moon. "</font><br /><br />In order to jumpstart a rudimentary carbon and nitrogen cycle on the Moon we have to ship nutrients too. Otherwise the seeds will never grow, even with proper watering. <br /><br />All plants need following macro nutrients (macro meaning for average season you need more than 10kg/hectar of them): carbon, oxygen, hydrogen, nitrogen, potassium, magnesium, calcium, phosphorus and sulfur. Also following micro nutrients are essential (micro = less than 1kg/hectar per season needed): boron, copper, iron, manganese, molybdenum, zinc and chlorine (in some cases cobolt and sodium too).<br /><br />Here on earth we take the first three macro nutrients for granted because there's adundance of them in water and carbon dioxide.There's also abundance of gaseous nitrogen which certain nitrogen fixation bacteria can collect and turn into useable form for plants (leguminous plants like peas, beans, clovers and alfalfa form symbiotic relationship with them, the bacteria lives in their root pods). Farms that don't use commercial N-fertilizer exploit this behaviour to grab the nitrogen from the air. Other plants get their nitrogen from decomposing humus. manure and manmade fertilizers.<br /><br />On the Moon we can take much less for granted. There's plenty of required minerals (but not necessary in a form suitable for plants) and oxygen but almost void of the other volatiles (C, H, N, Cl). Until there's machinery on the Moon to siphon out the trace amounts of volatiles from endless tonnes of regolith, we have to ship them to the moon, probably in a form of ammonia and methane.<br /><br />And it would be a smart move for NASA to try utilize carbon composites in the forthcoming lunar mission hardware so that obsolete descent stages etc might be scavenged for the precious C.