Hydroplonic (sp?) Gardens

[JANET G. BEUCLER]

After a trip to New Zealand  I was told to look into hydroplonics as a 
method to grow vegetables and spices that are otherwise not available 
over there.  Spinach, Mustard Greens, Lettuce, also the soil has no iron 
and i understand that hydroplonics allows the addition of metals into the 
vat.  I need to know more.  What resources are available on the net?  
Thanks in advance for references and/or advice.  Janet B.