Re: How do types of soil affect plant growth?

Hi Lauren.
    Soil (excluding the nutrient factor) mainly affect plants in its 
ability to maintain moisture and support the plant. The far end of the 
scales being relatively sand and clay.  When you consider nutrients and 
beneficial bacteria necesary for plants to grow then the relationships 
become more complex.  To see the relation soil has on plant growth one 
only needs to look outside.  Plants grow best where the soil most meets 
their needs. Calla lilys on waters edge; cactus in the desert; etc..  
    If you are going to change soil types in your experiment than you 
should try to keep you other variables constant as possible.  Water, 
Light, Fertilizer, and temperature.  
    You can measure the bio-mass by simply weighing the entire plant 
(roots also) with a scale.  You will have to carefully remove all the soil 
so as not to taint your results.  You might want to consider drying each 
plant before weighing.  This will give you a true weight of bio-mass.  
Hope this helps you.  There are many pages on the NET especially through 
Universities and Soil Co-ops on this subject.     
                                              Mark