topsoil
noun
                                                                                                                            
                                                            top·soil
                    
                                                                                                              
                                                                                                                                  ˈtäp-ˌsȯi(-ə)l  
                                                      
                                                          
            
                                
              
          
                                                      : surface soil usually including the organic layer in which plants have most of their roots and which the farmer turns over in plowing                                      
                
                    
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  Merriam-Webster unabridged




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