cultivation vs cultivation of plants

cultivation

noun
  • The art or act of cultivating; improvement of land for or by agriculture 

  • Advancement or refinement in physical, intellectual, or moral condition 

  • The state of being cultivated or used for agriculture 

  • Devotion of time or attention to the improvement of (something) 

cultivation of plants

How often have the words cultivation and cultivation of plants occurred in a corpus of books? (source: Google Ngram Viewer )