Why are many peasant farmers in less developed countries resistant to adopting practices and crops ...

Why are many peasant farmers in less developed countries resistant to adopting practices and crops even when they are genuine improvements?
 
  a. Peasant farmers have supernatural beliefs about farming and fear offending the spirit world.
  b. The peasant farmers do not understand that there are crops and practices that might be more efficient than the ones they use.
  c. Subsistence farmers know that, while not ideal, the plants and practices they have been using are well adapted to the local environment.
  d. Due to the backfire effect, objectively false beliefs often become stronger rather than weaker when presented with contradicting evidence.