Student or Learner
1) He cultivates seasonal crops on his land. OR He cultivates seasonal crops in his land.
2) I am going to sleep. OR I am going for sleep.
3) I am going to exercise. OR I am going for exercise.
Thanks in advance
"on his land" is correct. To use "in his land" suggests some sort of kingdom. "He does not allow Catholics in his land."
"to sleep" is correct. It expresses your intention to do something. To go "for sleep" suggests a destination involved, or a purpose. "Why are you going to the beach?" "I am going for sun and sleep."
"to exercise" is correct, for the same reason as above. "Why do you go to the gym?" "I go for exercise."