Just tell her straight out. Your an independent person and if you want to study it, dont let anyhing stop you. Are you asking because your mum doesnt want you to? Well, she shouldnt be choosing such things for you. Sit her down and talk to her calmly about your choice and why you want to study it. Shes your mother, not a monster, so I'm sure at 18 you should be confident enough with talking to your mum about your decisions. =)
Tell her, "there is something I have a passion for mom, it's agriculture." "I want to involve my whole life around it." "I feel it's a part of my whole beingness." "That is all I want to create, 'the survival of good agriculture', so we humans will live better, healthier and happier." "I want to do it through organic sustainable life." And emphasize "PASSION", when saying it. Look her in the eye and mean it.
personel Iwould figure that you are an adult it is time for you to take charge of your own life.
You always want to set the right atmosphere. And talking calmly will be a bonus, good luck.
this is almost as funny as the "how do i tell my mom and dad i'm scene" question
How about, "Mom, I am really interested in a career in Agriculture" ?
Mum, im gonna study Agriculture, Like it or Lump it hahaha...
masage her feet while telling her :)
ahahaha......thanks for the Like...