As to whom to start calling, try local first. Not that you can't get investors from anywhere else, but generally people in New Zealand are more likely to invest in New Zealand than people outside. Furthermore, you can start with the public agencies and quasi-public agencies whose charter involves developing New Zealand--not that they'll be your investors, but they are more likely than those outside of New Zealand to have some good leads. Look for government development agencies, local development agencies and industry chambers. I just did a quick google search for New Zealand business development and that turns up one federal agency and an organization focused on investment for sustainable business.
Don't forget local business groups, local universities and local investment groups. Find the business blogs related to New Zealand entrepreneurs.
If that doesn't seem to be working, start looking for investors elsewhere with interests in hydroponics and related fields. That's going to be harder, of course, and now is not a great time.
Basically, the process is: You develop your plan, search for investors with the right kind of interests, get an introduction, present a summary memo and, if you're lucky, get invited to do a pitch. If you get through that hoop, then it's lawyers and term sheets and detailed business plan work.
Good luck with it,