If you are going to purchase 300 acres, you are going to need a Belizean lawyer and I bet he can answer this question better than any of us. However, I will say that I have heard about people making small improvements to their land to avoid paying "speculation" taxes (IE clearing underbrush, building a $1000 shack over 10 years, etc could save you having to pay). But I am not a lawyer let alone a Belizean lawyer...
Also alot of countries have a limit as to how much land a foreign individual can own (as opposed to a foreign business). I can't remember off hand if Belize has such limits, but you might want to look into it. (IE you may have to start a business to real or imaginary to get that much land.)