I have to distribute power across and around my land (6.5 ha, 16 acrres)?

When covering a large area multiple grounds is a good idea in case one is compromised.

REAL EARTH GROUNDING POINTS CAN BE AS MANY AS REQUIRED ACCORDING TO YOUR SITUATION, PROVIDED YOU INSTALL AT LEAST 6 FEET THICK COPPER ROD ( ONE INCH DIAMETER ), AND PICK THE INSTALLATION POINT ON WET SOIL.

How many power points, what power/current, what distance?

I suspect the distances may be too large for a 220 volt line (assuming Europe) and will require transformers, and thus require a grounding point for each one.

But if no transformers are involved, one grounding point is ok.

18 acres, even in a square, involves distances of 800 feet or more. could be twice that at least.

1000 feet and 10 amps requires a heavy wire...

allowing 5 volts drop (high), that is 1/2 Ω round trip, 1/4 each.

#4 wire is 0.25 Ω per 1000 feet, so that would do, but 1000 ft of outdoor rated 4-3 would be very expensive, specially if you had to put it in conduit.

Consult a local electrician, who would know the local regulations.