"Effective":

A. Can hit the local 2m repeater.
B. Can work all states on 2m.
C. Can work moonbounce.
D. Can work weak stations via moonbounce.
E. Can make HF contacts with my kW rig.
F. Can make HF contacts with my 100 watt rig.
G. Can make HF contacts with my 5 watt rig.
H. Can make HF contacts with my 100 mW rig.
I. Can work some DX on HF.
J. Can work DX on all HF bands.
K. Can break pileups on rare DX stations.
L. Can create pileups of rare DX stations every time I transmit.
M. Can create pileups of rare DX stations every time I transmit with my
100 mW rig.
N. Can win major DX contests with ease.
O. Can have the loudest signal on 160 meters.
.. . . .

Then there's "optimum". . .

Roy Lewallen, W7EL

John wrote:
What's the minimum sized lot for an effective amateur radio antenna farm?
What's average and optimum?

73 de John, ks4xn