Respected researchers @ all I need some halp regarding my phosphate solubilizing acctivity experiment because I,m litle confuse about the measurement of this trait from the plats stick mathod actually I konw the respactive formula but still I,m confuse so how i can measure halo zone of the phosphate solubilizing activity?

(1) I have started the measurement of halo zone from the end point of Bactrial colony?

(2) I have started the halo zone measurement from center point of the bacterial colony?

(3) or I have started the halo zone measurement from both sides like one side to another side including the bacterial colony?

so can anyone know about that kindly help me and till me how I can museare it? and also give me some graphicall halo zone measurement examples for my better understanding