Measure plant pot amperage production
I think he wants to measure the resistance of the soil. I saw many projects (I was a science fair judge) that did it with an ohm meter or variation thereof. They would have several samples of soil and add nutrients to it, generally with water. Salt was the best conductor. Similar tests were performed using Ph as the measurement. An Ohm meter passes a current through the DUT (Device Under Test) and measures the voltage drop to determine resistance, maybe that is where amperage came from. I am guessing this is maybe about a seventh grade project. More information always helps.