... agricultural field and classroom experimentsOperating Temp: 5-50C (41-122 Degrees Fahrenheit)Calibration: Remove oxidation from metal rings by light phlishing.Great ... . Remove any obstruction to the soil that requires testiong, such as surface soil, grass, leaves, pebbles, etc.If the soil ... sprinkle some water onto the soil and leave for 25-30 minutes before testing.2. Before using the tester, be sure ...