We always use it for deciding if and when we should water our fruit trees. (keep in mind that on a hot summer day 4 or 5 mm of water a day evaporated from the ground, so if it rained 50 mm, you don't need to water your trees for about 10/12 days).
Step 1: WHAT YOU NEED
_plastic bottle (conic or funnel shaped);
_stick or cane.
_scales or capacity measure for liquids;