Crop Rooting Depth
Plant Rooting Characteristics
While the soil's texture impacts the amount of stored soil moisture, the plant's rooting characteristics determine how much of the soil moisture can be accessed by the plant. A deep rooted crop has access to a greater amount of soil moisture than does a shallow-rooted crop, usually allowing it to go longer between irrigations. The rooting depths of a number of crops are shown in the table below.
The rooting depth may be affected by the soil depth, constraining soil layers (hardpan, plowpan, etc.), or even abrupt changes in soil texture. When in doubt about the soil profile or rooting depth, use a soil auger or better yet a backhoe, to determine the rooting depth and soil profile textural characteristics.
Table. Depths to which the roots of mature crops will deplete the available water supply when grown in a deep permeable, well-drained soil under average conditions.
Source: Chapter 11, "Sprinkler Irrigation," Section 15, Natural Resources Conservation Service National Engineering Handbook