Depth Development of Roots with Time: An Empirical Description

PROPER irrigation scheduling requires information about the increase in rooting depth with time. This paper reviews the depth development of roots of 48 crop species by analyzing 135 reported field observations under generally favorable environmental conditions. In all cases, the time course of rooting depth followed a sigmoidal pattern. All data could be fitted to a single sine function when plotted on a normalized scale. This equation can be rearranged to calculate actual rooting depth as a function of time. It requires an estimate of the time needed by the crop to reach maturity and the maximum rooting depth to be achieved. Rooting depth data from the literature search were compiled into a table that presents the maximum rooting depth for 55 plant species.