The maximum rooting depth of crops in North Carolina is usually less than their potential rooting depth and is restricted by soil chemical or physical barriers. North Carolina subsoils have a pH of about 4.5 to 5.0, which presents a chemical barrier to root growth, as shown in Figure 11. Liming practices rarely improve soil pH below the 2-foot depth. Thus, for example, while corn has a potential rooting depth of 4 feet, when grown under North Carolina conditions, its maximum rooting depth is about 2 feet. Maximum rooting depths for several crops under North Carolina conditions are given in Table 2.
Soil properties that influence the plant's rooting depth.
The effective root depth is the depth that should be used to compute the volume of PAW in the soil reservoir. The effective root depth for a mature root zone is estimated to be one-half the maximum rooting depth listed in Table 2. Effective root depth is further influenced by the stage of crop development. Effective root depths for most aops inaease as top growth inaeases until the reproductive stage is reached. After this time, effective root depth remains fairly constant.