When implementing the crop root depth or the management allowable deficit
suggestions, please remember that all soils are different. Tillage, previous history, organic matter content, degree of aggregation, soil structure, compaction, soil chemistry, and existing ground cover, not to mention the large amount of spatial variability that is typically present all effect the soil's water holding capacity
. These are rough estimates. Your soil may have the same texture and be substantially different.
All numbers are rough estimates. Different crop varieties will have different rooting depths and drought tolerance. The rooting depth is also effected by soil type, irrigation management and history, and the soil depth to restrictive layers such as bedrock, plow pan, high water table, or compaction layer. Use own experience and variety-specific data if available.
Crop Root Zone Depths
Rooting Depth and Management Allowable Deficit
Reference: Washington State University