Development and validation of a model for soil wetting geometry under Moistube Irrigation

Area of Science:

• Agricultural Engineering
• Soil Science
• Hydrology

Background:

• Moistube Irrigation (MTI) utilizes semi-permeable porous walls for line source irrigation.
• Understanding soil water movement is crucial for optimizing irrigation efficiency.
• Soil hydraulic properties significantly influence water distribution patterns.

Purpose of the Study:

• To develop an empirical soil wetting geometry model for Moistube Irrigation (MTI).
• To simulate vertical and lateral soil water movement under MTI using the Buckingham pi theorem.
• To investigate the influence of soil hydraulic properties on MTI performance.

Main Methods:

• Developed an empirical model based on the Buckingham pi theorem.
• Conducted two experiments to calibrate and validate the model in silty clay loam and coarse sand soils.
• Measured soil water content using MPS-2 sensors over 100 hours with MTI placed at 0.2 m depth and 150 kPa pressure.

Main Results:

• Model calibration confirmed soil texture influences water movement (p < 0.05).
• The model showed good fit for wetted widths and depths (R² = 0.5-10%, R² = 0.50, d-index = 0.50).
• Percentage bias indicated underestimation of wetted depth after 24h (21.9% for silty clay loam, 3.9% for sandy soil).

Conclusions:

• The developed models are applicable for estimating wetted distances under specific MTI conditions (0.2 m depth, 150 kPa).
• Models are prescriptive and validated for the developed conditions; further field validation is recommended.
• MTI wetting geometry data can inform optimal placement depth for efficient irrigation water use.