Effect of Water Head and Irrigation Interval on Cumulative and Lateral Infiltration in Furrow Irrigation

Infiltration is considered as one of the most important soil parameters in the design and evaluation of furrow irrigation systems. Water is infiltrated through the wetted perimeter when it reaches a given point in the furrow until it recedes. The depth of infiltrated water at a given point, therefore, is a function of opportunity time, wetted perimeter, and soil intake characteristics (Oyonarte et al., 2002). Thus, in-depth knowledge of how the initial (e.g. initial water content) and boundary conditions (such as water head and wetted perimeter) of a furrow can act on the infiltration process is essential. Previous studies show that cumulative infiltration in furrow irrigation is highly affected by the water head and initial water content. In furrow irrigation, water infiltration into the soil is two-dimensional, both vertically and laterally (Bautista et al. 2014). Gravity forces are dominant in vertical infiltration, while suction forces dominate horizontal/lateral infiltration. Suction forces largely depend on soil matric potential, which is a function of the soil texture and structure, and play an important role in soil moisture retention, sorptivity, essential for plant growth, and lateral infiltration. Knowledge of lateral infiltration and edge effect is essential for designing furrow irrigation systems because many researchers have found that more than 60% of total infiltrated water is through the side walls of furrows. Several studies have been carried out to determine how initial and boundary conditions may affect the cumulative and lateral infiltration in furrow irrigation, but the combined effect of water head and initial water content on infiltration process is not investigated yet.  Therefore, the main objective of this study is to investigate the combined effect of various initial (i.e., irrigation interval or initial water content) and boundary (i.e., water level or the wetted perimeter) conditions on the cumulative and lateral infiltration.