Nano-irrigation: Hydraulic characteristics of the line-source emitters as a function of pressure heads under different soil types and bulk densities

Abstract

The soil water discharge of line source emitters under Moistube irrigation, commonly called nano irrigation, was investigated. Moistube is a pipe made of flexible semi-permeable membranes that has recently been used in Morocco to further minimize water consumption relative to drip irrigation. Being a relatively new technology, it is still in the experimental stage, therefore, there is little data on the critical parameters that would improve the water use efficiency. Before starting the field trials to test the system on crops, a series of soil box experiments were carried out to examine the water dynamics and discharge of laterals under two soil types at different pressure heads and at different dry bulk densities. The results showed that the discharge decreased when the laterals were buried compared to non-buried laterals, and decreased further with the compaction of the soil. The laterals discharge showed a decreasing trend as the soil texture becomes finer and the discharge decreases even more with soil compaction of the tested textures. We also found that the measured discharge at 2 m pressure head for the non-buried laterals was far greater than the value declared by the manufacturer. The exponent values of the fitted power function equations were much greater than 1, showing a laminar flow regime of the laterals and high sensitivity to pressure changes. The coefficient of variation was within the acceptable range (< 20%) and decreases with increasing operating pressure. Overall, our results suggest that 1) soil texture and compaction affect the laterals discharge and should be considered in the design of nano irrigation system in terms of laterals depth and spacing, , 2) make sure to adopt a suitable design or shorten the laterals in response to their high sensitivity to pressure changes, 3) as the technology is new and is still in its experimental stage, tests that mimic field conditions are still important before installation to achieve a homogeneous laterals discharge. Our findings would provide a preliminary basis to help professionals to design the system in Morocco.

Keywords

• nano-irrigation
• moistube
• succion du sol
• débit
• hauteur manométrique
• coefficient de variation