The effect of long-term drip irrigation and polyacrylamide application on soil water repellency in the quince orchard garden

Hydrophobic and wettability are important physical characteristics that have a great impact on soil hydraulic properties. On the other hand, hydraulic characteristics of the soil under the dripper are effective on the geometry wetting and subsequent plant growth and yield. Water repellency was reduced by surfactants. Little research showed that polyacrylamide (PAM) is reduces the soil water repellency. This study was conducted to investigate the PAM effects on variability of soil water repellency and wettability in drip irrigation system in quince orchard garden.
The experimental design was complete random block design in a split-plot form with "irrigation period of drip irrigation system" as main plots and PAM concentrations as subplots, with three replications. Main plots treatments consisted of control (uncultivated), 8 and 15 years old, and subplots treatments consisted of 0 (control), 10 and 20 mg l−1 PAM. Different concentrations of PAM were prepared inside an injection tank. At the irrigation time, experimental plots (except control) were irrigated with the PAM solutions where the water volume was similar for all orchard trees. A week after applying the PAM, the soil samples were taken from 0−30, 30−60 and 60−90 cm depths under the emitters. Water repellency index (WRI) was determined by a tension micro-infiltrometer according to intrinsic sorptivity method in the laboratory.
Results showed that the effect of irrigation period of drip irrigation system and PAM on water repellency index and water-soil contact angle () were highly significant (p The results showed that the period of drip irrigation system significantly increases the water repellency and soil-water contact angle and decreases the water uptake, especially in 0-30 cm soil layer. The application of PAM significantly reduces soil water repellency and soil-water contact angle and increases water uptake. Wetting and drying and soil organic matter under the dripper can increase the soil hydrophobicity in the garden that application of 20 mg L-1 PAM in drip irrigation systems significantly reduces soil water repellency.