The effect of plastic mulch and discharge on the soil wetting pattern and water retention in drip tape irrigation

Drip tape irrigation, if designed and implemented correctly, is an effective way to increase irrigation efficiency. The present research was conducted in order to investigate the effects of plastic mulch and discharge on the soil wetting pattern dimensions and water retention from a linear source. For this purpose, an experiment in the statistical design form of random complete blocks with four treatments including two factors of application or non-application of plastic mulch and discharge (2 and 4 liters per hour) was designed in three replications. This research was carried out in farm of the Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, in a soil with silty clay loam texture. The soil wetting pattern dimensions, 24 hours after the end of irrigation were determined. The soil moisture difference between the second and fourth days after irrigation was considered as a measure of soil water retention. The soil moisture was determined after 24 and 72 hours from the end of irrigation. According to the results, with the application of the mulch, the depth, width and wetted area of the soil increased by 13.59, 20.25 and 38.54 %, respectively, compared to the non-mulched treatments, which was significant. The soil moisture difference between the second and fourth days after irrigation decreased from 1.96% in the non-mulched borders to 0.65% in the mulched borders. With the increase of discharge from 2 to 4 liters per hour, the soil wetted depth decreased from 27.22 to 23.55 cm, the soil wetted width increased from 26.72 to 31.88 cm, and the soil wetted area increased from 602.17 to 658.28 cm2, which indicates significant effect of increasing discharge on these parameters in all cases. The increase in discharge increased soil water retention, but this effect was not significant. The application of mulch has a greater effect on increasing the soil wetting pattern dimensions and water retention than the increase in discharge. Therefore, the use of plastic mulch is recommended to increase the efficiency of the drip irrigation system.