Comparing Double Ring and Ponding Time Methods for Measuring Water Infiltration in Different Soils under Sprinkler Irrigation

Double Ring (DR) and Time of Ponding (TP) methods are two field methods for determining infiltration rate in the sprinkler irrigation system. However, the boundary conditions and the nature of the flow on the soil surface in the sprinkler irrigation system are different from the DR method. The aim of this study was to investigate the relationship between the measured infiltration intensity values with the double ring and ponding time methods in different soil textures. The first factor consisted of two methods and the second factor consisted of five soil textures in Isfahan province and the experiments were performed in three replications in the form of a factorial statistical design. The results showed that the infiltration intensity values obtained from the DR method were on average 2.7 times higher than the values determined in the TP method and the final infiltration values of the DR method were 5 times higher than those of the TP method. The difference of infiltration values was higher in the fields with coarser texture (sandy clay loam) and less in the field with clay loam texture. The maximum final infiltration rate was observed in the field with loamy sand soil texture and the minimum final infiltration rate was observed in the field with clay loam soil texture. The results indicate the need to adjust and correct the final infiltration of DR method in the design of sprinkler irrigation systems. It is suggested to use TP method to determine the infiltration velocity values for designing sprinkler irrigation systems. If DR method is used, it is recommended that the infiltration values be modified with the given development equations before application.