Investigating the effects of cow manure, vermicompost and Azolla fertilizers on hydraulic properties of saline-sodic soils

Purpose Soil salinity and sodicity are among the factors involved in soil degradation, especially in arid and semi-arid areas of the world. The use of modifiers, including organic matters, can be considered as an appropriate strategy to improve the fertility of saline-sodic soils.  Method In this study, saline-sodic control soil was collected from Karaj and mixed with three levels of 1%, 3% and 5% of cow manure, vermicompost and Azolla. The soil columns were then incubated at 20 °C and field capacity moisture for 5 months. The physical and chemical properties of the treatments were evaluated before and after incubation. Results After the incubation period, the lowest salinity level was observed in 5% Azolla and vermicompost treatments. The highest amount of change in sodium absorption ratio was related to 5% cow manure treatment. There was an insignificant difference in moisture levels in a given suction among the different treatments. After the incubation period, salinity and sodium absorption decreased and increased in most of the treatments, respectively. Moreover, the decrease of saturation dehydration coefficient in the treatments revealed the disruption of soil structure and conversion of large pores to fine grains as a result of adding the mentioned organic matters. Conclusion According to the results, cow manure at 1% level had no significant effect on soil properties. However, at higher levels, it had a negative effect on quality and conditions of the saline-sodic soil in terms of physical and chemical properties. In contrast, Azolla and vermicompost fertilizers at 5% proved to be suitable for correcting the saline-sodic soil.