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

Purpose Soil salinity and sodicity are two of the causes of soil degradation, especially in arid and semi-arid regions of the world. The use of modifiers, including organic matter, can often be an appropriate strategy to improve fertility of saline-sodic soils. Methods 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. Treatments were then incubated for 5 months at 20°C and field capacity moisture. The physical and the chemical properties of the treatments were evaluated before and after incubation. Results After the incubation period, 5% Azolla and vermicompost treatments were at the lowest salinity level. The highest amplitude of changes in sodium absorption ratio was related to 5% cow manure treatment. There was little difference between the amounts of moisture in a given suction in different treatments. After the incubation period, salinity decreased and sodium absorption increased in most treatments. Subsequently, we observed a decrease in the saturation dehydration coefficient in the treatments, indicating a disruption of soil structure and conversion of large pores to fine grains, which is one of the effects of adding these organic substances. Conclusion According to the findings, cow manure at 1% level had almost no effect on soil properties and at higher levels caused a decrease in the quality and conditions of saline-sodium soil in terms of physical and chemical properties. Whereas, Azolla fertilizer and vermicompost fertilizer at 5% level can be suitable for correcting saline-sodic soil.