Effect of Azolla compost and polyacrylamide on runoff and splash erosion of a saline-sodic soil

This study was conducted in order to amend a saline-sodic soil with Azolla compost and polyacrilamide (PAM) in a laboratory experiment. A factorial design of completely randomized test with three replications was used to compare the effects of the amendments. The soil sample was collected from saline-sodic marls of hilly lands around Manjil dam. Both azolla compost and PAM were used in four rates of 0, 5, 10 and 15 ton per hectare, and 0, 25, 50 and 75 kg per hectare, respectively. Soil samples were packed in a 30×35 cm drainable detachment tray, and subjected to a rainfall intensity of 95 mm h-1for 40 minutes. The runoff rate, sediment concentration and splash erosion rate were measured during the experiments, and sodium adsorption ratio and exchangeable sodium percentage of the soil were determined after the experiment. Results showed that the best treatment for reducing sodium adsorption ratio and exchangeable sodium percentage of the the minimum application of one of the amendments (25 kg ha-1 PAM, or 5 ton ha-1 Azolla compost). For decreasing sediment concentration and rainfall erosion rate, application of 5 ton ha-1 Azolla compost was the most appropriate treatment than the other combined treatments. Runoff rate was affected only by Azolla compost, and the application of 5 ton ha-1 Azolla compost resulted in the minimum runoff. In addition to these positive effects, Azola compost as an organic material may have effective functions in improvement of vegetation cover if it used in the field.