Diffusion pattern of injected liquid under the soil and the impact of aeration on it

Injecting Liquid fertilizers in trees root zone is one of the fertilizing methods that can be implemented either after air injection (aeration) or directly without aeration. This study focused on diffusion pattern of the liquid injected directly or after aeration under the soil in both dry and wet soils. To apply treatments associated with aeration, the compressed air was primarily injected for 3 seconds followed by injecting liquid for a certain time, whereas for direct liquid injection no air was applied into the soil. The applied liquid was made of water and mineral dyes to contrast the soil color. The soil was excavated in the vicinity of injection point and the area of diffused dyed particles was measured in different treatments. The results showed that diffusion rate in wet soil was significantly higher than that of dry soil but aeration before liquid injection had no significant effect on the liquid diffusion rate.  In wet soil, applying the air pressure upheaves the soil layer above the injection point and by cutting the pressure the soil subsides on its original point. The injected liquid flows horizontally into the fractures developed below the upheaved layer. In direct injection in wet soil, the liquid pressure itself was still adequate to upheave the top layer and the liquid flew horizontally below the top layer. In dry soil, on the contrary, due to high shear strength of soil, no upheaving occurred in both injection treatments and the injected liquid was restrained in close vicinity of injection point