The amount of shell sand in soil affects its physical properties and salt levels when exposed to simulated rainfall. By changing the ratio of shell sand to fluvo-aquic soil, researchers found that soil composition and salt ion levels changed. Decreasing shell sand content led to increased soil density and porosity, as well as changes in pH and electrical conductivity. Salt ions like Cl-, NO3-, Na+, Ca2+, and Mg2+ also varied with shell sand content. A 1:1 ratio of shell sand to soil showed the most significant improvement in soil quality, enhancing water storage and reducing salt levels. The right amount of shell sand can improve soil water retention and salt control.