Agricultural Publishing Company Limited . Water is the key to high-yielding crops. Even though it sounds like a contradiction, the reason to install tile drainage is to make more water available to the roots of the crop. To understand this, you have to understand how water behaves in the soil. Soil is like a giant sponge, full of holes of different sizes.
Water drains out of the large holes very easily, but the small holes hold onto water very tightly.
As the soil begins to dry, the large pores lose their water, so more of the soil's total moisture is held in smaller holes where it is gripped more tightly. However, water won't flow from a small hole into a large one unless there is pressure from more water pushing it. A tile drain is like an extra large hole in the soil. When the ground is saturated, the pressure of the excess moisture in the soil pushes water into the tile, where it can be carried away. As the excess water drains out of the soil's large holes and into the tile, the remaining water is left in smaller holes with their tighter grip.