Checkout This Groundwater Virtual Lab!
SOILS AND GROUNDWATER
Groundwater returns to the Earth's surface through these aquifers, which empty into lakes, rivers, and the oceans. As water moves it absorbs sediment and nutrients.
The soil's ability to retain water is strongly related to particle size. Clays retain more water than sand or silt, because the water molecules hold more tightly to the fine particles of a clay. Sands provide easier passage (or transmission) of water through. Clay type, organic content, and soil structure also influence soil water retention.
The maximum amount of water that a given soil can retain is called field capacity, whereas a soil so dry that plants cannot liberate the remaining moisture from the soil particles is said to be at wilting point.
"Retention of water" in soil science, refers to the amount of water the soil retains. The retention of water is due to the amount of available surface area of the soil's particles.
Given a particular sample of soil, the smaller the particle are, the larger the surface area. More surface area means more water absorbance. Water molecules hold onto the soil particle using ADHESION.
Silt - Silt has small particles and a large surface area for water molecules to adhere to. The interstitial spaces are small, yet plentiful and are large enough to house water molecules. Percolation through silt is slow, which means nutrients are able to be taken up by water and delivered to plants.
Clay - Clay has very small particles, but has almost no room for water molecules in the interstitial spaces! This means absorption is poor in clay. Since absorption is poor, water is not retained and plants don't grow well. The water molecules that are able to enter the interstitial spaces in the clay are held tightly by CAPILLARY ACTION and adhesion and percolation occurs very slowly, if at all.
Calculating the Surface Area of a Soil Sample
WHAT SOIL IS BEST?
Loam is soil mixture composed of about 40% sand, 40$ silt and 20% clay.