Dirt, Sand, and Silt: The Soil Composition Quiz

If soil particles are categorized by diameter, then sand is the largest (0.05mm to 2mm). If a particle is larger, then the spaces between them are also larger. Therefore, sand is the largest of the three primary soil textures.

If clay particles are the smallest, then they pack together very tightly with tiny pore spaces. If spaces are tiny, then water molecules struggle to pass through due to friction and surface tension. Therefore, clay has the slowest drainage.

If soil is made of solid particles, then there must be gaps between those solids. If we measure the volume of those gaps relative to the total volume, then we are measuring porosity. Therefore, the statement is true.

If soil has connected pore spaces, then water can move from one gap to the next. If we measure how easily this movement happens, then we are measuring permeability. Therefore, permeability is the ability of water to flow through.

If a soil combines the drainage of sand with the nutrient retention of silt and clay, then it creates an ideal growing medium. If these three are mixed in relatively equal functional proportions, then the soil is classified as loam.

If sand particles are large and irregular, then they cannot pack tightly together. If they cannot pack tightly, then they leave large "tunnels" or pore spaces. If spaces are large, then gravity pulls water through them rapidly.

If clay has very small pore spaces and high surface area, then it holds onto water molecules tightly. If it holds onto water instead of letting it pass through, then it has high water retention. Therefore, the statement is true.

If a particle is large enough to be felt individually by human nerves, then it feels rough or gritty. If sand is the largest particle size, then it provides that specific physical sensation of grittiness.

If silt particles are mid-sized (smaller than sand), then they are too small to feel gritty but large enough to feel like a powder. If they feel like powder or flour, then the texture is described as smooth.

If organic matter acts like a sponge, then it soaks up and holds water. If you mix this "sponge" into sand (which normally drains fast), then the mixture will hold more water than sand alone. Therefore, it increases retention.

If water sits on top of the ground and then moves downward into the top layer, then it is "infiltrating" the geosphere. If this is the initial entry point of the water cycle into the soil, then the statement is true.

If soil particles are measured on a scale of size, then clay is the finest (less than 0.002mm). If it is smaller than silt and sand, then clay is the smallest particle.

If clay holds water very effectively, then the pore spaces stay filled with liquid. If the pores are full of water, then there is no room for air (oxygen). If roots cannot "breathe," then the plant may die from being waterlogged.

If silt is between sand and clay in size, then it is "mid-sized" and drains faster than clay. If it has a specific mineral structure, then it feels slippery when wet. Therefore, A, C, and D are correct.

If soil is already full of water (saturated) or has tiny pores, then new water cannot enter. If water cannot enter, then gravity pulls it across the surface instead. Therefore, saturated clay creates the most runoff.

If we look at the USDA soil size scale, then silt is 0.002mm to 0.05mm and clay is anything smaller than 0.002mm. If 0.002 is greater than the size of clay, then silt is indeed larger.

If we are concerned with how water leaves the soil system, then we are looking at the flow rate. If we measure the speed at which water moves down and away, then we are measuring drainage.

If the soil stays wet, then it has high retention and low permeability. If clay is the particle that has the lowest permeability and highest retention, then the farmer's soil is likely high in clay.

If you dig a deep hole, then you see different layers (horizons) like topsoil and subsoil. If you look at this entire vertical cross-section together, then it is called a soil profile.

If sand provides drainage, then roots won't rot. If clay and silt provide water and nutrient retention, then the plant stays fed. If loam combines these traits, then it provides the best environment for most plants.