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SOIL TEXTURE�PREPARED BY: REWARD C. BULAY-OG�9/8/2025

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OBJECTIVES:

Identify and describe the different soil particle sizes (sand, silt, and clay) and their physical characteristics.
Classify soils using the Soil Texture Triangle into the 12 soil texture classes based on the proportion of sand, silt, and clay.
Analyze the relationship between soil texture, water movement, nutrient availability, and crop suitability through observation and computation activities.

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SOIL TEXTURE

Soil Texture
Soil texture refers to the relative proportion of sand, silt, and clay particles in a soil sample. These particles differ in size:

Sand – the largest particles; gritty, improves drainage and aeration.

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SOIL TEXTURE

Silt – medium-sized; smooth, holds water better than sand.

Silt – medium-sized particles

Size: Silt particles are smaller than sand but larger than clay (0.002–0.05 mm).

Feel: If you rub silt between your fingers, it feels smooth or floury (like baby powder).

Water holding: Because the particles are smaller, they fit more closely together, leaving smaller pores than sand.

This means silt holds water better than sand, but it doesn’t drain as fast.

Aeration: Since pores are smaller, there’s less air movement compared to sandy soil.

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Why does this matter?

Silt-rich soils are good at storing water for plants, but if there’s too much, they can become compacted and reduce root breathing.

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Analogy

Imagine a jar filled with sugar grains (medium-sized). Water doesn’t drain as quickly as with marbles (sand) but doesn’t stay stuck like in flour (clay).

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SOIL TEXTURE

Clay – the smallest particles; sticky when wet, has a high ability to hold water and nutrients.

Clay – the smallest particles

Size: Clay particles are tiny (less than 0.002 mm). You cannot see individual clay particles with the naked eye.

Feel: When wet, clay feels sticky and plastic-like (you can mold it). When dry, it becomes hard and compact.

Pores: Because the particles are so small, they pack tightly together, leaving very tiny pores.

Water moves very slowly → poor drainage.

But clay can hold a lot of water and nutrients → very fertile if managed well.

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Why does this matter?

Clay soils can store nutrients (like potassium, calcium, and magnesium) much better than sand or silt.

However, if too wet, they become waterlogged; if too dry, they harden and crack — both can stress plants.

Analogy

Imagine a jar filled with flour. When you pour water in, it stays trapped and doesn’t drain quickly. That’s like clay soil holding water.

Examples in farming

Crops that can tolerate wet conditions grow well in clay, such as rice, lotus, and some grasses.

With good management (plowing, adding organic matter), clay can also grow sugarcane, wheat, and maize.

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The soil texture triangle is used to classify soil into 12 texture classes (such as sandy loam, clay loam, or silt loam) based on the percentage of sand, silt, and clay.

Soil texture strongly affects:

Water movement and retention (sandy soils drain quickly, clay soils hold more water).
Nutrient availability (clay-rich soils retain nutrients better).
Root growth and farming practices (loamy soils are considered best for crops because they balance sand, silt, and clay).

1. Water Movement and Retention

Sandy soils:

Large particles = big spaces (pores) between them.

Water drains quickly → soil dries out fast.

Farmers need to water sandy soils more often.

Example crops: carrots, peanuts, watermelon (they like dry, loose soil).

Clay soils:

Tiny particles = very small spaces.

Water drains slowly → soil stays wet for a long time.

Can cause waterlogging (too much water around roots).

Example crops: rice, lotus (they thrive in water).

Loamy soils:

Balanced mix of sand, silt, and clay.

Hold enough water for plants but still drain well.

Example crops: corn, wheat, vegetables.

2. Nutrient Availability

Sandy soils Are Poor at holding nutrients, which means fertilizers wash away easily.

Clay soils Are Excellent at holding nutrients due to their tiny particles and negative charges that attract nutrients.

Silt and Loam: Medium to high nutrient availability, making them fertile for most crops.

💡 Farmers often add organic matter (compost, manure) to sandy soils to improve nutrient and water retention.

3. Root Growth and Farming Practices

Sandy soils: Roots can grow deep because the soil is loose.

Clay soils: Roots may struggle in compacted clay, especially when it’s dry and hard.

Loamy soils: Provide the best conditions — not too hard, not too loose, and plenty of nutrients.

💡 That’s why loam is called the “farmer’s gold” — it’s ideal for most crops.

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✅ Summary for students:

Soil texture determines how water moves, how nutrients are stored, and how roots grow.

Sand = good air, poor water/nutrients.

Clay = holds water/nutrients, poor drainage.

Loam = best balance → best for farming.

In short, soil texture helps us understand how soil behaves and is a key factor in agriculture, gardening, and environmental science.

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12 SOIL TEXTURE CLASSES

Soil Texture Class	Composition (approx.)	Key Characteristics	Examples of Suitable Crops/Uses
Sand	≥85% sand, little silt & clay	Gritty, drains fast, low nutrients	Carrots, peanuts, watermelon
Loamy Sand	70–90% sand, small silt & clay	Slightly more water-holding than sand	Potatoes, lettuce
Sandy Loam	50–70% sand, 20–30% silt, 10–20% clay	Gritty, good drainage & fertility	Corn, squash, tomatoes
Loam	~40% sand, 40% silt, 20% clay	Ideal mix, “farmer’s gold”	Wheat, rice, vegetables
Silt Loam	50–80% silt, less sand & clay	Smooth, holds water well, poor drainage	Rice, soybeans, alfalfa
Silt	≥80% silt	Smooth, slippery when wet, compacts easily	Rice, wetland plants
Sandy Clay Loam	45–65% sand, 20–35% clay, little silt	Heavy but drains better than pure clay	Sorghum, cotton
Clay Loam	25–40% clay, balance of sand & silt	Dense, sticky, fertile	Corn, wheat, sugarcane
Silty Clay Loam	35–55% clay, more silt than sand	Holds water well, prone to waterlogging	Rice, pasture grasses
Sandy Clay	35–55% clay, more sand than silt	Heavy, less sticky than silty clay	Legumes, fruit trees
Silty Clay	40–60% clay, more silt than sand	Sticky, smooth, compacting	Rice, wetland crops
Clay	≥40% clay	Dense, sticky, high nutrient retention, poor drainage	Rice, lotus, wetland plants

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DOS IN THE LABORATORY

Listen carefully to your teacher’s instructions before starting.
Wear proper safety gear (lab gown, gloves, goggles if needed).
Handle equipment with care and use them only for their intended purpose.
Label samples and chemicals properly to avoid confusion.
Dispose of waste materials in the correct container.
Report accidents or spills immediately to the teacher.
Keep your workspace clean and organized.
Wash your hands thoroughly after completing the experiment.

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DON’TS IN THE LABORATORY

Do not eat, drink, or chew gum inside the lab.
Do not run, shout, or play around while in the laboratory.
Do not touch equipment or chemicals without permission.
Do not leave experiments unattended.
Do not ignore safety rules or warning signs.
Do not clutter your lab table with unnecessary things.

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MATERIALS

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PROCEDURE

Prepare all the materials needed for the water flow and absorption test intended for soil and water relationship activities.
Fill the empty cup with soil.
125 ml of water is poured into each type of soil.
Observe the flaw in the water inside the cup.
Record the flow of water in the soil
2nd trial: repeat the process with the same soil and observe.

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PURPOSE OF THE ACTIVITY

See how soil texture affects water holding capacity and permeability.
Understand which soils are best for crops and plant growth.
Learn the relationship between soil structure and water movement in nature.
Apply this knowledge in agriculture, gardening, and environmental management.

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EXAMPLE PROBLEM: SOIL TEXTURE COMPUTATION

Given (Laboratory Data):

A soil sample was dried and separated into its components:

Mass of Sand = 200 g

Mass of Silt = 150 g

Mass of Clay = 100 g

What to Find:

The percentage of Sand, Silt, and Clay.
The soil texture classification using the soil texture triangle.

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EXAMPLE PROBLEM 2: SOIL TEXTURE COMPUTATION

Given (Laboratory Data):

A soil sample was dried and separated into its components:

Mass of Sand = 300 g

Mass of Silt = 100 g

Mass of Clay = 100 g

What to Find:

The percentage of Sand, Silt, and Clay

The soil texture classification