Teaching Organic Farming and Gardening

26 | Unit 2.1
Soil Physical Properties

soil texture Decision chart

Demonstration 1

This chart works fairly well in soils with mixed clay mineralogy. Soils with high amounts of 2:1

clays (smectite) will make longer ribbons. Soils with high amounts of 1:1 clays (kaolinite) will

make shorter ribbons. These texture names are not used in high ash soils.

start

Place about 2 tablespoons of soil in palm of hand. Add

water dropwise and knead the soil to break down all

its aggregates. Soil is at the proper consistency when

plastic and moldable, like moist putty.

→

Add dry soil to

soak up water

→

Does soil remain in a

ball when squeezed?

Is soil too dry?

→

→ Is soil too wet?

→

n n

Y Y

→

n sanD

Place ball of soil between thumb and forefinger, gently pushing the soil with the

thumb, squeezing it upward into a ribbon. Form a ribbon of uniform thickness and

width. Allow the ribbon to emerge and extend over the forefinger, breaking under its

own weight.

→

Y

→

Does soil form a ribbon?

loaMY n

sanD

→

→

Y

Does soil make a weak

ribbon less than 1 inch

long before breaking?

Does soil make a medium

ribbon 1–2 inches ong

before breaking?

n Does soil make a strong

ribbon more than 2 inches

long before breaking?

n

Y

→

Excessively wet a small amount of soil in palm and rub with forefinger.

→

Y

→

Y

→

Does soil feel

very gritty?

sanDY

loaM

→

Does soil feel

very smooth?

→

Neither gritti-

ness nor

smoothness

predominates

sIlt

loaM

loaM

Y

Y

Y

n

n

→

Does soil feel

very gritty?

sanDY

claY

loaM

→

Does soil feel

very smooth?

→

sIltY

claY

loaM

claY

loaM

Y

Y

Y

n

n

→

Does soil feel

very gritty?

sanDY

claY

→

Does soil feel

very smooth?

→

sIltY

claY

claY

Y

Y

Y

n

n

Neither gritti-

ness nor

smoothness

predominates

Neither gritti-

ness nor

smoothness

predominates

→ →

→ → →

→

→

→

→

→

→

→