Soil Moisture Determination

Soil moisture level is an important consideration when assessing field conditions for manure application or irrigation. Different crops require different optimal soil moisture for optimal growth. Soil moisture is also an indicator of potential runoff from the field surface. If a field is saturated, no additional moisture infiltration can occur, whether that be precipitation, irrigation water, or manure.

Soil moisture can be determined using probes, buried gypsum blocks, drying methods, or by hand. The most accurate is with probes or equipment installed in your field. The quickest way is with your hands, although this requires some practice.

When determining soil moisture levels by hand, use the following table.
  1. Know your soil type. This information can be found in the Maps section of your DNMP. If it is not available, there are apps and online programs (Soil Web Survey) that can help you determine your soil type.
  2. Pick an area that is representative of the entire field. Don't pick low or high spots, compacted areas, areas devoid of vegetation, or otherwise unless they are representative of the majority of the field.
  3. Kick off the top surface vegetation layer to expose the soil. Measure the soil moisture from the top 6 inches of the soil profile. To do this, loosen the soil with a trowel if necessary.
  4. Take a representative handful and gently squeeze it into a ball in your hand. Follow the descriptive guidelines on the following table to determine the soil moisture %. This might take some practice, so having a method of verification (soil moisture determination equipment) the first few times is recommended.
  5. Replication of this process is recommended at multiple locations in each field for best accuracy.
For great information and graphics on soil moisture determination, check out the NRCS printable guide: Estimating Soil Moisture by Feel and Appearance (PDF).

Available Moisture in the Soil

Sands and Loamy Sands

Sandy Loam and Fine Sandy Loam

Very Fine Sandy Loam, Loam, Silt Loam, Silty Clay Loam, Clay Loam, Sandy Clay Loam

Sandy Clay, Silty Clay, Clay

< 25% Soil Moisture

Dry, loose and single-grained; flows through fingers.

Dry and loose; flows through fingers.

Powdery dry; in some places slightly crusted but breaks down easily into powder.

Hard, baked and cracked; has loose crumbs on surface in some places.

25-50% Soil Moisture

Appears to be dry; does not form a ball under pressure.

Appears to be dry; does not form a ball under pressure.

Somewhat crumbly but holds together under pressure.

Somewhat pliable; balls under pressure.

50 - 75 % Soil Moisture

Appears to be dry; does not form a ball under pressure.

Balls under pressure but seldom holds together.

Forms a ball under pressure; somewhat plastic; slicks slightly under pressure.

Forms a ball; ribbons out between thumb and forefinger.

>75% Soil Moisture

Sticks together slightly; may form a weak ball under pressure.

Forms a weak ball that breaks easily, does not stick.

Forms ball; very pliable; slicks readily if relatively high in clay.

Ribbons out between fingers easily; has a slick feeling.

100% Field Capacity

On squeezing, no free water appears on soil, but wet outline of ball on hand.

On squeezing, no free water appears on soil, but wet outline of ball on hand.

On squeezing, no free water appears on soil, but wet outline of ball on hand.

On squeezing, no free water appears on soil, but wet outline of ball on hand.

Above Field Capacity

Free water appears when soil is bounced in hand.

Free water is released with kneading.

Free water can be squeezed out.

Puddles: free water forms on surface.