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).