Hurst Farm Supply Blog

Soil Moisture: When to Irrigate & When Not to Irrigate

Posted by Hurst Farm Supply on Sep 1, 2020 9:29:11 AM
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When it comes to monitoring soil moisture conditions, we think a “hands-on” approach is best!

Introducing the “feel and appearance” method, which consists of gathering physical samples of the soil on your land, firming them with your hand, and using your observations to estimate the amount of moisture that is available for your crops.

Here’s how it works.

1. Determine Your Soil Type

Different soils hold different amounts of moisture — plain and simple. If you’re unsure about the types of soil you’re working with, consult the U.S. Department of Agriculture-Soil Conservation Service County Soil Survey, copies of which are available at your local USDA-SCS offices, USDA-ASCS offices, county extension offices, and county and public libraries.

Additional information can be found in the pocket-sized soil moisture guides that are available at the Water District and Soil Conservation Service county and district offices.

2. Gather Samples

Now that you understand the type of soil that you’re working with, the collection can begin. Using the proper tools (soil augers, soil sampling tubes, spades, and shovels), take samples at one-foot depth intervals in the plant root zone (usually to a depth of four feet) in three different locations.

Measuring from one end of the field to the other, the first sample should be collected at one-fourth of the way across the field, the second at half way, and the third at three-fourths of the way across the field.

3. Analyze Samples

Firm your samples in your hand and observe the different ways that varying amounts of moisture cause them to react and appear. Compare their appearance to the visual resources provided to indicate soil moisture content and record your observations.

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4. Do the Math

After you’ve made and recorded your observations, add the total amount of water available in inches for all sites then divide that number by the total number of sites evaluated, which will give you the field average of the soil moisture available at the date the samples were collected.

Then, to obtain an estimate of the quantity of water that needs to be added to bring the soil to field capacity in the soil root zone area, subtract the field average from the soil’s total available water holding capacity.

5. Determine Dates

Finally, use the amount of soil moisture found in the upper two feet of the root zone area to determine the date to begin irrigation and the amount of water needed. As a good rule of thumb, you should start irrigation before the soil moisture level in that area falls below 50% available moisture. It should be completed before it falls below 25%.

The “feel and appearance” method is a great way to determine when and when not to irrigate, but the truth is, irrigation isn’t always a flawless science. For more helpful resources regarding this process (and any others on the farm), get in touch with the team at your nearest Hurst Farm Supply location. Click below to find contact info!

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Topics: Harvest