Determining Beginning Soil Moisture for Planning Decisions

 

 

The current Drought Monitor shows 19% of Nebraska in the “abnormally dry” or “moderate drought” categories and in the shadow of massive drought in Kansas (97%) and Colorado (88%). Being curious about beginning soil moisture in non-irrigated situations, we installed Watermark soil moisture sensors in six non-irrigated, no-till locations in Webster, Nuckolls, Thayer, and Clay counties.

 

 

This sensor information can be helpful as growers make planning and planting decisions. Granted, most planting decisions have already been made with inputs already purchased. Spring rains are also typically expected. However, information like this can help a grower be flexible in that planning should anticipated rains not be timely.

A grower may choose to not terminate a growing cover crop such as rye, instead growing it for feed.

 

 

 

Soil moisture sensors were installed at 1-, 2-, 3-, and 4-foot depths in non-irrigated, no-till corn and soybean stubble fields near Byron, Superior, Lawrence, Bladen, and Clay Center (Figure 2). The sensors were connected to Watermark dataloggers from the Irrometer company. Because the default soil temperature on the dataloggers is 70°F, a temperature sensor is also installed to ensure correct calibration of the soil moisture. Any farmer or crop consultant could do the same for his/her fields to determine the same information and wouldn’t need the datalogger.

 

Taking weekly readings at the same time each week, or even better, daily at the same time, would also give one an idea of beginning soil moisture. It’s best to allow at least 48 hours for the sensors to equilibrate to the current soil moisture conditions. This process is essentially the same as when sensors are installed for irrigation scheduling. The difference is these are non-irrigated fields with no current crop growing. For additional information and videos on using watermark sensors, please see the Nebraska Agricultural Water Management Network website.

 

 

Nuckolls County is shown as in “moderate drought” on the Drought Monitor. At the Superior location, we were hoping to also install into actively growing rye and winter-killed forage to determine beginning soil moisture in those conditions. The rye is currently 6 inches tall in the tillering stage and the soil probe wouldn’t go in the ground beyond 6 inches, so no moisture sensors were installed. The soil probe would only go in 12 inches in the winter-killed forage consisting of sorghum-sudan and radishes; thus, soil moisture sensors weren’t installed in that field either.

 

 

During installation, the 3- and 4-foot depths at all locations (except only the 4-foot depth at Clay Center), were very dry. The soybean stubble appeared drier than corn stubble. Two sites are located near Lawrence, one in corn stubble and one in soybean stubble across the road from each other. That data shows the differences in moisture between different residue types the most clearly. We were unable to install to the 4-foot depth at the Lawrence soybean stubble location. At most other sites, a hammer was used to help install to 4 feet. However, despite the difficulty in installing the 4-foot sensor, these graphs do not show them as dry or drier than the 3-foot at any location other than Bladen.

 

We don’t have a good explanation for that at this time. Data will continue to be collected until each field is planted and the results will be posted weekly at http://jenreesources.com. Additional information regarding each location is in each figure caption.