Monitoring Soil Moisture
Minnesota Department of Agriculture will be assisting us with monitoring the soil moisture at the demonstration site.
Summary of soil moisture monitoring information
January 20, 2023, Jeppe Kjaersgaard
Soil moisture content is measured continuously using permanently installed soil moisture sensors at 14 and 24 inches below the ground surface. A sensor pair is installed in all treatments, resulting in a total of 12 soil moisture sensors in the field (6 plots with two sensors each). The depths were selected to be below the tillage depth in the conventional tilled plots. While the reduced till and the no-till plots are not tilled to this depth, the sensors were placed at the same depth in all plots to allow for a direct comparison across the treatments.
The sensors are placed slightly off-center within the six plots thereby being located adjacent to other measurements but not impacted by soil sampling activities taking place in the field.
The soil moisture sensors were installed on April 21, 2021, and measurement collection started immediately after installation. Soil moisture information was collected throughout the first growing season through October where animals chewed through the cables connecting the sensors to the data logger, disrupting the measurements. The cables were repaired using specialized repair kits in June of 2022 and data collection resumed at that time.
At this time, there are no clear trends or patterns in soil moisture dynamics among the treatments. This is primarily due to the timeseries of data is not yet long enough to distinguish between impacts of antecedent soil properties and treatment effects. It is our expectation that differences among the treatments will become clearer towards year 4 and 5 of the study period.
An example of the soil moisture information being collected is shown in Figure 1 below with the volumetric water content at 14 and 24 inches averaged across all treatments for the 2021 corn crop. Overall, the soil water content is higher at 24 inches compared to at 14 inches. Both curves show a change of approximately 0.14 in3/in3 of water content between when the soil is at near saturation around when the sensors were installed and late August when crop water use was at its highest and the soil moisture was getting depleted. Assuming a rooting depth of 4 feet, this means the soil provided about (0.14 in/in x 48 in) 6.7 inches of soil moisture for the crop. The total corn water use for the growing season was about 16 – 18 inches. The 2021 growing season precipitation was 10.5 inches, however only 4 inches of rainfall was recorded through pollination with the rest falling during grain fill. As a result, while the precipitation for the growing season as a whole was near sufficient to meet crop needs, dry conditions during tasseling and early grain fill likely decreased yield.
Figure 1. Volumetric water content observed at 14- and 24- inch depth across all treatments during the 2021 growing season.
