Published on Wednesday, February 01, 2017
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Soil Temperature During the Growing Season
When it came to soil temperature, changes at both the 8 in and 16 in. depths were sporadic. Averages were calculated before and after June 20 to compare the soil temperatures after the irrigation water was turned on. At the 8 in. depth in the irrigated portion, the control had the highest overall temperature (Figure 1). The control was up to 9.0°F warmer compared to other treatments. At an 8 in. depth, drip-irrigated (tile/no tile), sub-irrigated (sensor/no sensor), and the water table control averaged 75.0°, 74.4° and 73.6°F, respectively. However, the non-irrigated treatments such as the control, contour tile, and 30 ft. tile averaged 78.4°, 74.6° and 76.8°F at the 8 in. depth, respectively.
Figure 1. CropX LLC. 8 in. soil temperatures from the irrigation portion of Beck’s water management study.
As we moved deeper into the soil profile, the 30 ft. tile had the warmest soil temperatures at the 16 in. depth (Figure 2). Soil temperatures in 30 ft. tile were up to 13°F warmer compared to other treatments. At a 16 in. depth, drip-irrigated (tile/no tile), sub-irrigated (sensor/no sensor) and the water table control averaged 73.4, 74.4 and 72.1 °F, respectively. The non-irrigated portions such as the control, the contour tile, and the 30 ft. tile averaged 74.5, 75.1 and 79.3 °F at the 16 in. depth, respectively. Overall, soil temperatures were cooler at both the 8 in. and 16 in. depths when irrigation was used. So why was the soil with 30 ft. tile so much warmer when compared to other non-irrigated treatments? One possibility could be the reduction in upper soil moisture. Moisture acts as a buffer to air temperature which can keep soil temperatures cooler. The 30 ft. tile averaged a 13% VWC reduction in soil moisture compared to irrigated treatments at the 8 in. depth. This reduction could explain why 30 ft. tile had the greatest 16 in. soil temperature.
Figure 2. 16 in. soil temperatures from the irrigation portion of Beck’s water management study.
Across treatments, soil temperatures in the tile spacing study had less variation compared to the irrigation study. Soil temperatures never varied greater than 4°F in the tile spacing study across treatments at both the 8 in. and 16 in. depths (Figures 3 and 4). Overall, soil temperatures were slightly warmer over the tile lines compared to between the soil lines. In the irrigation portion of the trial, we experienced a greater variation in temperature compared to non-irrigated treatment. At the 8 in. depth in 15 ft. and 60 ft., tile spacing averaged 75.3°F. At the 16 in. depth, the 15 ft. and 60 ft. soil temperatures averaged 74.1° and 73.9°F, respectively. Soil temperatures between the tile were lower compared to over the tile. Averaged across the summer soil temperatures, in between the tile was 0.2 to 0.9°F cooler compared to over the tile. This could possibly be explained by the upper soil moisture differences. Between the tile lines had greater upper soil moisture which were slower to warm up.
Figure 3. CropX LLC. 8 in. soil temperatures from the tile spacing portion of Beck’s water management study.
Figure 4. 16 in. soil temperatures from the tile spacing portion of Beck’s water management study.
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Author: Joe Bolte
Categories: PFR, PFR Reports
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