|AKUOKO, OHENE - Iowa State University|
|KOOL, DILIA - Iowa State University|
|Sauer, Thomas - Tom|
|HORTON, ROBERT - Iowa State University|
Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2018
Publication Date: 9/13/2018
Publication URL: https://handle.nal.usda.gov/10113/6472456
Citation: Akuoko, O., Kool, D., Sauer, T.J., Horton, R. 2018. Surface energy balance partitioning in tilled bare soils. Agricultural and Environmental Letters. 3:180039. https://doi.org/10.2134/ael2018.07.0039.
Interpretive Summary: Soil layers can be loose or dense. Tillage tends to loosen up soil layers but, after time, the soil becomes more dense again. Rainfall and the weight of the soil itself cause tilled soil to become dense. A common assumption is that these changes in soil density don't have a large effect on water and heat movement in the soil. In this study evaporation and heat flow were measured in soils after they were left untilled or with time after tillage. The results indicate that there is more evaporation from the tilled soil soon after tillage but that later, the evaporation is less than for the untilled soil. These findings indicate that knowing how the soil density changes is important to understanding energy flow in surface soils. The results are of interest to scientists interested in improving the accuracy of simulation models to predict tillage effects on soil properties.
Technical Abstract: Surface energy balance (SEB) partitioning is critical to heat and water budgets at the soil-atmosphere interface. Tillage can alter SEB partitioning by initially decreasing bulk density (BD), after which BD increases with time due to rainfall events and other factors. SEB partitioning determined by models or measurements is usually based on the assumption of constant surface soil BD. The objective of this study is to determine the effect of soil BD changes on SEB partitioning. SEB components were measured for two 4-day periods (Period 1 and Period 2) at a less recently-tilled (T1) and more recently-tilled bare soil site (T2). During Period 1, T1 and T2 had no differences in BD, net radiation, or soil heat flux, but evaporation was larger at T2. During Period 2, BD was 0.11 g cm-3 larger at T2 than T1. This resulted in a 7% larger partitioning of net radiation to soil heat flux at T2, which in turn caused 13% less evaporation at T2. The results of this research highlight the importance of considering dynamic soil BD measurements with time when determining SEB partitioning.