Surface Energy Balance Partitioning in Tilled Bare Soils

Core Ideas: Following tillage, soil bulk density increased after rainfall. Increases in soil bulk density decreased the available energy for turbulent fluxes. Surface energy balances in tilled soils are affected by changes in bulk density. 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 soil bulk density (ρ_b), after which ρ_b increases with time due to rainfall and other factors. The objective of this study is to determine the effect of ρ_b changes on SEB partitioning. We measured SEB components for two 4-d periods (Period 1 and Period 2) at an early-tilled (T1) and late-tilled (T2) bare soil site. During Period 1, ρ_b, net radiation_, and soil heat flux were similar for T1 and T2, but evaporation was higher at T2. During Period 2, ρ_b was 0.11 g cm‾³ larger at T2 than at T1. This resulted in a 7% higher soil heat flux at T2, which in turn caused 13% less evaporation. These results highlight the importance of considering dynamic ρ_b with time when determining SEB partitioning for tilled soils.