Simulation experiments on soil moisture evaporation affected by calcic nodule contents

The effect of calcic nodule content on soil moisture evaporation process was investigated in soil columns with uniform water supplement by simulating soil containing calcic nodules on the Northern Loess Plateau. Its aim was to provide an experimental base for estimation and modeling of soil water balance in this soil on the Loess Plateau. The results indicated that the differences in cumulative evaporation between soils with different calcic nodule mass fractions (calcic nodule mass / (calcic nodule mss + soil mass)) were little during the initial seven days and then increased a bit in the next days. There were not obvious differences in soil moisture evaporation rates during the experimental period. Soil moisture evaporation decreased with the increasing of calcic nodule mass fraction in soils. When calcic nodule mass fraction reached 0.5, soil moisture evaporation amount decreased by 8 mm, accounting for 10% of total soil water content. The negative relationship between soil moisture evaporation and calcic nodule content could be attributed to the decrease of soil water content resulting from the increase of calcic nodule content. The impacts of calcic nodules on soil moisture evaporation should be attributed to water absorption capacity of calcic nodule and its content as well as water allocation between soil and calcic nodules.