Simulations of Soil Water and Heat Processes for No Tillage and Conventional Tillage Systems in Mollisols of China

Soil water and temperature are important factors to reflect variations in soil heat and water flows especially for tillage systems. The objective of this study was to evaluate the performance of the CoupModel in predicting the effect of tillage practices on soil water and heat processes for conventional tillage (CT) and no-tillage (NT) systems with straw mulching on semi-arid and high-latitude Mollisols of northeast China. This model was calibrated and evaluated in a three-year tillage experiment from 2009 to 2011 in a field experiment station, using field measurements of daily soil temperature and water storage in profiles for CT and NT separately. The results showed that under the model, soil temperatures were well simulated at 0&ndash:90 cm soil depths for CT, as indicated by R2 &ge: 0.97, the nRMSE = 27.5&ndash:38.7% and &minus:1.02 &deg:C &le: ME &le: &minus:0.31 &deg:C, and soil water storage at 0&ndash:130 cm soil depth (R2 = 0.01&ndash:0.06, the nRMSE = 19.6&ndash:37.1%, 13.3 mm &le: ME &le: 28.2 mm) was simulated with more uncertainty. &ldquo:Moderate to good agreements&rdquo: were achieved for NT. In general, the temporal and spatial variations of soil temperature and water for NT were well simulated by CoupModel. Although NT decreased soil evaporation&mdash:thus improving soil water content, especially in the root zone soil&mdash:and lowered the soil frozen depths, it reduced the soil temperatures, which could influence crop growth. It was concluded that the CoupModel proved to be a functional tool to predict soil heat and water processes for CT and NT systems in high-latitude seasonal frost conditions of Mollisols in China to estimate the soil temperature, water, energy balance, and frost depth dynamics in relatively complex systems that combined plant dynamics with tillage and/or no tillage covered with straw mulching in the soil surface.