Seedling emergence of Winterfat (Krascheninnikovia lanata (Pursh) A.D.J. Meeuse & Smit) in the field and its prediction using the hydrothermal time model

Winterfat is a native shrub in the prairies of North America and seedbed conditions determine seedling establishment and population restoration. Thirteen seedbed treatments were created with 2–3 sowing dates and irrigation levels in the field over 2 years to quantify the effect of soil temperature and water potential on seedling emergence. Seedling emergence ranged from 3% to 69% of viable seeds in these field conditions. Higher seedbed temperatures associated with late sowing dates greatly reduced seedling emergence. An exponential relation of thermal time requirements between seed germination and seedling emergence was established. The constructed hydrothermal time model had variable accuracy in predicting field emergence, depending on soil temperature and soil water potential. The correlation between predicted and observed emergence can be as high as R2=0.79R2=0.79. Generally, the hydrothermal time model fits well for emergence when soil temperatures are 10–15 °C and soil water is >−0.5 MPa. These seedbed conditions occur in the spring when snow melts, favouring seedling emergence of winterfat. Results from this study provide practical information for restoration using winterfat.