Modelling seed germination and seedling emergence of flax and sesame as affected by temperature, soil bulk density, and sowing depth

Abstract

Quantitative knowledge of the cardinal temperatures, optimal sowing depth, and soil bulk density (ρb) required for germination and emergence of flax (Linum usitatissimum L.) and sesame (Sesamum indicum L.) is scarce. An experiment was conducted across eight temperature treatments to determine the cardinal temperature and physiological time (hour number under optimum temperature) required for germination (using beta, dent-like and segmented models). Another experiment was performed for quantifying the emergence response of flax and sesame to ρb (1, 1.1, 1.4, 1.7 g.cm−3) and sowing depth (1, 2, 3, 4 cm). The results revealed that the responses of flax and sesame germination to temperature were best explained by a dent-like model. Base temperature (Tb), lower optimum (To1), upper optimum (To2), and ceiling temperatures (Tc) of flax were estimated at 9.1, 20.2, 27.3 and 40.3 °C respectively. Further, the sesame Tb, To1, To2 and Tc was 13.6, 34.2, 38.2 and 41.8 °C respectively. The physiological time to 50% germination was 32.7 h in flax and 12.4 h in sesame. Best sowing depth and soil bulk density for sesame was 1–2 cm and 1–1.4 g cm-3, respectively. However, flax showed less sensitivity (to ρb and sowing depth) and emergence rate was reduced only in deeper sowing (4 cm). This results help understanding the biology of these crops and it provides data for developing future field emergence models to optimize the timing of crop sowing.