Effects of the sowing depth and temperature on the seedling emergence and early growth of wild barley (Hordeum spontaneum) and wheat

The experiment was conducted under a controlled environment to study the effects of different temperature regimes (15/10°C, 20/15°C, and 25/20°C day/night) and sowing depths (0, 2, 4, and 6 cm) on the seedling emergence and early growth (height gain) of wheat (cv. Marvdasht) and wild barley ( Hordeum spontaneum ). The cumulative emergence and plant height gain over time were modeled with the use of a logistic function. For a particular temperature regime, the maximum percentage emergence (E _max ) of wheat was higher than that of wild barley across all sowing depths. The maximum and minimum E _max values for both species occurred at 20/15°C and 25/20°C, respectively. The time taken to reach 50% of the E _max (i.e. E₅₀) increased with the sowing depth in both species under all temperature regimes. The E₅₀ of wild barley was greater than that of wheat for all temperature regimes, with maximum differences observed at 20/15°C. The greatest maximum plant height (H _max ) was observed at the surface planting for both plants. The H _max was reduced at temperatures either lower or higher than 20/15°C, with a more notable reduction in wild barley. At all temperature regimes, the time taken to reach 50% of the H _max (i.e. H₅₀) increased linearly with the sowing depth but, at higher temperatures, the accelerated growth rate reduced the H₅₀. The wild barley seedling emergence and height gain rate, as expressed relative to those of wheat, revealed the highest superiority of wheat over wild barley at 25/20°C and the sowing depth of 4 cm.