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 (Emax) of wheat was higher than that of wild barley across all sowing depths. The maximum and minimum Emax values for both species occurred at 20/15°C and 25/20°C, respectively.The time taken to reach 50% of the Emax (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 (Hmax) was observed at the surface planting for both plants. The Hmax 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 Hmax (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.