Modelling seedling emergence of Amaranthus retroflexus affected by soil depth

Aim of study: To determine and quantify the effect of seed burial depths on the seedling emergence pattern of Amaranthus retroflexus in field conditions. Area of study: West of Iran (Ilam). Material and methods: The seedling emergence of an A. retroflexus was studied in an outdoor pot experiment, burying the seeds at 0, 2, 4, 6 and 8 cm in the soil in Ilam (Iran) in two consecutive years, 2010 and 2011. Different models were tested to predict the cumulative seedling emergence, and the log logistic model was found to be the best for this A. retroflexus population. Newly estimated Tb values, slightly different each year, but lower than those of the references, were estimated and set at 2.6 ºC and 0 ºC in 2010 and 2011, respectively. Main results: The seedling emergence in the west of Iran take place over a period from early February to late May. The level of seed dormancy can be reduced during autumn and winter burial in the soil or after a dry storage. Seed dormancy reduction resulted in a lower base temperature for germination/emergence followed by increase of the seedling emergences. Moreover, light in the soil surface and higher fluctuation in temperature at shallower soil depths may stimulate the seed germination and seedling emergence of A. retroflexus. Research highlights: Total emerged seedlings and emergence pattern are affected by soil depth and the level of dormancy. The results obtained in this study can be used to optimize the timings of the weed management activities.