مدلسازي پويايي بانك بذر يولاف وحشي (Avena fatua) در مزرعه گندم

Modelling seed bank dynamics of wild oat (Avena fatua) in wheat fields

Wild oat seed bank dynamics was studied using a multi-stage single cohort population model. The model predicts the size of seed bank on the basis of seed outputs (germination and mortality) and inputs (produced seeds per plant and seed burial) with annual step. Seed mortality in soil is density dependent and reproductive effort of wild oat is described based on allometric relation between individual plant weight of weed and number of produced seeds per plant. The effect of wheat and wild oat densities on biomass of species in mixture is defined by using hyperbolic equations with predefined competition coefficients. Model was used for simulation of wild oat seed bank dynamics without control measures after calibration and validation against field data. The results showed that in pure stand of wild oat size of seed bank was independent to the initial seed density and reached to equilibrium after 5 years. This was due to reduction in reproductive effort of wild oat at high weed densities and increased density dependent seed mortality in soil, leading to equal input-output from seed bank. Sensitivity analysis on model parameters showed that in the presence of wheat, crop density and interspecific competition coefficient of wheat on wild oat were the most important factors in adjustment of the size of seed bank. An increase in wheat density by 20% or 20% increase in crop competition coefficient was able to drastically reduce annual rate of wild oat seed inputs to the soil. Relative wheat yield in weed infested field without control practices was 0.8 and 0.6 after 5 and 10 years, respectively when inter specific competition coefficient of wheat was increased by 20%. It was concluded that breeding wheat cultivars with higher competition ability against wild oat together with increasing wheat density are reliable management practices to prevent weed population in seed bank and yield loss.