Siyami et al. : The effect of physical priming of seed on traits and yield of corn (Zea mays L.) under water deficit conditions in Abstract. In order to study the effect of physical priming of seed on traits and yield of corn under water deficit conditions, a two years experiment was conducted during 2014-2015 as a split plot with three replications in Iran. The main factor includes two levels of irrigation (70 and 110 mm evaporation from pan class A as control and water deficit, respectively) after 8-9 leaves stage of corn and sub-factor includes corn seed treatment with gamma and beta rays, laser wave, magnetic field and ultrasonic waves, all in time intervals of 5 and 10 min. along with a non-primed control. Results indicated that maize seed priming under magnetic field of 5 and 10 min. and gamma and laser rays for 5 min. in normal irrigation regime were the best treatments with 20%, 18%, 16% and 13% increase value, respectively, while seed priming with gamma and laser rays for 10 min. under water deficit condition had the lowest grain yield.To increase corn grain yield in both normal and water deficit conditions, seed priming with the magnetic field in both time intervals, gamma and laser rays only in a short time is recommended.

In order to determine the critical period of weeds control in soybean in semi-arid regions two experiments were conducted at Tabriz, Iran, on soybean hybrid Williams, based on randomized complete block design. For weedinfested plots, weeds were hand removed after 20, 40 and 60 days after emergence (DAE) and were kept weed free thereafter. For weed-free plots, weeds were allowed to compete with crop plants from 20, 40 and 60 DAE thereafter. Weeds interference duration of 40 DAE or more and weed-free period of less than 40 DAE greatly reduced the number of pod bearing branches per plant. Significant reduction in soybean yield up to 50% with increasing of weeds interference duration indicates that weeds is highly competitive with crop, and their competition beyond 40 WAE, results in greater crop yield loss than 24%, compared to control. A Gompertz model provided the best fit for the maximum weed-infested experiment. The relationship of crop yield with weed-free period was best described by the Logistic equation. The best weeds control period in soybean field using 5% permissible yield loss was between 40-60 DAE.