Study of the effect of intensity and timing of topping on maize (Zea mays L.) grain yield under Khuzestan condition

To study the effect of the intensity and timing of topping on maize grain yield, an experiment was conducted for two years during 2002-2003 cropping seasons at Safiabad Agriculture Research Center (SARC) using KSC 704 maize hybrid. The experiment was carried out in factorial experiment using a Randomized Complete Block Design with four replications. Treatments were three levels of topping above the ear after anthesis (complete topping, one leaf left and two leaves left) and four topping dates (immediately after anthesis and three topping dates following anthesis with 10 days interval) and control treatment without topping. Results indicated that, there were significant differences among treatments for grain yield and 1000 kernels weight. Topping decreased grain yield and 1000 kernels weight. Control treatment had the highest grain yield (9.94 t/ha) and 1000 kernels weight (327.4 g), and complete topping treatment at anthesis had the lowest grain yield (8.15 t/ha) and 1000 kernels weight (269.79 g). Therefore, topping can decrease grain yield and 1000 kernels weight about 18 percent. There was no significant differences for protein content among treatments. The effect of topping and topping dates for forage yield was also significant. Complete topping with (6.57 t/ha) forge yield had the highest and two leaves with (2.63 t/ha) had the lowest level. Therefore, although topping produced about (6.57 t/ha) forage yield, however, reduced grain yields about (1.79 t/ha) or 18 percent, hence it is not recommended.