Effects of Drought Stress on Vegetative and Reproductive Stages of Forage and Kernel Corn Hybrids

Maize is one of the most important cereals which its global production is severely affected by drought in many parts of the world. One of the best ways of water management on field is to choose the proper variety which could be chosen indirectly by the traits affecting the grain yield.
In order to study the effect of drought stress in vegetative and reproductive stages in 14 corn hybrids, an experiment was conducted at the experimental field of Seed and Plant Improvement Institute of Karaj, in 2009. The Research Station located in 50°, 55´ eastern latitude and 35°, 47´ northern longitude with 1254 height above mean sea level (AMSL). The soil texture of the location was loam-clay with pH= 7.5 and the Electrical Capacity (EC) = 0.7 dsm-1. The experiment was carried out using split-plot in a randomized complete block design (RCBD) with three replications. The main plots consisted of three levels of irrigation regimes (irrigation after 70, 100 and 130 mm cumulative evaporation from evaporation pan class A) and sub-plots included 14 new corn hybrids Includes eleven new hybrids such as (K47/2-2-1-4-1-1-1×MO17¡ K3653/2×K19¡ KLM76004/3-2-1-1-1-1-1-1×K3545/6¡ K3653/2×MO17¡ K74/2-2-1-2-1-1-1-1×K3545/6¡ K47/3-1-2-7-1-1-1×MO17¡ K47/2-2-1-2-2-1-1-1×K3544/1¡ KLM76004/3-2-1-1-1-1-1-1×K3544/1¡ K47/2-2-1-2-1-1-1-1×K3544/1¡ KLM77029/8-1-2-3-2-3×MO17 and KLM76005/2-3-1-1-1-1×MO17) and three hybrid control (KSC704, KSC720, KSC700). Irrigation time was determined using daily evaporation rate of standard class A evaporation pan. To determine the volume of water per irrigation, a sample of each plot from depth of root development was prepared before irrigation. The samples were kept in oven 80°C for 24 hours. The weight of soil moisture content was calculated and the volume of water per irrigation was calculated using equations 1 and 2.
1: H = ρb (F.C - m) D
2: V = H × A
Where H is the water height in the plot, ρb is soil bulk density, F.C is the moisture level at field capacity, m is plot moisture mass desired at irrigation time, D is the root development depth, V is the volume of irrigation water in the plot, and A is the plot area. From each plot 10 plants were randomly selected to determine traits such as dry forage yield per hectare. In this experiment kernel yield per hectare, Dry forage yield per ha, Number of days until to pollination, number of days until silk emergence cords and period of pollination until silk emergence, ear length, ear diameter, number of ear in corn, number of kernels per row and number of rows per ear measured and calculated.
The results showed that hybrid differences in terms of number of days until the pollination, number of days until silk emergence cords, period of pollination until silk emergence and ear length was significant at 1% probability level. No significance differences were observed between hybrids for kernel yield, total number of kernels per ear, number of ear in corn and ear diameter. Hybrid and irrigation regimes interactions were not significant for any of the traits except for ear length that represent the same reaction of hybrids to the irrigation regimes. Evaluation of dry forage showed significant difference between years (P