Maize (Zea Mays L.) Growth and Yield Response to Ethephon Application under Water Stress Conditions

The aim of the present investigation was to study the growth, yield and yield components of maize (Zea mays L.) single cross 704 under different levels of irrigation, plant density, and ethephon in southern Iran where this particular crop has not yet been studied in detail. A field experiment was performed in the 2004 5 growing season at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. The experimental design was a randomized complete block with four replicates where the treatments had a split split plot arrangement. Irrigation level (low and high) was the main plot, plant density (53,333 and 80,000 plants/ha) the subplot, and ethephon level (0, 0.56, 0.84 kg/ha a.i., applied at the 6 leaf stage) the sub subplot. The results showed that the rates of foliar application of ethephon could play an important role in maize growth indices, and attribute to grain yield components. Application of ethephon was associated with a decrease in Leaf Area Index (LAI), Leaf Area Index Duration (LAID) and Crop Growth Rate (CGR). Furthermore, ethephon reduced plant and ear height. Increasing the application rates of ethephon showed a significant reduction in early season plant height and LAI, LAID. The control plants had lower grain yield than those treated with different rates of ethephon. Indeed, this research showed that under conditions of water stress, the maize plant is able to make better use of available water if vegetative growth is partially restricted early in the season. The results also indicated that the yield response of maize to ethephon application would vary with plant density and available water conditions. Ethephon treatment was found to be more beneficial for grain yield with higher plant densities and under water stress conditions.