Effect of water deficit on yield and yield components of grain maize (Zea mays L.) hybrids

Most of the croplands of Iran are located in arid and semiarid regions that water sources are limited. In recent years irregular consumption of water sources and continuous droughts led to incidence of water crisis in most regions of the country. Therefore, performing a management program is essential for reducing water deficit effects. In line with this approach, water deficit is mentioned as a useful way for researchers. Maize is one of the most important food sources for people and animal around the world. Hence, area under cultivation of maize is continuously increased due to more diversity, extensive compatibility, high yield and shorter growth period rather than other cereals. Maturity period is one of the important features before a maize hybrid is selected for cultivation. Selecting suitable hybrid with condition of the region, appropriate growth, reproduction and production can be expected. In order to water deficit and excess consumption of water in late maturity hybrids of maize, the necessity of investigating the growth, yield and water consumption in maize hybrids should be taken into account. Material and Methods: In case of evaluation of water deficit effects on yield and yield components of maize hybrids, a split plot experiment carried out based on randomized complete block design with three replications during 2014-2015 growing season. Main plots belonged to three irrigation levels (providing 100, 80 and 60 percent of water requirement (wr)) and sub plots belonged to six different maize cultivars including late (KSC704, KSC705), medium (KSC400, KSC500), and early (DC370, KSC260) maturity groups. Plots dimensions was 3×10 meters and heap width were considered as 75 centimeters. Irrigation was performed based on 100% wr up to stability of plants (four leaves stage) and subsequently experimental treatments were exerted. Calculated rate of irrigated water was measured by water meter with accuracy of one-tenth liter and separate irrigation was exerted with control of entrance faucets for each treatment. Results illustrated that the yield and yield components of all cultivars decreased significantly by deficit irrigation. The interaction between irrigation and hybrid showed that reduction of water requirement (from 100 to 60% wr) lead to 24% decrease in plant height of KSC705 (late), while the reduction of plant height in KSC370 (early) was reported as 26% in 2015. In 2014, diminish of irrigation from 100 to 60% wr caused 11% decrease of row per ear, however, with water deficit of 80 to 60% wr no statistical difference was observed in row per ear in 2015, water deficit from 100 to 80 percent water requirement led to 10% reduction in rows per ear and also 17% decline in rows per ear was indicated as a result of water deficit from 100 to 60% wr in this year. In the second year, in line with water deficit from 100 to 60% wr, kernels per row decreased by around 13%. In medium and early maturity maize hybrids kernels per row was about 7 and 13% lower than late maturity hybrids, respectively. In the first year, water deficit had no effect on 300 kernel weight, while water deficit from 100 to 60% wr led to 25% reduction of 300 kernel weight in the second year. 300 kernel weight in the late maturity hybrid of KSC704 was 19 and 28% higher compared to KSC500 (medium maturity) and KSC260 (early maturity), respectively. In appropriate conditions of irrigation, positive and significant correlation have been observed between 300 kernel weight and seed yield. Water deficit from 100 to 60% wr caused 20% of yield reduction in KSC705 (late) and KSC400 (medium) hybrids in the first year, however, water deficit from 100 to 60% wr had no significant reduction in the yield of early hybrid. In the second year, water deficit from 100 to 60% wr in KSC705 (late maturity), KSC400 (medium maturity) and DC370 (early maturity) led to 24, 28 and 24% decline in the yield, respectively. In 2015, the effect of hybrid on harvest index was significant and harvest index decreases in KSC705 hybrids (late) compared to KSC500 (medium) and KSC260 (early) was estimated as three and 6.5 percent, respectively. High yield in late maturity hybrids KSC704 and KSC705 was affected by the periority of traits such as plant height, rows per ear, number of kernel per rows, weight of 300 kernel, harvest index and biological yield. Severe water deficit revealed that this priority was not significant among hybrids. It can be concluded that late maturity hybrids is recommended for regions without water limitation and also moderate maturity hybrids is considered for conditions with limited water.