Effect of Selenium and Application Methods of Urea Top-dress on Yield and its Components and Quality Traits of Wheat under Rainfed Conditions

Introduction Wheat (Triticum aestivum L.) is the greatest nourishment for most of world’s population. In many lands of Iran, water is not enough for irrigation and also the most regions of country have arid and semi-arid climate. Water deficit is an important stressful factor for plant growth and crop productivity. Nitrogen is main component of proteins and enzymes. It is essential in all of the plant growth stages. Application of nitrogen is essential for retard leaf senescence, maintenance of photosynthetic leaf during grain filling period and increasing grain protein. The time and method of nitrogen fertilizer application are effective on grain yield. The reported that maximum of grain yield recorded when that nitrogen fertilizer was applied at sowing time along with foliar application at the tillering stage. In higher plants, the role of selenium is still unclear. Selenium can increase the tolerance of plants to induced oxidative stress include drought, salinity, high temperature. Selenium increases the tolerance of plants by transpiration or osmotic potential under water deficit. The current paper studies the influence of selenium and application methods of urea top-dress under rainfed conditions in order to promote improved drought stress tolerance and increase the quantity and quality of wheat. Materials and Methods In order to study the effect of selenium and application methods of urea top-dress on yield, yield components and quality traits of wheat under rainfed conditions, an experiment was conducted at Ashianeh-ye Sofla village, Khomeyn County, Markazi Province during 2012- 2013 growing season. This experiment was carried out as split plot based on randomized complete block design with four replicates. Experimental factors were included application methods of urea fertilizer in four levels (without application of fertilizer (control), application of 60 kg ha-1 at the tillering stage, application of 30 kg ha-1 at the tillering stage combined with foliar application of 200 mg L-1 before ear emergence and application of 20 kg ha-1 at the tillering stage combined with foliar application of 200 mg L-1 before ear emergence and 200 at the late ear emergence) and selenium in three levels (0, 5 and 10 mg L-1). Seed density was based on 100 kg ha-1 of Sardari cultivar. The seeds were sown by hand on 6-m rows with 15 cm spacing between rows. The distance between the plots was one meter. At the final harvest, 2 m2 was harvested from the middle of each plot and the grain yield was evaluated. Statistical analysis of data was performed with MSTAT-C software and means were compared with Duncan's test at the 5% level of probability.Results and Discussion The results showed that application of urea top-dressing fertilizer and selenium increased the spike number per m2. Maximum grain yield (1207.5 kg ha-1) was obtained from application of 60 kg urea per hectare at the tillering stage and without application of selenium, that was statistically similar to application of 30 kg urea per hectare at the tillering stage combined with foliar application of 200 mg L-1 before ear emergence with 1196.3 kg grain yield per hectare. This is due to that application of nitrogen increased spike number per area unit, grain number per spike and 1000-grain weight. Application of urea fertilizer significantly increased the grain selenium concentration and protein content. Foliar application of selenium at different urea levels increased the grain selenium concentration. The application of 60 kg urea per hectare at the tillering stage, application of 30 kg urea per hectare at the tillering stage combined with foliar application of 200 mg urea per liter before ear emergence and application of 20 kg urea per hectare at the tillering stage combined with foliar application of 200 mg urea per liter before ear emergence and 200 mg urea per liter at the late ear emergence increased the grain selenium by 48.28, 40.57 and 34.39% compared to control, respectively. Foliar application of selenium increased the amount of grain selenium compared to control. The highest grain selenium was obtained from application of 10 mg selenium per liter.Conclusions In conclusion, with application of urea fertilizer at the rate of 30 kg ha-1 as top-dressing at the tillering stage combined with foliar application of 200 mg L-1 before ear emergence can reduce the rate of urea fertilizer by 50% without reducing yield. Furthermore, foliar application of 10 mg L-1 selenium can moderate effect of drought stress, also increase grain quality. Therefore, application of urea fertilizer as top-dressing combined with spray along with foliar application of selenium improve the qualitative and quantitative yield of wheat under rainfed conditions.