Effects of Drought Stress and Micronutrients (Zinc and Manganese) on Morphological Traits and Yield of Millet (Panicum miliaceum)

Drought stress is one of the most important environmental abiotic stress causes a decrease in crop yield, especially in arid and semi-arid regions of the world. Millet is a traditional cereal cultivating in arid and semi- arid zones, tolerant to drought and salinity. The application of water stress, especially in the millet development stages (from stem elongation to later), reduced plant height and resulted in decreased production and storage of photosynthetic materials (Khazaee et al., 2005). In arid and semi-arid areas, not only water scarcity but also absorbable nutrient elements deficiency in soil always restricts plant growth. Micronutrients are essential for natural growth of plants and in addition to their cooperation in the structure of some organelles they are involved in many chemical reactions. The shortage of these elements may sometimes act as limiting factor of absorption of other nutrient elements and growth.spraying Manganese and Zn combining with the other spray treatments resulted in the highest growth parameters of the Setaria italica. The aim of this experiment is to investigate the effects of drought stress and spraying manganese and zinc micronutrients and their interactions on morphological traits, harvest index, seed per panicle and seed yield of common millet. To investigate the effects of different irrigation intervals and foliar application of micronutrients on Panicum miliaceum, an experiment was conducted as split plot arrangement based on randomized complete block design with three replications in Sarbisheh agricultural research farm in south Khorasan province on 2012. Each replication included three main plot factors based on irrigation levels (7, 14 and 21 days irrigation intervals). Each main plot had four sub plot factors which treatment of foliar application with micronutrients were conducted on them (foliar application treatment with manganese, zinc, manganese and zinc without foliar application). Plant height, the number of leaves per plant, flag leaf area, peduncle length, panicle length, harvest index of seed in the panicle and seed yield was measured. Drought stress cause significant differences on plant height, the number of leaves per plant, flag leaf area and peduncle length at 5% significance level and on panicle length and seed yield at 1% significance level. Drought stress decreases morphological traits by reducing photosynthesis, growth period length and material partitioning to organs. The effect of foliar application on plant height, panicle length, peduncle length and the number of leaves in plant and seed yield was significant at 0.01 probability. Foliar application had not significant effect on flag leaf area. Drought stress caused a significant difference at significance level of 5% on harvest index. The highest harvest index (53/46) was related to 7-day irrigation interval treatment. In the absence of sufficient water, material partitioning to reproductive organs and especially seed would be decreased which causes the reduction of harvest index. The effect of Zinc and Manganese foliar application on harvest index was significant at the significance level of 1%. The highest harvest index with 14.1% increase in compare to the control treatment was related to Zinc and Manganese foliar application treatment. Increasing morphological traits produced seed with higher power and finally harvest index of seed in panicle increased. Considering achieved results, the decrease of irrigation interval can increase the photosynthetic surface and consequently seed yield. Micronutrients foliar application also causes an increase in morphological traits and seed yield. Spraying micronutrients increased seed weight, number of seed per panicle and seed yield. The interaction of irrigation interval and micronutrients foliar application was significant too. The highest seed yield was related to 7-day irrigation interval and manganese and zinc foliar application with 222.6 grams per square meter.