چكيده لاتين :
Introduction: Water deficiency is one of the most limiting factors for crop production throughout the world. Addition of fertilizers to supplement farm soil nutrients is essential to achieving desired crop yields. In particular, microelements have important roles in seed formation and seed yield. Foliar spraying with fertilizer solutions containing microelements such as Zn and Si is shown to be beneficial to crop growth and productivity, especially under water limited conditions. This can be due to the high effectiveness of foliar feeding and rapid plant response. The application of nano-fertilizers in agricultural production of arid and semiarid countries such as Iran provides unique opportunities to enhance nutrient use efficiency by crops and reduce costs of environmental protection. Sharing 2.8% of total world oilseeds (around 107 million ton), sunflower is the fifth most important edible oil, which is cultivated under various environmental conditions because of its high yield and harvest index as well as its extensive adaptability and acclimation. (Ansarinia, 2011). The objective of the present study was to evaluate the effects of two irrigation regimes and different levels of nano and conventional ZnO and SiO2 fertilizers on yield, yield components and water use efficiency of sunflower.
2017Materials and Methods: The experiment was conducted as a split-plot based on a randomized complete block design with three replications at experimental field of Islamic Azad University, Birjand Branch, Birjand, Iran in 2014. The main plot was devoted to irrigation at two levels (irrigated after 100 and 200 mm cumulative evaporation from evaporation pan) and the sub-plot was devoted to foliar spray of ZnO and SiO2 at seven levels (nano ZnO, nano SiO2, ZnO, SiO2, nano ZnO + nano SiO2, ZnO + SiO2 and control or wihtout foliar spray). The measured traits included head diameter, seed number per head, 1000-seed weight, seed yield, biological yield, oil yield and water use efficiency for seed, biomass and oil. MSTAT-C statistical software used for data analysis and means were compared with Duncan multiple range test at 5% probability level.
Results and Discussion: The results showed that water deficit stress decreased head diameter, seed number per head, 1000-seed weight, seed yield, biological yield, oil yield and water use efficiency for seed, biomass and oil production by 16.9, 39.5, 18.5, 50.3, 33.3, 51.5, 73.7, 62.9 and 75%, respectively as compared to non-stress condition. Seed yield reduction due to water stress may be resulted from decreased leaf area and duration, which consequently led to depressed photosynthetic rate and increased partitioning of photosynthates to root rather than shoot. Foliar application of conventional ZnO fertilizer significantly increased head diameter, seed number per head, seed yield and oil yield by 10.2, 42.9, 59.7 and 70.3%, respectively as compared to no-foliar application treatment. It appears that ZnO fertilizer can raise yield of seed through enhancing photosynthetic rates and improving leaf area duration. Under the current research conditions, seed number in head had a more conspicuous contribution towards increasing final yield than the other yield components. Zinc fertilizer has a positive effect on auxin biosynthesis that can contribute to a better absorption of minerals and thus enhance plant growth (Marschner, 2012). The highest water use efficiency for seed and oil was obtained with ZnO treatment, which was 77.8 and 75% higher compared to the control treatment, respectively. This result can be attributed to greater seed and oil yields under this treatment relative to the other fertilizer treatments.
Conclusions: In general, it seems the use of zinc oxide fertilizer due to its role in improving plant physiological and biochemical functioning (Malakoti & Lotfolahi, 2004) resulted in enhanced photosynthetic capacity, which was accociated with increasing the fertilization of flowers and seed number per head, leading to a significant increase in seed yield. On the other hand, water deficit stress by closing stomatal aperture and decreasing the photosynthetic capacity and source strength significantly reduced seed number per head and 1000-seed weight, which caused a decline in seed and oil yield of sunflower . Our findings indicated that irrigation after 100 mm cumulative evaporation from evaporation pan and foliar application of conventional ZnO are best recommended for the production of sunflower under the conditions of this research.
