Introduction: Okra with the scientific name of Abelmoschus esculentus L. is one of the important vegetables in tropical and subtropical regions. In modern agriculture, recognizing plant nutritional factors and their effect on the quantitative and qualitative characteristics of plants is one of the most important aspects of success (Ahmadi et al., 2019). Today, the types of microelements are enriched with nanotechnology in the form of nanoparticles and nanoclates to create a suitable environment for the activity of microorganisms and increase of plant growth and production. In addition, through nanotechnology, various compounds of microelements and nano-iron chelates have been provided to improve the growth environment of microorganisms as well as suitable conditions for plant growth (Barmaki et al., 2010). With the use of nanofertilizers, fertilizer nutrients are released gradually in the soil, which increases the efficiency and quality of food sources due to higher absorption rate during the plant growth period (Barmaki et al., 2010). Therefore, the present study aimed to investigate the effect of different amounts of iron nano-chelate fertilizer on yield, yield components and content of okra seed mucilage under drought stress conditions in Sib and Sooran city.
Materials and Method: The present study was carried out in the spring of 2017 in a farm located in Morad Abad village of the central part of Sib and Sooran city in the form of split plots in a randomized complete block design with three replications. Experimental treatments include drought stress at three levels of irrigation at moisture of soil field capacity, irrigation at 80% of soil field capacity and irrigation at 60% of soil field capacity as the main factor; And application of iron nano-chelate fertilizer at four levels of 0, 3.5, 7 and 10 kg ha^-1 as a sub-factor. In this experiment, traits of plant height, number of fruits per plant, fresh and dry fruit yield, biological yield, percentage and yield of mucilage and percentage and yield of okra fruit oil were studied. Data were analyzed using SAS Var9.4 statistical software. Analysis of variance and comparison of means were performed by Duncan's test at a probability level of five percent.
Results and Discussion: The results showed that irrigation at soil moisture of soil field capacity and consumption of 10 kg ha^-1 resulted in the highest amounts of plant height, number of fruits per plant, fresh and dry fruit yield, biological yield, and mucilage and okra oil yield. However, no statistically significant difference was observed between the 10 and 7 kg ha^-1 fertilizer for the above traits. Also, in stress conditions (moisture 80 and 60% of soil field capacity), the use of nano-fertilizers in comparison with the non-use of fertilizers led to the moderation of the effects of stress on the mentioned traits. So that only for the yield of fresh fruit, in treatment of moisture 80% of soil field capacity consuming 10 kg per hectare of fertilizer caused a 20.05% increase in yield compared to not using fertilizer. And this amount was 19.29% for moisture in 60% of soil field capacity. Also in the present study it was observed that the highest percentage of fruit mucilage was obtained from moisture treatment in 60% of field capacity and the highest percentage of fruit oil was obtained from irrigation treatment in soil field capacity moisture. In one study, it was reported that water stress reduces photosynthesis by reducing leaf area, closing stomata, and reducing chlorophyll synthesis. Therefore, limiting photosynthesis also reduces plant growth and yield (Hopkins & Huner, 2004). The benefits of using iron chelate nano-fertilizer include increasing plant metabolism and more efficient absorption of micronutrients into specific plant tissues (Rasoli et al., 2013). Iron also plays an important role in chlorophyll synthesis and is one of the main components of chlorophyll (Taiz & Zeiger, 2002).
Conclusion: From the results obtained in the present study, it was concluded that stress in both 80 and 60% soil field capacity reduces all the studied traits of okra except mucilage percentage; However, the use of iron nano-chelate fertilizers was able to moderate the stress conditions for the plant. Therefore, it is suggested that the application of 10 and 7 kg ha^-1 of nano fertilizer reduced the adverse effects of stress. It is also recommended to use these amounts of fertilizer in non-stress conditions to improve plant yield.