Effect of foliar application of different forms of iron fertilizer on yield and forage properties of hairy vetch (Vicia villosa Roth) under drought stress conditions

IntroductionHairy vetch a plant that can be used in different ways, such as fodder, silage, grazing, and green manure and its seeds can be used to feed poultry. Like other legume family plants, vetch can improve and strengthen the soil and fix nitrogen. Iron (Fe) is an essential micronutrient to virtually all forms of life. Although Fe is the second most abundant metal element in earth’s crust its low solubility and high fixation in soil reduce its bioavailability to the plant roots. Fe plays a major role in redox reactions in metabolic processes such as photosynthesis, respiration, and nitrogen assimilation besides being involved in the biosynthesis of chlorophyll and hormones, Drought stress is the most common environmental stress that reduces crop production, and low soil moisture leads to the lack of low consumption elements, especially iron and zinc elements in plants, So With the aim of investigating the effect of foliar application of different sources of iron fertilizer on fodder characteristics of vetch, this research was conducted.Materials and methodsThe research was conducted in the agricultural research farm of the Agricultural Jihad Organization in Baneh city in Kurdistan province, at 2021 crop season. The experimental design was implemented as a split plot where different levels of irrigation include no irrigation (rainfed conditions), one irrigation and two irrigations in the main plots, and foliar spraying of different sources of iron fertilizer including, control (spraying solution with water), iron chelate (Fe-EDTA), iron nanochelate (Khizra) and non-chelated source of iron sulfate were placed in sub-plots in three replicates. In the study chlorophyll index, plant height, fresh forage yield, dry fodder yield, Fodder protein percentage, digestibility percentage, ADF, NDF, soluble carbohydrates, crude fiber and ash percent of fodder were measured.Results and discussionThe results showed that the main effect of irrigation and foliar spraying on all investigated traits was significant. Results revealed that the interaction effect of irrigation with iron fertilizer foliar application on chlorophyll index, plant height, digestibility percentage, cell wall NDF, fiber percentage, and ash percentage was a significant, In our study dry conditions, compared to the treatment of two times of irrigation, decreased the wet fodder yield and dry fodder yield and the protein content of fodder by 71.65, 50.16, and 58.58%, respectively, and increased the insoluble fibers in the acidic cell (ADF) by 48.15%. Also, under iron nano chelate treatment of fresh and dry fodder yield, the protein content of the fodder and the content of soluble carbohydrates increased by 84.35, 40.19, 22.90 and 64.08, respectively, and the insoluble fibers in the neutral cell wall (NDF) decreased by 11.60%. Among the interaction treatments of irrigation with the iron foliar application, the highest chlorophyll content (133.45 and 131.04 mg/g fresh weight respectively), plant height (23.81 and 23.43 cm respectively), fodder digestibility percentage (72 42.42 and 77.10% respectively), fiber percentage (37.75 and 40.98 respectively) and fodder ash percentage (19.37 and 21.01% respectively) And the lowest NDF of the cell wall (21.78 and 26.93% respectively) was recorded in the treatment of iron chelate (Fe-EDTA) and iron nano chelate with two times of irrigation. The results of the interaction treatments also showed that iron chelate (Fe-EDTA) under the one-time irrigation treatment could significantly increase the leaf chlorophyll content, the percentage of forage digestibility and the percentage of forage fiber compared to the control treatment.ConclusionIt can be concluded that foliar application of iron fertilizer from sources of iron chelate (Fe-EDTA) and nano-iron chelate (Khizra) with two times of irrigation to achieve the maximum quantitative and qualitative characteristics of the fodder of the cluster flower is recommended, therefore it can be stated that supplementary irrigation and foliar application of iron fertilizer can be a solution to improve the quantitative and qualitative characteristics of fodder in vetch.