Abstract
Background and objectives: The environmental and economic impacts of chemical fertilizers application have encouraged agronomists and growers to evaluate the use of alternative nutrient sources. The objectives of this study were to evaluate the effects of biological, chemical and organic fertilizers, as alone and integrative application on yield, yield components and physiological traits of sunflower under different irrigation levels.
Materials and methods: A two- field experiments were carried out as split plot based on randomized complete blocks design (RCBD) with three replications at the Piranshahr agricultural research station, West Azarbaijan province, Iran, during during 2016 and 2017. The main plots included different irrigation levels (Irrigation at 85, 70 and 55% field capacity) and the sub plots were including different fertilization levels: 100% of recommended chemical fertilizer (255, 25 and 25 kg ha-1 urea, triple superphosphate and potassium sulfate, respectively), 10 ton ha-1 vermicompost, 15 ton ha-1 vermicompost, biosuper+ azotobacter biofertilizer, 10 ton ha-1 vermicompost+ biosuper+ azotobacter, 15 ton ha-1 vermicompost+ biosuper+ azotobacter, 10 ton ha-1 vermicompost+ biosuper+ azotobacter, 10 ton ha-1 vermicompost+ biosuper+ azotobacter+ 50% chemical fertilizer and 15 ton ha-1 and vermicompost+ biosuper+ azotobacter+ 50% chemical fertilizer. Results: The results demonstrated that the irrigation at 55% of field capacity significantly decreased the plant height, stem diameter, head diameter, thousand seed weight, seed yield, biological yield, chlorophyll a, chlorophyll b, relative water content, head weight and number of seeds per head of sunflower. The highest achene yield of sunflower (4230 kg ha-1) was achieved in the normal irrigation with application of 15 ton ha-1 vermicompost+ biosuper+ azotobacter+ 50% chemical fertilizer. Also, the lowest achene yield (3051 kg ha-1) was observed in the severe stress conditions (Irrigation at 55%