Evaluation the Effects of Irrigation Periods and Chitosan as a Biological Elicitor on Onion (Allium cepa L.) Growth and Yield

IntroductionOnion (Allium cepa L.) is a species of the Alliacea family. It is of great economic importance in Hormozgan province, Iran, which is ranked the second among the largest producers of onion in Iran in terms of cultivated area (8147 ha) (Agricultural statistics, 2021). Conventional Irrigation have undoubtedly helped in improving both bulb yield and quality of onion, but lately, it was arising many novel trends in Irrigation. Using of chitosan as an antiperspirant compound is one of these trends, as it can improve the water use efficiency (Geries et al., 2020). Chitosan is a member of the polysaccharides which is considered a useful natural polymer and is produced by alkaline N-deacetylation of chitin. Ahmed et al. (2019) reported that positive effect of chitosan nanoparticles on onion, as it significantly promoted seed germination and radical length under salt stress. The best treatment on germination was 0.3% of nano chitosan. Growth variables (plant height, leaf area, fresh and dry weights of the shoot and root) were increased significantly. Nevertheless, data on the utilization of chitosan for onion are meager in Iran. In this way, this study was carried to consider the impact of irrigation periods and chitosan as a biological elicitor on onion cultivar of Taki yellow, uniquely the adjustment in yield and quality properties.Materials and MethodsThis study was carried out at the private farm in Sohrabi village, Shamil district, Hormozgan province, Iran, conducted during 2020-2021 growing season. The experiment was carried out as autumn planting. This experiment was conducted as split-plot arrangement based on a complete randomized block design with 3 replications. Treatments were three irrigation periods and three doses of chitosan as main and sub plot, respectively. In this experiment 3 irrigation periods (such as two days, four days and six days) and 3 doses of chitosan (including zero, 1000 and 2000 ppm) with constant density of 63 plants m-2 yield and yield components (such as mean onion weight, length and diameter, onion shape index and dry matter content) and harvest index of onion were measured.Results and DiscussionThis study was conducted to assess the potential effects of irrigation periods and foliar spraying with chitosan, on the growth, yield quality of onion bulbs. In this experiment, nearly all measured traits were significantly (P<0.01) affected by irrigation periods and doses of chitosan. Results showed two forms of chitosan treatments (chitosan 1000 and 2000 ppm) were the most effective treatments for vegetative growth characters (plant height and Dry weight of shoot per plant), yield and its components (bulb dry matter %, bulb length, bulb diameter and total bulb yield) while chitosan at 0 ppm gives the highest values for harvest index in each irrigation periods. Also, results showed more irrigation (Two days) was the most effective treatments for vegetative growth characters, yield and its components. Therefore, according to these results, under deficit irrigation conditions, chitosan can reduce the effects of drought stress on onion more than No foliar application. In this regard, Shamekh, Jafari &amp; Abdollahi (2021) the effect of proline, chitosan and its derivatives on photosynthetic pigments, chlorophyll fluorescence indices, qualitative characteristics and yield of greenhouse tomato (Lycopersicon esculentum Mill.) under deficit irrigation conditions and these researchers reported in their studies that under deficit irrigation conditions, chitosan and its derivatives can reduce the effects of drought stress on tomatoes more efficiently than proline.ConclusionThe obtained results indicated that foliar application with chitosan had an important role in promoting and improving plant vegetative growth, and this led to improve in yield and yield components of onion in higher irrigation periods (four days and six days). The examination inferred that using chitosan to deliver highest yield in good quality with great the economic benefit was gotten from foliar application at 2000 ppm.