Introduction: The most important problem that threatens food security of any country and the world is the lack of adequate water resources, so one of the ways to deal with this crisis is to use plants with low water requirements and high water use efficiency. Among the plants, we can name Quinoa, which is one of the plants that has been less studied and exploited in Iran. Since the planting date has the greatest impact on the physiological characteristics of the crop compared to other cropping treatments, so choosing the appropriate planting date can also create the greatest correlation between plant growth trends and climatic conditions. Undoubtedly, the use of biological fertilizers, in addition to the positive effects it has on all soil properties, is also economically, environmentally and socially fruitful and can be a suitable and desirable alternative to chemical fertilizers. Therefore, the aim of this study was to determine the response to deficit irrigation, planting date and application of different biofertilizers in quinoa.
Materials and Methods: This experiment was carried out during two cropping years 2019 and 2020 in a farm located in Moghan region in Iran. In this experiment, Titicaca cultivar of quinoa was cultivated in the form of split factorial design based on a randomized complete block design with three replications. Experimental factors included irrigation at three levels (normal irrigation, irrigation termination at bud stage and termination at seed filling stage) as main plot and factorial combination of planting date at three levels including (27 July, 11 August and 27 August) and three types of Nitrogenous biological fertilizer (seed inoculation with Azotobacter, seed inoculation with Azospirillum and inoculation with a mixture of Azotobacter and Azospirillum and control (without inoculation)) were also considered in sub-plots. Leaf Length and leaf Width at the physiological maturity stage was measured by randomly selecting 10 plants using a ruler with millimeter accuracy. At the end of the growing season, the product of two middle planting lines with a length of 4 meters was harvested by observing the half-meter margin effect and after drying in a ventilated oven at 70 °C for 24 hours, grain yield was determined. Kjeldahl method was used to measure nitrogen concentration and the percentage of protein was calculated. Finally, protein yield was obtained from the product of protein percentage in seed yield. The soil bacterial population was determined based on the methods recommended and the gridline interest method was used to determine the root colonization percentage.
Experimental data were analyzed before analysis of variance for homogeneity of test errors through Bartlett test and then analyzed using SAS (9.2) software and comparison of means at 5% probability level using Duncan multi-range test.
Results and discussion: The results of this study showed that the yield of quinoa increases under the influence of irrigation, planting date and biofertilizers, which is consistent with the results of other researchers' research. Irrigation termination in seed filling stage has no statistically significant difference with normal irrigation treatment, so it can be desirable in water shortage conditions. In terms of the planting date, the 11th of August treatment had the highest seed yield, and the combined use of azotobacter and Azospirillum had a significant effect on the vegetative indices and seed yield of quinoa. Therefore, it seems that the use of bio-fertilizers is one of the best ways to achieve optimal performance, which in the long run can lead to a reduction in the need for chemical inputs in agricultural systems.
Conclusion: The results of this research showed that although normal irrigation with the planting date of 11 August and inoculation with Azotobacter and Azospirillum biofertilizers had the highest amount of studied traits, especially seed yield (3049.7 kg/ha), but with the treatment of irrigation termination in the filling stage with the planting date of 11 August and inoculation with biofertilizers was placed in a same statistical group. Therefore, in terms of the importance of water consumption, it can be said that in the conditions of limited water resources, the treatment of irrigation termination during the seed filling stage has the most favorable results. Investigating the studied traits showed the positive effect of the use of biofertilizers, especially the combined use of Azotobacter and Azospirillum in the studied traits. Hence, the combined use of biofertilizers due to their high ability to fix nitrogen and provide nutrients needed by plants such as phosphorus, potassium, siderophore production and iron solubilization, synthesis of phytohormones such as auxin, cytokinin, gibberellin and synthesis of enzymes that grow and affect the growth of the plant, it showed positive effects on the examined traits, especially the seed yield.