The effects of irrigation with Caspian Seawater on Yield of Quinoa (c.v. Sajama) in Gorgan, northeastern Iran

Quinoa (Chenopodium quinoa Willd.) is a species belonging to the family Amaranthaceae s.l., domesticated at least 5000 years ago in the Bolivian-Peruvian highlands. Quinoa is a nutritious herb with favorable nutrition and potential for growth and production in adverse environmental conditions that can withstand salinity. Use of sea water in agriculture will increase farmers' income, sustainable production and food security. Therefore, this study was conducted to investigate the effect of mixed management of seawater with freshwater on the growth properties of quinoa Sajama cultivar.

To investigate the reduction of seawater salinity on growth and yield of quinoa Sajama cultivar, this study was conducted in a completely randomized design with three replications and based on potted cultivation in greenhouse conditions at Gorgan University of Agricultural Sciences and Natural Resources in 2016. At sixth-leaf stage, plants were exposed to 5 saline irrigation treatments, i.e., the control treatment (S1: 0.5 dS.m-1), 15 (S2: 4.3 dS.m-1), 30 (S3: 8.0 dS.m-1), 45 (S4: 11.8 dS.m-1), and 60 percent mixture of seawater and tap water (S5: 15.5 dS.m-1). Salinity stress was initially applied by irrigating the pots with saline water resulting from a mixture of 15% of the sea and tap water, and gradually the salinity of irrigation water increased until reaching the treatments being studied. After eighty-five days of germination, plants were harvested and plant height stem, leaf, and panicle fresh weights, no.of branches and inflorescence, grain and panicle yield, and 1000-kernel weight/plant. Shoot were oven dry for 48 h at 70 C and shoot biomass was recorded. Grains were collected from panicle to record 1000-grains weight and grain yield/plant.

The results inducted the effect of different moderation of irrigation regimes on the stem, leaf, and panicle fresh weights, grain and panicle yield, 1000-kernel weights, and plant height were highly significant (P<0.01), but branches and panicle number were significant at the 5 percent levels (P<0.05). The highest amount of 1000 kernel weights, grain, and panicle yield (4.8, 15.93, and 18.52 gr) were measured at irrigation by freshwater The results showed that increasing the salinity of irrigation water decreased some traits of growth and yield (stem, leaf, and panicle fresh weights, no.of branches and inflorescence, grain and panicle yield, 1000-kernel weight/plant, and plant height). Because in most irrigation traits mixing 15 and 30% of seawater and freshwater has resulted in less decline compared to other treatments, this treatment is recommended to irrigate quinoa in irrigation conditions with saline water of the Caspian Sea. Fifteen and 30 percent mixture of seawater and freshwater has resulted in decreasing 1000-kernel weights 22.9 and 27.1 percent, respectively.

In conclusion, saline irrigation provoked a decrease in quinoa plant growth and yield compared with non-saline irrigation; meaning that the morphological properties and yield of quinoa plants will be decreased due to salt stress. In conclusion, the highest values in most of the morphological traits were observed when using salinity irrigation water at a rate of 4.3 dS m-1 to irrigate quinoa plant under greenhouse conditions, which proves the high resistance of quinoa to salinity stress.