Effect of different levels of irrigation water salinity on quinoa (Chenopodium quinoa) yield and yield components in spring planting

Increasing population and needs for food on the one hand, and the limitation of conventional water resources and the gradual development of soil and water resources salinity on the other hand, make sustainable approaches and practices for production by unconventional water and soil resources more important. One of these strategies for direct access to appropriate options and salinity tolerate was halophytes plants and species with inherent salt tolerance. Quinoa, as a facultative halophyte, had ability to growing in saline regions and irrigation with unconventional and very saline waters. This research was conducted to investigate the effect of different levels of irrigation water salinity on yield components, biomass dry weight, seed yield and harvest index of quinoa in spring planting.

This experiment was conducted in a lysimetric condition with completely randomized design with three replications in National Salinity Research Center at Yazd province in 2017-18 growing season. The levels of salinity were four levels 5, 10, 15 and 20 dS m-1 of irrigation water. Twelve weighting lysimers with length 85 cm, width 25 cm and a height of 30 cm were prepared and then each of the lysimeters were filled with a sandy loam soil with a bulk density of 1.4 g cm-3. Seeds were sown at the beginning of March 2018; and the seedling were thinned to 10 plants per each lysimeter after reaching the four-leaf stage Irrigation carried out on the basis of soil moisture depletion at each irrigation considering about 20% leaching fraction. To control soil salinity, drainage water from the root zone was collected at each irrigation and its electrical conductivity was measured. At the end of the study, quinoa plants were manually harvested and dry biomass, grain yield and harvest index and traits such as plant height plant height, etc. were measured after drying and the effect of different levels of salinity on these parameters were investigated.

The results showed significant decrease of quinoa yields, yield components and harvest index with increasing in irrigation water salinity. Increasing salinity from 5 to 20 dS m-1 resulted in 29.5%, 77.0%, 11.7%, 17%, 29%, 39%, 40%, 39% and 19% reduction in dry biomass yield, seed yield and harvest index, plant height, panicle length, panicle width, number of branch, number of panicle per plant, and 1000-seed weight, respectively. The results of correlation analysis revealed that seed yield and dry biomass (R2=0.961**), plant height (R2=0.952**) and number of branch (R2=0.944**) were significantly correlated with grain yield.

Increasing salinity of irrigation water from 5 to 20 dS m-1 decreased biomass weight, seed yield and harvest index of quinoa in spring planting. However, there was no significant difference between salinity levels of 5 and 10 dS m-1 for seed yield, biomass weight and harvest index, but increase salinity more than 15 dS m-1 resulted to significant reduction of these traits.