Water deficient is one of most important issue in food security, especially arid and semiarid environment. The aim of this study was to evaluate the humic acid application in combination with irrigation levels on quinoa growth parameters, chlorophyll pigment physiological traits under saline- sodic soil. A field experiment, consisting three levels of humic acid (HA) treatments as control, HA1 and HA2 (0, 0.5 and 1 mg/kg soil, respectively) and three drought stress treatments (50%, 75% and 100%) water field capacity (FC) in a randomized complete block design (factorial) with three replications, was carried out in Khorasan Razavi provenance, Iran, during the dry season of 2019. The results showed that water stress decreased the chlorophyll a, chlorophyll b, total chlorophyll and carotenoids, but proline and protein contents increased with intensity of water deficient. Application of HA improved chlorophyll a, chlorophyll b, total chlorophyll and carotenoids in plants under three moisture levels. Proline and protein contents also increased with HA application. Plant height and total dry matter of quinoa increased in treatments with HA1 and HA2 application compared to control in all water stress during the growing season. The current study showed that HA were effective in alleviating drought stress and improving growth parameters.

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