Effect of Irrigation and Nutrition Management on Yield and Yield Components of Quinoa in Birjand Conditions

Quinoa is a plant that has received worldwide attention due to its ability to grow in different stresses. The seed protein content of this plant is higher than seeds and its protein quality is better than seeds and legumes. It is rich in the amino acids lysine, globulin, which makes it suitable for patients with celiac disease. These issues have led the food and agriculture organization of the United Nations (FAO) to prioritize its development, especially in countries facing environmental tensions.

An experiment was conducted during the two cropping years of 2019-20 as split plot in a randomized complete block design with three replications in the academic center for education, culture, and research (ACECR), Birjand, IR Iran in 2019 and 2020. The main factor was irrigation regimes at three levels (100% of reference evapotranspiration (ET0) (control), 65% of reference evapotranspiration, and 30% of reference evapotranspiration; the secondary factor was fertilizer levels at six levels (control, manure, vermicompost, NPK, 50% manure+ 50% NPK and 50% vermicompost+ 50% NPK). Water requirement was calculated using the FAO method using class A evaporation pan using equations 1 and 2. Then, considering the efficiency of 90% for water distribution in the field, irrigation was performed. In this method, to calculate the amount of water required by the plant, first evaporation was obtained from the daily pan evaporation (Ep) of the meteorological department and then multiplied by the pan coefficient (Kpan). The obtained value was the ET0. In this study inflorescence number per square meter, number of seed per plant, 1000 seeds weight, Chlorophyll index, leaf relative water content, seed yield and harvest index were measured.

The results showed that irrigation treatment of 30% of the reference evapotranspiration (severe stress) had a significant effect on the measured traits in both cropping years. In this treatment, seed yield decreased 38.4% and 32.6% compared to the 100% reference evapotranspiration treatment (control) in the first and second years, respectively. Also, yield and yield components were higher in integrated feeding systems than chemical and organic systems. The highest seed yield with an average of 3040.1 kg.ha-1 was obtained from 50% vermicompost+ 50% NPK application. Based on the correlation results, 1000 seed weight was one of the most important components affecting on seed yield of quinoa. In both years, with increasing the intensity of stress from 100 to 35% of reference evapotranspiration, SPAD reading showed an increasing trend. The results of trait correlation showed that there is a positive and significant correlation between harvest index and 1000 seed weight with seed yield (r = 0.74) and (r = 0.83), respectively.

According to the results of this experiment, different irrigation regimes have different effects on quinoa growth. It is concluded that in quinoa, the dry matter decreases with increasing drought stress. In compared to optimal irrigation treatment (100% of evapotranspiration), moderate and severe stress were significant decreased the number of fertile lateral branches per plant, inflorescence number per m2, number of seeds per plant, 1000 seed weight, Chlorophyll index and seed yield treatments. Also, there was not a significant difference in seed yield between mild stress (65% of reference evapotranspiration) and control. The quinoa response to fertilizer application under enough irrigation was almost constant.