The Effect of Seaweed Extract Foliar Application on the Growth and Yield of Different Genotypes of Quinoa (Chenopodium quinoa Willd.)

In recent years, population growth on the one hand and climate change on the other, have increased the need for higher agricultural production. With the expansion of cultivated areas and increasing use of chemical fertilizers, the health of the environment and humans has been jeopardized. Consequently, recent studies have begun on the type of fertilizers used, the best fertilizer composition, and how to use them. Various studies have shown that organic fertilizer can ensure the sustainability of agricultural systems’ production, sometimes as a replacement and most often as a supplement to chemical fertilizers. In conditions where climate change and the salinization of agricultural lands have had noticeable effects on the production of various crops, the need for resilient plants becomes more apparent. Quinoa (Chenopodium quinoa Willd.) is a crop that is resistant to environmental stresses and is nutritionally very rich, to the extent that its amino acid composition is compared to that of mother’s milk. The current research aims to investigate the effects of foliar application with seaweed extract on the growth and performance of different quinoa genotypes.

This research was conducted in the summer and autumn of 2020 at the educational and research farm of the Faculty of Agriculture and Natural Resources of the Islamic Azad University, Karaj unit. The study was carried out as a split-plot experiment (5×3), based on a randomized complete block design with three replications. The main factor in this research was the fertilizer factor, which included 3 treatments: control: (without foliar application with seaweed extract), foliar application with seaweed extract at a concentration of 10 percent, and foliar application with seaweed extract at a concentration of 20 percent, placed in the main plot. The other factor was the genotype of the quinoa plant, which included 5 genotypes: Giza1, Titicaca, Rosada, Kancolla, and Q12, placed in the subplot. At different stages of plant growth, traits such as seed saponin content, thousand seed weight, seed yield, days to physiological maturity, days to flowering, dry plant weight, fresh plant weight, stem diameter, inflorescence length, and plant height were measured.

The foliar application of seaweed extract had a significant effect on various traits, with a **1% significance level** for days to flowering, days to physiological maturity, inflorescence length, thousand seed weight, and seed saponin content, and a **5% significance level** for plant height. The simple effect of genotype was significant at the 1% level for all traits except for thousand seed weight. The interaction effect of foliar application × genotype was significant at the 5% level for days to flowering. The application of seaweed extract reduced the number of days to flowering by **3.8 days**, days to maturity by **4.8 days**, plant height by **5%**, and inflorescence length by **10%**. However, it had no significant effect on seed yield, as well as the fresh and dry weight of aerial parts. The highest seed yield was related to genotype Q12 (2477 kg.ha-1) and the highest thousand seed weight was related to the Giza 1 variety (2.47 g). Plant height showed a significant negative correlation with seed yield and thousand seed weight.

The use of seaweed fertilizer in the nutrition of different quinoa genotypes showed varying effects. However, the impact of this fertilizer in reducing the growth period of quinoa, which is one of the most important issues facing quinoa cultivation in our country, is very significant. The differences between the genotypes studied in this research were quite evident, but it seems that special attention should be paid to the purpose of quinoa cultivation when selecting the superior genotype. If the goal of quinoa cultivation is forage production, the Rosada genotype is recommended, otherwise, the Q12 genotype is advised.