The effect of nitrogen fertilizer on the yield, structure and quality of quinoa ( Chenopodium quinoa )

. Field experiments were conducted in 2021-2022 at the Russian


Introduction
Quinoa is an annual herbaceous plant up to 3 m tall with a thick cylindrical stem.The leaves are simple, in shape from lanceolate to almost triangular, as the leaves and stems age, they can significantly change their color to yellow-green, purple-red, and purple.The flowers of Chenopodium quinoa Willd are collected in panicles, the size and shape of which can vary significantly depending on the genotype and growing conditions, the flowers have a simple perianth, self-pollination is characteristic of the plant.Quinoa fruit is a non-opening singleseeded nut, almost round, flat, less than 2 mm in diameter, of various colors -white, yellow, red, black.Quinoa fruits are called grain in practice.This is the most economically valuable part of the harvest.Chenopodium quinoa Willd as a plant used for food has been cultivated since ancient times.Grain is characterized by high protein content, valuable biochemical composition.The adaptability of the plant to sharply changing climatic conditions allows it to be cultivated in various soil and climatic conditions.The plant is characterized by adaptability, plasticity, and ability to withstand various biotic and abiotic stresses.Chenopodium quinoa Willd is cultivated in conditions of low fertile soils, in arid conditions, various tillage systems and farming systems in general (Jacobsen, Christiansen, 2016;Jacobsen, 2017;Saeidi et al., 2020;Wang et al., 2020).
Foreign researchers have gained enormous experience in assessing adaptability, protein accumulation, formation, development of agrotechnological techniques, and yield programming.In the development of agricultural technologies for the cultivation of Chenopodium quinoa Willd, much attention is currently being paid to the regulation of the nutritional status of plants, especially in conditions of insufficient supply of macro-and microelements.Mineral nitrogen is actively involved in all metabolic processes in plants, it is a key factor in ensuring sustainable growth, yield, and protein productivity (Berti et al., 2000;Almadini et al., 2019;Saeidi et al., 2020;Wang et al., 2020;Ebrahimikia et al., 2021).
Although nitrogen has been a key element in increasing yields worldwide for more than four decades, the rate of nitrogen fertilizer use by plants remains low.Fractional nitrogen application is one of the ways to increase the efficiency of the use of nitrogen fertilizers by field crops, it can significantly reduce the loss of nitrogen fertilizers.Fractional nitrogen application can increase the yield and quality of quinoa grains (Montemurro et al., 2016;Kakabouki et al., 2018;Saeidi et al., 2020).
In Russia, studies have been carried out to assess the possibility and prospects of growing quinoa in the soil and climatic conditions of the Central Region using biological farming technologies, without the use of pesticides and mineral fertilizers (Grits, Dichenskiy, 2019; Kukharenkova, Kurenkova, 2020; Shitikova, Kukharenkova, 2022 and 2023; Shitikova et al., 2022).
The purpose of the experiment was to study the effect of nitrogen-containing fertilizers in different doses (from 60 to 120 kg d.a./ha) on protein content, qualitative characteristics of grain, and the formation of productivity in the conditions of the Moscow region of Russia.

Materials and Methods
Field experiments were laid on sod-podzolic soils on the territory of the Russian State Agrarian University -RSAU-MAA named after K.A. Timiryazev (city of Moscow).Cultivars of different ecological and geographical origin were studied: Titicaca (Denmark), Cherry Vanilla (USA), Regalona (Chile).Grain products of plants are used for food.The variants were placed by the randomization method.For sowing, an ordinary method was used (the distance between rows during sowing was 0.45 m), with a sowing rate of 5.0 million germinating seeds/ha.Experimental data were subjected to statistical processing (MO Excel).The following plant parameters were determined: the mass and number of grains in a panicle, the mass of 1000 grains.

Discussion
The duration of the quinoa growing season in our studies was 127 days in 2021 and 124 days in 2022.In the third decade of May, after sowing, shoots began to appear about 8-9 days later.In the following months, in late June and early July, the appearance of inflorescences could be observed on the plants.The whole process lasted until the end of September, until about the second or third decade.Nevertheless, crop yield is no less important indicator.Under the conditions of the field experiment, the yield significantly depended on weather conditions during the growing season (Table 1 The quinoa yield of all the studied cultivars in the conditions of 2022 was higher, by 1.76-2.51tons higher for Cherry Vanilla cultivar than in 2021, by 1.74 -3.03 tons for Titicaca cultivar, and by 1.29 -2.33 t/ha for Regalona cultivar according to comparable experiment variants.In the course of research, it was found that the use of nitrogen fertilizer has a positive effect on the quinoa yield.During the two years of the experiment, an increase in yield was observed depending on the dose of nitrogen.For example, the Cherry Vanilla variety has an increase in yield by 0.19-0.75tons per hectare, the Titicaca variety -by 0.50-1.29 tons per hectare, and the Regalona variety -by 0.48-1.04tons per hectare compared to the control group.The highest quinoa yields were achieved when applying a dose of nitrogen N120.In this case, the average yield over two years was 2.32 tons per hectare for the Regalona variety, 2.50 tons per hectare for the Cherry Vanilla variety and 3.02 tons per hectare for the Titicaca variety.Nitrogen fertilizer was applied twice: in the phase of 4-6 leaves and at the beginning of the panicle formation.These results suggest that the use of nitrogen fertilizer can significantly increase the yield of quinoa.It is especially important to note that all three varieties achieved the highest yields when applying a certain dose of nitrogen.This can be useful information for farmers and gardeners who are engaged in quinoa cultivation and strive to get the maximum yield.In addition, these research results confirm the importance of regular application of nitrogen fertilizer to ensure optimal growth and development of quinoa culture.Nevertheless, additional studies are needed to determine the optimal nitrogen doses for each specific variety and growing conditions.This will allow farmers to accurately determine the required amount of nitrogen fertilizer to achieve the highest quinoa yields.A higher payback of 1 kg N by an increase in grain yield in an average of two years was obtained when N60 was introduced into the phase of 4-6 leaves when cultivars of Titicaca and Regalona were grown -13.50 kg and 11.00 kg of grain per 1 kg of nitrogen.The Cherry Vanilla varietal was noticeably inferior to the Titicaca and Regalona varietals in terms of the payback of fertilizer nitrogen by the increase in grain yield.With wide-row sowing and regulation of the distance between seeds in a row only by the seeding rate, by the time of harvesting there were 540-660 thousand Cherry Vanilla and Titicaca varietal plants and 480-520 thousand plants/ha of Regalona varietal.Under the influence of nitrogen fertilizer, the grain weight from one plant changed, first of all ( The weight of grain from one plant increased significantly with the introduction of 120 kg of nitrogen/ha, especially in the more productive year 2022.It was 5.93 g in the Cherry Vanilla varietal, 8.13 g in the Titicaca varietal, and 6.99 g/plant in the Regalona varietal; it was 1.95 g more in the Cherry Vanilla varietal, 3.91 g in the Titicaca varietal, and 3.68 g/plant in the Regalona varietal than in the experiment variant without the use of nitrogen fertilizer.Quinoa plants form large, branched panicles up to 30 cm or longer, containing a large number of grains.The maximum number of grains, reaching 3.5 and 4.0 thousand grains/panicle, was found in the varieties Regalona and Titicaca with the addition of 120 kg of nitrogen/ha.The grain size of quinoa is not large, with a mass of 1000 grains ranging from 1.50-1.55g (Regalona variety, control variant) to 2.30 g (Cherry Vanilla variety, variant with the addition of N120).The grain diameter varies from 0.5 to 2.0 mm.Quinoa grain is a source of highquality protein.The assessment of the nutritional value of quinoa grain is mainly based on its protein content.During the research period, the protein content in quinoa grain with a moisture content of 14% varied depending on meteorological conditions, doses, and timing of nitrogen fertilizers and varietal characteristics of plants, ranging from 8.4% (Cherry Vanilla variety, control variant of the experiment, 2022) to 13.9%.(Regalona varietal, variant of experiment N120, 2022).

Conclusion
Studies demonstrate that when using nitrogen fertilizers Chenopodium quinoa Willd in agroecological conditions of the Central region of Russia provides higher yields and protein content in grain.The application of nitrogen fertilizer at a dose of N120 leads to an average grain yield of 1.3, 2.4, and 3.1 tons per hectare for plants of the varieties Regalona, Cherry Vanilla, and Titicaca, respectively, for two years.The most effective payback of 1 kg of nitrogen fertilizer in the form of an increase in grain yield is observed when cultivating Titicaca and Regalona varietals with the addition of N60 and averages 13.51 kg and 11.01 kg of grain per 1 kg N. Quinoa plants form panicles of various shapes and sizes, over 30 cm long with a large number of grains and a grain weight per plant reaching 5.7 g when applying 120 kg of N per hectare.

Table 1 .
). Quinoa grain yield and nitrogen fertilizer payback by crop increase.