Changes in flax yield and quality in response to various mineral nutrition

Alterações no rendimento e qualidade do linho em resposta a vários nutrientes minerais

Abstract

The researchers of Russian State Agrarian University, Moscow Timiryazev Agricultural Academy in 2013-2016 conducted a long-term stationary experiment to study chemical and toxicological properties of fiber flax, Voskhod variety, growing on sod-podzolic soil in the soil and climate of the Moscow region. Test plots were selected with following crop rotation options: without fertilizers, without liming; without fertilizers, with liming; N₁₀₀P₁₅₀K₁₂₀ (kg a.i./ha), without liming; N₁₀₀P₁₅₀K₁₂₀, with liming; N₁₀₀P₁₅₀K₁₂₀ + manure 20 t/ha, without liming; N₁₀₀P₁₅₀K₁₂₀ + manure 20 t/ha, with liming. The agro-climatic conditions of the growing seasons during the research years did not have a negative impact on the growth and development of fiber flax, the hydro-thermal index was 1.1 in 2013, -1.05 in 2014, 1.5 in 2015, and 1.5 in 2016. The maintained crop rotation and the introduction of a full range of mineral and organic fertilizers has been found to contribute to high yields of flax in terms of fiber (18.5-18.9 hwt/ha) and seeds (7.9-8.3 hwt/ha). The seeds contain 16.9-19.5% protein and 33.5-39.4% lipids. The yield of flaxseed oil from seeds ranged from 19.5-35.7% on average for different variants of the experiment. The peroxide number index was 2.5-1.5 mg-eq O₂/kg, the acid number index was 1.1-1.9 mg KOH/g, which corresponds to obtaining high-quality linseed oil in compliance with quality standards for all variants of the experiment.

Keywords:
fiber flax; fertilizers; fiber; seeds; linseed oil; chemical analysis

Resumo

Os pesquisadores da Universidade Agrária Estatal Russa, Academia Agrícola Timiryazev de Moscou, de 2013 a 2016, realizaram um experimento estacionário de longo prazo para estudar as propriedades químicas e toxicológicas da fibra de linho, variedade Voskhod, crescendo em solo sod-podzólico e no clima da região de Moscou. As parcelas-teste foram selecionadas com as seguintes opções de rotação de culturas: sem fertilizantes e sem calagem; sem fertilizantes e com calagem; N100P150K120 (kg ia/ha), sem calagem; N100P150K120 e com calagem; N100P150K120 + esterco 20 t/ha e sem calagem; N100P150K120 + esterco 20 t/há e com calagem. As condições agroclimáticas das épocas de cultivo durante os anos de pesquisa não tiveram impacto negativo no crescimento e desenvolvimento do linho têxtil, o índice hidrotérmico foi de 1,1 em 2013, -1,05 em 2014, 1,5 em 2015 e 1,5 em 2016. Verificou-se que a manutenção da rotação de culturas e a introdução de uma gama completa de fertilizantes minerais e orgânicos contribuem para altos rendimentos de linho em termos de fibra (18,5-18,9 hwt/ha) e sementes (7,9-8,3 hwt/ha). As sementes contêm 16,9-19,5% de proteína e 33,5-39,4% de lipídios. O rendimento de óleo de linhaça das sementes variou de 19,5 a 35,7% em média para diferentes variantes do experimento. O índice de peróxido foi de 2,5-1,5 mg-eq O2/kg, o índice de acidez foi de 1,1-1,9 mg KOH/g, o que corresponde à obtenção de óleo de linhaça de alta qualidade em conformidade com os padrões de qualidade para todas as variantes do experimento.

Palavras-chave:
linho fibra; fertilizantes; fibra; sementes; óleo de linhaça; análise química

1. Introduction

According to Food and Agriculture Organization of the United Nations (FAO) statistics, today a limited number of countries grow fiber flax for commercial purposes: Belarus, Belgium, China, Czech Republic, France, Lithuania, Netherlands, Poland, Russia, Ukraine, and Egypt. France is the leader in crop area, followed by Belarus and Russia. The rise of the flax-growing branch of agriculture in Russia in recent years has been facilitated by the adoption of the State Program for the Development of Agriculture until 2025 (Molajou et al., 2021a). This program significantly has deepened and expanded the economic measures of influence on the processes in the agrarian and agri-food spheres of the country, among which a significant place was and is given to subsidies and subsidies that stimulate the growth of production, including the flax-growing subcomplex (Molajou et al., 2021b; Afshar et al., 2022). However, in the global production of natural and synthetic fibers, flax occupies a limited market segment, as Table 1 shows. This corresponds to the fact that only 0.1 kg of flax fibers produced per year per inhabitant of our planet, which, of course, is extremely low (Rozhmina et al., 2018).

Table 1
Global production volumes of various types of fibers, 1970-2016 (thousand tons).

Year	Chemical fibers	Cotton	Sheep wool	Other animal wool	Flax	Silk	Total
1970	8,397	11,379	1701	-	703	46	22,226
1980	14,182	14,084	1646	-	620	69	30,601
1985	16,336	19,245	1763	-	763	68	38,175
1990	18,519	17,362	2007	67	688	83	38,726
1995	22,204	18,754	1520	55	716	113	43,373
2000	33,083	19,118	1343	48	528	111	54,232
2005	41,291	26,422	1219	50	1013	152	70,148
2010	51,266	22,480	1121	51	299	165	75,644
2015	67,535	25,916	1156	58	313	169	95,147
2016	68,377	20,912	1141	56	317	169	91,971
2016\1970, %	814	184	67	-	45	367	413

Despite the high productivity of modern fiber flax varieties, their maximum biological capabilities and potential of the variety in production conditions can be 30-50%, which is largely due to the insufficient use of mineral fertilizers in the optimal ratio of nutrients. The use of environmentally friendly, biologically active products can also increase the economic efficiency of flax cultivation through a natural positive effect on productivity. Consequently, with the rational use of soil resources, fertilizers, plant protection products, the results of selection and technological methods of cultivation of flax, it is possible to obtain high yields of fiber and seeds (Du et al., 2015).

The value of fiber flax is due to the variety of its uses (Duman, 2022; Dundar et al., 2021; Ahmad et al., 2021). Fabrics for various purposes are produced from flax fiber: clothing (linen fabrics), household, furniture-decorative, industrial, as well as special-purpose fabrics (medical and defense industries). In the EU countries and China, 30-50% of the production of linen fabrics is textile fabrics for the production of clothing, in Russia the production of technical fabrics accounts for about 50% (Grishina et al., 2016; Grigoryeva et al., 2021).

Flax seeds are a valuable source of various substances: proteins (18-23%), fats (30-40%), phospholipids, macro- and microelements (Abu-Zaid et al., 2022). Flaxseed oil rich in polyunsaturated fatty acids (Omega-3 and Omega-6) is produced from the seeds. Flax seeds and linseed oil are used for food, medical, and technical purposes.

Harsh competition in the sales market, including in the flax sector, has set domestic producers the task to obtain high-quality fiber, seeds, and oil, end ensure strict control of their finished product quality and chemical composition (Belopukhov et al., 2010; Enakiev et al., 2018; Man et al., 2021; Dmitrevskaya et al., 2022).

Given the above, the objective of our research was to adapt the fiber flax, Voskhod variety, to the soil and climatic conditions of the Moscow region and to study the chemical composition of flax seeds and flaxseed oil in response to the application of mineral and organic fertilizers and without fertilizers.

2. Material and Methods

The studies were carried out in 2013-2016 as part of the long-term field experiment of Russian State Agrarian University, Moscow Timiryazev Agricultural Academy, started by Professor A.G. Doyarenko in 1912 (Filippova et al., 2018; Mazirov et al., 2021). The soil of the experimental plot is sod-medium and slightly podzolic, old-arable (more than 200 years under arable land), naturally acidic and floating (according to the FAO classification - Podsolluvisol). The soil characteristics of the experimental site are presented in Table 2.

Table 2
Properties of the 0-20cm soil layer of the experimental plot 60 years after the start of the experiment (Leonidovich et al., 2015).

Parameters	Experimental mean
Solid phase density, g/cm3	2.65
Soil density, g/cm3	1.53
Maxim. hygroscopicity (MH), %	1.25
pH, pH meter units	5.2
Humus carbon (C), %	1.03
Total nitrogen, %	0.079
C/N*	13
Р2О5 (mobile), mg/kg	520
К2О (metabolizable), mg/kg	160
Total metabolizable alkali, m-eq/kg	97

• ^*
  C/N is the ratio of carbon to nitrogen.

All fields with permanent crops are divided into 11 plots; fields with crop rotation are divided into 9 plots being fertilized as follows: 1 - N; 2 - P; 3 - K; 4 - without fertilizers; 5 - NP; 6 - NK; 7 - PK; 8 - manure + NPK; 9 - NPK; 10 - manure; 11 - without fertilizers (Table 3). The crop rotation plot has no 10th and 11th options.

Table 3
Long-term field experiment scheme.

PERMANENT
	121			122				123				124				125				126
011
Manure
NPK				W.				P				B				C
NPK + manure	F							O				A				L
PK	A			R				T				R				O				F
NK	L			Y				A				L				V				L
NP	L			E				T				E				E				A
04	O							O				Y				R				X
K	W
P
N
	With liming
CROP ROTATION
	131				132				133				134				135			136
NPK
NPK + manure					C								F				W.			P
PK	B				L				F				A							O
NK	A				O				L				L				R			T
NP	R				V				A				L				Y			A
04	L				E				X				O				E			T
K	E				R								W							O
P
N
	Without liming

Since 1949 (7th crop rotation), liming has been introduced into the experiment, as one of the essential factors in the cultivation of acidic soddy-podzolic soils. Lime is applied to half of each field, in the form of dolomitized limestone - once per crop rotation (the dose is based on the values of the hydrolytic acidity of the soil).

Doses of mineral fertilizers in 1973 were increased and amounted to N₁₀₀, Р₁₅₀, К₁₂₀ for food elements. Phosphorus and potash fertilizers are applied at the same time for pre-sowing treatment, and nitrogen fertilizers - in 2 periods: in the fall (N₅₀) and in the spring as top dressing (N₅₀).

Since 1973, to study the aftereffect of fertilizers, their plot application was stopped on even fields (132, 134, 136) of the main crop rotation, and each field has been fertilized with a continuous single dose of N₁₀₀Р₁₅₀К₁₂₀. Manure also has not been applied to these fields. For permanent winter rye, 20 tons of manure are applied annually per hectare in 8 and 10 variants.

Variants of field experiments were selected in the crop rotation: zero level (no fertilizers, no liming) - variant 1; zero level (without fertilizers, with liming) - variant 2; N₁₀₀P₁₅₀K₁₂₀, without liming - vatriant 3; N₁₀₀P₁₅₀K₁₂₀, with liming - variant 4; N₁₀₀P₁₅₀K₁₂₀ + manure 20 t/ha, without liming - variant 5; N₁₀₀P₁₅₀K₁₂₀ + manure 20 t/ha, with liming - variant 6.

The agricultural flax cultivation technique was as follows: in the fall, the primary plowing was carried out with MTZ 12+21+UNIA 2+1 vehicle (small reversible plow), in the spring - harrowing (moisture closure) with MTZ-80+BZTS-1.0 vehicle, cultivation with MTZ-80+ZBC-300 vehicle. Seeding rate of seeds was 22 mln.pcs./ha. Sowing was carried out with MTZ-80+AMAZOND9-30 vehicle. The area of the plots was 50 m², the registration plot area was 25 m². The predecessor in all the years of research is the first-year clover. Nitrogen fertilizers were applied in the spring before sowing; phosphorus, potash, and manure - in the fall. Liming has been carried out once every 4-5 years based on the hydrolytic acidity of the soil, during the years of our research it was not carried out. The soil is soddy-podzolic, medium and light loamy, old arable, according to agrochemical indicators (average values during the years of research): soil density 1.5-1.6 g/cm³, humus content (Tyurin) - 2-2.5%, P₂O₅ (Kirsanov) - 170-180 mg/kg, K₂O (Maslova) - 90-100 mg/kg, N, readily hydrolysable (Tyurin) - 5-5.5 mg/100 g, pH_(water) - 5.5-6.

Agroclimatic conditions of the growing seasons 2013-2016 did not have a negative effect on the growth and development of fiber flax, the yield of which was mainly determined by the studied factors. The HDC (hydrothermal coefficient), which characterizes the degree of moisture in the growing season, was 1.1 in 2013, -1.05 in 2014, 1.5 in 2015, and 1.4 in 2016. Thus, 2013 is a poorly humid year, 2014 is a moderately dry year, and 2015 -2016 is a fairly humid year.

The fiber and seed yield data were calculated for the variants of the experiment in accordance with the existing guidelines and recommendations (Mikhailouskaya and Bogdevitch, 2009; Berezovsky et al., 2020; Dudarev, 2022; Rihaczek et al., 2020). Samples of seeds and oil were obtained from Voskhod fiber flax (Russian selection).

Chemical analysis of seeds for the content of the total amount of lipids and proteins, as well as the fatty acid composition of flaxseed oil was performed by near infrared spectroscopy (NIR), SpectraStar XL 2500XL-R, in accordance with GOST 32749. Flaxseed oil was obtained by cold pressing in accordance with GOST 5791. Determined linseed oil yield, acid number according to GOST 50457 and peroxide number according to GOST 51487. Elemental analysis of seeds was determined by atomic absorption spectroscopy (AAS) (KVANT-Z ETA instrument model). All tests were performed in triplicate, confidence intervals with a significance level of 95% were calculated in Excel.

3. Result and Discussion

The productivity of agricultural crops is closely dependent on the presence of the basic elements of mineral nutrition in the soil. Therefore, the forms and doses of fertilizers applied under flax directly affect the yield of flax and the quality of the resulting flax products.

In our studies, the field experiment was carried out on the territory of the “Long-term field experiment of Russian State Agrarian University, Moscow Timiryazev Agricultural Academy”, known abroad as the “Moscow permanent study area”. Fiber flax has been grown in this experiment for over 100 years. The multifactorial experience of long-term use of fertilizers, both individually and in various combinations, is a method of understanding the basic patterns of the formation of flax yields and soil fertility conditions in the Non-Black Earth Zone of Russia (Mikhailouskaya and Bogdevitch, 2009).

Our data show high yields of flax from plots with a full range of mineral fertilizers, together with the introduction of manure and liming, both in fiber (18.5-18.9 hwt/ha) and in seeds (7.9-8.3 hwt/ha) (Table 4).

Table 4
Yield of fiber flax, Voskhod varieties, hwt/ha.

yield/variant	1	2	3	4	5	6	SD 05
2013
flax straw	50.5	54.9	56.9	60.4	60.1	65.6	2.6
fiber	16.4	16.9	17.0	17.6	17.5	18.9	0.8
seeds	6.9	7.0	7.1	7.9	7.6	8.2	0.4
2014
flax straw	48.3	50.2	55.8	57.2	57.2	62.3	2.5
fiber	15.3	15.7	16.0	17.0	16.6	18.5	0.8
seeds	6.4	6.6	6.7	7.7	6.8	7.9	0.3
2015
flax straw	50.1	52.3	54.5	56.6	60.5	64.6	2.5
fiber	15.9	16.5	17.1	17.9	16.9	18.5	0.7
seeds	6.7	6.7	7.1	7.4	7.8	8.3	0.3
2016
flax straw	50.0	52.1	54.3	56.5	60.2	64.2	2.4
fiber	15.5	16.3	17.5	17.4	16.5	18.3	0.6
seeds	6.4	6.5	7.0	7.3	7.5	8.2	0.3

• SD: significant differences.

Plots with N₁₀₀P₁₅₀K₁₂₀, without liming (variant 3) produced higher yield by 6.1 hwt/ha of flax straw, by 0.8 hwt/ha of fiber, by 0.3 hwt/ha of seeds relative to zero level plots (without fertilizers, without liming) (variant 1). A similar increase in yield was on plots with liming. The average yield increase over three years of research on plot with N₁₀₀P₁₅₀K₁₂₀, with liming (variant 4) was by 5.6 hwt/ha of flax, by 1.1 hwt/ha of fiber, by 0.9 hwt/ha of seeds relative to the zero-level plot (without fertilizers, with liming) (variant 2).

The introduction of organic fertilizers (manure) together with mineral fertilizers (variant 5, 6) contributed to an average increase in yield by 3.5 - 6.1 hwt/ha of flax straw, by 0.4 - 1.1 hwt/ha of fiber and by 0.4 - 0.5 hwt/ha of seeds relative to options with a full complex of fertilizers (variants 3, 4) over three years of research.

Liming promoted an increase in the yield of flax straw by 1.4 - 5.5 hwt/ha, fiber by 0.4 - 1.6 hwt/ha and seeds by 0.1 - 1.1 hwt/ha relative to plots without liming.

Thus, the use of mineral fertilizers together with manure and liming (variant 6) has led to the increase in the yield of flax straw by 30%, fiber by 17%, and seeds by 21% compared to the variant without fertilizers and liming (variant 1).

The harvested flax seeds were analyzed for the content of the total amount of proteins and lipids (Table 5).

Table 5
Chemical composition of fiber flax seeds, % on absolutely dry basis.

variant	1	2	3	4	5	6	SD 05
2013
proteins	17.2	17.5	18.0	18.9	19.1	19.5	0.7
lipids	34.1	34.7	36.7	37.9	38.4	38.7	1.3
2014
proteins	16.9	17.7	18.9	18.9	19.3	20.1	0.8
lipids	33.5	35.3	36.9	37.5	37.9	38.8	1.3
2015
proteins	17.4	17.3	18.3	19.2	19.4	20.0	0.7
lipids	34.2	34.9	36.5	37.4	38.2	39.4	1.4
2016
proteins	17.3	17.1	18.2	19.0	19.3	20.1	0.7
lipids	34.0	34.5	36.4	37.1	38.1	39.2	1.3

• SD: significant differences.

Plots treated with a full set of mineral fertilizers together with manure and liming (variant 6) produced seeds with the higher content of protein by 2.7% and lipids by 5.1% relative to plots without fertilizers and liming (variant 1). Liming of plots contributed to the higher content of protein and lipids in flax seeds by 0.3%-0.9% and 0.3-1.8%, respectively, relative to plots without liming on average over three years of research.

An important feature of the quality of the obtained flaxseed oil is its yield (%), acid (AN) and peroxide (PN) numbers. We have determined these indicators when obtaining flaxseed oil from seeds (Table 6).

Table 6
Quality indicators of flaxseed oil of fiber flax seeds, Voskhod variety.

indicator / variant	1	2	3	4	5	6	SD 05
2013
oil yield, %	19.5	20.0	25.5	30.4	31.3	35.7	1.1
PN, mg-Eq О2 /kg	2.4	2.4	2.0	1.9	1.7	1.6	0.08
AN, mg КОН/g	1.8	1.8	1.3	1.1	1.1	1.1	0.05
2014
oil yield, %	20.0	21.2	25.8	29.6	30.6	34.9	0.9
PN, mg-Eq О2 /kg	2.4	2.1	1.9	1.8	1.7	1.5	0.06
AN, mg КОН/g	1.9	1.7	1.5	1.2	1.1	1.1	0.05
2015
oil yield, %	19.8	22.3	24.9	30.0	33.2	34.7	1.02
PN, mg-Eq О2 /kg	2.5	2.3	1.9	1.9	1.6	1.5	0.07
AN, mg КОН/g	1.9	1.8	1.5	1.2	1.2	1.1	0.05
2016
oil yield, %	19.5	22.0	24.5	30.0	32.9	34.5	1.00
PN, mg-Eq О2 /kg	2.3	2.3	1.9	1.9	1.5	1.5	0.07
AN, mg КОН/g	1.8	1.8	1.5	1.2	1.2	1.1	0.05

• SD: significant differences.

Hydroperoxides are the main primary oxidation products of unsaturated fatty acids. The peroxide number, which characterizes the content of organic hydroperoxides in the oil, is one of the most important indicators of oil quality for its oxidation state (Tables 6). The primary oxidation products of oils and fats are unstable and easily decompose, transforming into secondary oxidation products, which are a complex group of compounds including various aldehydes and ketones, hydrocarbons, epoxy compounds, relatively stable alcohols, acids, hydroxy acids, and others. Aldehydes and ketones impart unpleasant taste, odor, and toxicity to fats. It should be noted that, although usually for edible vegetable oils, maximum admissible level of PN is 10 mg-eq O²/kg, a change in taste (rancidity) and odor of highly unsaturated linseed oil usually begins at PN less than 3-5 mg-eq O₂/kg oil. The acid number (AN), which characterizes the content of free fatty acids, should not exceed 2 mg KOH/g oil (Bozan and Temelli, 2008; Mohanan et al., 2018; Cheng et al., 2019).

The flaxseed oil yield ranged from 19.5-35.7% on average for different variants of the experiment. The yield of oil of flax seeds increased significantly on experimental plots with the use of a full set of mineral fertilizers (variant 3, 4) 5 - 10.4% relative to plots without fertilization (variant 1, 2). Plots treated with a full set of mineral and organic fertilizers (variant 6) showed an increase in the yield of flaxseed oil by 14.9-16.2% relative to the zero level plots (variant 1)

The PN was 2.5-1.5 mg-eq O₂/kg and the AN was 1.1-1.9 mg KOH/g, which corresponds to the production of high-quality linseed oil in accordance with quality standards (TU U 15.4 - 32448339 - 001: 2005) for all variants of the experiment. Both AN and PN were lower in the fertilized variants relative to the variants without fertilizers.

The fatty acid composition of flaxseed oil is represented by the content of the total of saturated fatty acids 9.0-14.1%, the total of unsaturated fatty acids - 85.9-91.0%; the composition of unsaturated fatty acids had a high content of diet-essential α-linolenic acid - 46.9-60.9% (Table 7).

Table 7
Fatty acid composition of flaxseed oil, %.

Variant	Year	Total saturated fatty acids	Total unsaturated fatty acids	Total palmitic and stearic acids	α-linolenic acid content
1	2013	13.5	86.5	12.9	47.6
2		13.4	86.6	12.8	47.8
3		11.2	88.8	12.1	50.2
4		11.0	89.0	11.5	55.3
5		9.5	90.5	11.0	55.5
6		9.3	90.7	10.9	60.1
SD 05		0.4	3.5	0.4	2.0
1	2014	14.1	85.9	13.2	46.9
2		13.6	86.4	12.9	47.1
3		11.6	88.4	11.8	50.5
4		11.2	88.8	11.7	56.2
5		9.3	90.7	10.8	55.9
6		9.1	90.9	10.5	59.8
SD 05		0.4	3.2	0.4	1.9
1	2015	13.8	86.2	13.1	47.9
2		13.2	86.8	13.0	47.9
3		11.3	88.7	11.6	50.7
4		11.1	88.9	11.3	54.6
5		9.5	90.5	10.9	55.5
6		9.0	91.0	10.6	60.9
SD 05		0.4	3.4	0.3	2.0
1	2016	13.6	86.4	13.2	48.0
2		13.1	86.9	13.2	47.9
3		11.0	89.0	11.7	50.5
4		11.0	89.0	11.5	54.5
5		9.3	90.7	10.4	55.5
6		9.1	90.9	10.1	60.5
SD 05		0.4	3.3	0.4	1.9

• SD: significant differences.

The application of fertilizers, according to the variants of the experiment, contributed to a decrease in the amount of saturated fatty acids and an increase in the amount of unsaturated fatty acids in linseed oil. Variants treated with the full set of mineral fertilizers (variant 3, 4) had a decrease in saturated fatty acids and an increase in unsaturated fatty acids - 2.1-2.5% relative to the zero level plots (variant 1, 2). The same changes were in the composition of fatty acids of flaxseed oil in variant 6 (4.1% - 4.8%) relative to variant 1. Liming slightly influenced the fatty acid composition of the oil according to the variants of the experiment.

A wide variety of the content of elements in flax seeds provides a wide range of their medico-biological properties, which allows the seeds to be used as additives for the production of various food products. Table 8 shows the results of elemental analysis of long flax seeds.

Table 8
Content of chemical elements in fiber flax seeds, Voskhod variety, mg/kg (average for 2013-2016).

Element	variant						SD 0.5
	1	2	3	4	5	6
Mg	5400	5620	5523	5614	5123	5123	210
Ca	2215	2410	2421	2451	2510	2623	120
Fe	2321	2415	2241	2531	2512	2457	118
K	1652	1655	1685	1701	1670	1589	110
Zn	20.5	20.5	21.1	24.9	24.5	25.1	1.5
Mn	10.5	9.5	9.0	9.1	8.9	9.5	0.9
Cr	11.5	10.0	8.1	10.5	9.3	10.1	0.9
Si	4.3	4.3	4.5	4.5	4.5	4.5	0.5
Al	3.0	3.1	3.5	3.0	3.5	3.0	0.4
Cu	0.5	0.5	0.5	0.5	0.5	0.5	0.1
Pb	0.2	0.2	0.2	0.2	0.2	0.2	0.1
Cd	0.2	0.1	0.1	0.1	0.1	0.1	0.1
Hg	0.03	0.01	0.02	0.01	0.02	0.01	0.01

the content of chemical elements in seeds can be grouped as follows:

• $highcontent,1500-5620mg/kg-Mg,Ca,Fe,K$;

• $3.0-25.1mg/kg-Zn,Mn,Cr,Si,AI$;

• $0.01-0.5mg/kg-Cu,Pb,Cd,Hg$.

Trace elements with high concentrations in agricultural products are classified as heavy metals of different hazard groups. Our studies have not found the exceeded MPC thresholds in the variants of the experiments.

4. Conclusion

Thus, as a result of our studies conducted in the conditions of the Moscow region on the territory of the Long-term stationary experiment of Russian State Agrarian University, Moscow Timiryazev Agricultural Academy, where fiber flax has been grown for more than 100 years, with the maintained crop rotation and the introduction of a full range of mineral and organic fertilizers, we obtained high yields of flax fiber (18.5-18.9 hwt/ha) and flax seeds (7.9-8.3 hwt/ha).

The content of protein and lipids in seeds was 16.9-19.5% and 33.5-39.4%, respectively. Acid and peroxide numbers of linseed oil meet quality standards. In the fatty acid composition of flaxseed oil, the content of the total of saturated fatty acids is 9.0-14.1%, the content of unsaturated fatty acids is 85.9-91.0%. There was a high content of essential α-linolenic acid is 46.9-60.9%. The content of chemical elements in flax seeds was high for magnesium, calcium, iron, potassium (1500-5620 mg/kg), medium for zinc, manganese, chromium, silicon, aluminum (3.0-25.1 mg/g), and low for copper, lead, cadmium, and mercury (0.01-0.5 mg/kg).

Acknowledgements

The article was made with support of the Ministry of Science and Higher Education of the Russian Federation in accordance with agreement Nº 075-15-2020-905 date November 16, 2020 on providing a grant in the form of subsidies from the Federal budget of Russian Federation. The grant was provided for state support for the creation and development of a World-class Scientific Center “Agrotechnologies for the Future”.

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Publication Dates

• Publication in this collection
  02 June 2023
• Date of issue
  2024

History

• Received
  21 May 2022
• Accepted
  29 July 2022