The timing of oilseed flax sowing in the steppe zone of Western Siberia

. In the steppe zone of the Omsk region from 2020 to 2022 two sowing periods (May, 15 and 25) of Severny oilseed flax with a seeding rate of five million germinated seeds per hectare on four chemicalization backgrounds were tested. With the norm for the steppe zone of the HTC 0.78 all the years of the experiments this indicator was only 0.37-0.58. Having sowed in the third decade of May, the yield of oilseed flax seeds with the use of a tank mixture of herbicides (Agritox, WC 1 l/ha and Legion, EC 0,4 l/ha) with a working fluid flow rate of 200 l/ha 0.868 tons of oilseeds were obtained from 1 ha and 1.009 t/ha were obtained with the help of a complex chemicalization, where Lingohumate 100 g/ha was used during the leaf development phase in a mixture of herbicides and Isagry Bor 0.5 l/ha during the building phase. They provided a profitability level of 197 %. Similar results were obtained having used only herbicides – 179.9 %. Ammophos’s introduction during sowing did not bring a significant increase in yield and reduced economic indicators. Having sowed in the second decade of May, the annual oilseeds yield was significantly lower and, accordingly, the level of profitability was decreasing sharply from 27.8 to 87.8 %.


Introduction
Oilseed flax (Linum usitatissimum L.) is a fibrous dicotyledonous plant in the flax family (Linaceae) with potential economic value, which has a long history of cultivation in agriculture and is grown throughout the world [1,2].
Research on the technology of oil flax cultivation is carried out in different regions of the Russian Federation -in the Krasnoyarsk Kray [3,4], in the Stavropol Kray [5], the Volgograd Oblast [6], in the Middle Urals [7], in the Southern Trans-Urals [8], in the Northern Trans-Urals [9], in the Omsk Oblast [10].Here are presented data for the southern forest steppe [11].When cultivating oilseed flax in Siberia, the optimal sowing time is at the end of the second decade of May, when early spring weeds emerge [12].In the Northern Urals, the optimal sowing time is considered to be in the first decade of May [7].In the conditions of Northern Kazakhstan, it is advised to shift the sowing of flax to the third decade of May [13].
It should be noted that the sowing time also affects the composition of linseed oil [14].

Conditions and methods of research
Field experiments were laid in the steppe zone of the Omsk Oblast (Odessa district) on ordinary chernozem, medium-thick, low-humus, heavy loam.The content of humus in the topsoil is 4.6 %, total nitrogen 0.31 %, phosphorus 0.16 %, pH 7.0.Oil flax (Severnyi variety) was sown at a rate of 5 million germinating seeds per 1 ha to a depth of 3-4 cm in two terms: May 15 and 25 in crop rotation: peas -wheat -wheat -flax -wheat -barley.
The repetition in the experiment is fourfold, the plot area is 60 m 2 (2 x 30).Used 4 chemicalization backgrounds: I -herbicide tank mix in herringbone phase (Agritoks 1 l/ha and Legion 0.4 l/ha with a working fluid flow rate of 200 l/ha); II -sowing application of ammophos N12P52 and tank mixture of herbicides; III -complex chemicalization (tank mixture of herbicides + Lignohumate 100 g / ha in the herringbone phase and Isagri Bor 0.5 l / ha in the budding phase); IV -to the third option additionally N12P52 when sowing.

Research results
Accounting for the reserves of productive moisture in a meter-long soil layer showed that during the first sowing period in the second decade of May, the indicators were annually less than 90 mm, and this is a bad level (Table 1).In the third decade of May, when sowing flax, a satisfactory moisture content was noted in 2021 and even good in 2022.By harvesting flax, there were no differences in moisture reserves between sowing dates.They were very bad in 2020 and in 2021-2022 -bad.
The poor supply of soil with moisture, especially in the upper ten-centimeter layer, affected the fullness of flax seedlings.When sowing in the second decade of May, this figure averaged 58.3-60.0% over 3 years (Table 2).On crops in the third decade of May, the completeness of seedlings was higher by 19.0-20.0%.Insufficient rainfall during the growing seasons in all years of experiments led to a significant thinning of flax crops.Depending on the background of chemicalization, the survival rate of flax plants when sown in the second decade of May, on average for 3 years, was 46.8-54.4% (Table 3).An increase in the chemical treatment used contributed to an increase in survival by 2.3-7.6 %.On crops sowed in the third decade of May, the survival rate was higher by 9.4-13.9%.However, the advantage of this sowing time decreased as the chemicalization background increased.
The best development of flax plants sowed in the third decade of May was reflected in the yield of seeds.Although the lack of moisture for all three years of experiments, allowed to obtain an average of only 0.868 tons of seeds per 1 ha against the background of the use of herbicides (Table 4).The introduction of 1 q of ammophos per 1 ha during sowing increased the seed yield by only 0.065 t/ha, which was within the experimental error.
Increasing the level of chemicalization, although it led to an increase in yield, but up to a maximum of 1.105 t/ha.On crops sowed in the second decade of May, the level of flax seed yield was significantly lower.The difference with the use of herbicides averaged 0.456 t/ha, and with ammophos -0.374 t/ha.As the background of chemicalization increased, the differences increased to 0.387 t/ha.Of all the factors in the experiment, the time of sowing, then the background of chemicalization, played a decisive role.Years of research did not have a significant effect, since they were close in terms of moisture levels.
Despite the low yield of flax seeds, especially during the first sowing period (0.412-0.739 t/ha), direct costs were inferior to production costs (Table 5).According to researchers in the Sverdlovsk oblast, the minimum yield threshold at which the sales proceeds cover the amount of production costs is 5.4 c/ha [15].As a result, for all options, a conditionally net income from 3826 to 9985 rubles per 1 ha was received.At the same time, the level of profitability decreased when using ammophos both against the background of herbicides and complex chemicalization.
On crops sowed on May 25, the yield of flax seeds increased significantly.Naturally, all economic indicators grew.The level of profitability turned out to be higher with complex chemicalization -197.0 %, although direct costs were higher than when using only a tank mixture of herbicides by 999 rubles / ha.The introduction of ammophos led to a decrease in economic indicators, but remained expedient.

Conclusion
With the formed costs for the cultivation of oil flax and average prices for seeds, the best option in arid conditions was the use of complex chemicalization (tank mixture of herbicides Agritoks 1 l/ha and Legion 0.4 l/ha with Lignohumate 100 g/ha in the herringbone phase and Izgari Bor 0.5 l/ha in the budding phase) with a profitability level of 197.0 %.Similar results and with the use of only a tank mixture of herbicides -179.9 %.In arid conditions of three years of research, the use of ammophos during sowing led to a decrease in economic indicators, but remained expedient.The level of profitability was 27.8-57.9%.

Table 1 .
Reserves of productive moisture in a meter layer of soil, mm

Table 2 .
Completeness of seedlings of oil flax,%

Table 3 .
Survival rate of oil flax plants, %

Table 4 .
Oil flax seed yield depending on sowing time, t/ha

Table 5 .
Economic efficiency at different sowing dates for oil flax (average for 2020-2022)