Effects of continuous application of Samurai and Zellek Super herbicides on cotton fields against weeds in the conditions of Uzbekistan

. This scientific article provides data on the effectiveness of successive application of herbicides against annual and perennial weeds in cotton fields on arable lands plowed with simple and two-sided plows. When the herbicide Samurai (1.5 l/ha) is applied separately, the annual weeds are effectively lost (86.8-90.2%), and have a weak effect on perennials. When Zellek Super (1.0 l/ha) herbicide is used separately, it has a weak effect on annuals (24.0-32.0%), effectively reducing weeds. Both perennial weeds (90.5-93.0%) and perennial weeds are effective when applied in series with Samurai (1.5 l/ha) and Zellek Super (1.0 l/ha) herbicides 88.9 -93.3% loss. Cotton yield will increase by 1.8-5.4 q/ha compared to the control option. Consecutive application of Samurai (1.5 l/ha) and Samurai (1.5 l/ha) and Zellek Super (1.0 l/ha) herbicides against annual and perennial weeds is recommended.


Introduction
Today, cotton is grown on 33 million hectares in 84 countries around the world, with an annual yield of about 25 million tons. More than 3,000 species of weeds are prevalent in world agriculture, and 1,800 of them cause enormous economic damage, of which more than 200 species are in strong competition with major agricultural crops [1][2][3][4][5]. As a result of a combination of agro-technical and chemical control measures against them, high results are being achieved in the United States, Brazil, Australia, China, India, Pakistan, Germany, South Korea, Russia and a number of other countries [2,4,[6][7][8][9][10].
In cotton-growing countries, surface tillage against weeds, application of herbicides before plowing and in combination with sowing of seeds, plowing the soil to a depth of 22-25 cm and application of herbicides in combination with sowing of seeds, deep once every 2-3 years (32-35 cm) [11,14]. It was found that as a result of plowing and application of herbicides before sowing and during the period of cotton weeding, an additional 5-6 quintals of cotton per hectare is obtained. Improving the phytosanitary condition of cotton fields by agro-technical measures alone is not always possible [12,[17][18][19][20][21].
Turkish scientists conducted a two-year study of a total of 118 plots of cotton fields in southeastern Anatolia (Şanliufa and Mardin provinces) in Turkey in 2010-2011. The type and intensity of weeds per square meter were studied [4,7,13,14]. The study found 23 Compared with the results of similar studies carried out in the region over 25 years ago; it was observed that the weed species, their frequency and density have been changed, significantly. It is predicted that further changes will continue in the future due to increase of irrigation, changes of the cropping pattern and weed control strategies, and also global warming.
Another similar experiment was conducted in dryland conditions of the Brazilian Northeast to determine the number of viable weed seeds (seedbank) in an upland cotton crop, and its distribution in the soil profile, before and after using various herbicide treatments [17,20,21]. A randomized block design in a split-plot block scheme with 6 replications was used, where the main plots were constituted by a factorial (13 treatments and 2 sampling soil depths), and the subplots by 2 sampling dates. The seedbank was determined by germination of the recovered weed seeds obtained from different soil depths. The highest number of viable weed seeds in the area was found before the application of the herbicide treatments at 0 -10 cm soil depth. The treatments metalachlor + diuron; diuron + pendimethalin and the control (no herbicide treatment, weeded weekly during the entire cotton crop cycle) were the most effective in reducing the weed seedbank in the area [16].
In order to improve the agrotechnology of cotton growing in Uzbekistan, it is important to conduct research on tillage and the use of effective herbicides in the soil to ensure the phytosanitary status of the agrophytocenosis and increase soil fertility and cotton yield.
Therefore, it is important to conduct research to determine the effectiveness of basic tillage methods and the sequential and sequential application of modern herbicides in the fight against weeds in cotton fields, as well as their widespread introduction into practice. Thus, the aim of the study is to develop agrotechnology for the production of high-quality cotton from cotton through the sequential application of herbicides with different tillage methods and areas of action in the combat against weeds in irrigated meadow alluvial soils.

Materials and methods
Field experiments were conducted in 2007-2010 in the alluvial soils of the experimental meadow of the Tashkent State Agrarian University, located in the Urta Chirchik district of Tashkent province, Uzbekistan.
The climate of the oasis is sharply changing, the winters are short and last 1.5-2.0 months. January average temperatures range from -3 0 C to -11 0 C, but in the foothills and plains the absolute low temperatures range from -30 0 C to -33 0 C, and in some places to -35 0 C. In summer it is characterized by high temperatures. The average temperature in July is +27-28 0 C, the absolute maximum temperature is +44-46 0 C, the effective total temperature in most districts is 4400-4700 0 C, the amount of atmospheric precipitation in the irrigated lands of the region is 250-400 mm per year. The main part of precipitation is observed in March and April and is almost dry in summer [20,21].
The dynamics of reactive forms of nutrients in the soil (N-NO3, P2O5, and K2O) was studied. To do this, samples were taken from 0-30, 30-50 cm layers of soil; nitrogen-nitrate, reactive phosphorus, exchangeable potassium flame photometer, soil volume mass, and porosity were determined by Kachinsky in the cylindrical method before planting and at the end of the application period [17,18].
According to the mechanical composition of the alluvial soils of the meadows of Tashkent region are mainly heavy sand, groundwater at a depth of 1.2-2.5 meters, humus content in the layer 0-30 cm 1.3%, total nitrogen content 0.120%, phosphorus 0.150%, potassium 1, 50% and the amount of their reactive forms was N-NO3 27.3 mg/kg, P2O5 33.8 mg/kg, and the amount of K2O was 125 mg/kg, the soil of the experimental soils was moderately active in terms of nitrate nitrogen, reactive phosphorus [9,10,12]. Stomp and Samurai herbicides are sown in conjunction with seed sowing. Zellek Super herbicide was applied when the height of annual and perennial weeds was 10-15 cm; the number of weeds was taken into account after each watering. The weeds in the cotton field were accurately accounted for in 1 m 2 plots of rectangular shape marked in each option.
The accuracy and reliability of the obtained data were analyzed mathematically and statistically by B A Dospekhov's dispersion method [17,21].
The studies (2017-2020) were conducted in 14 options, 4 repetitions, and 4 tiers. The area of each option was 7.2 m x 20.0 m = 144 m 2 , and the identification area was 72.0 m 2 . The total area of the experiment is 0.8064 hectares. Along with planting Samurai 33% and Stomp 33% herbicides, Zellek Super 10.4% herbicide was sprayed using a manual sprayer after the first watering of the cotton. In the experiment, cotton variety S-6524 was grown. The Scientific Research Institute of Cotton (Uzbekistan) methodology was used in the research [1,6,8] (Table 1).

Agrophysical and agrochemical properties of soil when plowing with twosided cultivator and applying herbicides
The amount of humus in the soil at the beginning of the application period was 1.29-1.30% in the control and experimental options, slightly decreased at the end of the application period (0.03%), in the control option at the beginning of the application period N-NO3-27.0 mg/kg, most in the good option it was 28.9 mg/kg. The amount of reactive phosphorus and exchangeable potassium was also slightly higher in the experimental options than in the control option. It was found that this difference between the options remained at the end of the validity period.
At the beginning of the application period when plowing to a depth of 30 cm in a normal plow. The volumetric mass of soil in layers 20-30 and 30-50 cm is 1.32, respectively; 1.33; 1.32 and 1.35 g/cm 3 , soil porosity 49.2; 48.8; 49.2 and 48.1%, while the volume mass of the soil in the plowed soil at a depth of 30 cm in a two-sided plow was 1.30, respectively; 1.31; 1.31 and 1.33 g/cm 3 ( Fig. 1 and 2).

Influence of plowing and herbicide application methods on weeds, and growth, development and yield of cotton
In the experimental field, annual weeds such as Cynodon dactylon L, Sorghum halepence L, Convolvulus arvensis L, Cyperus rotundus L, Chenopodium album L, Echinochloa macrocarpa Vasing, Solonum nigrum L, Portulasa oleraceae L perennials such as Vasing and Amaranth occurs. To get rid of them effectively, it is necessary to apply, apply, mix, mix or alternate herbicides with different areas of action. This is because drugs that kill annual weeds well have a weak effect on perennials, while herbicides that effectively kill perennials have a weak effect on perennials [12].
In the field experiment (2017-2020), the number of annual weeds in the control (without herbicide) option in the first accounting period on a simple plowed field was 31.9 pieces/m 2 in 3 years, while in the options using herbicides their number was significantly reduced compared to the control option. When applied Samurai 33% preparations 1.0, annual weeds when applied at the rates of 1.5 and 2.0 l/ha are 82.8, respectively; decreased by 85.7 and 87.1%, respectively, with the Samurai 33% (1.5 l/ha) and the Zellek Super 10.4% (1.0 l/ha) used sequentially, the figure being 89.8% (Table 2).
Samurai 33% herbicide affected perennial weeds only from seeds. Perennial weeds were 3.15 pcs/m 2 in the control option. The land was plowed in a two-sided plow, the annual herbicide in the without herbicide option decreased by 30.9% in the annual herbicide and 20.6% in the perennial weed in the conventional plowed area. The highest rates of weed reduction were observed when the Samurai 33% (1.5 l/ha) and Zellek Super 10.4% (1.0 l/ha) herbicides were applied consecutively, 92.7% per year, perennials weeds decreased by 93.7%. When the 33% herbicide Samurai was applied separately at a rate of 1.5 l/ha, these figures were 85.7 and 19.0%, respectively ( Table 2).
In areas plowed with a normal plow, the dry mass of annual weeds averaged 29.5 g/m 2 in the control (without herbicide) option in Report 1, while in the options using herbicides it was 2.66-24.2 g/m 2 or 18 compared to the control option. 0-91.0% decrease was taken into account. Samurai 33% herbicide 1.0; When applied at the rates of 1.5 and 2.0 l/ha, the dry mass of weeds was 80.3, respectively; 87.0 and 89.5%, while Samurai 33% (1.5 l/ha) and Zellek Super 10.4% (1.0 l/ha) were used in series, while these figures were 2.66 g/m 2 or 91.0% (Table 3).
While the dry mass of perennial weeds was 4.50 g/m 2 in the control option, their dry mass was controlled in the options using Stomp 33% (2.0 l/ha) and Samurai 33% (2.0 l/ha) herbicides decreased by 13.3-17.1% compared to Samurai was found to be reduced by 33% (1.5 l/ha) and Zellek Super 10.4% (1.0 l/ha) by 90.0% when applied consecutively (Table  3).
When plowing was carried out on a two-sided plow, there was a 25.4% decrease in the without herbicide option 8, while in the options where the herbicides were applied, there was a 30.0-93.3% decrease compared to the control option. The highest scores are Samurai 33% 1.5; When applied 2.0 l/ha (36.0; 37.8%) and Samurai 33% (1.5 l/ha) and Zellek Super 10.4% (1.0 l/ha) herbicides were applied sequentially ( 93.3%) were observed. Thus, when plowing the land on a two-sided plow and applying herbicides in a row, annual weeds are reduced by 89.0-94.0%, perennial weeds by 91.4-93.3%, creating favorable conditions for the growth and development of cotton (Table 3).
In the first experimental system in 2007-2010, the average yield in the control (without herbicide) option in the fields plowed with a simple plow was 26.4 q/ha, Stomp 33% herbicide 2.0 l/ha in the norm, 29.1 q/ha, Samurai 33% herbicide 1.0; 28.9 when applied at 1.5 and 2.0 l/ha; 29.5 and 29.4 q/ha, Zellek Super 10.4% to 1.0 l/ha, while Samurai Zellek Super 10.4 with 33% (1.5 l/ha) was 30.4 q/ha when applied consecutively (Table 4).

%
Among the options in areas plowed with a two-sided plow, high-yield Samurai 33% (1.5 l/ha) and Zellek Super 10.4% (1.0 l/ha) were obtained from successively applied options, averaging 31.8 q/ha in 4 years. ha, Stomp 33% (2.0 l/ha), Samurai 33% (1.5 l/ha) 29.9-30.8 q/ha in herbicide-treated options and 28.2 quintals (q)/ha in without herbicide control options was noted (Table 4). The effectiveness of herbicides in areas plowed with a two-sided plow can be explained by the fact that cotton yields are higher than in areas plowed with a simple plow.