Justification of technologies of minimum (surface) tillage

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Introduction
Minimal technologies for tillage in the production of agricultural products provide for the rejection of plowing, reducing operating costs, increasing labor productivity. As a result of the use of minimal tillage technologies ("mini-till"), it becomes possible to accumulate and use crop residues to accumulate organic matter in the soil, to preserve the soil structure, to preserve moisture in the surface layer of the soil. At the same time, the role and importance of the plant protection system is increasing.
Considering the use of wide-cut and combined agricultural machinery (AM), "mini-till" technologies contribute to reducing soil density.
At the same time, in the Middle Urals, for the main processing of perennial grasses, when preparing the soil for corn for silage, potatoe, and vegetables, it is recommended to use real tillage. According to the recommendations of agricultural scientists of the Middle Urals, the Kuban State Agrarian University, the All-Russian Research Institute of Agriculture and Soil Protection from Erosion, "the use of surface treatments is even desirable ...", "... zero and surface methods of basic tillage cannot be systems in crop rotations, but can be used as methods for individual crops within the boundaries of existing systems" [1, p. 9].
Researchers clearly define the need for the use of combined systems of basic tillage with a combination of "deep tillage with zero and surface methods", considering the frequency of their use: on sod-podzolic and forest soils for no more than 2 years consecutively (such soils in the Sverdlovsk region -72.5%), on various types of chernozems for 3-4 years (in the Sverdlovsk region -17.6%).
It is necessary to note the work of scientists in recent years on the study of issues related to tillage. The researchers considered the following questions: -study of processing methods and their effect on the structural and aggregate composition of soils, on the agrophysical state, properties and indicators, on soil compaction [2,3,4,5]; -study of cultivation methods and their impact on soil fertility, on soil hardness and moisture availability, on hardness and yield, on moisture accumulation, study of basic processing methods and their impact on agrochemical properties and indicators, the impact of resource-saving tillage technologies on the water regime [6,7,8]; -study of the methods of basic processing and their impact on the yield, productivity and quality of crops, on the littering of fields [9,10]; -study of the effect of basic processing methods, fertilizer systems on the economic efficiency of crop cultivation, the effectiveness of various methods of basic tillage [11,12].
In different regions of the Russian Federation there are different types of soils from sodpodzolic to chernozems. All of them have different agrophysical properties. In our study, we will first consider density and hardness.
Density is the mass of a unit volume expressed in kg/m 3 (g/cm 3 ). There is a concept of equilibrium density and optimal density. The equilibrium density of the soil is formed in natural conditions under the effect of natural factors. Optimal density is the density of the soil that provides the highest yield of agricultural crops. According to the ratio of equilibrium and optimal density, it is possible to decide on the type of basic tillage.
Hardness is the property of the soil to resist compression and wedging [13]. The soil hardness is the main criterion determining the traction resistance of the AM, expressed in kg/cm 2 . According to the classification, soils can be from "loose" -less than 10 kg/cm 2 to "solid" -more than 100 kg/cm 2 . The optimal hardness for grain crops is 5-25 kg/cm 2 , for tiller crops -5-15 kg/cm 2 . Hardness over 25-30 kg/cm 2 is critical. The hardness is influenced by density, humidity, and the relationship between individual particles.

Materials and Methods
The research methods: experimental, computational and analytical, economic and statistical, comparative and system analysis, etc. The research was carried out from August 2021 to October 2022 in the fields of the educational and experimental farm of the Ural State Agrarian University, in the branch of the FSBSI URFANITS Ural Branch of the Russian Academy of Sciences, the Research Institute of Agriculture -Uralniiskhoz.

Results and Discussion
The hardness is significantly influenced by the tillage method. The hardness after flat-cutting treatment is 3.6% lower than when plowing, but the lowest soil hardness after disk harrow treatment is 9.2% lower than plowing. The hardness, in turn, and the speed of the machinetractor unit (MTU) affect the treatment depth. The results of experimental studies on the effect of hardness and speed of MTU movement, on the technological operation cultivation to a depth of up to 10 cm, on the treatment depth are shown in Figure 1.
The results of studies on the effect of the hardness and MTU speed on the processing depth are subject to the following mathematical dependencies: -with soil hardness of 0.51 MPa y = -0.238x + 11.9; -with soil hardness of 0.81 MPa y = -0.384x + 13.2; -with soil hardness of 1.2 MPa y = -0.482 x + 14.2.
When calculating the composition of the machine-tractor unit, it is necessary to consider that solid soils have a higher resistivity, but a lower rolling resistance coefficient. For a more accurate formation of the unit, at any technological operation, it is necessary to consider the increase in the resistivity of agricultural machines with an increase in the operating speed of the unit [14,15]. Theoretical dependences of these values are proposed by Yu.K. Kirtbay (1) (for technological operation -plowing), which can be used for any technological operation for tillage, S.A. Iofinov (2). (1) where k0 is the specific resistance of the soil at the speed of movement V0; V0 = 8 km/h; -the increment of the traction resistance in fractions of the initial resistance 0 (kN/m) per 1 km/h increase in the movement speed (for agricultural machines surface treatment = 0.005); -the actual movement speed; c -degree indicator (for modern machines c = 1.5; с -coefficient characterizing the increment of traction resistance as a percentage (for surface treatment с = 3-4%).
Over the past decades, the designs of the working bodies of agricultural machines have changed significantly, therefore, it is more rational and correct to use the value V0 = 8 km/h (operating speeds at nominal specific traction resistance) for calculations.
The results of experimental studies processed in the Matlab program are presented in Figures 2, 3, 4. The effect of the operating speed on the specific traction resistance at a hardness of 0.51 MPa is subject to the following mathematical dependence: y = -0.0025x 2 + 0.08893x + 1.154.
(3) At hardness of 1.2 MPa, it obeys the following mathematical dependence: For surface treatment, as providing the lowest soil hardness, a variety of AM can be used. The following types can be attributed to the system of machines for minimum tillage: -for basic processing, after harvesting -combined cultivators (combined tillage tools), mulching cultivators; discators. If necessary, chisel plows can be used.
-for early spring harrowing (closing of moisture) -coupling of tooth harrows, tooth chain harrows; -for sowing grain crops -sowing complexes, seeders; -for crop treatment -wide-cut self-propelled sprayers. Domestic and foreign manufacturers of agricultural machinery offer a wide selection of these agricultural machines, we will present their brief characteristics in Table 1. For use in minimum tillage systems, "new", in our opinion, agricultural machines are of particular interest that are little used in agriculture in Russia -tooth chain harrows. These agricultural machines are developed and manufactured in LLP "NPC Agroengineering" (city of Qostanay, Rep. of Kazakhstan) [16]. With the help of tooth chain harrows (according to the developer-manufacturer), it is possible to perform early spring harrowing (closing of moisture), with sufficient precipitation in the region, it is possible to perform a technological operation to level the winter tillage, can be used both on stubble and on plowed "furrow" field. The working body is an "anchor" chain with teeth (from 2 to 4, Fig. 5), with a working tooth length of 70 mm, rotating in bearing units. The chain pitch, depending on the width of the grip, is 96 mm or 102 mm.
The experience of using tooth chain harrows is available in the branch of the Federal State Budgetary Scientific Institution "Ural Federal Agrarian Research Center of the Ural Branch of the Russian Academy of Sciences" -Ural Research Institute of Agriculture (URFANITS UrB RAS -Uralniiskhoz). In this institution, a chain-tooth harrow with a grip width of 6 meters, with 4 teeth on a link, 180 mm long, was operated. In this study, we will make calculations on the formation of the optimal composition of the unit with tooth chain harrows of various gripping widths -12 m; 18 m; 24 m.
Initial data for calculations: traction characteristics of tractors on various gears; specific traction resistance -0.9 kN/m; rolling resistance coefficient -0.12 (for treated stubble, tilled arable land); operating speeds from 9 km/h to 16 km/h (studies when creating harrows were carried out at operating speeds up to 19 km/h), the traction force reserve is 7.5%.
Traction resistances of aggregates. Hourly productivity is determined by the formula: where e is a coefficient that considers the units of measurement of the unit speed. e = 0.1; Bp -the working width of the unit grip, m; BP = ξBa, where ξB -the coefficient of the grip width use considers the difference between the working width of the grip from the constructive one: ξB = where GT.W, GT.P, GT.CR, GT.HD -average hourly fuel consumption during the shift, kg/h when performing basic (clean) work, during idling on turns, crossings and engine idling (during stops of the unit with the engine running). The average hourly fuel consumption is taken according to reference data or calculated using the specific fuel consumption per 1 ef.hp and the degree of engine loading.  Figure 6.
It can be seen from the presented calculations that the most optimal variant of the unit for carrying out the technological operation is the unit consisting of Belarus 2022 + BZC-12. The performance of this unit is almost 2 times higher than that of the Belarus 1025 + BZC-12 unit, the specific fuel consumption is 1.3% higher. It is impractical to use a more powerful tractor for the BZC-12. From the calculations presented, it can be seen that the most optimal variant of the unit for carrying out the technological operation is the unit consisting of K-744R1 + BZC-18. The performance of this unit is 37.7% higher than that of the Versatile 2375 + BZC-18, and the specific fuel consumption is 31.4% lower.
Calculations for the unit consisting of a tooth chain harrow BZC-24. K-744R1 + BZC-24. The technological operation can be performed on the transmission IV1 -15.9 km/h, with a pulling force of 33.4 kN.  From the calculations presented, it can be seen that the most optimal variant of the unit for carrying out a technological operation is an aggregate consisting of K-744R1 + BZC-24 (without using the unit at an operating speed of 19 km/h). The performance of this unit is 4.2% lower than the unit composed of K-744R2 + BZC-24, but the specific fuel consumption is 9.9% lower, with the unit composed of Versatile 395 + BZC-24 has the same performance, the specific fuel consumption is 4.6% lower.
The authors also have studies on the formation of machine-tractor units in the implementation of resource-saving technologies in agricultural production [17,18].
To compare and determine the economic efficiency of using tooth chain harrows, let's compare their technical and economic indicators with traditional harrowing units based on the tractors presented above: Belarus 2022, K-744R1 (Fig. 9).
The unit is part of Belarus 2022 + BGZ-12×2. Initial data: the resistivity of medium-tooth harrows is 0.55 kN/m, the operating weight without harrows is 2290 kg.
Traction  From the information obtained during the analysis and presented in Figure 9, the following can be seen: when using the unit as part of Belarus 2022 + BZC-12, the hourly performance is 19.9% higher, the specific fuel consumption is 16.6% lower than that of the unit as part of Belarus 2022 + BGZ-12×2; the units as part of tractor K-744P1 with harrows with a working width of 18 m -the hourly performance is the same, and the specific fuel consumption in the unit with BGZ-18×2 is 6.4% lower, due to the fact that the tractor's traction force is used by 74.8%; when using the unit as part of K-744P1 + BZC-24, the hourly performance is 15.2% higher, the specific fuel consumption is 13.2% lower than that of the unit consisting of K-744R1 + BGZ-24×2.

Conclusion
The use of "mini-till" technologies, in addition to reducing labor and financial costs, reduces the soil hardness, which favorably affects the optimal formation of machine and tractor units. In turn, the hardness is significantly influenced by density, humidity, and other factors. To comply with agrotechnical requirements, when performing technological operations for tillage, during sowing, it is necessary to consider the effect of soil hardness and working speed on the treatment depth. These factors must be considered when forming the MTU. As a result of experimental studies, it was revealed that an increase in the vertical component of the tractor's traction force will have an effect on reducing the treatment depth, with an increase in the working speed, an increase in the soil resistance force. Thus, during the technological operation, cultivation to a depth of 10 cm, with a hardness of 0.51 MPa, the processing depth will decrease by 13.7% or up to 8.63 cm when the working speed changes from 8 km/h to 14 km/h; at a hardness of 0.81 MPa -by 21.2%, up to 7.88 cm; at a hardness of 1.2 MPa -by 24.4%, up to 7.56 cm.
During experimental studies on the effect of working speed on the specific traction resistance at different soil hardness, the following was revealed: despite the deepening of the working bodies with an increase in working speed, the specific traction resistance, at a hardness of 0.51 MPa, with an increase in speed from 8 km/h to 14 km/h -increased by 12.3% or up to 1.91 kN/m; at a hardness of 0.81 MPa increased by 10.1%, from 1.58 kN/m to 1.74 kN/m (lower resistivity as a result of greater deepening of the working body with increased working speed, with increased hardness); at a hardness of 1.2 MPa increased by 12.9%, from 1.39 kN/m to 1.57 kN/m. When using tooth chain harrows in minimal tillage systems, it must be considered that the agrotechnically permissible humidity for tillage, for all types of soils -from 13% to 22%, humidity for high-quality treatment, with a minimum resistivity -15-17%.
When forming aggregates with a tooth chain harrow BZC-12, the best option is an aggregate consisting of a tractor Belarus 2022, with BZC-18 and BZC-24 -with a tractor K-744R1. In a comparative analysis of aggregates with tooth chain harrows, with traditional harrowing aggregates, it was revealed that the technical and economic indicators of the former exceed the indicators of traditional harrowing aggregates.