Process modeling of the first inter-rowcultivation in laboratory conditions

. The paper considers the formation process of secondary soil ridges by working bodies with flat discs during the first mechanized inter-row cultivation of crops in laboratory conditions. Taking account of the agrotechnical requirements and the physical and mechanical properties of the soil, we adopted the reference profile of the soil ridge formed during mechanized inter-row cultivation of crops, which can conditionally be accepted as ideal, as well as the original optimization criterion сэ1 k . After practical implementation of studies in the tillage bin and statistical processing of the obtained data, the corresponding equations were obtained in which the independent process factors were expressed in natural and encoded values. It was found that a change in the speed of a cultivator within 1.2 ... 2.4 m / s, with angles of attack α к of flat discs from 5º to 20º, increases the distance at which the soil is thrown off and the thickness of the soil layers covering the sides and the upper base of the primary ridge ( k сэ1 → max ). At angles of attack α к of flat discs within the limits of 25º ... 30º and the speed of the cultivator from 1.2 m / s to 1.6 m / s, an increase in the thickness of the covered soil layers h пр , occurs, and the coefficient k сэ1 is maximum ( (k сэ1 = 0.98 with a flat disc diameter of 0.3 m).


Introduction
At present, the method of mechanized row crop weeding is complemented with a chemical one -treatment with selective herbicides or a combined one -the application of mechanical and chemical methods [1,2,3,4,5,6,7]. The analysis of the methods for calculating the estimated indicators of technical means of inter-row cultivation of crops by ridge technology showed that in theories of determining the geometric dimensions and surface shapes of working bodies in inter-row cultivators, there are currently issues that have not been resolved. Moreover, the data obtained from the studies conducted by many scientists cannot be applied to new working bodies with flat discs in inter-row cultivators. Consequently, additional theoretical and experimental confirmation of the optimal structural and operational parameters of the cultivator working bodies mentioned above is required [8,9,10].

The study objects and research methods
A working body of a cultivator with a flat disc mounted on a domestic or imported interrow cultivator is proposed for mechanical weeding of row crops with the use of ridge technology. The proposed working body of the cultivator will make it possible to cut weeds between the rows of cultivated crops, as well as to cover undamaged weeds on the sides of the ridges and between the stems of the cultivated crop on the upper base of the soil ridge [1,2,3].
The working body with a flat disc ( Fig. 1)   The working body with a flat disc: 1 -A-blade (sweep); 2 -shank; 3 -bracket; 4 -screw; 5disc; 6 -holes; 7 -additional disc; 8 -axle; 9 -flat disc; 10 -bolt In the presented working body of the cultivator, it is possible to change the angle of attack of flat discs and the magnitude of their penetration into the soil. These parameters have a direct impact on the quality of cultivation and the geometric parameters of the initial soil ridge.
For laboratory studies of the working body, a laboratory complex was used (Fig. 2), consisting of a tillage bin with a trolley and a rail track, a drive unit, and measuring instruments. Two gangs from the cultivator with interchangeable working bodies of various sizes were mounted on the trolley. In addition, between the gangs with the working bodies, soil ridge models were placed in the tillage bin, the sizes of which corresponded to the sizes of soil ridges formed during sowing in the field. Cultivator gangs with working bodies were pulled on the trolley along the rail track by an electric motor with the use of a cable, chain transmission and drums.
To approximate the conditions of the laboratory experiment to real field ones and to ensure the coefficient of friction against the soil, the soil identical to the soil in the bin was glued to the sides and the upper base of the ridge model (Fig. 3). In the lower part of the ridge model, hooks were mounted to prevent the model from being shifted from its place on the soil surface due to the force of the soil movement. In laboratory conditions, working bodies with flat discs were tested in full compliance with the requirements of GOST (state standard), with soil moisture in the tillage bin of 19 ... 23% [9,10].
The geometric dimensions of the formed secondary ridge of the soil during the first mechanized cultivation (Fig. 4), formed by the working bodies with flat discs, were controlled by the original device, the novelty of which was confirmed by RF patents No. 148575 and No. 150391. For a joint agrotechnical assessment of the influence of variable independent factors of the process of mechanized crop cultivation, it is advisable to apply such an optimization parameter, the main component of which will be the cross-sectional area of the secondary soil ridge. It was found that the covered soil hпр with a thickness of 2 ... 4 cm during the first mechanized cultivation of row crops will make it possible to cover weed seedlings on the sides and the upper base of the primary soil ridge between cultivated plants.
Thus, it is advisable to apply the reference profile of the secondary soil ridge, formed during mechanized cultivation of crops, with natural falling of soil from the sides of the ridge at an angle γ. Such a profile of the secondary ridge can be considered ideal.
With various combinations of variable factors and the interaction of flat discs with soil, the cross-sectional profile of the formed ridges, as a rule, looks as follows (Fig. 5). The ridge profiles obtained by the action of working bodies with flat discs with specific structural and operational parameters were compared with the reference profile of the secondary soil ridge. The depth of soil cultivation during the first mechanized cultivation of crops was 5 cm. For various options with the angle of attack of flat discs and the speed of the cultivator, every 0.5 meters the thickness of the soil layers covered on the ridge model was measured.
The optimization criterion for mechanized cultivation of row crops was the original coefficient of compliance with the standard kсэ1, which will allow us to assess the quality of the formed secondary soil ridges by adding the required soil layer to the primary ridge formed during sowing: where эт The variation levels of independent factors during the formation of the secondary soil ridge are presented in Table 1.

Research results
The where kсэ1 -coefficient of compliance with the standard; vк -the speed of the inter-row cultivator, m/s; αк -angle of attack of a flat disc of the working body in an inter-row cultivator, degrees. Table 2 gives the evaluation results of equations 2, 3, 4 and 5 by the criteria of Student's t-test, F-test and Cochran's C test. Graphic displays of the response surfaces for various types of interaction of the speed of the working bodies with flat discs and the angle of attack of flat discs at the first mechanized cultivation of crops are presented in Fig. 6.  (Fig. 6 a, b) makes it possible to increase the distance of the thrown-off soil and the thickness hпр of the soil layers covering the sides and the upper base of the primary soil ridge, i.e. kсэ1 → max. In addition, a change in the angle of attack αк of flat discs from 5º to 30º at all speed options of the cultivator also gives a possibility to obtain the maximum value of the coefficient kсэ1.

Discussion
The study of the working bodies with flat discs with a diameter of 0.3 m (Fig. 6 c) allowed us to find that a change in the speed vк of the cultivator within 1.2 ... 2.4 m / s, with angles of discs from 5º to 20º, increases the distance of throwing off the soil and the thickness hпр of the soil covering the sides and the upper base of the primary ridge ((kсэ1 → max). At angles of attack αк of flat discs within 25º ... 30º and the speed of the cultivator from 1.2 m / s to 1.6 m / s, the thickness of the soil layers covered hпр increases and the coefficient kсэ1 is maximum (kсэ1 = 0, 98). A further increase in the speed vк the cultivator from 2.0 m / s to 2.4 m / s helps to maximize the thickness of the covered soil layers (hпр > 0.03 m) and, naturally, the secondary ridge of an increased soil size, and the coefficient kсэ1 tends to zero.
The use of flat discs with a diameter of 0.35 m during the first mechanized cultivation of crops made it possible to establish that the speed vк of the cultivator has a significant effect on the maximum value of kсэ1 at αк = 5º ... 15º. At angles αк = 20º ... 30º of attack of flat discs, a change in the speed vк of the cultivator from 1.6 m / s to 2.4 m / s contributes to an increase in hпр of more than 0.03 m and, correspondingly, to the formation of a secondary soil ridge of maximum dimensions, i.e. эт ф мо1 мо1 S S < , and kсэ1 → min.

Conclusion
Analyzing equations 6-9, we can conclude that among linear terms the absolute term of the equation has a strong influence on the optimization parameter Y. Of the non-linear terms of the equation, the angle attack х2 2 of flat discs of the working bodies has the greatest influence on Y, and the speed х1 2 of movement has the smallest influence.