The article presents results of the testing of some physical laws of the phenomenon of interaction between soil and the working parts of agricultural machines destined to the soil tillage. The authors try, gradually, to clarify the quality of the approximation of the tillage draft forces of the tillage machines, offered by the multitude of mathematical models and their variants from the literature. The presented material reflects the situation that the authors consider to be characterized, apparently, by heterogeneity regarding the use of formulas for the draft soil tillage force. In essence, a disputed response between the practical and didactic utility is outlined, that is simple formulas (which are very particular, because they take into account few parameters of the phenomenon) that approximate very well the experimental values, vs. complex formulas, with a large number of parameters that characterize (explain) the phenomenon well, but which require a large number of data for application and have lower accuracy than simple formulas. A third way, also with great age, namely, that of statistical interpolation formulas, with high accuracy, but small generality, based on concrete experiences (which are difficult to generalize) and which often do not fully satisfy dimensionality requirements (for the physical correctitude). It is presented in the paper.

The empirical and theoretical estimation of the draft force of agricultural machinery for soil tillage, has been the target of scientific research for about one hundred years. The results obtained so far may seem contradictory or divergent. The article presents the results of some research on the usual calculation formulas of the draft force of agricultural machines for soil tillage. Although apparently these formulas are different, analyzing the structure of the formula, we find cohesion and coherence embodied in a simple generalization and easy to use both theoretical and experimental. Moreover, the formulas are convertible between them, the two languages used for their definition (the mechanics of deformable solids and that of the phenomenological description), are only different forms of expression for the same phenomenon. Another problem that is addressed in the research whose results are presented in this article is that of highlighting the dependence of the draft force on the tool speed (in the field) of the soil tillage machine. Exposure is complemented by an algorithm that highlights the dependence of the draft force on the tillage tool speed. Also like a consequences of the draft tillage force structure, finally, a third problem addressed in these researches and whose results and perspectives are given in this paper is that of optimizing the working processes of agricultural machinery for soil tillage. The treatment of the problem starts from the hypothesis of the most general formula of the traction resistance force and proposes some ways to solve the optimal problem.

The article continues the exposition of the results obtained in researching an agricultural machine for processing soil, designed for research with applications including exploitation. The MCLS (complex machine for soil tillage) was designed to research the working processes of the instruments intended for soil processing. The MCLS cultivator is a modulated machine (it can work for three working widths: 1, 2, and 4 m, with tractors of different powers) that is designed to use a wide range of working bodies. The experimental data obtained with the structure with a working width of 1 m and the results of their processing within the framework of the theory of random vibrations are presented in this article. The experimental results are analysed as random vibrations of the supports of the active working bodies. As a result, the main characteristics of random vibrations are exposed: the distribution function, the average value, the autocorrelation, and the frequency spectrum. These general results regarding random vibrations are used for several critical applications in the design, execution, and exploitation of some subassemblies and assemblies of agricultural machines of this type. The main applications include estimating the probability of the occurrence of dangerous load peaks, counting and selecting the load peaks that produce fatigue accumulation in the material of the supports of the working bodies, identifying some design deficiencies or defects in the work regime, and estimating the effects of vibrations on the quality of soil processing. All of the outcomes are composed of applications in MCLS research and exploitation. The applications pursue well-known objectives of modelling the working processes of agricultural machines: safety at work, increasing the quality of work, optimising energy consumption, and increasing productivity, all in a broad context to obtain a compromise situation. The material and the method are based on experimental data acquisition, processing, and interpretation.

This paper is the first of a series of works devoted to the general issues of organic fertilizer spreading machines. Although the working process of solid organic fertilizer machines does not contain a large number of random constituents, however, the basic component, the material administered, gives the random characteristic of the process. In addition, another random component that influences the working process of the machine is the interaction of the work organ that performs the tearing and distribution of the scattered material with this material, as well as the movement of the fragments of material onto the surface of the device. A third random component is the movement of the material scattered into the atmosphere. The fragments of scattered material exhibit shape irregularities due to fragments during dislocation from the mass of feed material and due to particle collisions while moving into air until the contact with the soil. Therefore, the phenomenon of spraying the organic fertilizer on the layer from the soil surface is, as a whole, a random process. Consequently, it is logical to have experimental research prioritized in the study of the work on the distribution of solid organic fertilizers. The role of this article is to present the experimental results, some conclusions and to prefigure several theoretical or theoretical-empirical research directions. The results contained in this article are basics in all the other essays related to the topic machine.

The subject of this article is the estimation of the water erosion given by different sources during the history of over one hundred years of observations. The differences between the estimates made at the near times, or at the appreciably different times, are viewed for the approximation, of the random behaviour of the factors involved in the water erosion process, but also for the changes (apparently in time) of the intensity of the factors involved. The so-called climatic changes, characterized mainly by apparently (at the scale of human life) nonperiodic changes of meteorological factors, produce effects including on the factors involved in water erosion, which are not in the category of meteorological parameters, such as soil erodibility, but also the geometric parameters of the slopes. By default, there are effects in vegetal cover and management parameters. From this point of view, the influencing factors of mathematical models for predicting water erosion should be recalculated or periodically reviewed.