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.

Clusters play an important role in driving competitiveness, innovation and jobs creation in the EU. Romania currently has successful clusters in various economic sectors and services, including 7 clusters in agro-food. Agriculture has been and remains the support of the human existence, which is an important pillar of the Romanian rural economy.The agro-food sector had oscillating evolutions in the post-accession period, mainly generated by the need to get in line with the EU requirements. Stimulating smart technology assimilation across all economic sectors including agro-food value chains, promoting enterprise growth and clusters 4.0 is critical to many EU Member States. Partnerships between countries, regions, cities and clusters are essential in the next industrial modernization process, based on innovation. Clusters 4.0 calls for development of a generation of advanced cluster policies to respond to these new industrial challenges by facilitating cross-sectoral value chains, fostering internationalization, stimulating inter-regional investment and accelerating entrepreneurship and skills in digital production, environmental production, circular economy, service innovation and creative economy. In order to be ready for the future, clusters must be geared towards creating a smart value chains, international cooperation and cross-sectoral partnerships. This research paper proposes a model as a tool for agro-clusters to become "smart", also this proposal providing information on the most important steps in the creation and development of smart agro-clusters. The used research methodology was based on analysis and synthesis of the information on the economic and social aspects of the development of the agro-food sector and of clusters in Romania. In conclusion, the authors of this paper wanted to emphasize the necessity of the development of smart agro-clusters for the future smart specialization of the regions.

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This article presents results obtained by the author in an attempt to introduce new parameters that influence the working process of agricultural soil working machines, in the classical formulas that mathematically model the tillage draft force. This article naturally introduces soil moisture. To introduce soil moisture into the calculation formulas of the tillage draft force, other physical parameters affected by soil moisture were used: density, cohesion, adhesion, etc. In this article, is explicitly describes, only the variation of soil density with its moisture. Considering some phenomena such as soil swelling or shrinkage, required the development of an adequate mathematical model of the expression of the density of soil-water mixture, concerning the concentration of water and the densities of dry soil and water. The final formulas obtained are tested to experimental results from the literature. Finally, the author sets out his opinion regarding the use of the results in design calculations and regarding the elevation to the rank of physical law of a mathematical model represented by a formula with a large number of parameters, which in turn are still dependent on many others parameters.

Information on soil nutrition level or soil pollution level can lead to the establishment of some recommendations or a strategic decision-making program for the reference area development. The specific soil analysis is essential both from an economic point of view and from an environmental point of view. To achieve an adequate management of the nutrients into an agricultural field, it is necessary to conduct an agrochemical study at an interval of 3–5 years, in which, the relevant agrochemical indicators for the evaluation of the nutrient supply state must be analysed, to determine fertilizer doses and/or recommended amendments for the expected crops. The agrochemical study must contain the analysis bulletin that provides the following information: pH value, humus and total nitrogen content, phosphorus (P) and potassium (K) content, C/N ratio (carbon / nitrogen), nitrogen index (NI), as well as the main microelements.