This paper presents theoretical and experimental research studying the influence of process parameters on the quality of biomass pellets. A validated mathematical model was developed, expressing the density of biomass pellets as determined by moisture content, compression pressure, process heat, the initial density of the material, pelleting speed and initial volume of the material. The experiments for determining the influence of these parameters on the compression of biomass into pellets and optimizing the process were conducted on a heated single pellet compression device, using fir sawdust as raw material. To describe and study the process, four input and control parameters were varied—raw material moisture, pelleting speed, maximum force applied and pelleting die temperature. From the experiments, it was noticed that overall, moisture and pressure have the most important effect on the compression process and pelleting speed, and heat applied also affected the process. Pellet density decreased when pelleting speed and material moisture increase and the density increased with a higher compression pressure and higher heat during the process.

In agrotechnical practice, it was found that between qualitative indices, which express the sowing precision achieved by precision planters determined in the laboratory, and those determined under operating conditions, that there are certain differences, which are sometimes quite significant. The decrease in the value of the quality indices was manifested by the increase of the number of mistakes, either of the number of double planting holes (with at least two seeds), or of the number of missing planting holes. Both cases are unfavorable for the agricultural producer, generating production losses. This paper discusses the influence of the degree of soil grinding on sowing precision in operating conditions, by determining the spectrum of the vibrations induced in the mechanical structure of row units of a precision planter in contact with the soil of three different plots for three working speeds: 4, 6, and 8 km·h⁻¹. Later, the vibrations were simulated under laboratory conditions, on the stand, by means of rubber hemispheres (with diameters between 30 and 100 mm, corresponding to soil fractions resulting from the determination of the degree of soil grinding) mounted on rubber bands, which actuated the seed meters, for testing under an accelerated regime, outside of the optimal agricultural periods (out of season: beginning mid-May until the end of March), in order to obtain the accuracy of the precision planters. It was found that the sowing precision determined in stationary conditions on the stand, and on a plot with an appropriate degree of seedbed preparation, decreased between 2.92% (at 4 km·h⁻¹) and 6.67% (at 8 km·h⁻¹). The main objective of the tests was to reduce labor costs, which was necessary for the staff involved for determining the qualitative indices of work in real field operating conditions, eliminating fuel consumption, while reducing the duration of testing dependent on meteorological factors (season, temperatures, and precipitation, etc.).

In the context of agricultural soil degradation caused by the extensive use of chemical amendments, ecological alternatives with minimal detrimental impact on ecosystems are gaining popularity. Recent advancements in processing technologies have improved the quality and extraction efficiency of bioactive compounds, particularly when multiple conventional or innovative techniques are being used to potentially overcome the most common limitations. This paper proposes the development and testing of a hybrid technology design that employs two extraction techniques, namely ultrasound and high pressure, that can be used either separately or in tandem. An initial assessment of the prototype potential for isolating the desired compounds was made, by testing three various working regimens for the processing of a mixture of onion, pea, and soybean. By incorporating the bioactive compounds produced during the experimental phase in the seedling transplantation holes, we were able to test the potential of stimulating the development rate of vegetables and reducing the attack of pests. The extracts obtained using the hybrid technology showed positive results when used to reduce pest attacks (decreasing average attack frequency by 7%), however had negative effects when used to promote biostimulation, when acted as an inhibitor. The hybrid extraction approach improved the mass transfer into solvent by 14% when compared to high-pressure processing and by 7% when compared to sonication.

The goodness-of-fit analysis performed over the results provided by a model presented in a previous paper proved that the theoretical data were very well correlated with the experimental data with regard to the traction force (with Pearson coefficient r² over 0.9); however, the model was less accurate in predicting traction efficiency, with r² = 0.203. In order improve the model and obtain a better fit between the theoretical and experimental data (especially for the traction efficiency), the model was updated and modified by taking into account the geometry of the tire cross section, which was considered to be a deformable ellipse. Due to the deformable cross section, the minor axis of the tire–ground contact super ellipse decreased compared with the previous model (from 0.367 m to 0.222 m), while the major axis increased (from 0.530 m to 0.534 m). As a result, different data for the traction force and traction efficiency were obtained. The effect of the wheel travel reduction (wheel slip) over the tire–soil shear area was also investigated, and the hypothesis of a constant shear area (independent of wheel slip) provided the most accurate results. The goodness-of-fit analysis performed using the data predicted by the modified model showed that the Pearson coefficient increased significantly with regard to the traction efficiency (from 0.203 to 0.838), while it decreased by only 2.7% with regard to the data for the traction force, still preserving a high value (r² = 0.896).

The current study focuses on analyzing the impact of integrating an optical sorter in a seed-separation technological flow, in terms of increasing the quality of the maize seeds appropriate for sowing. The study showed that there are situations when the use of optical separation may result in a number of difficulties in removing a variable rate of good seeds from the raw mass, which can bring economic disadvantages. The identified issue encouraged the development of several flow assessment approaches in order to determine the problem’s essence and to develop the best strategy for action. The key finding was that the evaluated optical sorting equipment cannot eliminate impurities without also removing good seeds, resulting in every 1% increase in impurity level and a rate of 0.70% of the good seeds lost. Therefore, farmers must carefully consider the scenarios where integrating optical sorting into their technological flow is a suitable option, considering the input material quality, the selling price of the product, and the risk of missing an important quantity of high-quality seeds. The working method described may be of significant importance to other farmers who intend to choose the components of grain-cleaning processes effectively.

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.