Currently manufactured tractors are equipped with a three-point hitch, which is used to connect semi-mounted implements to the tractor. The tractor three-point hitch is operated hydraulically, using various types of control. The most commonly used control is a force, positional and a mixed one. Each of these types of control has its specific characteristics and some advantages and disadvantages. Finally, each type of control is suitable for certain soil and terrain conditions. Particular attention was paid to a force control, which is improving the use of the tractor with a mounted implement, but on the other hand, adversely affects the uniformity of working depth of implements on soils with variable resistance. Based on theoretical analysis and experimental measurements, there has been determined the effect of soil resistance on the tillage depth, depending on initial conditions for implement deepening. Initial conditions for implement deepening are given by the tillage depth, soil resistance, and the cutting width of a plough. It was found that soil resistance strongly affects the tillage depth, and with increasing soil resistance the tillage depth decreases non-linearly. A gradual increasing of soil resistance is associated with a less-marked decreasing of the tillage depth. These facts will be further used in research, development and experimental verification of new control systems of the three-point hitch of tractors.

Mojžiš M., Vitázek I., Varga F., Lindák S. (2015): Experimental determination of lethal doses of heat in thermal weed control. Res. Agr. Eng., 61 (Special Issue): S9-S12.Thermal weed control performed by weeders working on physical principles is already commonly used on farms dealing with bioproducts. It helps to reduce strenuous human labour and to effectively control weeds and, to some extent, pests and diseases threatening the crops. It also prevents other weeds from spreading by destroying them in the early growth stage. In addition, development of weeds is inhibited when the soil is not being ploughed. Effective deployment of these machines in practice is currently addressed by experts in the field, as well as the possibility of rational use of heat energy while achieving the maximum effect on weeds. This method in particular helps to reduce costs of thermal treatment, which are the key factor limiting widespread deployment of weeders. The paper introduces long-term research based on laboratory and field experiments, which is intended to broaden the knowledge regarding this issue.

The paper presents the main drawbar parameters of tractor (drawbar pull, drawbar power and wheels slip) operating in a grass plot and evaluates the utilization of specially modified tyres with spikes. These prototypes of driving wheels were designed at the Department of Transport and Handling of the Slovak University of Agriculture in Nitra. The designed mechanism with spikes is mounted on standard tractor tyres, in which grooves were made. Spikes are hidden in grooves during transportation on a route. on the grassy landscape or soil, the spikes are ejected in order to improve the drawbar parameters. During operation, the drawbar pull and the rotation speeds of wheels were measured, whereupon the wheel slip was calculated. Results show the highest increase in tractor speed at the second gear and high load in utilized prototypes of the driving wheels (1.89 km·h ). Measurements also demonstrate the highest improvement of drawbar power under the aforementioned conditions in case of tractor with prototypes of driving wheels (1,719.87 W) in comparison with tractor using the standard tyres (1,061.57 W).

Unconventional ways of growing plants, when we return to non-chemical methods of controlling weeds, require new weed control methods. One of the few physical methods, which found wider application in practice, is a flame weeder with heat burners based on the use of gas (LPG). However, the process of practical use of this flame weeder has a number of factors that positively or negatively affect the effectiveness of weed control. A precise setting of flame weeders is influenced, for example by weed species, weed growth stage, weather, type of crop grown, but also heat transmission and heat absorption by plant. Many variables that enter into the process must be eliminated for their negative impacts on achieving the best results in fighting against weeds. In this paper, we have focused on naming these parameters, on field trials that confirm the justification of the precise setting of parameters, and recommendations for practice to achieve a higher efficiency of thermal weed control. AbstraktNetradičné spôsoby pestovania rastlín, keď sa vraciame k nechemickým spôsobom ničenia burín, vyžadujú nové metódy regulácie zaburinenosti. Jednou z mála fyzikálnych metód, ktoré našli širšie uplatnenie v praxi, je termická plečka s tepelnými horákmi na báze využitia plynu (LPG). Do procesu praktického používania tejto termickej plečky však vstupujú mnohé faktory, ktoré priaznivo či nepriaznivo vplývajú na efektívne ničenie burín. Presné nastavenie termickej plečky podmieňujú napr. druh burín, rastové štádium burín, počasie, druh pestovanej plodiny ale aj prenos tepla a absorpcia tepla rastlinou. Množstvo premenných, ktoré vstupujú do tohto procesu, je nutné eliminovať tak, aby negatívne nevplývali na dosiahnutie čo najlepšieho výsledku v boji s burinami. V práci sa sústreďujeme na pomenovanie týchto parametrov, poľné pokusy, ktoré potvrdzujú opodstatnenie presného nastavenia parametrov a odporúčania pre prax, ktoré umožnia dosiahnuť vyššiu efektívnosť termického ničenia burín.

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