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This paper analyzes the problems related to the reconstruction of a semi-mounted berry harvester into a self-propelled one specified for exploitation on smaller orchards. The components of the self-propelled machine, their purpose and mutual functional connection are described in details, which retained the principle of unilateral picking of half the row of bush berries from its semi-mounted predecessor. Among the most important general design features, the following stand out in particular: the drive of the harvester working components, which is achieved by means of appropriate combinations of hydraulic and mechanical power transmissions, which allows it to be highly adaptable to different working conditions on the terrain, and the control device, which is designed to maintain the movement of the machine in the direction set by the driver, without decreasing the safety and passability requirements of the machine itself. In the technology of berry fruit production in the Republic of Serbia, the harvesting process is still the basic limiting factor. Manual picking participates as much as 75% in total production costs. The costs of mechanical harvesting are between 2.05 and 2.27 times lower in comparison to manual picking, depending on whether the machine is a towed or self-propelled. The paper also provides a comprehensive analysis of the energy parameters of work for both versions of the harvester. The results indicate that power losses on rolling and slipping are lower in the self-propelled version 10 and 40%, respectively, while in the semi-mounted version the power lost on the climb is 60-70% lower compared to the self-propelled version. As the harvesting process is still a limiting factor in berry fruit production, in addition to reducing costs by applying mechanized solutions, one of the goals of the work is the optimization of applied technical solutions for the same.

Novi rekonstruisani kombajn ELEKTRONIK SP-09, je samohodna mašina koja je od svoga predhodnika ELEKTRONIK SP-07 zadržala princip jednostranog ubiranja polovine reda žbunastog jagodastog voća. Mašina je posebno prilagođena za branje remontantnih sorti maline bez potpore, mada se može uspešno koristiti i za druge vrste voća žbunaste forme. Razdeljivač usmerava jednu polovinu račvastog žbuna do jedinice za protresanje, gde vibrirajuće palice odvajaju bobice. Iz mase plodova, koji se transportuje kosom transportnom trakom na horizontalnu, struja vazduha iz ventilatora uklanja primese. Transportna traka može puniti male gajbice, a kapacitet prostora za odlaganje punih gajbica je oko 200 kg. Hidrostatički pogon pokreće SUS motor snage 50 kW. Parametri rada radnih delova se podešavaju da bi otpali samo zreli plodovi. Mogu se podešavati: - amplituda i frekvencija oscilovanja, - prečnik valjka i dužina palica, - prečnik palica, - radna brzina berača-kombajna. Među najvažnijim opštim konstruktivnim karakteristikama ističu se: - jednostavan modularni dizajn, koji omogućava: • uskladjivanje mašine sa specifičnim potrebama korisnika, • brzo i jednostavno prilagodjavanje za ubiranje različitih vrsta jagodastog voća. - pogon radnih komponenata kombajna ostvaruje se pomoću odgovarajućih kombinacija hidrauličnih i mehaničkih prenosnika snage, što mu omogućava veliku prilagodljivost različitim radnim uslovima na terenu (sl. 2 i 3). - posebna oscilujuća glava sa glatkim, plastičnim palicama na otresajućoj koloni; - pred-separator za uklanjanje nečistoće manjih dimezija; - dodatni separatorski transporter, koji olakšava uklanjanje oštećenih plodova; Pogon hidrauličkog sistema čine četiri jednosmerne zapreminske pumpe stalnog protoka: P1, P2, P3 i P4. Paralelno su spregnute, a pogon im omogućava zajedničko vratilo, koje snagu od dizel SUS motora kombajna (M) preuzima preko jednostepenog kaišnog prenosnika prenosnog odnosa i=1. Ovaj tip prenosnika, uz tiši rad, jednostavnu konstrukciju i

In agricultural production, sowing is one of the most important agro-technical operations that influence the quality of the product and yield. The crops sowing quality, including wheat, depends on properly prepared soil, that is, on the quality of soil cultivation. However, despite well-executed soil cultivation, satisfactory results cannot always be achieved if sowing is not done in an appropriate manner. The achieved depth of sowing affects the speed of sprouting, rooting, resistance of plants to low temperature and drought, intensity of budding, growth and development, and achieving the highest yield in certain conditions. In unfavorable agro-technical conditions, and especially in the conditions of dry farming, optimal conditions for high-quality sowing often cannot be ensured by applying the conventional method. Therefore, new cultivation and sowing systems are being applied in order to perform high-quality sowing in time. During the experiment, the influences of the tillage system and sowing method on the sowing depth and the depth of the formation of the tillering nodes were registered. The results of two-year study are given, where four methods of tillage were applied, namely conventional tillage at depths of up to 25 cm and three reduced tillage methods at different depths. Reduced cultivation with a discc harrrow was done at a depths between 8 and 12 cm, and reduced cultivation with rototiller was done at depths of 5-10 cm and 10-15 cm. During the tests, the sowing depth and the depths of the tillering nodes were determined by direct measuring of the knots positions of the analyzed plants. Furthermore, it was verified that depth of the knot has a significant effect on the resistance of wheat to low temperatures during winter and lack of moisture during summer droughts. Achieved results enable further optimization of applied cultivation and sowing systems.

The article is focused on the behaviour of the basic properties of dairy cow's solid manure over the maturation period. The manure was exposed to mechanized aerobic processing by mechanically turning-over. Performed analysis comprehended measurements of mass participation percentages of organic components, mineral matters, H2O, N, P2O5 and K2O, as well as measurements of PH-values during the seven weeks of supervised test period of effective aerobic preparation of the composting material. Through maturation, large growth of averaged mass percentages of nitrogen, phosphorous-pentoxide and potassium-oxide, more than triple in comparison to the initial levels in a fresh solid, has been verified. Following a possible common approach in the scientific and technical practice, an analytical semi-empirical approach was used in describing the changes over the time of manure properties during composting, supported by prototype of the machine Kompomat 1. Combining the analytical theory of diffusion partial differential equations and application of numerical methods to non-linear fitting of the experimental output data, it was verified that all acquired manure parameters follow an identical general exponential law (R2all properties = 0,906 - 0,990; RMSEall properties = 0,010 - 2,544). Clear relationships between the values of basic parameters of solid manure under mechanized aerobic fermentation (y) and composting duration lap time (x) have been established.

This paper presents the tests results of three types of hay mowing machines (later in text: mowers), namely a self-propelled oscillatory mower-conditioner and two tractor-mounted mowers with oscillatory and rotary blades, used to mow alfalfa grown under dry land conditions in the region of central Serbia during three seasons in 2014, 2015 and 2016. Although characterized by older design, they are still commonly used at smaller and medium size farms in this region. Therefore, their optimal exploitation parameters are still of large importance for hay quality and production efficiency and sustainability. The exploitation parameters of all three mowers generally increased linearly with higher speeds, having high R2 values (over 0,8), with rare exceptions. The regression coefficients b clearly showed that the self-propelled mower-conditioner achieved maximum increase in production performance (b = 0,3606), compared with the oscillatory (b = 0,1158) and rotary mowers (b = 0,1414). Mower design had a significant (p ≤ 0,001) effect on cutting and chopping losses, production performance, and specific fuel consumption (p ≤ 0,05). The tests confirmed the superiority of the self-propelled mower over the two mowers aggregated with tractors.

One of the technical factors from agricultural nozzles and overall plant protection is droplet diameter, which exclusively depends on working pressure, ISO number and nozzle type. Therefore, this paper was aimed to describe mathematical model for droplet size distribution. Through field exploitation experiment, data was used from three ISO numbers of nozzles (hollow cone 80 015; 02 and 03), two air-assisted sprayers (axial and radial fan) and two permanent crops (vineyard and an apple orchard). Water sensitive papers were used for evaluation of droplet diameters, and digital image analysis with Image J software was used for data processing. Mathematical model through homogenous diffusion equation and simplified differential equation shows that droplet size distribution had exponential function of modelling. Theoretical mathematical model was confirmed in experimental results, where coefficient of determination of exponential regression model for 80 015 nozzles was 0.93 with 5.15 of RMSE. The same coefficient for 80 02 nozzles was 0.96 with 2.88 of RMSE and for 80 03 nozzle R2 was 0.93 with 3.25 of RMSE. In addition, it is proved that droplet diameter depends on operating pressure with very high negative correlation (80 03 nozzles: r = −0.98; 80 02 nozzles: r = −0.97; 80 015 nozzles: r = −0.95). This data will help future researchers in their papers to facilitate and describe similar models for plat protection processes, and all agricultural producers to determine optimal operating pressure which is immensely important in economic, biologic, technical and ecologic aspect.

The paper analyzes the motion of idealized spherical homogeneous fertilizer particle along the straight vane attached to flat rotating disc. The analysis, based on the assumption on the pure rolling of the particle along the vane (without sliding), has been performed in the non-inertial reference coordinate system, which rotates together with the spreader disk. The particle motion along the vane is described by hyperbolic cosine function, which is the solution of the ordinary in-homogenous secondorder differential equation having constant coefficients. Solution of this kind represents an approximation of the real motion of fertilizer particle along the radial vane fixed to horizontal disc rotating at constant angular velocity. However, it can be very useful for optimization of centrifugal spreader design and working parameters, as well as for further analysis of the whole fertilizer spreading process that also includes particle flight., U radu je analizirano kretanje idealizovane, loptaste, homogene čestice mineralnog đubriva duž radijalne lopatice postavljene na rotirajućem disku centrifugalnog rasipača đubriva. Analiza, zasnovana na pretpostavci o kotrljanju čestice duž lopatice bez klizanja, izvedena je u neinercijalnom referentnom koordinatnom sistemu koji rotira zajedno sa diskom za rasipanje đubriva. Kretanje čestice duž lopatice je opisano hiperboličnom kosinusnom funkcijom, koja predstavlja rešenje obične homogene diferencijalne jednačine drugog reda sa konstantnim koeficijentima, koja opisuje dinamiku čestice. Rešenje ove vrste predstavlja aproksimaciju stvarnog kretanja čestice đubriva duž lopatice diska koji rotira konstantnom ugaonom brzinom. Međutim, može biti veoma korisno za optimizaciju dizajna centrifugalnog raspršivača i njegovih radnih parametara, kao i za dalju analizu čitavog procesa rasipanja đubriva koji obuhvata i let čestice u vazduhu po napuštanju lopatice.