Sažetak: U ovom radu ispitan je stepen ušteda pri primeni najsavremenijih tehničkih sistema za satelitsko navođenje i automatsko upravljanje pri obavljanju poljoprivrednih operacija tokom cele sezone. Uzorno imanje bila je Poljoprivredna korporacija Beograd koja se prostire na oko 21.000 hektara obradive površine. Analiziran je uticaj oblika parcele i pravca kretanja agregata traktor-priključna mašina pri kalkulisanju ušteda usled smanjenja preklopa susednih prohoda. Izvršena je analiza ušteda po kulturama (kukuruz, pšenica, soja, šećerna repa i detelina) i po operacijama za svaku kulturu pojedinačno, prema tehnologiji proizvodnje primenjenoj na uzornom imanju. Detaljno su prikazani podaci samo za pšenicu i ječam. Poređenjem ostvarenih stepena uštede zaključeno je pri kojim operacijama je primena navođenja ekonomski najopravdanija i koliki nivo opremljenosti uređajima za navođenje i upravljanje je potreban. Posebno je analizirana funkcionalna zavisnost ekonomskih ušteda u gorivu i inputima za operacije distribucije mineralnog hraniva i hemijske zaštite biljaka. Tabelarno je data procena stepena svih očekivanih ušteda za operacije koje se odnose na pet analiziranih kultura.

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This paper analyzes theoretically the motion and mass quantity of eight fruit types, roundish in shape, along rotating sizing machines. Mathematical model of the motion of fruit on the rotating disc is solved in spherical coordinate system which is tied to the disc. The exact solution is simplified introducing assumpions that are do not significantly affect the accuracy of the solution. Starting from differential equation of fruit motion on a rotating disk of the sizing machine, all forces acting on fruit were determined as well as velocities and time necessary for fruit to reach the disk rim if found in some upper position on the cone. Mass quantity analysis comprised sized fruit mass and weight capacity. New empirical coefficients were introduced: extent ratio, feed ratio and distribution ratio. The results obtained for the adopted values k e = 0.7, k f = 1, k d = 0.5 coincide approximately with those reported to date for fruit mass quantity rate on sizing machines. It was found that mass quantity rates vary considerably, depending on fruit diameter and mass. Fruit numbers mass quantity ranges from 8949 crops/h for apple to 40,157 crops/h for deep frozen raspberry. Mass quantity varies from 229.1 kg/h for cherry to 2054.7 kg/h for apple.

Large investments, research efforts and time have been allocated till nowadays for innovation of agricultural tractors and machinery, with the primary aim to increase their productivity, reliability, durability, as well as the environmentally friendly, safe and easy usage. Following this general trend, present work is focused on theoretical analysis of the forces acting on the links of the three-point hitch mechanism. The simulation algorithm and computer code have been developed for calculation of draft forces by two methods (following ASAE D497.4 standard and Goryachkin approach), depending on the three point linkage geometry and mouldboard technical characteristics, and calculation of forces acting on lower and upper links of three-point hitch mechanism. Calculated forces values, based on ASAE draft, exposes smaller differences compared to experimental values, while for the Goryachkin method improvement is possible by entering experimental values for soil resistance coefficient k and coefficient of dynamic resistance ε, as we did in this study performing measurements on the aggregate comprehending tractor IMT 539 (IMT Belgrade, Serbia) and two furrow moldboard plough PTO 2.25 (OLT, Osijek, Croatia).

Original scientific paper This paper analyzes the differences in mass yield of moist rapeseed grain for six different passes of combine harvester along the plot. The Mann-Whitney U test and Z-statistic are used for analysis needs. For harvest pass 1 and pass 4 the Z-value is only 0,211, whereas the statistical significance level to confirm this finding is 0,8333, therefore there is not statistically significant difference between yield levels in mentioned passes. It is established that there are another three pairs of similar harvest passes, of which two are adjacent, while all other passes exhibit statistical difference with respect to the yield. The approximate value of the effect size r indicator is applied for all passes, where a statistically significant difference turned out to exist between them. The highest difference is noted between pass 2 and pass 3, the effect size r value amounting to 0,464, which can be considered a large effect size according to Cohen's criterion. This paper suggests extending the current routine implementation of yield analysis to an automated post-processing system. Keywords: Mann-Whitney U test; median; pass; rapeseed Testiranje lokacijske specifičnosti prinosa u različitim žetvenim prohodimaIzvorni znanstveni članak U ovom radu analizirana je razlika u masenom prinosu vlažnog zrna uljane repice za 6 različitih prohoda žitnog kombajna duž parcele. Za potrebe analize korišten je Mann-Whitney U test i Z statistike. Za prvi i četvrti prohod je Z vrijednost svega 0,211, a razina statističke značajnost kojim se ovo tvrdi 0,8333, te nema statistički značajne razlike između vrijednosti prinosa u ovim prohodima. Utvrđeno je da postoji još tri para sličnih prohoda, od kojih su dva susjedna, dok su svi ostali prohodi statistički različiti u odnosu na prinos. Približna vrijednost statističkog pokazatelja effect size r primijenjena je za sve prohode kod kojih se ispostavilo da se statistički značajno razlikuju. Najveća razlika uočena je između drugog i trećeg prohoda za koje vrijednost effect size r iznosi 0,464 što bi se po Cohenov kriteriju smatralo srednjim utjecajem. Ovaj rad sugerira proširenje trenutne rutine analize prinosa ka automatiziranoj naknadnoj analizi.