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Udžbenik Remontne mašine i radionička praksa napisana je prema programu predmeta istog naziva koji slušaju studenti druge godine Poljoprivrednog fakulteta smera Poljoprivredna tehnika. Udžbenik sadrži 5 poglavlja: 1. Uvod u remontne mašine i radioničku praksu, 2. Merenje i kontrola u proizvodnom mašinstvu, 3. Obrada materijala skidanjem strugotine, 4. Obrada materijala bez skidanja strugotine i 5. Tehnologija spajanja metala.

European Union’s promotion of the use of sustainable and renewable resources requires use of at least 10 % of synthesized biodiesel in liquid fuels by the year 2020. This legislation has stimulated various types of petrodiesel and bio-based component blends production, and development of methods for exact, effective and reliable quantification of biodiesel content. The method for determination of the biogenic fraction in liquid fuels by direct measurement of the 14C activity concentration via liquid scintillation counting (LSC) technique was developed in few laboratories worldwide. It is based on different 14C signatures of the two components: the biogenic component reflects the modern atmospheric 14C activity, and no 14C is present in fossil fuels. The quantity of 14C in the fuel is the criterion for bio-fuel presence. This method is regarded as fast, simple, accurate and sensitive determination procedure for the mass assessment of biogenic fraction in biofuels. Laboratory for low radioactivity at the Department of Physics, University of Novi Sad (UNS), Serbia, and Laboratory for low-level radioactivities of the Ruđer Bošković Institute (RBI) in Zagreb, Croatia have developed two different methods for biogenic fraction determination in liquid fuels [1, 2]. Both laboratories tested the stability of prepared samples by measuring the same samples after some period of time and used the same set of mixtures with the known fractions of the biogenic component, i.e. FAME produced from either sunflower oil or lard fat. The comparison revealed in general good agreement of the results and also indicated some constraints of the methods used, The RBI evaluation technique is limited by the SQP(E) values lower than 600 where the count rates of the biogenic and the fossil samples become indistinguishable. The lower the SQP(E), the larger the relative differences between the measured and the expected biogenic fraction for 600 < SQP(E) < 700. The biogenic fraction can be successfully determined at SQP(E) > 700. The two-step calibration procedure that UNS used implements quench correction and therefore offers more reliable 14C determination in fuels in comparison to one-step calibration method. The application of these calibration curves is limited to samples with chemically identical bio and fossil components. It can be used for precise biogenic fraction determination in examined fuel samples if the components of the fuel mixture are well known in advance. The obtained results showed very important limitation of used methods as the samples have to be analyzed as soon as possible after preparation in order to obtain reliable results.

European Union’s promotion of the use of sustainable and renewable resources requires use of at least 10 % of synthesized biodiesel in liquid fuels by the year 2020. This legislation has stimulated various types of petrodiesel and bio-based component blends production, and development of methods for exact, effective and reliable quantification of biodiesel content. The method for determination of the biogenic fraction in liquid fuels by direct measurement of the 14C activity concentration via liquid scintillation counting (LSC) technique was developed in few laboratories worldwide. It is based on different 14C signatures of the two components: the biogenic component reflects the modern atmospheric 14C activity, while no 14C is present in fossil fuels. The quantity of 14C in the fuel is the criterion for bio-fuel presence. A great variety of biogenic matrices in fuels results in a wide range of quenching properties of different fuel mixtures. The laboratories participating in this intercomparison study developed two different calibration techniques. The Ruđer Bošković Institute data evaluation method is based on calibration curves for purely biogenic and purely fossil liquids, and does not depend on the exact chemical composition of the organic liquid. The limits of the method are defined by the SQP of app. 690 below which the count rate of biogenic and fossil liquids become indistinguishable from one another. The University of Novi Sad data evaluation method is very dependent on the composition of the examined fuels, so the obtained results in this case were relatively good. Future investigation should also test whether this calibration method is suitable for some other fuel matrices, for example for various types of domestic oil used in everyday life. Testing advantages and limitations of the two methods will continue in the future.

A method of direct measurement of14C activity concentration via liquid scintillation counting (LSC) is recognized as good and fast method for determination of biogenic component in liquid fuels. Two laboratories that used this14C technique participated in this survey: Laboratory from University of Novi Sad (UNS), Serbia and Laboratory from Ruđer Bošković Institute (RBI), Croatia. Each laboratory used its own calibration methods on the same set of samples (produced diesel-based bio-fuels and commercially available domestic oils). From the obtained results it can be concluded that each method which uses 14C technique for determination of biogenic component in liquid fuels has its advantages and disadvantages. RBI data evaluation method is based on two calibration curves, for purely biogenic and purely fossil liquids, and the calibration does not depend on the exact chemical composition of the organic liquid. The limits of the method are defined by the SQP(E) of approximately 690. Below this value the count rates of biogenic and fossil liquids become close to each other or even indistinguishable from one another and the obtained results for biogenic fractions are not reliable. In this intercomparison UNS used two different methods, one for produced bio-diesels and the other one for domestic oils. UNS data evaluation method is very dependent on the composition of the examined fuels, so the obtained results with the "two-step" method were relatively good in the case of diesel mixtures with biogenic component. In the case of biogenic oil samples (bought on market), UNS "two-step" method did not give realistic results, and with the "one-step" method the limitation is large quenching in the samples, so for the samples with SQP(E) less than 700 this method could not give expected results. Samples prepared with liquid fuels are usually colored and the main challenge for determination of biogenic component in both laboratories is handling of highly quenched liquids.

There are few novel methods for biogenic component determination in liquid fuels by direct measurement of 14C via liquid scintillation counting (LSC) technique. The basic idea of all used methods is the same: different 14C signatures of the biogenic and the fossil components – in the case of biogenic component there are a presence of modern 14C activity from the atmosphere and in the case of fossil fuels there should not be 14C activity in the sample. This paper presents inter-laboratory comparison between two different methods used in Laboratory for Nuclear Physics from University of Novi Sad, Serbia and in Laboratory for Low-level Radioactivities from Rudjer Boskovic Institute, Croatia. Both laboratories used the same samples, the same detectors – liquid scintillation counter Quantulus 1220 but different calibration methods. Laboratory for Low-level Radioactivities is using quenching properties of modern liquids for calibration (I. Krajcar Bronic et al, 2016) and Laboratory for Nuclear Physics is using two step method for calibration (I. Stojkovic et al, 2017).

This paper presents the results of the survey of groundwater samples from Vojvodina region, Serbia. By measuring the activity concentration of radioactive isotope tritium (half-life 12.32 years) the groundwater’s age could be estimated. Tritium is directly incorporated into the water molecule (H3HO), so it participates in the hydrological cycle and can be detected in groundwater. The presence of tritium in groundwater indicates recharge of aquifer by modern precipitation (i.e., recharge after 1952). Modern groundwater is renewable, as opposed to the older and fossil water, and in this sense it can be better utilized. On the other hand, modern groundwater is more vulnerable to contamination from the surface. It is important to know the approximate age of groundwater for better water resources planning and management. This study included 35 groundwater samples from deep wells and natural sources and 1 surface water sample from the lake, all collected in Vojvodina region from four different hydrogeological systems. In all collected samples stable isotopes δ2H and δ18O were measured in order to determine the origin of groundwater. For understanding and interpretation of the obtained results, geology and hydrogeology of researched area was taken into consideration. The main conclusion is that the groundwaters in Vojvodina region are mostly young (not older than 10 years) and that they are mostly supplied by precipitations. There is no direct connection between groundwater age and the corresponding hydrogeological system.

U radu su prikazani rezultati prvog dela istraživanja podzemnih voda sa teritorije AP Vojvodine. Merenjem koncentracije aktivnosti radioaktivnog izotopa tricijuma (period poluraspada 12.33 godina) može se odrediti starost mlađih voda. Postojanje 3H u podzemnim vodama ukazuje da se sistem prihranjivao sa vodama starim najviše 62 godine. Moguće je razlikovati podzemne vode koje su u toku poslednjih šezdesetak godina imale veze sa padavinama, od izdanskih voda koje nemaju tako brzu vodozamenu.Pored izmerene koncentracije aktivnosti tricijuma određivani su i stabilni izotopi δ2H i δ18O. This paper presents the results of the first part of the survey of groundwater from Vojvodina region. By measuring the activity concentration of the radioactive isotope tritium (half-life of 12.33 years) one can determine the age of young water. The presence of 3H in groundwater indicates that the system was supplied by waters that are more than 62 years old. It is possible to distinguish the subterranean waters influenced by precipitation in the last sixty years, aquifer waters that do not have such quick water exchange. Beside measured concentrations of tritium activity the ratio of stable isotopes δ2H and δ18O have been also determined.

This paper gives the results of research on the condition and needs for engines and tractors in agriculture, water management and forestry in Serbia. It was concluded that in agriculture around 408.000 of two-axle tractors, 190.000 of single-axle tractors and around 290.000 of moto tools are used, and they have all been used for more than 15 years. Annual needs for this machinery were also determined for a period from 2014 to 2020 and it includes 21.000 of two-axle tractors, 15.000 of single-axle tractors and 15.000 of moto tools, as well as 20.000 diesel engines. This way, revitalized industry could cover 80% of all requirements. . U radu su izloženi rezultati istraživanja u oblasti stanja i potreba za motorima i traktorima u poljoprivredi, vodoprivredi i šumarstvu Srbije. Utvrđeno je da poljoprivreda koristi oko 408 hiljada dvoosovinskih traktora, 190 hiljada jednoosovinskih i oko 290 hiljada motooruđa i prosečna starost preko 15 godina. Utvrđene su potrebe godišnje od 2014 do 2020 i to 21.000 dvoosovinskih traktora, 15.000 jednoosovinskih i 15.000 motooruđa kao i 20.000 dizel motora godišnje. Revitalizovana domaća industrija može da pokrije oko 80% svih potreba. .

The results of this research considered the influence of sub soiling and manure on penetrometer cone indexes were presented in this paper. Standard technology, employing plows for the basic soil tillage, was used in the production of soya bean. Four variants in to 3 repetition were implied during researching. In the first variant the soil was only plowed. In the second variant the soil subsoiled after winter barley harvesting and then plowed. In the third variant manure was spread out and then plowed and in the fourth variant the soil was subsoiled, manure was spread out and at the and soil was plowed. The same soil was subject of the two-year research, more exactly the same farming measures were applied two year continually. The cone index was measured by electronic penetrometer two times during vegetation, the first time after sowing, and the second after soya bean harvesting. The average cone index at the depth of 3.5 to 24.5 cm was used to determine the influence of subsoiler and manure. The lowest values of cone index were measured in variants where manure was spread out, which clearly indicates that the spreading the manure is an appropriate farming measure for the reduction of soil compaction. The influence of subsoiler has not lead to the significant changes in cone index relative to the first control variant for two years. Besides, after F-test ANOVA it was shown that there were not statistically significant differences at the significance threshold of 5% in neither of either variants. The largest yields were measured in variants in which livestock manure was spread out, more exactly in variants 3 and 4. In yield comparison to the control variant it was shown that in variant 2 where subsoiler was applied the yield was increased by 6.84%, in variant 3 where livestock manure was applied the yield was increased by 33.05%, and in the variant 4 where subsoiler and livestock manure were applied the yield was increased by 35.33%. U radu su prikazani rezultati ispitivanja uticaja podrivanja i svinjskog stajnjaka na otpor prodiranja konusa penetrometra. Za proizvodnju soje primenjena je klasična tehnologija kod koje se osnovna obrada obavlja plugovima. Tokom ispitivanja obuhvaćene su četiri varijante u 3 ponavljanja. U prvoj varijanti zemljište je samo orano plugom. U drugoj varijanti zemljište je podriveno nakon ubiranja ozimog ječma, a zatim poorano. U trećoj varijanti po zemljištu rasturen je svinjski stajnjak, pa zatim zaoran i u četvrtoj varijanti zemljište je podriveno, rasturen je stajnjak, koji je potom isto zaoran. Isto zemljište je predmet dvogodišnjeg ispitivanja, odnosno iste mere primenjene su dve godine kontinualno. Otpor prodiranja konusa meren je elektronskim penetrometrom dva puta u toku vegetacije, prvi put nakon setve, a drugi put nakon ubiranja soje. Za analizu uticaja podrivanja i stajnjaka korišćen je otpor konusa na dubini od 3,5 do 24,5 cm. Najmanje vrednosti otpora konusa izmerene su u varijantama gde se primenio stajnjak, što jasno ukazuje da je unošenje stajnjaka prava agrotehnička mera za smanjenje sabijenosti zemljišta. Uticaj podrivanja i nakon dve godine primene nije doveo do značajnih promena u otporu konusa u odnosu na kontrolnu varijantu. Ipak, nakon statističke analiza pokazalo se da ni na jednoj varijanti nisu dobijene statistički značajne razlike u otporu konusa za prag značajnosti 0,05%. Najveći prinosi izmereni su isto kod varijanti gde se primenio stajnjak, odnosno na varijanti 3 i 4. Poređenjem prinosa soje vidi se da je kod varijante 2 sa podrivačem prinos povećan za 6,84%, kod varijante 3 gde je primenjen samo stajnjak povećan za 33,05%, a kod varijante 4 gde je primenjeno podrivanje i stajnjak za 35,33%.

This paper shows the results of analysis of soil compaction influence on sunflower yield on headland and inner part of a field, and chemical changes in soil. Soil compaction after sprouting was 67.70% greater on headland than in the inner part, while before harvesting, there was an increase of 13.44% in soil compaction. Large number of passages, which caused intensified soil compaction on headlands, poor conditions for the root system development, and poor microbiological activities led to yield reduction, which was 8.98% in total mass and 9.13% in dry grain mass. Chemical analysis of soil on headland and in the inner part of a field showed almost the same humus, nitrogen and other microelements concentration on headlands and in the inner part of a field. The total number of microorganisms is larger in the inner part of the field, while the number of actinomycetes is larger on headland. There are no significant differences in numbers of nitric bacteria and fungus. U radu su prikazani rezultati ispitivanja uticaja sabijanja zemljišta na uvratinama i unutrašnjem delu parcele na prinos suncokreta, hemijske i biološke promene u zemljištu. Sabijenost zemljišta na uvratinama posle setve bila je za 67,70% veća u odnosu na unutrašnji deo, dok je povećanje sabijenosti zemljišta na uvratini pre ubiranja iznosilo 13,44%. Veliki broj prelaza doveo je do intenzivnijeg sabijanja zemljišta na uvratinama, uslovljavajući nepovoljne uslove za razvoj korenovog sistema i slabije mikrobiološke aktivnosti, radi čega smanjenje biološkog prinosa iznosi 8,98%, a mase suvog zrna 9,13%. Hemijska analiza sastava zemljišta na uvratini i unutrašnjem delu parcele pokazala je da je sadržaj humusa na uvratinama i u unutrašnjem delu pacele skoro isti, kao i sadržaj azota i ostalih makrohraniva. Ukupan broj mikrooganizama je veći u centralnom delu parcele, dok je broj aktinomiceta veći na uvratinama. Značajnije razlike u broju azotobaktera i broj gljivica ne postoje.

This paper shows the results of analysis of scientific farming measures influence on soil compaction, more exactly on cone resistance on headland and inner part of a field. Soil compaction before fertilizing was 57,27% greater on headland than in the inner part, while after harvesting, there was an increase of 50,97% in soil compaction. The results of research show that it is impossible to increase quality of land on one time period. More years are needed and using manure. U radu su prikazani rezultati ispitivanja uticaja agrotehničkih mera na sabijenost zemljišta, odnosno otpor prodiranja konusa penetrometra na uvratini i unutrašnjem delu parcele. Sabijenost zemljišta na uvratinama pre prihrane bila je za 57,27% veća u odnosu na unutrašnji deo, dok je nakon ubiranja razlika bila manja i iznosi 50,97%. Rezultati istraživanja pokazali su da se ne može značajno uticati na smanjenje sabijanja zemljišta za jednu godinu. Za to je potrebno više godina i primena stajnjaka.

This paper shows the results of analysis of soil compaction influence on sunflower yield on headland and inner part of a field, chemical and biological changes in soil. During the 5 years investigation, soil compaction after sowing was 23.01% greater on headland than in the inner part, while before harvesting, there was an increase of 28.43% in soil compaction. Large number of passages, which caused intensified soil compaction on headlands, poor conditions for the root system development, and poor microbiological activities led to yield reduction, which was 33.57% in total mass and 35.25% in dry grain mass. Chemical analysis of soil on headland and in the inner part of a field showed higher humus concentration on headlands, due to poor microbiological activities. U radu su prikazani rezultati ispitivanja uticaja sabijanja zemljišta na uvratinama i unutrašnjem delu parcele na prinos suncokreta, hemijske i biološke promene u zemljištu. Sabijenost zemljišta na uvratinama tokom 5 godina ispitivanja posle setve bila je za 23,01% veća u odnosu na unutrašnji deo, dok je povećanje sabijenosti zemljišta na uvratini pre ubiranja iznosilo 28,43%. Velik broj prelaza doveo je do intenzivnijeg sabijanja zemljišta na uvratinama, uslovljavajući nepovoljne uslove za razvoj korenovog sistema i slabije mikrobiološke aktivnosti, radi čega smanjenje biološkog prinosa iznosi 33,57%, a mase suvog zrna 35,25%. Hemijska analiza sastava zemljišta na uvratini i unutrašnjem delu parcele pokazala je da je veći sadržaj humusa na uvratinama nego u unutrašnjem delu pacele zbog slabije mikrobiološke aktivnosti.

This paper shows the results of analysis of soil compaction influence on sunflower yield on headland and inner part of a field, and chemical changes in soil. Soil compaction after sprouting was 67.70 % greater on headland than in the inner part, while before harvesting, there was an increase of 13.44 % in soil compaction. Large number of passages, which caused intensified soil compaction on headlands, poor conditions for the root system development, and poor microbiological activities led to yield reduction, which was 8.98% in total mass and 9.13% in dry grain mass. Chemical analysis of soil on headland and in the inner part of a field showed almost the same humus, nitrogen and other macroelements concentration on headlands and in the inner part of a field. U radu su prikazani rezultati ispitivanja uticaja sabijanja zemljišta na uvratinama i unutrašnjem delu parcele na prinos suncokreta i hemijske promene u zemljištu. Sabijenost zemljišta na uvratinama posle setve bila je za 67,70 % veća u odnosu na unutrašnji deo, dok je povećanje sabijenosti zemljišta na uvratini pre ubiranja iznosilo 13,44 %. Veliki broj prelaza doveo je do intenzivnijeg sabijanja zemljišta na uvratinama, uslovljavajući nepovoljne uslove za razvoj korenovog sistema i slabije mikrobiološke aktivnosti, radi čega smanjenje biološkog prinosa iznosi 8,98 %, a mase suvog zrna 9,13 %. Hemijska analiza sastava zemljišta na uvratini i unutrašnjem delu parcele pokazala je da je sadržaj humusa na uvratinama i u unutrašnjem delu pacele skoro isti, kao i sadržaj azota i ostalih makrohraniva.

This paper shows the results of analysis of soil compaction influence on wheat yield, chemical and biological changes in a soil on headland and inner part of a field. During five years of investigation, soil compaction after sowing was 30.56% greater on headland than in the inner part, while before harvest, an increase in soil compaction was 37.65%. Large number of passages, which caused intensified soil compaction on headlands, poor conditions for the root system development, and poor microbiological activities led to yield reduction, which was 31.55% in biological yield and 26.39% in dry grain mass. Chemical analysis of soil on headland and in the inner part of a field showed higher humus concentration on headlands, due to poor microbiological activities. U radu su prikazani rezultati ispitivanja uticaja sabijanja zemljišta na uvratinama i unutrašnjem delu parcele na prinos pšenice, hemijske i biološke promene u zemljištu. Sabijenost zemljišta na uvratinama tokom 5 godina ispitivanja posle setve bila je za 30.56% veća u odnosu na unutrašnji deo, dok je povećanje sabijenosti zemljišta na uvratini pre ubiranja iznosilo 37.65%. Velik broj prelaza doveo je do intenzivnijeg sabijanja zemljišta na uvratinama, uslovljavajući nepovoljne uslove za razvoj korenovog sistema i slabije mikrobiološke aktivnosti radi čega smanjenje biološkog prinosa iznosi 31.55%, a mase suvog zrna 26.39%. Hemijska analiza sastava zemljišta na uvratini i unutrašnjem delu parcele pokazala je da je veći sadržaj humusa na uvratinama nego u unutrašnjem delu parcele zbog slabije mikrobiološke aktivnosti.

The results of research of influence of tractor wheel on changes in soil and maize, sunflower, soybean and sugar beet yield were presented in this paper. The measurements were carried out during seeding and harvesting on headland and central part of parcels. The yield reducing on headland was established at wheat by 20.4%, maize by 30.96%, soybean by 6.99%, sunflower 30.67% and sugar beet by 30.97% in relation to central part of parcels. U radu su izloženi rezultati ispitivanja uticaja točka traktora na promene u zemljištu i prinos pšenice, kukuruza, suncokreta, soje i šećerne repe. Merenja su obavljena u vreme setve i ubiranja na uvratinama i na centralnom delu parcele. Utvrđeno je smanjenje prinosa na uvratinama kod pšenice za 20,4 %, kukuruza za 30,96 %, soje 6,99 %, suncokreta 30,67 % i kod šećerne repe za 30,97 % u odnosu na centralni deo parcele.