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The thesis focused on description and characteristics of spring wheat and barley and their life cycles. Thesis deals with the issue of very dangerous weed plants and deals with the possibilities of their regulation by using herbicidal preparations in the growth spring cereals. Weeds are problematic plants that negatively affect the quality of production and also the economy of cultivation. Part of the thesis is the evaluation of a small plot experiment, which was performed in the crop of the spring barley on the land of the company AGRO Dolní Bukovsko in the cadastral area of the village Sedlíkovice in the direction (of Veselí nad Lužnicí) and in the spring wheat on the land of the above mentioned company in the cadastral territory of the municipality of Radonice in year 2017. Results of weed frequency and economic evaluation of the experiment are presented in tables and graphs.

<p>Vreme (rok) setve jedan je od najvažnijih faktora u proizvodnji strnih žita i praktično određuje intenzitet delovanja svih ostalih činilaca proizvodnje p&scaron;enice. Među brojnim faktorima koji određuju visinu prinosa, najče&scaron;ći uzrok malih prinosa ozime p&scaron;enice vezan je za vreme setve izvan optimalnog roka, upotreba neadekvatnih količina semena i izbor sorti nedovoljno prilagođenih datim agroekolo&scaron;kim uslovima. Osim toga, vreme setve predstavlja ekonomski najjeftiniju agrotehničku meru i najisplativiji način za povećanje prinosa zrna ozime p&scaron;enice, međutim eventualno ka&scaron;njenje u setvi ne može se na adekvatan način nadoknaditi ni jednom drugom agrotehničkom merom. Ekstremne vremenske prilike već predstavljaju izazov za proizvođače, a mnogobrojni klimatski scenariji predviđaju dalje povećanje njihove učestalosti u budućnosti. Upravo će u ovakvim promenljivim vremenskim uslovima optimalno vreme steve uz adekvatnu gustinu useva i izbor odgovarajućih genotipova biti od velike važnosti u cilju ublažavanja negativnog delovanja vremenskih činioca na visinu i stabilnost prinosa, kao i na tehnolo&scaron;ki kvalitet zrna ozime p&scaron;enice.<br />Prevashodni cilj istraživanja u disertaciji bio je proučavanje uticaja različitog vremena, gustina setve i njihove interakcije na prinos, komponente prinosa i kvalitet zrna različitih sorti p&scaron;enice. Istraživanje interakcije vremena, gustina setve i sorti ozime p&scaron;enice izvedeno je na oglednim poljima Instituta za ratarstvo i povrtarstvo na Rimskim &scaron;ančevima, u periodu od proizvodne 1981/82. do 2012/13. godine, na ogledu pod nazivom &bdquo;Rokovi setve&ldquo;. Ogled se postavlja svake godine, na zemlji&scaron;tu tipa karbonatni černozem, a izvodi se kao trofaktorijalni (Split-split-plot dizajn), u četiri ponavljanja, sa rasporedom varijanti po slučajnom blok sistemu.<br />Tokom 32-godi&scaron;njeg ispitivanog perioda, prinos zrna je znatno varirao u zavisnosti od vremenskih uslova i kretao se u proseku za sve tretmane od 4,35 t ha-1 u 2003., do 8,70 t ha-1 u 2013. godini. Na osnovu jednačine trenda prinosa, uočeno je da je godi&scaron;nje povećanje prinosa, u proseku za sve tretmane iznosilo 10,7 kg ha-1. Iz 32 analizirane godine izdvojeno je 5 godina sa najvećim prinosima, 12 godina sa malim prinosima p&scaron;enice, dok se preostalih 15 godina moglo označiti kao srednje rodne godine. U pogledu temperaturnih uslova i uslova vlažnosti u rodnim, srednje rodnim i nerodnim godinama postojale su značajne razlike između ovih grupa. U rodnim godinama, variranje prinosa u zavisnosti od rokova setve bilo je najmanje. Najveći prinos zrna, tokom posmatranog perioda, u proseku za sve ispitivane sorte i gustine setve ostvaren je setvom u II roku (11-20. X), i bio je značajno veći u odnosu na sve ostale rokove izuzev I roka. Između I i III roka, nije ostvarena statistički značajna razlika u visini prinosa, ali su prinosi u oba ova roka bili značajno veći u odnosu na novembarske i decembarski rok setve. Drugi rok odlikovao se najmanjim variranjem prinosa tokom istraživanog perioda. Novembarska setva smanjivala je prinos u proseku za 11%, a decembarska za 27%, u odnosu na prinose iz optimalnih agrotehničkih rokova. Prosečno dnevno smanjenje prinosa zrna iznosilo je 38 kg dan-1. Najmanje smanjenje prinosa prilikom ka&scaron;njenja u setvi bilo je u rodnim, zatim u srednjerodnim, a najveće u nerodnim godinama. U optimalnim rokovima setve (I i II rok) gustina od 500 kl. zrna m-2 bila je optimalna, dok je u kasnim rokovima (novembarskim i decembarskom), povećanje količine semena (do najvi&scaron;e 700 kl. zrna m-2),<br />imalo opravdanja. Odlaganje setve od I do V roka, uticalo je na povećanje sadržaja proteina, vlažnog glutena, moći upijanja vode, sedimentacionu vrednost, zapreminu i vrednosnog broja sredine hleba, kod obe sorte. Na osnovu prosečnih vrednosti za sve rokove setve, sorta Zvezdana ostvarila je bolje parametre kvaliteta u odnosu na NS 40S.</p> / <p>Sowing date is one of the most important field crop management measures in the production of small grains and it practically determines the intensity of all other factors in wheat production. Among many factors which determine yield, sowing outside the optimum period, use of inappropriate seed rates and selection of cultivars insufficiently adapted to a given agro-ecological conditions, are recognized as the most common causes of low yields of winter wheat. Moreover, sowing date is economically cheapest field crop management measure and a cost-effective way to increase grain yield. However, eventual delay in sowing cannot be adequately compensated by any other field crop management measure. Extreme weather events are already a significant challenge for grain producers and are predicted to increase under numerous future climate scenarios. In these altered weather conditions, optimal sowing date with an adequate sowing density and choice of appropriate genotypes will be of great importance in order to mitigate the negative effects of climate factors on yield stability, as well as on the bread making quality of winter wheat.<br />The aim of this research was to investigate the effects of different sowing dates, sowing densities and their interactions on yield, yield components and grain quality of different wheat cultivars. The study of interaction of sowing dates, sowing densities and cultivars of winter wheat was carried out on experimental fields of the Institute of Field and Vegetable Crops, in the 1981/82. &ndash; 2012/13. period. The experiment was set each year, on the calcareous chernozem soil, as a three factor trial (split-split-plot design), in four replications, with variants in the randomized block design.<br />During the 32-year studied period, grain yield has varied considerably depending on weather conditions and ranged from 4.35 t ha-1 in 2003., to 8.70 t ha-1 in 2013., on average for all treatments. It was observed that the annual increase in yields during the investigated period was 10.7 kg ha-1. From the 32 years analyzed there were 5 years with high yields, 12 years with low grain yields, while the remaining 15 years could be identified as a medium yielding years. There were significant differences in temperature regimes and moisture conditions between these three types of years. Yield variation caused by the different sowing date was much lower in high yielding in comparison to low yielding years. For the entire examined period, on average of all tested cultivars and planting densities, the highest grain yields were obtained in the II sowing date (11-20. X), and were significantly higher in comparison to all other sowing dates, except the earliest (I sowing date). There were no statistically significant differences in yields between I and III sowing date, but they were significantly higher in comparison to sowing in November and December. Second sowing date had the lowest yield variation during the studied period. Sowing in November reduced yield by 11% and December sowing by 27% on average, compared to optimal (October) sowing dates. During the investigated period, average daily reduction of grain yield was 38 kg day-1. The smallest decline in yields caused by the delay in sowing was in high yielding years, followed by medium yielding, and the largest yield decline was found in low yielding years. In the optimal sowing dates (I and II), a density of 500 viable kernels m-2 proved to be optimal, while in the later sowing dates (November and December), increasing the sowing density up to 700 viable kernels m-<br />2, was justified. Delay in sowing from I to V sowing date caused an increase in the bread-making quality parameters such as protein content, wet gluten content, water absorption capacity, Zeleny sedimentation value, bread loaf volume and value number of bread, for both cultivars examined. On average for all sowing dates and densities, cultivar Zvezdana achieved higher values for almost all bread-making quality parameters tested in comparison to NS 40S.</p>