UTJECAJ POSTRNIH USJEVA NA PRINOS I KOMPONENTE PRINOSA U EKOLOŠKOM UZGOJU KUKURUZA

The second crop use in organic agriculture is a known method of maintaining the soil tilth, soil protection against environmental deterioration, soil nutrients conservation and even the weed control. The nitrogen conservation from previous leguminose crop is even more important, especially in the organic agriculture where use of N-fertilizers is the strictly forbiden, and second crops can be used as a catch crops for nutrients in rotation prior to the crops with the high N requirement. The choice of the proper second crop has, however, been insufficiently investigated, especially for agri-environmental conditions of the Panonian agricultural area in Croatia. The second crop experiment was established in Valpovo, Croatia, in the eutric brown soil type, during the years 2005 and 2006. The aim of the experiment was to investigate the effects of different second crops and their combinations on maize (Zea mais L.) yield and yield components in organic agriculture after soybean (Glycine max L.) in crop rotation. The experimental design was set up as a CRBD in four repetitions, with soybean as a previous crop in crop rotation. The six second crop treatments were: O – Control, without second crop; WW – winter wheat (Triticum aestivum L.) second crop; RY – rye (Secale cereale L.) second crop; FP – fodder pea (Pisum arvense L.) second crop; WP – mixture of the WW and FP; and RP – mixture of RY and FP. The WW treatment had the highest second crop dry mass, whereas FP had the lowest dry mass. The highest plant density was recorded for FP, and it was higher than the RP plant density, which also had the lowest plant height. The achieved maize yields were the highest for RY, but they were not significanlty different from the O, RP, and WW treatments. However, the yield achieved by RY treatment was significantly higher than the yields recorded for WP and FP treatments. The absolute mass and hectolitre mass did not show any statistical differences among treatments.Upotreba postrnih usjeva u ekološkoj/organskoj poljoprivredi je priznata metoda za održavanje ugorenosti tla, zaštite tla protiv vremenskih neprilika, konzervacije hraniva u tlu te čak i borbe protiv korova. Konzervacija dušika od prethodnog leguminoznog usjeva je čak važnija funkcija, posebice u ekološkoj poljoprivredi gdje je upotreba mineralnih dušičnih gnojiva izrijekom zabranjena, te postrni usjevi mogu poslužiti za čuvanje dušika od ispiranja iz tla za sljedeći usjev u plodoredu s visokim zahtjevima za dušikom. Nažalost, izbor postrnih usjeva nije dostatno istražen, posebice za agroekološke uvjete u Hrvatskoj. Stoga je postavljen pokus u Valpovu, Republika Hrvatska, na eutričnom smeđem tlu, tijekom 2005. i 2006. godine, s ciljem da se istraže učinci različitih postrnih usjeva i njihovih kombinacija na komponente prinosa i prinos kukuruza (Zea mais L.) u ekološkoj (organskoj) poljoprivredi, a u plodoredu iza predusjeva soje (Glycine max L.). Pokus je postavljen kao potpuno slučajan blok raspored u četiri repeticije, sa šest tretmana postrnih usjeva: CT – kontrola, bez postrnih usjeva; WW – ozima pšenica (Triticum aestivum L.); RY – ozima raž (Secale cereale L.); FP – stočni grašak (Pisum arvense L.); WP – mješavina WW i FP; te RP – mješavina RY i FP. WW tretman imao je najveću masu postrnih usjeva, dok je FP imao najmanju masu postrnih usjeva. Najgušći sklop zabilježen je na FP tretmanu, značajno viši nego sklop na RP tretmanu, koji je također imao i najnižu visinu stabljika usjeva kukuruza. Ostvareni prinosi kukuruza bili su najviši na RY tretmanu, no nisu bili signifi-kantno različiti od O, RP i WW tretmana. Ipak, prinos zabilježen na RY tretmanu bio je signifikantno viši od prinosa na WP i FP tretma-nima. Apsolutna i hektolitarska masa nije se statistički razlikovala između tretmana

EKONOMSKA ODRŽIVOST PRIMJENE POSTRNIH USJEVA U EKOLOŠKOM UZGOJU KUKURUZA

Although organic crop production has numerous advantages, concerns about economic sustainability, both environmental and financial, make farmers reluctant to convert their conventional production into the organic production. Certain agricultural methods, such as second crop use, can alleviate some problems regarding soil tilth, erosion prevention, nutrients availability and weed control, thus contributing toward more sustainable crop production. Also, the added value crop growth, such as maize (Zea mais L.) hybrid\u27s parental line production, with lower yields but higher prices, can contribute to sustainability of organic production. In order to test the hypothesis that the use of second crops can contribute toward the sustainability of organically grown maize after soybean (Glycine max L.) as a previous crop in the crop rotation, the experimental site was established in Valpovo, Croatia, in the eutric brown soil type, during the years 2005 and 2006. The experimental design was set up as a CRBD in four repetitions, with six second crop treatments: CT – Control, without second crop; WW – winter wheat (Triticum aestivum L.) second crop; RY – rye (Secale cereale L.) second crop; FP – fodder pea (Pisum arvense L.) second crop; WP – mixture of WW and FP; and RP – mixture of RY and FP. In order to assess the soil surface protection and evaluate the weed suppression, the second crop coverage had been recorded. Regarding the economic sustainability, the second crop use depending costs were analysed in relation to the extra produced maize yield. The RY treatment had the highest profitability, followed by WW, RP and O. The WP and FP revealed lower relative profitability than O, thus presenting the evidence of sustainability risk of these treatments.Premda ekološka poljoprivreda ima brojnih prednosti, zabrinutost zbog održivosti, i ekološke i ekonomske, farmere često odvraća od prijelaza s konvencionalne proizvodnje na ekološku. Intenzifikacijom plodoreda uporabom postrnih usjeva, mogu ukloniti neke probleme vezane za ugorenost tla, prevenciju erozije, dostupnost hraniva i suzbijanje korova, doprinoseći na taj način održivosti proizvodnje usjeva. Također, uzgoj usjeva s dodatnom vrijednošću, kao što su roditeljske linije za proizvodnju hibrida kukuruza (Zea mais L.), s nižim prinosima ali višom cijenom, može pridonijeti održivosti (profitabilnosti) ekološke proizvodnje. U namjeri da se potvrdi hipoteza da postrni usjevi mogu doprinijeti održivosti ekološkog uzgoja kukuruza u dvopoljnom plodoredu sa sojom (Glycine max L.) kao prethodnim usjevom, postavljeno je pokušalište u Valpovu, Hrvatska, na eutričnom smeđem tlu, tijekom 2005. i 2006. godine. Pokus je postavljen kao potpuno slučajan blok raspored u četiri ponavljanja, sa šest tretmana postrnih usjeva: CT – kontrola, bez postrnih usjeva; WW – ozima pšenica (Triticum aestivum L.); RY – ozima raž (Secale cereale L.); FP – stočni grašak (Pisum arvense L.); WP – smjesa WW i FP; te RP – smjesa RY i FP. U cilju određivanja zaštite površine tla i evaluacije suzbijanja korova, zabilježena je pokrivenost postrnim usjevima. Glede isplativosti, analizirani su relativni troškovi upotrebe postrnih usjeva u odnosu na dodatno proizvedeni urod kukuruza. RY tretman je zabilježio najvišu profitabilnost, a pratili su ga tretmani WW, RP i O. Tretmani WP i FP pokazali su se manje profitabilni od O, time pružajući dokaze o rizičnoj održivosti ovih tretmana

Oxygen abundance as indicator of chemical homogeneity for groups of young stars

V magistrskem delu je raziskana kemijska homogenost Orionovega kompleksa molekularnih oblakov na podlagi meritev zastopanosti kisika v posameznih zvezdah. Najprej so predstavljene osnove zvezdne spektroskopije. Opisana sta spekter črnega telesa in formacija absorpcijskih črt. Podrobneje je opisan teoretični Voightov profil absorpcijskih črt z upoštevanjem tlačne in termične razširitve, opisani pa so tudi premiki in razširitve črt, ki izvirajo iz zvezdne dinamike. Predstavljena je tehnika Echelle spektroskopije, HR in Kielov diagram ter spektralna klasifikacija zvezd na podlagi podobnosti v njihovih spektrih. Sledi opis procesov življenja zvezd -- od njihove formacije iz molekularnih oblakov in obdobja na glavni veji, do razvoja v orjakinje ter smrti zvezd in obogatitve okoliškega prostora z elementi nukleosinteze. Predstavljene so tudi glavne fizične in kemijske značilnosti Orionovega kompleksa. V praktičnem delu naloge so uporabljena spektroskopska opazovanja 30 zvezd iz območij molekularnih oblakov v Orionu in Samorogu v območju valovnih dolžin od 395 do 680,nm. V glavnem so to vroče zvezde glavne veje, nekaj pa je tudi orjakinj. Opisan je postopek obdelave surovih spektrov v programu IRAF, za katere sem nato z uporabo programa iSpec določil vrednosti radialne hitrosti, atmosferskih parametrov (efektivna temperatura, gravitacijski pospešek na površju, mikro- in makroturbulenčna hitrost, projekcija rotacijske hitrosti in koeficient robne zatemnitve) in zastopanosti kisika. Zastopanosti kisika sem določil pod predpostavko kemijske homogenosti kompleksa v kovinskosti in zastopanosti $alpha$ elementov -- pričakoval sem torej enakomerno zastopanost kisika v različnih spektralnih tipih zvezd. Območji sta glede na zastopanosti kisika v zvezdah homogeni. Določena absolutna zastopanost kisika v opazovanih zvezdah znaša $A$(O)$=(8,33 pm 0,49),$dex, določena relativna zastopanost glede na železo pa [O/Fe]$=(-0,26pm0,49),$dex. Povprečna velikost napake določene zastopanosti kisika vseh zvezd je enaka $0,54,$dex. Raziskani so tudi vplivi posameznih parametrov na končne določene zastopanosti kisika. Med vsemi parametri na končno napako najbolj vplivata natančnost določitve efektivne temperature in gravitacijskega pospeška na površju.The Master’s thesis explores the chemical homogeneity of the stars of the Orion Molecular Complex, based on measurements of Oxygen abundance in individual stars. Stellar spectroscopy is introduced, followed by the description of a blackbody spectrum and the formation of absorption lines. Theoretical Voigt profile of absorption lines is described in detail by taking pressure and thermal broadening into account. Doppler shift and rotational broadening of lines that originate from the star dynamics are described as well. Furthermore, the Echelle Spectroscopy technique, HR and Kiel diagram, and the spectral classification of stars, based on similarities in their spectra, are presented. The process of the stellar life is describedfrom the formation in molecular clouds and the main sequence phase, to the evolution into giants and finally deaths that enrich the surrounding environment with the elements of stellar nucleosynthesis. Theoretical part is concluded with the presentation of physical and chemical features of the Orion Complex. In practical part, spectroscopical observations of 30 stars from the molecular cloud areas in Orion and Monoceros, covering the area of wavelengths from 395 to 680 nm, have been used. Mainly, these are hot main sequence stars, including a few giants. It is described how raw spectra have been processed in IRAF programme and how iSpec programme has been used to determine the radial velocities, atmospheric parameters (effective temperature, gravitational acceleration on the surface, micro- and macro-turbulence velocities, the projection of the rotational velocity and the limb darkening coefficient) and most importantly, the Oxygen abundances of observed stars. Oxygen abundance have been determined under the assumption that Orion complex is chemically homogeneous in metallicities and abundances of $alpha$ elements – therefore, the Oxygen abundance should not vary between different spectral types. Considering Oxygen abundance, the Orion Complex is proven homogenous. The determined absolute Oxygen abundance in the observed stars is $A$(O)$=(8,33pm0,49),$dex, while the determined abundance, relative to iron is [O/Fe]$=(-0,26pm0,49),$dex. The average spread of determined Oxygen abundances of all stars is equal to 0,54,dex. Lastly, the relations between the determined Oxygen abundances and uncertainties of individual parameters have been researched. Among all the parameters, what affects the Oxygen abundances the most, is the accuracy of determining the effective temperature and the gravitational acceleration on the surface

Low-grade metamorphic rocks of the Tethys subduction–collision zone in the Medvednica Mt. (NW Croatia)

The low-grade metasedimentary rocks of Medvednica Mt. (Northwest Croatia) are associated with ortho-greenschists (metabasalts). The Lower to Upper Triassic age of the protolith of the low-grade metamorphic rocks belonging to the Stari Potok, Adolfovac, Tusti Breg, Bliznec, Mrzljak, and Sljeme lithostratigraphic units is determined on the basis of conodonts and field relationships. The metamorphic age of the Triassic metasedimentary rocks from the Risnjak lithostratigraphic units is assumed to be Jurassic. Petrographic and geochemical analyses of ortho-greenschists point to a tholeiite basic magmatic protolith rock having T-MORB (transitional midocean-ridge basalt) characteristics. The ortho-greenschists of the Sljeme lithostratigraphic unit underwent retrograde metamorphism and show metamorphic zoning from the epidote–amphibolite facies to the lower parts of the greenschist facies. However, the greenschists of the Tusti Breg and Bliznec units are characterized by prograde metamorphism ranging from lower to higher greenschist facies. This metamorphism is associated with Jurassic subduction (165–150 Ma) and closure of the Western Tethys. Retrograde metamorphism took place during the collision of the Adriatic and Eurasian plates in the Lower Cretaceous (125–110 Ma)