Sunflower is the most important oil crop in the Republic of Croatia. In the last two decades, it has been grown on average on 33,506 ha with a average grain yield of 2.66 t/ha. Weeds represent one of ...the most important causes of biotic stress, and their action is reflected in the competition for nutrients, water, light and space. The weed flora in sunflower crops in Croatia is extremely diverse, and we will most often meet: Polygonum persicaria L., Polygonum lapathifolium L., Ambrosia artemisiifolia L., Chenopodium polyspermum L., Amaranthus retroflexus L., Solanum nigrum L. emend Miller, Abutilon theophrasti Medik, Datura stramonium L., Xanthium strumarium L., Convolvulus arvensis L., Cirsium arvense (L.) Scop., Echinochloa crus-galli (L.) Pb., Setaria glauca (L.) Pb., Setaria viridis (L.) Pb., Digitaria sanguinalis (L.) Scop., Panicum spp. and Sorghum halepense (L.) Pers. For many years, weed control was based on the intensive use of chemical preparations, which were most often used after sowing and before emergence, in double or triple combinations. In addition to a number of advantages of using chemicals in sunflower production, the problem of broadleaf weeds was not satisfactorily solved until the advent of Clearfield, Clearfield plus and Express sun technology, i.e. hybrids tolerant to herbicides from the group of imidazolinone (imazamox) and sulfonyl-urea (tribenuron-methyl) at the beginning of this century. Integrated plant protection, including integrated weed management, with its holistic approach and greater application of direct and indirect non-chemical measures, is only environmental quality solution for controlling weeds in sunflowers.
S ciljem utvrđivanja utjecaja vremenskih uvjeta na komponente uroda ulja suncokreta, u radu su analizirani trogodišnji rezultati poljskih pokusa. U pokusima posijanim u Osijeku 2013., 2014. i 2015. ...godine bilo je 15 hibrida suncokreta: dva strana hibrida i 13 hibridnih kombinacija Poljoprivrednog instituta Osijek. U periodu prije sjetve (siječanj – ožujak), najveća je količina oborina bila 2013. (213,1 mm), zatim 2015. (167,9 mm), a najmanja 2014. (109,5 mm). U vegetacijskome periodu (travanj – rujan), u 2014. bilo je najviše oborina (487,3 mm), u 2013. 475,7 mm, a u 2015. najmanje (251,6 mm). U 2013. godini, u vegetacijskome periodu, srednja mjesečna temperatura zraka bila je 19,1°C, u 2015. 19,9°C, a u 2014. 18,6°C. Od navedenih godina, statistički značajno na nivou P=0,05, najviše vrijednosti analiziranih svojstava zabilježene su 2013. godine: urod zrna 6,47 t ha-1, sadržaj ulja 51,69% i urod ulja 3,05 t ha-1. Urod zrna, sadržaj ulja i urod ulja bili su manji 2015., a najmanji 2014. godine. Najveće vrijednosti uroda zrna i ulja (6,95 i 3,39 t ha-1) imao je Matej, novopriznati hibrid suncokreta Poljoprivrednog instituta Osijek, a po sadržaju ulja od 53,44% bio je na trećem mjestu. Za visoke urode zrna i ulja suncokreta, pored optimalne temperature zraka, jako je bitna količina i raspored oborina prije, a također i tijekom vegetacije.
With the purpose of determining the influence of weather conditions on the yield components of sunflower, the results of three-year field trials are analysed in the paper. In the trials sown in ...Osijek in 2013, 2014 and 2015, there were 15 sunflower hybrids: two foreign hybrids and 13 hybrid combinations of the Agricultural Institute Osijek. In the period before sowing (January – March), the highest amount of precipitation was in 2013 (213.1 mm), then in 2015 (167.9 mm), and the lowest in 2014 (109.5 mm). In the growing period (April – September), the highest amount of precipitation (487.3 mm) was in 2014, 475.7 mm in 2013, and in 2015 it was the lowest (251.6 mm). In 2013, during the growing period, the mean monthly air temperature was 19.1°C, in 2015 19.9°C, and in 2014 18.6°C. Of these years, statistically significant at the P=0.05, the highest value of the analysed traits was recorded in 2013: grain yield of 6.47 t ha-1, oil content 51.69% and oil yield 3.05 t ha-1. Grain yield, oil content and oil yield were lower in 2015, and the lowest in 2014. Matej, a newly recognized sunflower hybrid of the Agricultural Institute Osijek had the highest values of grain and oil yield (6.95 and 3.39 t ha-1), and by its oil content of 53.44%, it was in the third place. For high grain and oil yields of sunflower, in addition to the optimal air temperature, the amount and distribution of precipitation before and also during the growing season are very important.
The reason for this examination is today’s wide usage of chlorophyll a fluorescence (ChlF) among researchers worldwide to measure photosynthetic efficiency. Although the instructions of the ChlF ...measuring device clearly emphasize the need for methodology adjustments, depending on the specific plant species, many researchers use the usual 30 min of dark adaptation before measurement. Namely, before any ChlF measurement, it is necessary to determine the specific duration of the leaf adaptation to the conditions of darkness of each plant tissue. Because of the numerous uses of the ChlF measurements, we decided to conduct this research to determine whether the appearance of the curves and parameter values depend on the time of sunflower leaf tissue adaptation to dark conditions. Therefore, this research aimed to examine the optimal adaptation time of sunflower tissue to dark conditions to obtain timely precise measurements and credible appearance of ChlF transient curves as well as accurate parameter values. The research was carried out on the sunflower hybrid Luka with 0, 15, 30, 45, 60, 75 and 90 min of dark adaptation in the vegetative, budding and flowering stages in the field conditions. According to the analyzed transient curves and parameters, it was determined that sunflower leaves should be kept in dark conditions for at least 15 min before the measurement of ChlF, which leads to the complete oxidation of PSII and the electron transport chain prior to a saturating pulse of light.
The aim of this research was to investigate the variability of photosynthetic performance index (PIABS) and leaf temperature values measured in V6 development phase on 13 sunflower hybrids, grown in ...stressful conditions. The pot trial was made up of two treatments, one (T1) with 60% Field Water Capacity (FWC), and the other one (T2) with 80% FWC. Significant differences between T1 and T2 treatments were established for both of these parameters which prove their dependence on the water content in the soil, while the influence of hybrid was evident only in the case of PIABS. Although in T1, as opposed to T2, all sunflower hybrids reacted by increasing leaf temperature, reaction to stress conditions measured with PIABS parameter was not uniform. Some of the hybrids reacted by decreasing PIABS values, while others reacted by increasing their PIABS values. Therefore, it can be concluded that changes in parameters were independent of each other, which was confirmed by correlation analysis. Investigated parameters are suitable for determining the existence of undesirable environmental conditions that cause stress in plants and can be used in breeding of sunflower to withstand abiotic stress conditions, i.e. in selection of stress tolerant hybrids.
In this research we have determined germination energy and germination of seeds of sunflower hybrids ‘Luka’ and ‘Apolon’, at the beginning of storage and 6, 12 and 18 months after of storage period ...(2011-2012) in the floor concrete storage at two different air temperatures and humidity (S-1: air temperature 15-18°C and relative air humidity 65-70%) as well as in climate chamber (S-2: air temperature 10-12°C and relative air humidity 60-65%), stored in four treatments (Control: processed-untreated seed; T-1: treated with A.I. metalaxyl-M; T-2: treated with A.I. metalaxyl-M + A.I. imidacloprid and T-3: treated with A.I. metalaxyl-M + A.I. clothianidin). Based on the obtained results we have determined that sunflower hybrid ‘Luka’, compared to hybrid ‘Apolon’, in the given storage conditions and with the same seed treatment has 5-8% higher germination energy and seed germination and that in climate chamber both hybrids have 5-7% higher germination energy. Seed treatment of both sunflower hybrids with A.I. imidacloprid maximally reduced initial germination energy and seed germination in all tested periods and conditions of storage. On the average, natural seed, after 18 months of storage did not have better seed quality compared to seed treated with A.I. metalaxyl-M while other treatments had more significant influence on reduction of germination energy and seed germination, 6-15%. On the average, compared to other variants, seeds treated with A.I. metalaxyl-M after 18 months of storage in both storage conditions had higher germination energy by 4-15%, and seed germination by 2-12%.
The reason for this examination is today’s wide usage of chlorophyll a fluorescence (ChlF) among researchers worldwide to measure photosynthetic efficiency. Although the instructions of the ChlF ...measuring device clearly emphasize the need for methodology adjustments, depending on the specific plant species, many researchers use the usual 30 min of dark adaptation before measurement. Namely, before any ChlF measurement, it is necessary to determine the specific duration of the leaf adaptation to the conditions of darkness of each plant tissue. Because of the numerous uses of the ChlF measurements, we decided to conduct this research to determine whether the appearance of the curves and parameter values depend on the time of sunflower leaf tissue adaptation to dark conditions. Therefore, this research aimed to examine the optimal adaptation time of sunflower tissue to dark conditions to obtain timely precise measurements and credible appearance of ChlF transient curves as well as accurate parameter values. The research was carried out on the sunflower hybrid Luka with 0, 15, 30, 45, 60, 75 and 90 min of dark adaptation in the vegetative, budding and flowering stages in the field conditions. According to the analyzed transient curves and parameters, it was determined that sunflower leaves should be kept in dark conditions for at least 15 min before the measurement of ChlF, which leads to the complete oxidation of PSII and the electron transport chain prior to a saturating pulse of light.
Suncokret je u Republici Hrvatskoj najvažnija uljarica. U posljednja dva desetljeća prosječno se uzgajao na 33.506 ha
s prinosom zrna od 2,66 t/ha. Korovi predstavljaju jedan od najvažnijih uzročnika ...biotičkog stresa, a njihovo djelovanje
ogleda se kroz kompeticiju za hranjiva, vodu, svjetlost i prostor. Korovna flora u usjevima suncokreta u Hrvatskoj
iznimno je raznolika, a najčešće susrećemo: Polygonum persicaria L., Polygonum lapathifolium L., Ambrosia artemisiifolia
L., Chenopodium polyspermum L., Amaranthus retroflexus L., Solanum nigrum L. emend. Miller, Abutilon theophrasti Med.,
Datura stramonium L., Xanthium strumarium L., Convolvulus arvensis L., Cirsium arvense L. Scop., Echinochloa crus-galli L.
Pb., Setaria glauca L. Pb., Setaria viridis L. Pb., Digitaria sanguinalis L. Scop., Panicum spp. i Sorghum halepense L. Pers. Dugi
niz godina borba protiv korova u suncokretu bazirala se na intenzivnoj primjeni kemijskih sredstava, koji su se najčešće
koristili nakon sjetve i prije nicanja, u dvostrukim ili trostrukim kombinacijama pripravaka. I pored niza prednosti upotrebe
herbicida u proizvodnji suncokreta, problem širokolisnih korova, zbog ograničenog izbora herbicida, nije na zadovoljavajući
način riješen. Pojavom kultivara Clearfield, Clearfield plus i Express sun tehnologije, odnosno kultivara tolerantnih na
herbicide iz kemijske skupine imidazolinona (imazamoksa) i sulfonilurea (tribenuron-metila) herbicida, početkom ovog
stoljeća znatno je olakšano suzbijanje širokolisnih korovnih vrsta u suncokretu. Osim spomenutih mogućnosti, a u skladu
s novim trendovima, integrirana zaštita bilja od korova holističkim pristupom, odnosno primjenom izravnih i neizravnih
nekemijskih mjera pruža ekološki prihvatljivo rješenje u borbi s korovima u suncokretu.
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