EFFECT OF RIPENESS AND RELATED GROWING PRACTICES ON VIRGINIA TOBACCO I. YIELD, PRICE AND PETIOLE SAP NITRATE CONTENT AS AN INDICATOR OF LEAF RIPENESS FOR HARVEST

Istraživanje s ciljem utvrđivanja utjecaja visine zalamanja (17 i 20 listova za berbu), metode berbe (7, 4 i 3 berbe) i zrelosti (nezreli, zreli i prezreli) na prinos, cijenu i sadržaj nitrata u soku rebra u vrijeme berbe, provedeno je 2006. i 2008. godine. Primijenjen je split-split plot dizajn s čeiri ponavljanja. Viši prinosi u vršnom segmentu ostvareni su višim zalamanjem i obratno u dva niža segmenta. Utjecaj metode berbe na prosječne vrijednosti istraživanih svojstava bio je mali. Zrelost listova u vrijeme berbe u 2006. u pet od šest segmenata nije imala utjecaj na prinos. U 2008. najviši prinosi u vršna tri segmenta ostvareni su berbom zrelih listova. Najviše prosječne cijene u drugom i trećem segmentu ostvarene su berbom zrelih, a u višim segmentima prezrelih listova. Različito zreli listovi u vrijeme berbe u nekim segmentima su proizveli različite rezultate ovisno o visini zalamanja i metodi berbe. Sadržaj nitrata u soku rebra lista u vrijeme berbe kada su postignuti podjednaki ili viši prinosi i cijene opadao je odlaganjem berbe i, uz neke izuzetke, od donjih prema gornjim segmentima. Međutim, na osnovi rezultata ovog istraživanja nije bilo moguće odrediti kritične raspone sadržaja nitrata koji bi se mogli koristiti za procjenu zrelosti listova duhana za berbu.The investigation aiming to determine the effect of topping heights (17 and 20 leaves for harvesting), harvesting methods (7, 4 and 3 harvests) and ripeness (unripe, ripe and overripe) on yield, price and petiole sap nitrate content at harvesting time, was carried out in 2006 and 2008. A split-split plot design with four replications was applied. Higher yields in top segment were achieved with higher topping, and converse in two lower segments. The effect of the harvest method on the average values of the investigated properties was small. Leaf ripeness at harvesting in 2006, in five out of six segments, had no impact on yields. In 2008 the highest yields in the top three segments were achieved by the harvest of ripe leaves. The highest average prices in the second and third segments were realized by harvesting ripe leaves and in the higher segments overripe leaves. Different ripe leaves at harvesting time in some segments produced different results depending on height of topping and method of harvesting. Petiole sap nitrate content at harvest when equal or higher yields and prices were achieved decreased by delaying harvesting and, with some exceptions, from lower to higher segments. However, based on the results of this research it was not possible to determine the critical nitrate content ranges that could be used to estimatia the ripeness of tobacco leaf for harvestin

EFFECT OF RIPENESS AND RELATED GROWING PRACTICES ON VIRGINIA TOBACCO II. TOTAL NITROGEN, PROTEINS, NICOTINE AND REDUCING SUGARS

Istraživanje je provedeno u 2006. i 2008. kako bi se utvrdio utjecaj visine zalamanja, metode berbe i zrelosti lista u vrijeme berbe na sadržaj ukupnog dušika, bjelančevina, nikotina i reducirajućih šećera. Postupci u pokusu bili su visina zalamanja (17 i 20 listova za berbu), metoda berbe (3, 4 i 7 berbi) i zrelost listova u berbi (nezreli, zreli i prezreli). Primijenjen je split-split plot dizajn s četiri repeticije. Koncentracija istraživanih kemijskih svojstava proučavana je u listovima iz trećeg (6 i 7 list) i sedmog (14 i 15 list) segmenta na stabljici. Visina zalamanja nije utjecala na prosječni sadržaj ukupnog dušika, bjelančevina, nikotina i reducirajućih šećeri. Utjecaj metode berbe na istraživan kemijski sastav bio je mali. Odgađanje berbe uzrokovalo je smanjenja prosječnog sadržaja ukupnog dušika i bjelančevina, povećanja sadržaja nikotina, a sadržaj redukcirajućih šećera povećavao se do optimalne zrelosti ili prezrelosti. Međutim, prisutnost interakcija ukazuje da berba listova duhana u različitim stadijima zrelosti može proizvesti nekonzistentne rezultate ovisno o metodi berbe i visini zalamanja.The study was carried out during the 2006 and 2008 to determine the influence of topping height, method of harvest and leaf ripeness at harvesting time on the content of total nitrogen, nicotine, proteins and reducing sugars. Treatments in the experiment were topping height (17 and 20 harvesting leaves), method of harvest (3, 4 and 7 harvests) and ripeness of leaves at harvesting (unripe, ripe and overripe). A split-split plot design with four replications was applied. The concentration of investigated chemical properties was studied in the leaves from the third (6th and 7th leaf) and seventh (14th and 15th leaf) stalk segments. Height of topping did not affect the average content of total nitrogen, proteins, nicotine and reducing sugars. The influence of the method of harvest on the investigated chemical composition was small. Delaying harvest caused decreases in average total nitrogen and proteins content, increases in nicotine content, and the content of reducing sugars increased to optimal ripeness or overripeness. However, the presence of interactions suggests that harvesting tobacco leaves at different stages of ripeness can produce inconsistent results depending on the method of harvest and the height of topping

THE EFFECTIVENESS OF CONTROL OF SUCKERS, AND RESIDUES OF MALEIC HYDRAZIDE IN FLUE-CURED TOBACCO ACCORDING TO THE AMOUNT OF APPLIED AGENTS

Cilj istraživanja bio je utvrditi učinkovitost kontrole rasta zaperaka te sadržaj ostataka maleinskog hidrazida u osušenim listovima virdžinijskog duhana s obzirom na količinu primijenjenog sredstva i položaj listova na stabljici. U 2008. i 2009. organizirani su poljski pokusi kod osam proizvođača duhana koji su reprezentativno predstavljali uzgojno područje duhana u Hrvatskoj. Postupci u pokusima nakon otkidanja cvata bili su: (1) bez primjene kemijskih sredstava za kontrolu zaperaka, (2) primjena maleinskog hidrazida 14 l/ha i (2) primjena smjese maleinskog hidrazida 9 l/ha s kontaktnim sredstvom u koncentraciji od 5% . Primjenom maleinskog hidrazida u količini od 14 l/ha i kvalitetnom i pravovremenom primjenom smjese maleinskog hidrazida u količini od 9 l/ha s 5%-tnim kontaktnim sredstvom postiže se podjednaka učinkovitost u kontroli broja i težine svježih zaperaka. Prolongiranje vremena primjene maleinskog hidrazida nakon zadnje primjene kontaktnog sredstva smanjilo je učinkovitost kontrole broja i težine svježih zaperaka. Prosječni sadržaji ostataka maleinskog hidrazida u listu duhana u 2008. kada je korišten u količini od 9 l/ha i 14 l/ha bili su 17, 27 mg/kg i 27, 35 mg/kg, a u 2009. prosječni sadržaj ostataka bio je 44,84 mg/kg i 70,34 mg/kg. Sadržaj maleinskog hidrazida opadao je od vršnog prema donjim položajima na stabljici i bio je u korelaciji s brojem dana od primjene maleinskog hidrazida do berbe duhana.The objective of the study was to determine the effectiveness of the control of suckers and the maleic hydrazide residues content in the dried leaves of flue-cured tobacco due to the amount of applied agents and leaves positions on the stalk. In 2008 and 2009 field experiments were organized at eight family farms, which represented the whole tobacco growing areas in Croatia. Treatments in experiments after topping were: (1) without the use of chemicals to control the suckers, (2) application of maleic hydrazide 14 l/ha, and (3) application of mixture of maleic hydrazide 9 l/ha with the contact agent at a concentration of 5 %. Application of maleic hydrazide in the quantity of 14 l/ha and high-quality and timely application of mixture of maleic hydrazide in the amount of 9 l/ha with 5 % concentrated contact agent achieved similar effectiveness in controlling the number and fresh weight of suckers. Delay time of application of maleic hydrazide after last application of contact agents reduced the effectiveness of the control number and fresh weights of suckers. The average maleic hydrazide residues content in tobacco leaf in 2008 when it was used in the amount of 9 l/ha and 14 l/ha were 17.27 mg/kg and 27.35 mg/ha, while in 2009 average residue contents were 44.84 mg/kg and 70.34, respectively. The maleic hydrazide content declined from upper to lower stalk positions and was correlated with the number of days from the application of maleic hydrazide to harvest of tobacco leaves

Use of a chlorophyll meter to evaluate the ripeness of flue-cured tobacco leaves for harvesting

Da bi se utvrdila mogućnost korištenja klorofilmetra u procjeni optimalne zrelosti listova flue-cured duhana za berbu, provedeni su dvogodišnji poljski pokusi. Postupci u pokusu bili su gnojidba dušikom (25 i 35 kg ha-1) i vrijeme berbe (rana, srednja i kasna berba). Relativni sadržaj klorofila 7., 11., 15. i 17. lista mjeren je u vrijeme berbe. Nakon berbe i sušenja tih listova analizirani su prinos i cijena te sadržaj nikotina i reducirajućih šećera. Nije bilo signifikantnog utjecaja gnojidbe dušikom na prosječni prinos, cijenu i sadržaj reducirajućih šećera. Međutim, dobivene su dvije interakcije gnojidba x vrijeme berbe za prinos. Viša gnojidba dušikom rezultirala je višim prosječnim sadržajem nikotina, ali samo u 15. i 17. listu u 2010. S obzirom na vrijeme berbe rezultati istraživanja su, uz nekoliko izuzetaka, pokazali da su viši prinosi, cijene, sadržaji nikotina i sadržaji reducirajućih šećera ostvareni srednjom ili/i kasnom berbom. Za pronalaženje raspona indeksa sadržaja klorofila u okviru kojeg bi se trebala provoditi berba listova duhana korišteni su matematički parametri odnosa između indeksa sadržaja klorofila u vrijeme berbe i istraživanih svojstava. U ovom istraživanju optimalno vrijeme za berbu listova duhana bilo je u rasponu indeksa sadržaja klorofila od 11-15.In order to determine the possibility of using chlorophyll meter to estimate the optimal ripeness of flue-cured tobacco leaves for harvest, two-year field experiments were carried out. Treatments in the experiments were fertilization with nitrogen (25 and 35 kg ha-1) and harvesting time (early, middle and late harvest). The relative chlorophyll content of leaves 7, 11, 15 and 17 was measured at harvest time. After harvesting and drying these leaves, yield and price, as well as the content of nicotine and reducing sugars, were analysed. There was no significant influence of nitrogen fertilization on average yield, price and reducing sugars content. However, two interactions fertilization x harvesting time for yield were obtained. Higher nitrogen fertilization resulted in higher average nicotine content, but only in the 15th and 17th leaf in 2010. Given the time of harvest, the results of the research, with a few exceptions, showed that higher yields, prices, nicotine contents and reducing sugars contents were achieved in the middle and/or late harvest. To find the chlorophyll content index range within which the tobacco leaf harvests should be carried out, the mathematical parameters of the relationship between chlorophyll content index at harvest and investigated properties were used. In this study, the optimal time for tobacco leaf harvesting was in the chlorophyll content index range of 11 to 15 CCI

INFLUENCE OF TOPPING HEIGHTS AND RIPENESS ON AGRONOMIC TRAITS OF FLUE-CURED TOBACCO CULTIVARS FROM THE LOWER AND UPPER STALK POSITION

Utjecaj visine zalamanja i zrelosti na agronomska svojstva listova duhana s donje i gornje polovice stabljike flue-cured sorti duhana istraživan je tijekom 2004-05. i 2007. godine. U tu svrhu organizirana su istraživanja u glavnom uzgojnom području duhana u Hrvatskoj po split-split plot metodi. Postupci u pokusu u polju bili su (1) visina zalamanja (20 i 17 listova za berbu), (2) zrelost lista u vrijeme berbe (nedozreli, zreli i prezreli) i (3) sorta (HVT 1, VJ 1, DH17). Zalamanjem duhana na 20 listova za berbu postignuti su veći prosječni prinosi, cijena po kilogramu i vrijednost po hektaru listova duhana gornjih branja u usporedbi s nižim zalamanjem. Generalni trend većih prinosa listova duhana s donjih položaja na stabljici ustanovljen je berbom u stadiju optimalne zrelosti, a gornjih branja u stadiju lagane nedozrelosti. Isti trend utvrđen je za cijenu duhana, s izuzetkom gornjih branja u godini s izuzetno malo oborina u fazi intenzivnog rasta i početka dozrijevanja. Te godine je svaka odložena berba povećala cijenu. Značajna interakcija između godine, sorte i zrelosti lista u vrijeme berbe za vrijednost po hektaru i interakcija između godine, sorte i visine zalamanja za cijenu po kilogramu upućuju na zavisnost agronomskih pokazatelja sorti o proizvodnim uvjetima tijekom rasta i dozrijevanja, visini zalamanja i zrelosti lista duhana u momentu berbe.The influence of topping heights and ripeness of leaf at harvest on the agronomic traits of Virginia tobacco cultivars was studied during 2004-2005 and in 2007. For this purpose, research in the main tobacco cultivation area in Croatia was organised, the split-split plot method being employed. The factors examined in the field trial were: (1) topping height (20 and 17 leaves for harvest), (2) the ripeness of the leaf at the time of harvest (unripe, ripe and overripe) and (3) cultivar (HVT 1, VJ 1, DH 17). Topping at 20 leaves for harvest resulted in greater average yields, price per kilogram and value per hectare of tobacco leaves of upper primings as compared with lower topping height. With respect to the ripeness of the leaves at the moment of harvesting, results of the investigation show a general trend towards greater yields of leaves in the lower position on the stalk with harvest in the stage of optimum ripeness and from upper stalk position in a slightly unripe stage. The same trend was determined for the price of tobacco, with the exception of upper primings in a year characterised by very small precipitation in the vigorous growth and early ripening period. That year every delay of harvesting increased the price. The considerable interaction between year, cultivar and ripeness of leaf at time of harvest with respect to value per hectare and the interaction between year, cultivar and topping height for price per kilogram suggest the dependence of agronomic traits of cultivars on the production conditions during the stage of vigorous growth and maturation, height of topping and ripeness of leaf at harvest