The effect of long-term mineral and organic-mineral fertilization on accumulation of heavy metals in soil and plants was studied in stationary field experiment with continuous tobacco cropping system. Five treatments were selected in this study, including CK (control without fertilization), NP (nitrogen+phosphorus), NK (nitrogen+potassium), NPK (nitrogen+phosphorus+potassium) and NPK+FYM (nitrogen+phosphorus+potassium+manure). Total and available Pb, Cd, Ni, Mn, Zn and Cu content in soil, as well as concentration of the elements in tobacco leaves were determined. The application of mineral fertilizers did not significantly increase the total Pb, Cd, Ni, Zn and Cu content in the soil as compared to unfertilized control. The addition of manure (NPK+FYM treatment) decreased total Ni. There was significant increase of available Ni and Mn in treatment receiving NPK+FYM. A comparison of unfertilized treatment indicated that long-term mineral fertilization had no significant effect on studied metals in oriental tobacco leaves. A considerable decrease in Cd (2.2-2.8 times), Zn (1.7-3.3 times) and Cu (2.2-3.8 times) concentrations in the leaves compared with control without fertilization was detected due to long-term NPK+FYM fertilization. This study demonstrated that the risk of heavy metals' accumulation in tobacco leaves associated with long-term mineral and organic-mineral fertilization was low.

The effects of the different potassium rates (0, 75 and 450 kg K 2 O ha -1 ) on nutrient concentrations in the above-ground biomass and chemical characteristics of sun-cured tobacco have been studied in a stationary field trial. Annual fertilization with 75 kg K 2 O ha -1 was adequate to maintain soil K concentration near the initial value. It was found that yield of cured leaves was not significantly affected by rate of K application when oriental tobacco was grown on soils with high available soil K. With the increase of K fertilization rate the content of the potassium in leaves increased from 0.65 to 4.49%. The concentration of Ca and Mg in the leaves ranged from 2.03 to 5.23% and from 0.52 to 0.71%, respectively and decreased with increases in added potassium. No effect of K rates on nicotine and protein content was noted. Only the reducing sugars' content tended to increase to 11.42% at the highest K rate. Fertilization with moderate potassium rates (75 kg K 2 O ha -1 ) on soils high in available K is necessary to maintain the good potassium reserves. When oriental tobacco was grown on alkaline soils with high available K and Ca, potassium fertilization improves K nutrition and therefore may favorably affect burning properties of tobacco. ) върху концентрацията на N, P, K, Ca и Mg в надземната биомаса на ориенталски тютюн и химичния състав на сухия тютюн. Системното торене със 75 kg K 2 O ha -1 е адекватно за поддържане на нивото на калия в почвата близко до изходното. Стопанският добив е повлиян слабо от калиевата норма при отглеждане на тютюна на почви с високо съдържание на подвижен калий. Съдържанието на калий в листата нараства с увеличаване на калиевата норма. Концентрацията на 510 Journal of Central European Agriculture, 2012, 13(3), p.510-518 DOI: 10.5513/JCEA01/13.3.1078 Са и Mg в листните тъкани се понижава от нарастването на торовия калий. Нормата на торене с калий не влияе върху съдържанието на никотин и белтъчини в сухия тютюн. Единствено съдържанието на разтворими въглехидрати показва тенденция към повишение при най-високата торова норма.Ключови думи: калиево торене, ориенталски тютюн, химичен състав Подробно резюмеИзискванията на тютюна към калия са високи. Калиевото торене допринася главно за подобряване на някои качествени признаци на сухия тютюн -горяемост, цвят, еластичност. То увеличава добива сух тютюн, пазарната му стойност и съдържанието на K и Mn в листата при отглеждане на тютюна на почви, бедни на усвоим калий (Leggett, et al., 1977). Link and Terrill (1982) установяват, че торенето с калий на почви с високо съдържание на подвижен калий води до повишаване концентрацията на калия в сухия тютюн, но добивът и качеството остават непроменени. В настоящото проучване се проследява влиянието на калиево торене и на създадените от системното торене контрастни запасености на елемента в почвата върху добива, концентрацията на макроелементи в надземната биомаса на ориенталски тютюн и химичния състав на сухия тютюн. Изследванията са проведени върху стационарен полски опит със системн...

<p>The effect of long-term mineral and organic-mineral fertilization on selected soil properties (pH, total humus and N, available phosphorus, potassium, calcium, magnesium, iron and manganese content) was studied in a stationary trail with tobacco monocropping system. The trial was established on Rendzic Leptosols in 1966. Five treatments were selected for this study, including control without fertilization (Check), nitrogen + phosphorus (NP), nitrogen + potassium (NK), nitrogen + phosphorus + potassium (NPK) and nitrogen + phosphorus + potassium + manure (NPK + manure). Soil samples at a depth of 0–25 cm were collected from all studied plots every year (2014, 2015 and 2016). The results indicated that maintaining humus content at the initial level is not possible through yearly mineral fertilizer application. Long-term mineral phosphorus fertilization increased 5.5–5.7 times available <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">P<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">2<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">O<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">5</span></span></span></span> in the soil compared to the initial level. The soil available <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">K<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">2<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">O</span></span></span> content in NK and NPK treatments increased, respectively, by 41.1% and 44.9% over the initial level. A remarkable increase in available phosphorus (25.5 times) and potassium (2.5 times) content in the soil compared with the initial level was found due to longterm NPK + manure fertilization. The NPK + manure treatment was found to be the most efficient management system in accumulating of total humus and N, available <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">P<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">2<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">O<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">5</span></span></span></span>, <span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">K<span style="font-family: TimesNewRomanPSMT; font-size: 5pt; color: #231f20; font-style: normal; font-variant: normal;">2<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">O</span></span></span>, Fe and Mn in a long-term fertilized Rendzic Leposol, under a tobacco monocropping system.</p>

This study of a legume’s rhizosphere in tripartite symbiosis focused on the relationships between the symbionts and less on the overall rhizosphere microbiome. We used an experimental model with different garden pea genotypes inoculated with AM fungi (Rhizophagus irregularis and with a mix of AM species) to study their influence on the population levels of main trophic groups of soil microorganisms as well as their structure and functional relationships in the rhizosphere microbial community. The experiments were carried out at two phenological cycles of the plants. Analyzes were performed according to classical methods: microbial population density defined as CUF/g a.d.s. and root colonization rate with AMF (%). We found a proven dominant effect of AMF on the densities of micromycetes and actinomycetes in the direction of reduction, suggesting antagonism, and on ammonifying, phosphate-solubilizing and free-living diazotrophic Azotobacter bacteria in the direction of stimulation, an indicator of mutualistic relationships. We determined that the genotype was decisive for the formation of populations of bacteria immobilizing mineral NH4+-N and bacteria Rhizobium. We reported significant two-way relationships between trophic groups related associated with soil nitrogen and phosphorus ions availability. The preserved proportions between trophic groups in the microbial communities were indicative of structural and functional stability.

PURPOSE: The genus Nicotiana is a well-defined group of species of which tobacco (Nicotiana tabacum L.) is the most important crop plant and plays a significant role in the economies of many countries. Recent advances in molecular genetics of the crop allowed the identification of many important genes and their location on chromosomes. However, the genetic analysis of this inbreeding, highly homozygous plant that serves as a model in many other studies is still very much work in progress. METHODS: A large proportion of the tobacco genome is represented by highly repeated DNA sequences, which makes molecular markers, based on them, an obvious first choice in diversity studies. Here we present an assessment with Inter-Simple Sequence Repeat (ISSR) markers of the intra- and inter-cultivar variability in a set of Bulgarian tobacco varieties. RESULTS: The screening of the 4 primers revealed a varying number of bands generated by different primers. The total number of bands varied between 4 and 13. No correlation between the total number of bands and the number of polymorphic bands was observed. Testing with ISSR primers revealed that plants with different DNA profiles can be found in varieties used. The highly similar profiles when E7 primer was used in two of the tested varieties from different production types indicate that the DNA fingerprinting technique may present a particular challenge in this crop. CONCLUSIONS: The present study demonstrates the power of the ISSR technique as a tool for diversity identification in tobacco.