Tibor Szili-Kovács

Long-term outcome of nitrogen immobilization to restore endemic sand grassland in Hungary

Soil nitrogen immobilization by carbon amendment is a management technique used for conservation purposes to increase the competitive ability of late-seral plant species over early-seral species based on their different tolerance of low soil nitrogen content. We immobilized nitrogen over six growing seasons on three ex-arable fields with poor sandy soils in the Hungarian lowland in order to restore endemic sandy grassland. Sucrose and sawdust were applied at rates based on previous laboratory experiments using local soils. We tested the efficacy of long-term carbon amendment for lowering soil nitrogen availability and favouring late-seral native species over early-seral weed species. Carbon amendments resulted in significant increase in soil microbial biomass C and reduced soil nitrogen availability after 2 years. Total vegetation cover was reduced by reducing soil nitrogen availability, but total species richness was not impacted. Cover of early-seral species decreased, and species richness and cover of late-seral species increased irrespective of nitrogen immobilization. However, after 4-6 years reducing soil nitrogen availability hampered the spread of moss under vascular vegetation. Synthesis and applications. This study supports the efficacy of carbon amendment as a tool to immobilize available soil nitrogen in the upper soil layers. However, the desired impact on vegetation was not fully achieved despite application over several years. Nitrogen immobilization was most relevant to bryophytes, lacking deep root systems, which may explain the responsiveness of this group to N limitation. The different impact of N availability on the complex of early-seral, late-seral vascular species and that of the bryophyte layer provides opportunity for directing state transformations in arid grasslands. Bryophyte cover can be suppressed through carbon amendments in order to enhance the germination and establishment of grassland species. The advantage of the method is that it opens bryophyte cover gradually without disturbing the soil surface, possibly avoiding the establishment of invasive species. However, further studies are required for deeper insight.

Environmental Impact of Soil Pollution with Toxic Elements from the Lead And Zinc Mine at Gyöngyösoroszi (Hungary)

Toxic elements from the lead (Pb) and zinc (Zn) mine at Gyöngyösoroszi (Northeast Hungary) cause pollution and potential risk to the ecosystem and human health. The aim of this work was to determine the contamination level at two sites planted with willow (Salix sp. L.) and corn (Zea mays L.) along the Toka valley, to evaluate soil quality by biological and biochemical parameters, and to assess potential risk for human health. Total arsenic (As), cadmium (Cd), copper (Cu), Pb, Zn, and mercury (Hg) contents in polluted soils reached values up to 384, 28.8, 493, 2827, 4417, and 4.46 mg kg−1, respectively. Values of these elements in the polluted soil for willow were 3.7 to 31 times higher and in corn were 2.3 to 20.9 times higher than in the unpolluted soil. All measured parameters therefore indicated soil pollution. Plant emergence percentage and plant and microbial biomass decreased whereas water‐extractable organic carbon (C), phosphatase activity, and corn root infection by arbuscular mychorrizal AM fungi and toxic metal content of the tested plants increased significantly. The results showed a high soil pollution level and consequently a great potential risk for human health (value of the additive hazard quotient was 11.21) and indicated the necessity for remediation of the site.

Effects of nitrogen fertilization on carbon flows in soils with contrasting texture

One of the biggest challenges for the safe maize production is the yield stability in a wide range of environments with different soil fertility, weather conditions, prevailing pests and diseases as well as cultural practices. In order to achieve it, new hybrids with higher tolerance to biotic and abiotic stress are continuously being created. In order to compare performance of maize hybrids in environments with different levels and types of stress, and relate it to the stalk lodging incidence, we compared performance of 64 maize hybrids obtained by crossing 16 inbred lines with four inbred testers in three different environments. Two environments at same location (Rugvica) differed in crop rotation, and the third environment at location Botinec was considered as dry because of low water capacity of the soil. Mixed models that included all design elements and genetic background of hybrids were used to analyze the effect of lodging on yield in different environments. The results show that stalk lodging had a significant effect on yield, but significant lodging x environment interaction indicates that this effect was rather environment specific.Sweet pepper Istra F1 hybrid was grown in a greenhouse on K rich soil. For evaluation of K antagonism, two K rates (55 and 85 kg ha-1) were applied in a randomized complete block design with four replications. Total number of fruits, total number of BER affected fruits as well as average fruit mass were recorded for each harvest. Fruit and leaf K and Ca content were determined at three plant growth stages (at the stage of the first, third and fifth fruit cluster). Higher K rate gave higher : average fruit mass (169.45 g), total number of fruits per plant (7.95), number of BER affected fruits per plant (3.82), K in leaves (5.44% DM), K in fruits (6.35% DM), but negatively correlated with Ca concentration in fruits (0.57% DM) and leaves (3.24% DM). This resulted in decreased marketable yield of sweet pepper fruits.

Comparison of soil microbial communities from two distinct karst areas in Hungary

Karst areas belong to the most exposed terrestrial ecosystems, therefore their study have a priority task in Hungary, as well. The aim of this study was to compare the structure, activity and diversity of soil microbial communities from two distinct Hungarian karst areas (Aggtelek NP and Tapolca-basin). Soil samples were taken three times from 6 distinct sites, from different depths. Soil microbial biomass C (MBC), microbial biomass N (MBN), basal respiration (BRESP) and substrate induced respiration (SIR) were measured. The phylogenetic diversity of bacterial communities was compared by Denaturing Gradient Gel Electrophoresis (DGGE). The highest MBC, MBN, BRESP and SIR values were measured in the rendzina soil from Aggtelek. On the basis of biomass and respiration measurements, microbial communities differentiated mainly according to soil depths whereas DGGE profiles of bacterial communities resulted in groups mainly according to sampling sites.

Diversity and ecological tolerance of bacteria isolated from the rhizosphere of halophyton plants living nearby Kiskunság soda ponds, Hungary

Many halophytes and halophilic microorganisms are capable to adapt to the extremities of saline habitats. This study reveals the taxonomic diversity and ecological tolerance of bacteria isolated from the rhizosphere of three different halophytes (Bolboschoenus maritimus, Puccinellia limosa and Aster tripolium) living in the vicinity of Kiskunság soda ponds. Following a sampling in September 2013, altogether 76 bacterial strains were isolated using two different media. The strains were identified on the basis of 16S rRNA gene sequencing following ARDRA grouping. Salt and pH tolerance of the strains were examined by measuring their growth in broths containing 0-15% NaCl (w/V) and characterized with pH 7-12 values. Among the strains genera of Anaerobacillus, Bacillus and Exiguobacterium (Firmicutes), Agromyces, Isoptericola, Microbacterium, Micrococcus, Nocardiopsis, Nesterenkonia and Streptomyces (Actinobacteria), Halomonas and Idiomarina (Proteobacteria) and Anditalea (Bacteroidetes) were identified. The Bolboschoenus and Puccinellia samples characterized with the highest pH and electric conductivity values were dominated by Bacillus, Halomonas and Nesterenkonia, respectively. The salt tolerance of the bacterial strains was strongly dependent on the sampling location and plant species. In contrast, growth of bacterial strains in broths with alkaline pH values was more balanced. The strains from the Puccinellia sample showed the widest salt and pH tolerance.

METABOLIC ACTIVITY AND GENETIC DIVERSITY OF MICROBIAL COMMUNITIES INHABITING THE RHIZOSPHERE OF HALOPHYTON PLANTS

A preliminary study was conducted to compare the community level physiological profile (CLPP) and genetic diversity of rhizosphere microbial communities of four plant species growing nearby Kiskunság soda ponds, namely Böddi-szék, Kelemen-szék and Zab-szék. CLPP was assessed by MicroResp method using 15 different substrates while Denaturing Gradient Gel Electrophoresis (DGGE) was used to analyse genetic diversity of bacterial communities. The soil physical and chemical properties were quite different at the three sampling sites. Multivariate statistics (PCA and UPGMA) revealed that Zab-szék samples could be separated according to their genetic profile from the two others which might be attributed to the geographical location and perhaps the differences in soil physical properties. Böddi-szék samples could be separated from the two others considering the metabolic activity which could be explained by their high salt and low humus contents. The number of bands in DGGE gels was related to the metabolic activity, and positively correlated with soil humus content, but negatively with soil salt content. The main finding was that geographical location, soil physical and chemical properties and the type of vegetation were all important factors influencing the metabolic activity and genetic diversity of rhizosphere microbial communities.

Fertilizer effect on Carbon Dynamics of different texture soils under tomato cultures

The risk of nitrate (NO3) leaching is enhanced under tomato culture because of the high water demand, especially in fertilized coarse‐texture soils. To avoid this, slow‐release fertilizers or manure use is recommended. We studied the effect of a slow release and a common fertilizer on the carbon (C) and nitrogen (N) dynamics of drip‐irrigated tomato culture at a macro‐pot (lysimeter) field trial in three different texture soils. The treatments included an initial blanket application of slow‐release fertilizer to all the pots 1 week after planting, followed by supplemental application of N 3 or 6 weeks later. The C and N contents of the microbial biomass differed among the soils. They were significantly less in sandy soil than in the other loam texture soils. A close relation (r2 = 0.85) was found between microbial C and N. Their mean ratio was 6.7, being lowest in the sandy (6.0), and the highest in the clay loam (7.0) soil, but without significant difference. The rate of cellulose decomposition tended to decrease in the sandy soil in each of the three observed periods. The two highest N addition treatments (120 and 180 kg.ha−1 N) accelerated cellulose decay compared with the control and low N addition (60 kg.ha−1 N), especially in the clay loam soil. Nitrate adsorbed by ion‐exchange resin bags in the 0‐ to 30‐cm soil depth did not differ significantly between treatments, and there was no enhancement in nitrate leaching due to repeated fertilizer application.

Substrate induced respiration in soils developed under four stages of succession on a colliery heap

Substrate induced respiration as a measure of active part of the soil biomass increased in the chronosequence of spoil succession. This change observed first in the top (0–5 cm) and later in the bottom (10–15 cm) layer relating probably to the vegetation and soil fauna succession. SIR better than by the total organic C can indicate soil succession, because this latter was partly originated from the fossil organic matter. Water extractable C and N were also increased during chronosequence providing easily accessible substrate for decomposer community.

Nesterenkonia pannonica sp. nov., a novel alkaliphilic and moderately halophilic actinobacterium

An alkaliphilic and moderately halophilic bacterial strain characterized by optimal growth at pH 9.0-10.0 and with 5-7 % (w/v) NaCl, designated BV-35T, was isolated from water of a soda pan located in Kiskunság National Park, Hungary. Cells of the orange-pigmented colony were Gram-stain-positive, non-motile and non-endospore-forming coccoid rods. The isolate was strictly aerobic, catalase-positive and oxidase-negative. Strain BV-35T displayed a peptidoglycan similar to type A4α, l-Lys-l-Glu (A11.54 according to www.peptidoglycan-types.info) but containing additionally 4-aminobutyric acid. Menaquinone-7 (MK-7) was the predominant isoprenoid quinone, and anteiso-C15 : 0 and anteiso-C17 : 0 were its major cellular fatty acids. The DNA G+C content of strain BV-35T was 65.4 mol%. Based on 16S rRNA gene sequence similarities, the novel isolate showed the closest relationship to Nesterenkonia populi GP 10-3T (97.9 %). The DNA-DNA relatedness between BV-35T and N. populi was 46.7 %. The distinguishing phenotypic and genetic results of this polyphasic study revealed that strain BV-35T represents a novel member of the genus Nesterenkonia, for which the name Nesterenkonia pannonica sp. nov. is proposed. The type strain is BV-35T (=DSM 29786T=NCAIM B 02606T).

Gellertiella hungarica gen. nov., sp. nov., a novel bacterium of the family Rhizobiaceae isolated from a spa in Budapest

A novel alphaproteobacterium, strain RAM11T, belonging to the family Rhizobiaceae was isolated from the pool water of a thermal bath in Budapest, Hungary. Based on the 16S rRNA gene sequence strain RAM11T shows the highest sequence similarity values to Ensifer adhaerens Casida A (97.44 %), to Ensifer (syn. Sinorhizobium) americanus CFNEI 156T (96.87 %) and to Rhizobium azooxidifex Po 20/26T (96.76 %). The new bacterium is strictly aerobic, its optimum growth occurs at 20-37 °C, between pH 7 and 9 and without NaCl. It is motile due to a single polar flagellum, capable of budding and forms rosettes in liquid culture. The major isoprenoid quinone of strain RAM11T is Q-10, the major cellular fatty acids are C18 : 1ω7c and 11-MeC18 : 1ω7c. The polar lipid profile contains phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylcholine, an unidentified aminolipid and an unidentified phospholipid. The G+C content of DNA of the type strain is 62.9 mol%. Strain RAM11T (=DSM 29853T=NCAIM B.02618T) is proposed as type strain of a new genus and species with the proposed name Gellertiella hungarica gen. nov., sp. nov.