The study presents results of a three-year experiment of variability of different Dutch potato varieties in Serbia: Adora and Cleopatra (early), Innovator and Frisia (mediumearly) and Desiree and Kondor (medium-late). The research was conducted during 2008, 2009 and 2010, in three different soil and climatic locations: Zemun (100 m a.s.l.), Srbobran (86 m a.s.l.) and Guča (370 m a.s.l.). The four-repplicate field trials were set up using standard methodology according to the random block desing. The analysis of variance suggest that number of tubers per plant, number of market tubers per plant and total tuber yield were significantly fluctuating depending on genotype (G), year (Y) and the location (L). In addition to individual influences of different factors, their interactions were also pronounced (G x Y, G x L, Y x L, G x Y x L). In the three-year period average, the highest total yield was recorded in Zemun (35.80 t ha‫,)¹-‬ followed by Guča (29.32 t ha‫,)¹-‬ while the lowest average yield recorded was in Srbobran (27.38 t ha‫.)¹-‬ The highest average yield of tubers in the three-year period was recorded in the Cleopatra variety, followed by Adora variety, while the lowest average yield was recorded in the variety Frisia. Obtained results show that the highest yields over observed locations were recorded in early varieties that formed medium number of tubers per plant (Cleopatra and Adora) and medium late varieties (Desiree and Kondor) that expressed good resistance to high air temperatures and stress caused by drought.

The assessment of the weed infestation effect on biomass yield of Miscanthus × giganteus in the first year of its commercial yield was conducted on two types of soil with different productive ability – Luvic Chernozem and Calcic Gleysol. The formed mass of weeds was higher on Luvic Chernozem and the infestation had grown according to the stages of Miscanthus growth. The biomass of weeds depended on the planting density of Miscanthus as well as on the weather conditions during the studied years. Weed infestation of crops very significantly influenced the formation of aboveground biomass of Miscanthus, so that the yields in the first year of commercial harvesting in the control where the weeds were removed manually were significantly higher compared to the crops in which weeds were not removed. The obtained results showed that weeds significantly affect the initial growth and development of Miscanthus plants that are, in general, slow, especially in the year of the crop establishment. The study evaluates the impact of a manual method of suppression and weed infestation of crops on the commercial yield of Miscanthus.

The aim of this investigation was to estimate the effects of crop density on the plant height (PH), ear height (EH), leaf number per plant (LN), ear length (EL), number of rows per ear (NRE), number of grain per row (NGR), number of grain per ear (NGE), grain weight per ear (GWE), cob weight (CW), 1000-grain weight (1000-GW), ear diameter (ED) and grain yield (GY) in staygreen maize hybrid Dijamant 6 (FAO maturity group 600). Three crop densities (51020 plants ha-1, 59524 plants ha-1 and 71429 plants ha-1) were tested. The field experiment was carried out during 2006 and 2007 at Srem region (Putinci: latitude 44? 59? 19" N; longitude 19? 58? 11" E). Plots were organized as completely randomized block system design in four replications. PH (284.3 cm), EH (119.9 cm), LN (13.9), EL (20.8 cm), GWE (232.5 g), CW (56.4 g), 1000-GW (378.4 g) and GY (13.56 t ha-1) were significantly higher in 2006 (favorable climatic conditions) than in 2007 (258.5 cm, 112.8 cm, 13.2, 17.9 cm, 192.9 g, 46.9 g, 232.7 g and 11.50 t ha-1, respectively). Increasing crop density significantly increased the PH, EH and GY, and significantly decreases the EL, NGR, NGE, GWE, CW and 100-GW. The crop density of 71429 plants ha-1 is the optimal for growing this hybrid in Srem region. On that crop density hybrid more efficiently used available resources and achieved the highest grain yield. [Projekat Ministarstva nauke Republike Srbije, br. TR 31053]

To select isolates suitable for use in biological control of pathogenic fungi and as plant growth promoting (PGP) agents, Pseudomonas spp., indigenous to the rhizosphere of wild alfalfa and clover plants growing on the old magmatic hill Vagan (Serbia), were isolated. Isolates were selected on the basis of intrinsic antibiotic resistance (IAR) and PGP traits: phosphate solubilization, production of siderophores, hydrogen cyanide (HCN), acyl homoserine lactones (AHLs), indole acetic acid (IAA) and enzymatic activities. The results of the genotyping by repetitive sequence-based polymerase chain reaction, using ERIC and (GTG) 5 primers, and phenotyping by IAR clustered the isolates in five groups, represented by two isolates from alfalfa (Q1 and Q16) and three from white clover (B25, B28 and B29). Isolates Q16 and B25 showed production of HCN, IAA and AHLs. Good phosphate solubilization and production of siderophores were observed on Q1 and Q16. The Q16 isolate exhibited high enzymatic activity. The most promising PGP isolates, Q16 and B25, showed the best antifungal activity against Trichoderma viride, and good antifungal effect against Aspergillus fumigatus and Aspergillus niger, while Penicillium verrucosum was the most resistant fungus. Pseudomonas sp. B25 exhibited higher antifungal potential than Q16. The selected isolates could be further investigated as biological control agents and tested in field conditions to confirm their PGP efficacy.

This study evaluated the effects of the application of microbial inoculants (N-fixing Klebsiella planticola and Enterobacter spp.), two rates of composite mineral fertilizers, and their combination on microbial biomass carbon (MBC), dehydrogenase (DHA), and proteinase activity (PTA) in Lessivated Cambisol and yield-related properties of maize and wheat grains in a two-year trial. Unfertilized soil was used as a control variant. MBC was measured using the chloroform fumigation-extraction method, DHA was determined spectrophotometrically by measuring the intensity of the formed red-colored triphenyl formazan, while PTA was determined using a titration method by measuring the degree of gelatine decomposition. In grain samples, P was determined spectrophotometrically, K—by flame emission photometry, N—on an elemental carbon/nitrogen/sulfur (CNS) analyzer, and crude proteins—by calculation of N content. Measuring both crops’ yield was carried out at the end of the vegetation. The results indicated that mineral fertilizers are not, in general, negative for soil microbiota when used in the context of sustainable agriculture without monoculture. There is a significant increase in the values of soil MBC, DHA, and PTA in the variants with combined application of bacterial inoculants and lower rates of mineral fertilizers. The highest values of these parameters were determined in the period with a better distribution of precipitation during the vegetation period of the year. The mentioned combination also resulted in a higher grain yield of maize and wheat comparing to the application of lower rates of the NPK nutrients solely. The combined application of high rates of mineral fertilizers and bacterial inoculants resulted in significantly increased N, P, K, and protein content in the grains of crops, and the same applied to yield. Concluding, studied bacterial inoculants can be used to specify the replacement of nitrogen fertilizers, stimulating the microbial biomass and enzyme activity in the soil, helping to ensure that the supply of nutrients contributing to an optimized yield of crops is maintained.