Soil microorganisms and their activities are essential for maintaining soil health and fertility. Microorganisms can be negatively affected by application of herbicides. Although effects of herbicides on microorganisms are widely studied, there is a lack of information for chloroacetamide herbicide dimethachlor. Thus, dimethachlor and well known linuron were applied to silty-loam luvisol and their effects on microorganisms were evaluated during112 days long laboratory assay. Dimethachlor and linuron were applied in doses 1.0 kg ha−1 and 0.8 kg ha−1 corresponding to 3.33 mg kg−1 and 2.66 mg kg−1 respectively. Also 100-fold doses were used for magnification of impacts. Linuron in 100-fold dose caused minor increase of respiration, temporal increase of soil microbial biomass, decrease of soil dehydrogenase activity, and altered microbial community. Dimethachlor in 100-fold dose significantly increased respiration; microbial biomass and decreased soil enzymatic activities. Microbial composition changed significantly, Proteobacteria abundance, particularly Pseudomonas and Achromobacter genera increased from 7 to 28th day. In-silico prediction of microbial gene expression by PICRUSt2 software revealed increased expression of genes related to xenobiotic degradation pathways. Evaluated characteristics of microbial community and activity were not affected by herbicides in recommended doses and the responsible use of both herbicides will not harm soil microbial community.

MATERIAL AND METHODS Sample collection Actinomycetes were isolated from soil (Haplic Fluvisol) located near Nitra (Slovakia-latitude 48° 31' 35.97'' N, longitude 18° 11' 46.82'' E), one compost, one vermicompost and soil amended with compost or vermicompost. Vermicompost and compost were applied to the soil at a total dose of 20 Mg.ha −1. The applied compost was prepared by mixing straw (11% by dry weightdw), hay (3% by dw), silage (32% by dw), sheep manure (9% by dw), cow manure (34% by dw) and soil from the subsoil (11% by dw). Vermicompost was prepared by mixing the compost (41% by dw), cow manure (20% by dw), peat and forest litter (21% by dw), soil (10% by dw), a compound of grass, straw and hay (6% by dw) and the fill vermin (2% by dw). The fill vermin (older vermicompost) containing earthworms and cocoons of earthworms (70 earthworms dm −3) was added to the compost. The basic chemical and microbial characteristics of soil samples and both composts (Table 1) were determined according to the defined values: oxidizable carbon (Cox) by the Tiurin method, total nitrogen (Nt) by the Kjeldahl distillation method, pH (H2O) and microbial biomass carbon (Cmic), which was determined by the fumigation-extraction method of Vance et al. (1987). Plant diseases caused by pathogenic fungi are a severe problem for agriculture, and some organic fertilizers have shown a suppressive capacity due to the antagonistic action of microbial communities inhabiting those substrates. The purpose of this work was to isolate and identify actinomycetes from soil, compost and vermicompost able to antagonize phytopathogens. In total, out of 352 actinomycetes successfully recovered on Pochon medium and of which were selected representative 22 mycelium forming isolates, which were subjected to morphological and genotypic characterization. Genetic characterization based on 16S rDNA fragment sequencing revealed that, all the actinomycete isolates belong to the genus Streptomyces. The antifungal activity of isolates was tested against eight phytopathogenic fungi, and they were most activated against Rhizoctonia solani, Alternaria tenuissima, Aspergillus niger and Penicillium expansum. Isolates 51VK13 (Streptomyces sampsonii) and 12VK13 (Streptomyces flavovariabilis) isolated from soil amended with vermicompost showed the greatest antagonistic activity. Their bioactive potential was also confirmed by presence of genes for nonribosomal peptide synthetase (NRPS) and polyketide synthase types I and II (PKS-I and PKS-II). It can, therefore, be concluded that soil amended with organic fertilizers such as compost, and in particular vermicompost, provides a lower incidence of phytopathogens, especially fungi. Isolated actinomycetes have also shown high potential for the production of bioactive compounds useful in the control of plant diseases. ARTICLE INFO

There is a growing interest in the issue of inoculation of rhizobacteria into the agricultural soil because this group of bacteria can  increase  productivity and quality of  agriculturally important crop and contributes to the stability of agroecosystems. The aim of our work was to isolate and characterize of plant growth promoting traits (production of IAA, siderophores, phosphate solubilisation, antifungal activity) of rhizobacteria belonging to a group of plant growth promoting rhizobacteria (PGPR), and isolated from rhizosphere of maize (Zea mays L.) in luvisols.  Quantitative representation of rhizobacteria of maize was 7.4 . 106 CFU.g-1 dry soil. A total of eleven species of maize rhizosphere where isolated and confirmed as PGPR in vitro. The  all  isolates  showed positive indole-3-acetic acid (IAA) production ranging between 1.39 and 15.74 µg.ml-1. Seven  strains (63.6  %) has been shown with low and 1 strain with intermediate solubilisation index of phosphates and the  positive production of siderophores showed  7 isolates (63, 6 %). Except for the isolate KmiJP17B089, all others inhibited the growth of Sclerotinia sclerotiorum and Rhizoctonia solani by more than 50 %. In the case of Fusarium graminearum, on the other hand, we observed a very low inhibitory activity. The most active  in observed traits were  three isolates identified by the 16S rRNA gene sequencing and NCBI database using the BLAST  resource as Bacillus altitudinis strain KmiJP17B089, Bacillus aryabhattai strain KmiJP17B090  and  Bacillus megaterium strain KmiJP17B091. These results suggest the possibility to tested in vivo these Bacillus species as potential biological fertilizer  to increase maize production.

Bacteria with positive properties on plant vitality are also called PGPB (Plant Growth Promoting Bacteria). Their presence can be observed not only in the root area but also in the above-ground parts of plants like endophytic bacteria. The aim of our study was to characterize promoting features of bacteria from Bacillus genus and compare them with Pseudomonas simiae WCS417 (plant growth promoting strain). The work was carried out in locality Kolíňany near Nitra (40°26´46´´N, 79°58´56´´W) and root samples were taken from 6 randomly selected plants of maize (Zea mays L.) in vegetative plant growth stage BBCH 14-15. Bacteria isolated from plant roots were identified and tested to biochemical parameters. From the biochemical features, we observed the detection of siderophores, determination of indole-3-acetic acid (IAA), monitoring the ability to dissolve phosphates and antifungal activity. Bacterial suspensions were applied to maize seeds and tested in vivo controlled conditions. Tested isolates were identified as Bacillus flexus, Bacillus megaterium and Bacillus subtilis. All 3 strains achieved the middle – class of phosphate solubilization index (2.00 ≤ SI ˂ 4.00), produced phytohormone IAA and showed positive production of siderophores and inhibited growth of Fusarium culmorum to more than 50%. All differences between tested strains and control strain P. simiae WCS417 were also statistically confirmed. All strains showed positive results in monitoring plant growth promoting properties. The effect of three Bacillus strains on maize seeds in vivo conditions showed significant differences in root length (P<0.0001) and weight of the young plant (P<0.001) compared to control.

Inoculation of Streptomyces to improve oilseed rape (Brassica napus L.) yields and minimise the use of chemical fertilisers is a promising sustainable strategy. In this study, we isolated 72 actinobacterial strains from rhizosphere of oilseed rape and maize and from bulk soil for screening and characterising their antimicrobial activity. Nine promising strains, identified as Streptomyces sp. by morphology, physiological characteristics, and 16S rRNA gene sequencing, were selected for their plant growth-promoting traits and in planta experiments. The actinobacterial strains were positive for IAA production, siderophore production, and HCN production. In planta experiments were conducted by soaking the oilseed rape seeds in the actinobacterial suspension, followed by plant growth under controlled conditions in a cultivate chamber (22–28 °C, 8 h dark/16 h light, constant humidity 80%). We recorded root and shoot length (cm) and seedling fresh weight (g). For most of the abovementioned parameters, a significant enhancement was observed with strain KmiRC20A118 treatment. The length of the root increased by 53.14%, the shoot length increased by 65.6%, and the weight of the fresh plant by 60% compared to the control. The integrated application of PGPS (Plant Growth Promoting Streptomyces) from the rhizosphere of oilseed rape is a promising strategy to improve the growth of oilseed rape.