IMPACT OF ORGANIC AND MINERAL FERTILISERS ON POTATO AND TOMATO YIELD IN BULGARIA

In recent years, organic farming, or the production of organic food of plant or animal origin, has been increasingly discussed in our country. A few growers decided to reorient production on their farms. The aim of the study was to evaluate the yields of potatoes and tomatoes under organic, mineral and organic-mineral fertilisation within the framework of a multi-year vegetable crop rotation.The experiments were carried out on alluvial-meadow soil (Mollicfluvisol) in the village Tsalapitsa (42.191734 N, 24.580252 E), Plovdiv region, like every subsequent year, regardless of the crop experienced, the variants were placed on the same area. The results for the yields and the quality of production showed that there was a lack of a clear, unequivocal answer for the choice and recommendation of organic or mineral fertilisation. The highest yield of potatoes was obtained (3242 kg/da) in the variant with mixed fertilisation. The highest tomato yield was recorded in the variant with mixed fertilisation (4307.4 kg/da), and the lowest in the control (without fertilisation) – 1670.1 kg/da.The fertilisation system as a complex, dynamic mechanism is influenced by several factors. The integrated fertilisation system, i.e., the combination of mineral and organic fertilisation increases the overall efficiency, reflected in the productivity and some of the quality indicators of experimental crops, regardless of the increase in the degree of damage by insect herbivores and fungal pathogens

Impact of Compost Application Rate on Lettuce Plant Growth and Soil Agrochemical Status

One way to reduce environmental stress and safeguard soil fertility and ecological sustainability in crop production is by adding compost to the soil substrate. Supplying the soil with organic matter improves its chemical and physical characteristics, leading to better plant growth and development and increasing yield. The study presents a pot experiment with lettuce on leached cinnamon forest soil (Chromic Luvisol). Research has studied changes in soil NPK before and after vegetation and the effects of the compost on plant production and quality. Increasing the amount of compost in the soil substrate led to an increase in the fresh mass and yield of lettuce and to an increase in the accumulated N, P, and K (%) in the plant tissues (R2=0.91, 0.96 and 0.68, respectively). After the experiment\u27s conclusion, the soils remained very well stocked in P2O5 content. The K2O stock in the soil was medium, i.e. when compost is applied, plant-available potassium increases relative to the initial soil. Total N remained very low; the applied composts provided large amounts of nitrogen for growing lettuce but did not leave the soil in good ecological status

Impact of Compost Application Rate on Lettuce Plant Growth and Soil Agrochemical Status

One way to reduce environmental stress and safeguard soil fertility and ecological sustainability in crop production is by adding compost to the soil substrate. Supplying the soil with organic matter improves its chemical and physical characteristics, leading to better plant growth and development and increasing yield. The study presents a pot experiment with lettuce on leached cinnamon forest soil (Chromic Luvisol). Research has studied changes in soil NPK before and after vegetation and the effects of the compost on plant production and quality. Increasing the amount of compost in the soil substrate led to an increase in the fresh mass and yield of lettuce and to an increase in the accumulated N, P, and K (%) in the plant tissues (R2=0.91, 0.96 and 0.68, respectively). After the experiment\u27s conclusion, the soils remained very well stocked in P2O5 content. The K2O stock in the soil was medium, i.e. when compost is applied, plant-available potassium increases relative to the initial soil. Total N remained very low; the applied composts provided large amounts of nitrogen for growing lettuce but did not leave the soil in good ecological status

Soil nematodes in the rhizosphere of a metal accumulating plant in a pollution gradient from a non-ferrous metal factory in Bulgaria

Nematodes were studied at sites with low, medium and high level of soil metal contamination in the area of a non-ferrous metal plant. Soil total metal concentrations ranged from values below their maximum permissible concentrations (MPC) in soil to 48, 44, 16 and 4 times higher than the MPC for Cd, Pb, Zn and Cu, respectively.  Nematodes were isolated from uncultivated, monoculture stands of the metal accumulating mustard weed (Lepidium draba L., Brassicaceae) in April, May and June 2015. Overall, 55 nematode genera were identified during the investigation: 50 genera at low, 39 at medium, 37 at high levels of soil metal pollution. Several nematode diversity measures and the specific responses of some nematode genera differentiated the three investigated sites. Both nematode richness (S) and diversity (H') of genera correlated negatively with the soil metal concentrations in the following order: Cd>Pb>Zn>Cu. Several genera (Alaimus, Cylindrolaimus, Paramphidelus, Scutylenchus, Steinernema) were common at the least contaminated site and were either rare or not found at the rest of the sites. Some genera (Clarkus, Filenchus) were most abundant at the medium level of contamination. The abundance of eleven genera correlated negatively with the metal concentrations in the samples. Most of the negative correlations (Acrobeles, Coslenchus, Geomonhystera, Plectus) were in the following order: Cd>Zn>Pb>Cu. The abundance of nine genera correlated positively with the metal concentrations and most of their correlations were in the order: Cu>Pb>Zn>Cd. Faunal profile analyses of the free living nematode assemblages revealed higher values of Structure index (SI) at low (75–91%) and medium (77–87%) levels of contamination in comparison with the most polluted site (35–46%). Nematode structure metabolic footprints (SFP) at low and medium levels of contamination were much higher than at the high pollution level. Both SI and SFP at the medium level of metal contamination indicated low bioavailability and low toxicity of Pb (1290 mg kg-1soil), Cd (34 mg kg-1soil), Zn (1779 mg kg-1soil) and Cu (190 mg kg-1soil) for the free-living nematodes, isolated from the rhizosphere of the mustard weed at this site. The rhizosphere of the metal accumulating plant might be protective for these nematodes, providing conditions of reduced bioavailable metals in contaminated soil during the vegetation period of the plants

Correlation between bacterial abundance, soil properties and heavy metal contamination in the area of non-ferrous metal processing plant, Southern Bulgaria

In the present study, the correlation between bacterial abundance and soil physicochemical properties along the heavy metal contamination gradient in the area of non-ferrous metal processing plant was assessed. Our results showed that bacterial abundance (number of heterotrophic bacteria and number of 16S rRNA gene copies) decreased with 45–56% (CFU) and 54–87% (16S rRNA gene) along the Zn, Pb and Cd contamination gradient. The total bacterial abundance (16S rRNA gene) increased exponentially in contrast to the abundance of heterotrophic bacteria. The reduction of bacterial abundance in heavily contaminated soil indicated that the soil properties (soil pH, total organic carbon, inorganic ions, soil texture) could modify the effects of heavy metals and the response of microorganisms to that stress in long-term contaminated soils

L3 rootlet recurrent melanocytic schwannoma – case report and literature review

First described by Miller in 1932, melanocytic schwannoma (MS) (melanotic schwannoma, pigmented schwannoma) is a rare variation of peripheral nerve sheet tumours with ectodermal origin occurring predominantly in somatic, but also in the autonomic peripheral system with around two hundred cases in the literature. Predominantly benign tumours, MS are still imaging and pathological challenge and can be easily misdiagnosed with more aggressive peripheral nerve tumours.We report a case of melanocytic schwannoma on L3 sensory rootlet with systematic literature review of nearly 200 cases presented in intracranial, paraspinal region, thoracic, abdominal or pelvic cavities and skin. Two-thirds of cases are part of Carney complex.We present a case of a 61-year-old male with a 3-month history of low back pain, progressive numbness and stiffness in the right thigh, shin and knee, tibial and peroneal paresis causing gait disturbance and neurological claudication. MRI findings present “sand clock” type intradural extramedullary tumour formation with extension to the L3 rootlet through right L3-L4 foramen, hypointense on T2 and hyperintense on T1. Pathological diagnosis of sporadic type melanocytic schwannoma was made via immunohistological and ultrastructural analysis. Thirteen months after total resection there was clinical and MRI evidence of recurrence of the tumour. Total resection and radiosurgery was performed with a recurrence free period of 14 months.A gold standard for melanocytic schwannoma treatment is gross total surgical resection. Despite being considered benign tumours, MS have a local or metastatic recurrence of around 13%. MRI imaging in most of the cases is insufficient and only exhaustive pathological and immunohistological examination is the key to diagnosis. Need of postoperative radiation therapy is still controversial. For the first time, a criterion for postoperative adjuvant therapy was established