Bulgarian Journal of Soil Science

104-111

Authors: Biser Hristov

The paper deals with physico-chemical properties of Regosols in Bulgaria. Ten soil profiles are studied in North and South part of the country. These soils are spread mainly on unconsolidated rocks (regolith), slopes and eroded terrains in semi-arid areas. Sediments in these areas are manly alkaline with good sorption capacity. Regosols are moderately acidic to slightly alkaline soils. Exchangeable Ca2+ is almost equal to the soil cation exchange capacity. The amount of exchangeable Ca2+ is between 8 to 26 mequ/100g. Regosols have high base saturation from 75 to 100 %

122-139

Authors: Venera Tsolova, Ivona Nikova, Biser Hristov, Kalin Ruskov, Alexandar Zdravkov

The content of Si, Al, Fe, Ti, Mn, Mg, Ca, Na, K, S, P, C, Cu, Pb and Zn were determined in order to reveal geochemical patterns of soils in the Bobov dol valley, Bulgaria. Since the Bobov dol Thermal-electric Power Plant (TPP) is situated in the valley this paper pays attention to the geospatial distribution of Cu, Pb, and Zn due to their diverse vital significance. Elements assemblages and geospatial distribution pathways are also discussed in the light of the past 40 years of operation of the Thermal Power Plant. According to the results obtained the average content of Cu (27.04 mg kg-1 ), Pb (21.96 mg kg-1 ) and Zn (57.95 mg kg-1 ) is higher than the average content of elements in local soil parent rocks: Cu (20.03 mg kg-1 ), Pb (6.07 mg kg-1 ) and Zn (46.60 mg kg-1 ). Compared to the precautionary threshold concentrations adopted for assessing the soil contamination in Bulgaria the elements contents are lower including their maximum values. However, the geoaccumulation indexes reveal an initial stage of contamination of soils with Pb. Lead tends to follow a separate mode of geospatial distribution which is controlled by both the geogenic factors and the aerosol emissions of TPP. Copper accumulation is more strongly affected by technogenic depositions and dominated in urban and technogenic zones under the form of oval spots. Konyavska Mountain is the domain of Zn revealing an altitudinal gradient of distribution. Its accumulation proceeds slowly in topsoil, but still, Zn is the most abundant element in studied soils from the Bobov dol valley. The petrogenetic pattern of geochemical suits still predominated in studied soils wherein the iron has the greatest affinity for studied elements. Soil medium reaction (pH) and organic carbon do not control the processes of distribution and accumulation of Cu, Pb and Zn. The lack of statistical correlation with organic carbon resulted from the siliciclastic nature of soil parent rocks and also reveals the prevailing geogenic origin of studied elements.

147-153

Authors: Zornitsa Mitreva, Veneta Krasteva,Veselin Pankov

Method is developed for the field rating of main soil characteristics that define the suitability for growing emmer and einkorn wheat. Soil texture of the fallow land, depth of the humus horizon, depth of the soil profile, texture differentiation of the soil profile, soil reaction, humus content and groundwater level have been evaluated. The method is harmonized with the officially accepted in Bulgaria parametric methods of the system of field ratings and the categorization of the agricultural lands. The end result is an evaluation of the soil conditions and a soil rating.

170-186

Authors: Zornitsa Popova

Water distribution could be quite non-uniform along the furrow length under surface irrigation. This “down field” disuniformity is usually combined with “inter-row” nonuniformity of irrigation water and nitrogen fertilizer distribution. Spatial variation of application depth and nitrogen (N) fertilization rate in the furrow plot produces yield, drainage and nitrogen losses. In addition to that, due to year-to-year variability of climate, regional irrigation depths range significantly (from 0 to 360 mm/season in the studied field). The objective of this paper is to study the impact of global nonuniformity of irrigation water and N fertilizer distribution within a furrow plot on yield, water and nitrogen losses when climate variability is taken into account. Six maize vegetation seasons with contrastive probability of exceedence of irrigation depth PI are considered. Irrigation water is distributed according to six scenarios for “downfield” and “inter-row” non-uniformity by using the validated FURMOD model (Popova, 1990; 1992; Popova and Kuncheva, 1996). Nitrogen fertilization broadcast corresponds to two scenarios of lateral non-uniformity. The validated CERES-maize model (Jones and Kiniry, 1986;Gabrielle et al, 1995; Popova et al.1999; 2001- b; Popova and Kercheva, 2005) is applied with the different “climate-irrigation nonuniformity-fertilization nonuniformity” scenarios to simulate water&nitrogen cycle and crop growth on a daily basis in 30 representative points along “median”, “high intake” and ”low intake” furrows of the set. It is established that yield, water and nitrogen losses vary over uniformity scenarios and studied 30-year period. Combination of non-uniform irrigation/N-fertilization with the high irrigation demand seasons (having probability of exceedance PI<11%) causes losses of yield by 2 to 14.5 % of potential maize productivity, irrigation water (up to 40-45% of applied depth) and nitrogen (up to 10-12% of N-rate). Model runs show that poor distribution uniformity of irrigation water and N fertilizer should be maintained especially in the case of high irrigation requirements. Different strategies aiming at reduction of heterogeneity sources of “inter-row” and “down-field” uniformity of water distribution and fertilizer broadcast are recommended.

5-19

Authors: Metodi Teoharov

In this article is presented stage development of Bulgarian Soil Science – from 1911 year until our days. Fonder of soil science of Bulgaria is Nikola Pushkarov. Nearly, with his life is finished the first stage (1947). Pushkarov developed the first cientific program of soils with basic tasks. Second stage of development (1947-1969) is stage of rapid development of soil science associated with the reorganization of agriculture in Bulgaria. Third stage (1969-1989) is stage of modernization of equipment, strengthening of international relations and recognition, advanced science servicing of agriculture. Fourth stage is stage of reforms, changes and integration into European research area.

26-32

Authors: Biser Hristov, Ekaterina Filcheva, Plamen Ivanov

This paper deals with the contents and composition of organic matter in soils with stagnic properties. Study on the content and composition of soil organic matter, shows that these soils have low content of organic carbon. Soil formation proceeds under influence of acid plant residues from forest and seasonal waterlogging caused by the surface stagnating waters. The total carbon content decreases sharply in subsurface horizons. The amount of fulvic acids (Cf) prevail over humic acids (Ch) and type of humus is humic-fulvic and fulvic.

51-63

Authors: Yovana Todorova, Ivaylo Yotinov, Stilyana Lincheva, Yana Topalova

Heavy metals are widespread pollutants with significant environment risk due to high toxicity and clear tendency for accumulation in different matrices – soils, sediments, biota. The main research objective of this work is to assess the impact of heavy metal pollution on key structural and functional parameters of microbial communities in sediments of river-dam sequence of small hydropower cascade Middle Iskar, Bulgaria. The content of heavy metals (As, Cd, Cu, Hg, Pb, Zn) was measured during the low water summer periods of 2012, 2013 and 2014. The evaluation of site quality and heavy metal pollution was done by use of one integrated index - Pollution Load Index and it was compared to total count of sediment microbiota and count of coliform bacteria, also with total dehydrogenase activity and index of phosphatase activity. The assessment of heavy metal pollution in river-dam sequence of cascade indicates the higher metal concentrations and high Pollution Load Index in dam sediments. At low level of pollution in river sites, the both structural and functional microbial parameters react to local variations of heavy metal concentrations and high negative correlation (r=-0.8÷-0.9) exists between variables. But in dam sites, the microbial community is more resistant to pollution and structural parameters react conservatively with long reaction time. The enzyme activities are more adaptive and sensitive indicators for different level of environmental impact in this case. The complex phosphatase and dehydrogenase activities have a high potential to be used as reliable parameters for precise assessment of hazardous sediment pollution in complicated ecological situations with cumulative impacts.

78-91

Authors: Mariyana Lyubenova

The paper deals with meta-analysis of 259 dendrochronological series of mountain trees – Bosnian pine, Norway spruce and beech from 14 locations in Bulgaria for eustress investigation. The chronologies were analyzed by the original SPPAM 2.0 application. The tree ring width sequences were approximated with polynomials with determination coefficients, R*R ≥ 0.45. The growth index (It – the ratio between measured and approximated value of tree ring width) was computed. Years with It less than the threshold values were considered as eustress ones. The four grade scales for assessment of frequency, duration and depth of eustress was proposed. For the studied tree species and locations, the obtained eustress periods are as follows, respectively for the Bosnian pine, Norway spruce and beech: 42 (K=9.1), 30 (K=3.4) and 37 (K=3) on average. The obtained eustress characteristics are respectively: Average Depth, Aav = 0.16, 0.26 and 0.28; Average Duration, Dav = 2, 2.5 and 2.3 years; and Average Frequency, Fav = 10, 33 and 34 years over 100 years. The risk for The stands of two studied locations of spruce and three locations of beech were established to be in some risk. They require further monitoring. The predominance of cold-dry and hot-wet years in total number of adverse climatic years (with eustress) for the Bosnian pine, as well as hot-dry and cold-wet years for spruce and beech stands was established. The influence of climatic types of years on the eustress appearance for tree years periods have also been investigated. Proposed holistic approach for meta-analyses of series (eustress identification in radial growth of stems) is convenient for the fast monitoring of forest communities state and for recognizing the stands under risk. The capability of approach allows expression of reactive functional types of trees (PFTs) as groups of trees with the similar behavior to the influence of climatic types of years, and with similar characteristics of eustress periods. These PFTs can support the development of different local, regional and global models. The originality of approach applied includes: meta-analysis, new software, characteristics, indixes and coefficients.