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.