Bulgarian Journal of Soil Science

9 - 17

Authors: Angelos Tsikas, Paraskevi Karanikola, Michail Orfanoudakis

Red wood ants build their nests as above-ground mounds by collecting organic materials from the forest floor. The effects of ant nest to the soil carbon and nitrogen along with the soil pH, were measured. There was an increase in pH with distance from the nests while there was a decrease in C and N concentration with the distance from the nest increases. The carbon content at the mound and nests center was differ, with carbon percentage more than double at the nests mound than in the center of the nest. In contrast the nitrogen percentage was higher at the nest center but with no significant difference. The pH was increased at the nests center while the soil was more acidic at greater ratio. Red wood ants’ mounds do not significantly alter the C and N concentrations in the forest ecosystem, but they increase spatial heterogeneity of the forest floor by storing organic matter and nutrients

33 - 41

Authors: Vania Kachova

Three tree species are studied: coniferous plantation of black pine / Pinus nigra Arn./ and deciduous: birch / Betulla alba L./ and ash / Fraxinus pennsylvanica Marsh/, on the territory of Baikusheva neighborhood in Pernik, near the mine "M. Tolbuhin ”, after performed 45 years ago reclamation. The accumulation of organic matter in the mining spoil and humus composition are analysed. High amounts of org.C are found under all three types of woody plants (tC% = 3.65 ÷ 9.50 in top layers 0-20cm). This is also due to the presence of large amounts of coal carbon particles in the substrate. Humus accumulation is more pronounced under deciduous species and especially under the newly studied species of Fraxinus pennsylvanica Marsh (Humus% = 11.42 ÷ 16.38). But here the process of humification takes place to a lesser extent (~ 10 ÷ 16%). On the contrary, under the coniferous plantation of Pinus nigra Arn. is accumulated less org. C (tC% = 1.34 ÷ 3.65), but the humification processes are going in the highest degree (~ 18 ÷ 32%). However, this is also associated with the formation of the largest amounts of the more mobile parts of the organic matter: fulvic acids (Cf ~ 11% from tC). Among deciduous species under Fraxinus pennsylvanica Marsh, fulvic acids move in the range of the lowest values (4-5% of tC).

59 - 64

Authors: Nelly Gadjalska; Rossitza Petrova; Snejan Bozhkov; Viktoriya Kancheva

The study and analyses of erosion have shown that the main factors determining erosion processes under equal soil and climatic conditions are the intensity and structure of artificial rain and the ground slope. The main factor, artificial rain intensity, depends mainly on the soil infiltration rate. In sprinkle irrigation, the soil infiltration is preceded by interaction between the soil and the rainfall drops. Failure to observe this interaction has often caused irrigation erosion problems due to the impact drops on the soil. It has been proved that the bigger are rainfall drops and their intensity, the bigger are the damages to soil structure. The most important factors on which depends the degree of erosion are erosion resistance and slope of the soil surface. Bulgarian soils are classified in a seven-degree scale, based on Qcritical - erosion-safety discharge. This paper deals with the feasibility to choose irrigation equipment suitable for agricultural crops and having appropriate characteristics of the irrigation sprinklers in dependence of soil resistance and land slope. Both analytical and experimental approaches have been used in solving the problem. Nomograms, aiming at determining the required parameters of irrigation equipment in order to prevent soil erosion, are presented. They are created on the base of experimental approaches for sprinkler equipment characteristics. The intensity and structure of the artificial rain in relation to the nozzle and the working pressure head of the sprinklers, on one side, and the soil erosion stability in relation to the difference in the land slope and rain intensity, on the other, have been studied. The analysis of nomograms allows following conclusions about the application of three classes irrigation equipment in the erosive-safe area of land with high slope:  High pressure sprinklers set with the appropriate blendes are to be applied to terrains of soils with medium to high degree of erosion resistance regardless of the slope. In the set with nozzles the field of application is the same as by 2-3 degree of erosion resistance, but the limit of the slope is 7 %. The erosion-safe area of medium pressure sprinklers application is wider as they can be used in soils of low erosion resistance (1-2 and 2) by limiting the slope to 3-5 %. For soils with moderate resistance (2-3) the slope limit is 3-7 %, and for soils with high resistance (above 3), the sprinklers are applicable on steep slopes.

78 - 95

Authors: S. U. Oghoje; J. E. Ukpebor; E. E. Ukpebor**

This study was designed to investigate the efficiency of using locally produced chicken manure digestates (CMD) as nutrient supplement for the removal of diesel range organics (DRO) from petroleum products polluted soils by land farming process. Soils samples spiked with hydrocarbon mixture (HCM), 5 % and 10 %) were treated with three rates of the CMD (0, 10 or 20 %) for a 336 days period. Soil samples were collected at day 1, 14, 28, 56, 84, 168 and 336 time interval and the samples were extracted using standard methods. The concentrations of DRO at various sampling periods were determined using a gas chromatography equipped with a flame ionization detector (GC – FID). The percentage removal of the DRO and the significance differences of the different treatments were evaluated using statistical tools. Results obtained showed that the use of 10 and 20 % CMD led to the removal of about 50 and 58 % of the DRO respectively from the 5 % HCM polluted soils and about 41 and 35 % respectively for the 10 % HCM polluted samples at day 56 and by day 84, the percentage removal of the DRO increased to about 60, 76 and about 46, 52 respectively using the two rates of treatments; in the 5 and 10 % HCM polluted samples respectively. These values were reasonable considering the level and toxicity of HCM pollution. Significant differences (P < 0.05) between the treatments and the various control samples were observed in the removal of the DRO from day 56 to 168. And at the end of 336 days, the 10 and 20 % CMD treatments enhanced the removal of about 81, 96 and 56, 67 % from the 5 and 10 % HCM polluted soils respectively but no significant differences were observed between the control and the treatment samples particularly in the 10 % HCM polluted soils at this date. This study has revealed that: the use of chicken manure digestates could facilitate the removal of reasonable proportion of DRO in a short remediation time of 56 days from high and toxic petroleum polluted soils. The efficacy of the CMD was observed to decrease as the remediation period increased. It was also observed that 10 % CMD treatment was optimal for the removal of DRO at a short remediation period and repeated application of the nutrient supplement would be required if remediation period exceeded 56 days. Furthermore, it could be concluded that CMD is an effective inoculant and nutrient supplement during bioremediation of the DRO from toxic petroleum polluted soils. These findings are contributions to the existing data on organic stimulation for removal of diesel and by extension petroleum hydrocarbons from soils.