Three alluvial soil samples with different textures were artificially polluted with chloride solutions of Cd, Pb, Co and chromate solution for Cr. The aqua-regia extracted concentration ranges in the artificially polluted soils were 1134 - 1489 mg·kg^-1 for Pb, 854 - 938 mg·kg^-1 for Cr, 166 - 346 mg·kg^-1 for Co and 44 - 54 mg·kg^-1 for Cd. The aqua-regia extracted metals were the highest in the spiked clay soil due to its high adsorption capacity. Rock phosphate (PR), lime-stone (LS) and Portland-cement (Cem) were mixed with the spiked soils at 1% and 2% rates (w/w) and incubated at 30 C for 2, 7, 14, 30, 60, 150 and 360 days. The extracted DTPA metals significantly decreased with different magnitudes with increasing the incubation period accompanied by increases in both pH and EC. The data showed that cement (Cem) treatment dropped the DTPA-Pb from @ 1000 to @ 400 mg·kg^-1 in all the studied soils (60% decrease) in the first 2 months while it gradually decreased from 400 to 200 mg·kg^-1 (20% decrease) in the next 10 months. Limestone (LS) and rock phosphate (PR) materials were relatively less effective in lowering DTPA-Pb after 12 months of incubation. The data showed also that cement (Cem) treatment was the most effective one in lowering DTPA-Cd by @ 60% as compared to the un-amended soils after 12 months of soil incubation. Extractable DTPA-Co and Cr showed consistent decreases with time down to nearly 50% of un-amended soils due to the effect of the added amendments after 12 months of incubation with superior reductions for the cement treatment in all the investigated soils. The statistical analysis confirmed that in all the studied metals and treatment, cement treatment (Cem) was significantly the most effective in lowering the DTPA extracted metals as indicated from LSD test. It was found that up to 73% and 57% of the applied Pb and Cd, respectively, were fixed by only 1% cement. However, the present study showed that from the practical and economic points of view, that 1% Cement was the best treatment to immobilize Pb and Cd from all the artificially polluted soils.

Potential N2‐fixation was investigated in a number of samples representing soils and water courses under the effect of some industrial wastes in Helwan area of Egypt. Microbiological analysis of soil and water samples showed the general enrichment of fungi, actinomycetes and bacteria including N2‐fixers. Among asymbiotic N2‐fixers, azospirilla compared to azotobacters and clostridia were found to be present with rather higher densities in all samples tested. Generally, the microbial numbers increased by increasing the distance from the Industrial Complex at Helwan, which could be attributed to the high levels of salinity and total heavy metals near the factories. The results indicated that the industrial wastes near the factories exerted inhibitory effects on the acetylenereducing activity in soils, which seriously reduces their biological fertility. Such effects were decreased by getting away from the factories. Significantly negative correlations were recorded between densities of N2‐fixers or N2‐ase activity and salinity and total heavy metals content in both soil and water samples.

Spatial information about soils generally results from local observations which are destructive and time consuming. Geophysical techniques could help soil mapping since they are non-destructive and fast. Electrical resistivity is interesting for soil studies due to a wide range of values and as it depends on soil characteristics. This work aims to study soil spatial variability using electrical resistivity. GPS defined grid points of 40X40 m were installed in the experimental western farm (EWF) in the Faculty of Agriculture of Cairo University in Giza. Electrical resistivity was measured at 40 points using 4-electrodes Wenner array in a line perpendicular to the path direction. Soil resistivity data from 2depths profiling mode was considered to produce two apparent resistivity maps and geostatistically tested. Soil resistivity taxa were sampled and analyzed for soil moisture, EC and bulk density. Krigged soil resistivity maps were produced for depths (i.e. 30 and 60 cm). Kriging and Semivariogram interpretation was conducted, and the spatial dependency of top and subsoil resistivity were moderate (48.4% and 68.6% respectively). Highly significant negative correlations were recorded in the topsoil between apparent or true resistivity and soil moisture, EC or bulk density. The obtained models were used to produce conjugated moisture and EC maps and geostatistically investigated. The spatial dependency of the top and subsoil moisture or salinity were moderate. Soil moisture and EC are the most significant factors for controlling soil electrical resistivity. The method used opens the way to the development of semi-automatic soil mapping from electrical resistivity data.

Sekem commercial organic farm was chosen for the present work; it is located at Belbeis 20 Km northeast of Cairo city which represented sandy soils. Five plots in Sekem farm were chosen to represent different periods of organic farming application, i.e. 0, 12, 15, 18 and 23 yrs. Surface (0-20 cm) and subsurface (20-40 cm) soil samples were collected in both winter and summer season. The collected soil samples were subjected to the dry sieve analysis to determine and separate the dry aggregate size of ˂0.25, 0.25-0.50, 0.50-1.00 and 1.00-2.00 mm diameter. The distributions of total organic carbon were studied in the whole soil and its aggregate fractions. The data showed that total organic carbon significantly increased by increasing the period of organic farming in the surface samples especially in the longest period of organic farming. Total organic carbon was concentrated in the finest aggregate fraction (˂0.25 mm) for both summer and winter seasons and it was also increased by increasing the period of organic farming. The investigation of the humic and fulvic separates using infrared (IR) spectrophotometry, showed the dominance of carboxylic bands in fulvic especially in the subsurface soil samples which indicated its acidic function. Humic separates showed a relative increased in the intensity of aromatic bands as compared to fulvic separates with increasing the period of organic farming.

Normal alluvial (FFS), calcareous (WNS) as well as sewage farm (ARS) soil samples amended with peptone nutrient solution were subjected to increasing concentrations of Pb, Cd, Zn and Ni then incubated for 7 days at 25 o C. Total bacteria recorded the highest colony forming unites (cfug-1) in Abu-Rawash soils (ARS) even in the presence of increasing levels of Cd, Zn and Pb followed by the normal alluvial (FFS) and calcareous (Wadi-El-Natrun) soils. Under Ni stress, calcareous soil showed the highest population density which may be due to the lime effect. In the alluvial soil, counts were substantially reduced to 1% compared to plain soil applying only 3 mg Cd/kg soil while it was 10% in Abu-Rawash soil. For Pb-and Zncontaminated soils, microbial density in alluviall soil recorded almost the same density as in Abu-Rawash and was higher than in calcareous soil. Dehyrogenase activity (DEH) decreased by 32% in the FFS, 35% in ARS and 17% in WNS as the applied Cd increased from 3 to 8 mg/kg soil. Increased amounts of Zn and Ni inhibited dehydrogenase (DEH) activity by higher 36-44% in FFS and ARS compared to that of WNS (17-22%). A significant positive correlation coefficient (P<0.05) was observed between microbial counts and DEH activity in almost all examined heavy metalpolluted soil. Sixty-seven bacterial isolates from the three heavy-metal-contaminated soils were in vitro examined for their ability to tolerate increasing concentrations of Cd, Zn, Pd and Ni in their culture media. A screening of 67 bacterial isolates was conducted on solid nutrient agar medium supplemented with increasing concentrations of the investigated metals. Nineteen isolates were selected according to their heavy metal tolerance. Some isolates were found to be able to grow in a medium containing up to 700 mg Pb/kg others were tolerant to 75 mg Zn/kg. A maximum tolerable level of 25 mg Ni/kg soil was recorded with the isolates Nos. B-1, B-24, B+27, B-30, B+41, B+55 and B+64. The cultural, morphological and physiological characteristics of the heavy metal-resistant isolates were examined. The majority were Gram-positive long rod-shaped motile sporeforming isolates belonging to the genus Bacillus. The minimum inhibitory concentrations (MIC) of the examined heavy metals were designated for these isolates in submerged liquid cultures. For all examined isolates, culture OD600 increased with time reaching a maximum after 10 day and declined thereafter. Among the examined isolates, the two Gram-positive Bacillus isolates Nos. B-48 and B+41 were the most tolerant to all heavy metals. The identities of these isolates were analyzed using the Sole-Carbon Cource Utilization Profile (Biolog, Inc., Hayward, CA2000). The isolate No. B-48 was identified as Bacillus amyloliquefaciens and No. B+41 as Bacillus thuringiensis.