In this study, soil samples (0-5 cm depth) were taken from ten different roadside fields of intensive traffic regions of Van-Turkey in order to determine the effects of heavy metal pollution on enzymes and microbial activities of soils. Basal soil respiration (BSR), arylsulphatase (ASA), alkaline phosphatase (APA) and urease (UA) enzyme activities, and heavy metal contents (Pb, Cr, Ni, Cd, Fe, Mn, Cu and Zn) of soils significantly changed with 5, 25 and 45 m from the roadside of soil sampling positions. BSR, ASA, APA and UA activities significantly increased while the heavy metal contents generally decreased from the sampling position of 5 m through 25 and 45 m. Significant positive correlations were found among BSR, ASA, APA and UA. Chromium, Mn and Pb contents gave the significant negative correlation with ASA, APA and UA.

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Article Info Received : 21.06.2017 Accepted : 20.10.2017 The objective of this study was to determine the relationship between soil properties and different topography and land uses in the Van Lake Basin, Turkey. It has sharp and sheer slopes, and the big differences on altitude generally occur from the mountainous formations. Surface soil samples (0-20 cm) were taken from 40 different points with three different topography (backslope, footslope and terrace) and three different landuses (wheat, clover and pasture). Some of the studied soil properties (soil texture, electrical conductivity [EC], pH, lime content, organic matter content, macro and micro nutrients) changed in response to land use and topography. The clay, boron content, pH and EC values increased from the backslope to the terrace. Soil organic matter and EC values were lower in cultivated wheat and clover fields than in uncultivated pasture. The EC values had significant positive correlations with CaCO3, organic matter, K, B, Cu contents at 5% level and with Mg at 1% level statistically. The soil nutrient contents of cultivated wheat and clover fields were generally lower than the uncultivated pasture. The nutrient contents of soils in cultivated fields decreased due to nutrient uptake by crops. Soil texture, EC, pH, lime, organic matter and nutrient contents significantly varied in different topographic positions due to leaching, transporting and accumulation.

In this study, effects of different iron sources and doses on plant growth criteria in soybean (Glycine max L.) seedlings were investigated. The experiment was conducted according to factorial experimental design with three replications under controlled conditions. Atakişi variety of soybean (Glycine max L.) cultivar was used as a plant material. Three soybean seeds were sown each plastic pot having 1.3 kg soil:sand mixed in 1:1 ratio. Three different Fe sources (FeSO4.7H2O, Fe-EDDHA and nanoFe) were applied to the pots with three different doses (0-15-30 mg Fe kg-1). The experiment was ended after five weeks of seed sowing. Shoot length, shoot fresh and dry weights, root length, root fresh and dry weights and number of compound leaf in soybean seedlings were determined at the end of the experiment. The highest shoot fresh and dry weights, root fresh and dry weights, compound leaf number were determined in 15 mg kg-1 nano Fe applications as 3.56 g, 0.83 g, 2.30 g, 0.33 g and 5, respectively. Increasing the application dose of nano-Fe from 15 to 30 mg kg-1 caused to decrease in fresh and dry weights in soybean seedlings. Generally, shoot growth decreased and root length increased in soybean seedlings by increasing Fe application doses. Seedling growth in soybean generally increased depend on the Fe sources in the following order; FeSO4.7H2O < Fe-EDDHA < nano-Fe.

In this study, the effects of reduced tillage (RT) and conventional tillage (CT) systems on some soil properties of wheat fields in Northern Iraq (Duhok Province) under a hot and dry climatic condition were investigated. This study was carried out in a randomized plot design with four replications at three locations (Bardrash, Sumail, and Zakho) in the seasons 2017-2018. Four fields in each location at Duhok Province were equally separated into two groups for CT and RT systems. A group of 24 soil samples for each tillage system were taken from the locations. Soil organic matter content, pH, EC, bulk density and total porosity values were significantly (p<0.05) affected by different tillage systems. Soil pH, EC and bulk density values generally significantly reduced with the RT compared with CT. On the other hand, soil OM content and total porosity were significantly increased with the RT system in all locations under a hot and dry climatic condition. In all locations, RT system decreased bulk density and increased total porosity with conserving soil OM due to preventing from rapid mineralization. However, rapid mineralization of soil OM in the CT system under dry climate condition caused increases in EC which indicated that there were high soluble ions in soil solution.

Article Info Received : 27.11.2015 Accepted : 22.03.2016 In this study, effect of mycorrhiza on growth criteria and phosphorus nutrition of lettuce (Lactuca sativa L.) under different phosphorus fertilization rates were investigated. Phosphorus were added into growing media as 0, 50, 100 and 200 mg P2O5/kg with and without mycorrhiza applications. Phosphorus applications significantly increased yield criteria of lettuce according to the control treatment statistically. Mycorrhiza application also significantly increased plant diameter, plant dry weight and phosphor uptake by plant. The highest phosphorus uptakes by plants were determined in 200 mg P2O5/kg treatments as 88.8 mg P/pot with mycorrhiza and 83.1 mg P/pot without mycorrhiza application. In the control at 0 doses of phosphorus with mycorrhiza treatment, phosphorus uptake (69.9 mg P/pot), edible weight (84.36 g), dry weight (8.64 g) and leaf number (28) of lettuce were higher than that (47.7 mg P/pot, 59.33 g, 6.75 g and 20, respectively) in the control without mycorrhiza application. It was determined that mycorrhiza had positive effect on growth criteria and phosphorus nutrition by lettuce plant, and this effect decreased at higher phosphorus application rates.

The toxic chemical substances released into the environment have adversely affected the natural environment, human health, and agricultural production efficiency [1]. The contamination of agricultural soils with several heavy metals including cadmium, lead, copper, and chromium has been widely reported [2]. Much research has been conducted regarding heavy metal contents in soils of Turkey and European Union Countries. The heavy metal contents of soils in Turkey's Bartin Region have been reported for Pb, Zn, Ni, Cu, Cd, Mn, Cr, and Fe in the range of 100-400 mg kg-1 , 20-300 mg kg-1 , 1-100 mg kg-1 , 50-100 mg kg-1 , 1-3 mg kg-1 , 1-60 mg kg-1 , 1-150 mg kg-1 , and 1-1,000 mg kg-1 , respectively [3]. The highest mean values of Al, Cd, Cr, and Pb in cultivated soils of Van Lake Basin in Turkey were determined as 103.57 mg kg-1 , 0.514 mg kg-1 , 2.79 mg kg-1 , and 2.48 mg kg-1 , respectively [4]. The limit values for Cu,