الفهرس 
Introduction
Trace elementsOnly 14 pages are availabe for public view
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Abstract
It was established that mineral fertilizer is one of the most pollutants that affect environment and public health concern in numerous areas of the world. The experiments were performed to investigate the ability of substituting the mineral fertilizers particularly or totally with organic fertilizers (Sewage sludge and town refuse). Two field experiments were conducted during the two successive seasons of (2000/2001) and (2001/2002) in a clayey soil in Talkha district, Dakahlia Governorate (North Nile delta region). Each of organic fertilizers used was applied individually and in combination with the other at two depths (20 and 30 cm subsurface). A randomized complete block design (R.C.B) was used with the treatments (control, town refuse, mixture 10% SS, mixture 20% SS, mixture 30% SS and sewage sludge), all treatments were added at two depths (20 and 30 cm subsurface), then there are 12 treatments, the soil was prepared and ploughed and then made as tunnels with the two depths, the mixtures were applied and recovered by the same soil before cultivating the crop. All agricultural practices were done as followed by farmers in this region. The obtained results of the present study could by summarized as follows: 1?Increasing the level of sewage sludge in the mixtures from zero to 100% resulted in an increase in plant height, leave humidity, stems humidity, leaves number, leaf area and chlorophyll content of potato plant. 2? The addition of organic fertilizer into the soil increased both of total and available nitrogen and phosphorus in the soil as affected by increasing sewage sludge level in the mixtures. 3?Applying the organic fertilizers at the depth of 20 cm subsurface resulted in increasing the tested parameters in comparison with addition at 30 cm. 4?Increasing sewage sludge percentage in the mixtures caused reducing starch, specific gravity and potassium content in the potato tubers. 5?Also, N, P, Fe, Mn, Zn, Cu and Cd concentration in tubers increased sharply as sewage sludge levels increased, and this increase was high significant. Thus, it can be concluded that adding organic fertilizers to soils has an important role in improving the chemical properties of the studied soil which reflected on the plants growth, yield and quality. Also, it can be reported that using sewage sludge and town refuse compost of Mansoura City as a partial fertilizers do not cause any toxicity hazards. But more studies and investigation must be done on sewage sludge applied to soils in order to avoid trace elements accumulation with advancing the time.