الفهرس 
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Abstract
The most important goals pursued by the government in the present time are safe disposal with utilization of crop residual for preserve the environment. Therefore, the aim of this study was investigating the effect of residual quantity and mixing depth in soil on improving the soil properties. The field experiments were carried out during two successive seasons (winter 2011-2012 and summer 2012) on a clay loam soil at the research farm of the Faculty of Agriculture - Mansoura University. Experimental area was prepared by using conservation tillage system (Chisel plough once followed by rotary plough once).Two types of crop residual were chosen (Rice straw - Cotton stalks). Three quantities (275, 550, 1100 g/m2 from rice straw and 200, 400, 800 g/m2 from cotton stalk) mixed each quantity in three soil layers depth (0-10), (0-20) and (0-30 cm) two times, once with bio-activator and another without bio-activator. The bioactivator consists of Trichoderma viridae and Bacillus megaterium var phosphaticum by 1:1 ratio. The most important results achieved in the study were the following - Increasing the quantity of crop residues in the soil increased the soil biological activity. Increasing the depth of mixing layer for the same quantity of crop residues decreased the soil biological activity in the same layer. Addition of bio-activator to the treatments with crop residues increased the biological activity in soil in comparison with treatments without bioactivator. Increasing the quantity of crop residues in the soil increased the organic matter in soil. from the obtained results, it may be recommended that mixing crop residue in the soil layer (0-20 cm) depth with quantities of 550 g/m2 from rice straw and 400 g/m2 from cotton stalk.