الفهرس 
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Abstract
Increasing the heavy metals concentrations in the soil due to the increased human activity including using of wastewater in irrigation, addition of swage sludge, mineral fertilizers and pesticides to soils,...... etc not only affects the growth of plants and microorganisms in soil, but also it affects human health through the food chain. The danger of heavy metals in the soil represented in the difficulty of getting out of them.
The objective of the study:-
The study aims to investigate the effect of seed bed preparation systems and some plant growth promoting bacteria on heavy metals availability and on crop productivity.
Research Methods:-
Field experiments were carried out for this study in clay soil in for four connected seasons (May 2009: April 2011). Three systems were chosen for seed bed preparations which were classified according to ASAE, 1984, to:
1- Conventional tillage system (Ch2 + L): Two passes chiseling followed by wooden land leveler. 2- Intensive tillage system (Ch2 + R): Two passes chiseling followed by rotary tiller.
3- Conservation tillage system (Ch + R): One pass chiseling followed by rotary tiller.
These systems have been applied to prepare the soil for rice and wheat crops for four connected seasons at three major plots, while in the fourth season; each main plot was divided into four subplots, according to adding the plant growth promoting bacteria: -
1- Control Treatment: Without adding any Microorganisms.
2- Bacillus megatherium var. phosphaticum 3- Bacillus subtilis
4- Anabaena oryzae 231 (Cyanobacteria)
The measurements of the study are: concentration of available lead, nickel, zinc and copper, total count of bacteria, shear resistance, moisture content and crop yield.
The results showed the following:
The conservation tillage systems led to the highest total count of bacteria, the highest moisture content, the lowest soil shear resistance in root zone, the highest crop yield in comparison with the intensive and conventional tillage systems But it led to Some heavy metals accumulation in the soil surface such as lead element but this problem was dissolved due to adding Bacillus megaterium or Bacillus subtilus which decreased the concentration of availabile lead in the surface layer about 47.5 and 41.9% respectively in comparison with without adding soil microbes under the same tillage system. Also adding Bacillus megaterium not only decreased some heavy metals availability such as lead metal but also it demonstrated positive effect on wheat crop yield.
Basing on the previous, conservation tillage system (CH+R) with adding Bacillus megaterium was one of the most suitable seedbed preparation systems to prepare the soil for wheat crop.