الفهرس 
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Abstract
This work is undertaken to investigate the effect of applying some inorganic fertilizers and different pesticides on the fertility status of different soil types (namely; sandy, silty and clayey ones) to raise its productivity. Also, the results of treating the soils with the used pesticides concerning the soil content of harmful pests, specially nematodes have been evaluated.
The thesis comprises three chapters:
Chapter I: Introduction
It presents information about soil origin, the physical and chemical properties of soils, soil fertility and plant nutrition. Additionally, the role of pesticides to control the soil content of harmful pests such as nematodes is illustrated.
The objective of this work is also reported.
Chapter II: Experimental section
It includes firstly: the materials used such as the soil samples (ordinary and nematode-infected samples), fertilizers and pesticides.
Secondly: the different preparations: ordinary soil samples, nematode-infected soil samples, nematode extraction, solutions of fertilizers and solutions of pesticides.
Thirdly: treatment of the soil samples with fertilizers and pesticides.
Fourthly: studying the response of nematode (melodigyne incogenita) to the used nematicides.
Chapter III: Results and Discussion
These areas studied in this work representing the three different soil types are Abassa, Azazi and Elaem. The soil textures are dominated with sand for Abassa, silt for Azazi and clay for Elaem regions.
a- Effect of the different fertilizers on the fertility of the considered soil types.
Sandy soil
Evaluation of the soil fertility status reveal that the soil samples from Abassa area (sandy) are alkaline in nature and they are poor in the OM content which increases only on nitrogen fertilization with N10. The untreated soil sample has a normal EC value which increases on applying the fertilizers except in case of N10 where it is clearly decreased.
The value of CEC of the control ( 6.11 meq ̸ 100g soil ) decreases on all treatments except with P15 where the CEC is obviously increased to 8.19 meq ̸ 100g soil.
The data indicate that the soil samples contain satisfactory available N and K, whereas the P content is relatively low even after treatment with the fertilizers.
Generally, N10 and P15 fertilizers application show the best improvement in the soil fertility parameters of the silty soil in Abassa region.
Silty soil
There is no considerable change in the porosity % percentage when applying the three fertilizers on the soil samples for Azazi area (silty soil). The pH values of the fertilizers-treated samples are changed within a narrow range. The EC value of the control soil solution (3.6 ds/m) is decreased all over the whole treatments except on using P5 and N5 where it is increased up to 5.17 and 4.92. The CEC values of the silty soil do not show a considerable changes on treatment with the fertilizers. The available macronutrients NPK ions exhibit different behaviors on addition of the fertilizers, N concentration increases and decreases throughout the whole addition. Application of all the three fertilizers decreases the heavy elements content in the soil solution compared with the control.
Clayey soil
The data obtained show slight changes in both bulk density and porosity percentages.
It is also observed that, in some cases, there is a decline in the OM as EC increases.
The solution- pH is found to be directed towards the neutral range, although it still in the alkaline region; this may be better for the productivity of the soil.
The clayey soil has the highest CEC compared with the sandy and silty ones.
The concentration of the available macro nutrients NPK indicates that the N content of the soil samples increases in all cases and achieving the highest values on treatment with N5 and N10, whereas P content decreases on applying the three used fertilizers. The available K content increases on applying the P and N fertilizers but decreases markedly with the K fertilizer. The concentrations of the harmful ions (Co, Cd and Pb) are lower than those in the control specimen with all the used fertilizers. A decrease of the concentration of the ions Na+ , Mg+ +, SO4- -, Cl- and HCO3- is observed with P10 and P15 treatments, but that of Ca ++ cations increases with all fertilizers.
b- Effect of the different pesticides on the fertility of the considered soil types.
According to the data obtained, it could be concluded that application of the considered pesticides, to the soil samples, has negative effects on the studied soil types. Examples of such effects are changes in the physical and chemical properties of the soil samples and also accumulation of the heavy metal ions in the soil.
Generally, V10 is more preferable for sandy soil followed by T10 then F10. Whereas, in silty soil, V10 is more tolerable than T10 and F10. In clayey soil, T10 is the acceptable pesticide compared with F10 and V10.
c- Effect of the tested pesticides (nematicides) on the reduction of root- knot nematode (Meloidogyne incognita) content in the considered soil types.
The effects of the used nematicides on the nematode population in the different soil suspensions are recorded before and after individual application of each nematicide to determine the reduction of root knot M.incognita nematodes in the studied cases.
In both sandy and clayey soils, Vydate causes the highest reduction in nematode population followed by Temik then Furadan. On the other hand, Temik is more preferable for silty soils than the other two nematicides. Furadan, however, records the lowest efficacy than both Temik and Vydate.