الفهرس 
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Abstract
In this study, corncob biochar was used as a soil amendment for irrigated soils with Al-Moheet drain water to improve their properties and address the negative effects of heavy metals, after its use was adopted all over the world in the agricultural sector. In Egypt, despite its ubiquity, there is relatively little literature on biochar soil application or water treatment. In addition, the application of drainage water in agriculture in the presence of biochar is very limited in Egypt due to that some researchers still refute and underestimate biochar effects upon water and soil productivity. Consequently, the present work aimed to study effects of corncob biochar addition to sandy soil irrigated with contaminated Al-Moheet drainage water on wheat productivity and some soil physicochemical and biological properties. To achieve this aim, the following objectives were conducted:
1- To determine Al-Moheet drainage water suitability for irrigation.
2- To evaluate drainage water effects upon wheat yield and quality grown in sandy soil treated with corncob biochar.
3- To evaluate effect of Al-Moheet drainage water used for irrigation of sandy soil treated with corncob biochar on heavy metals status in this sandy soil.
4- To evaluate effects of corncob biochar upon some soil physicochemical and biological properties irrigated with drainage water.
To achieve the objectives of this research, two separate experiments were conducted, the first was crop lysimeters experiment for wheat yield and quality parameters at a private farm, Shosha district, El-Minia Governorate, Egypt and the second was soil incubation experiment for soil biological parameters at the facilities in Faculty of Agriculture, Minia University, Egypt.
Research results revealed that insignificant and small amounts of heavy metals at all biochar application rates reside in the water-soluble form, which is possibly available for plant uptake and or vulnerable to leaching than the other soil-biochar mixture adsorbed fractions. Overall, this study indicated that heavy metals applied in drainage irrigation water to sandy soil treated with biochar rarely migrate to any depth in soil and very little reach the groundwater via the process of intensive surface irrigation. Heavy metals concentration after final irrigation event and wheat harvest was within permissible limits in the leachate and soil. However, results of this research confirmed that Al-Moheet drainage water electrical conductivity value (5.89 dS m-1 at 25 0C) lies under degree of restriction on use ’’Severe’’, indicating that nonstop irrigation use with such drainage water may cause a severe salinity problem in soils on the long run.
Comparison of heavy metal concentrations of biochar treated soils with control showed that total heavy metals had accumulated significantly in topsoil horizon. Most available heavy metal concentrations in all soil leachate fractions were below the method detection limits from all the biochar treated and un-treated lysimeters. Mean concentrations of Ni, Cd, and Pb in wheat crop were far below concentrations considered phytotoxic to wheat plants. After final irrigation event, more than 90% of Ni, Cd and Pb contained in the drainage water of Al-Moheet drain were present and adsorbed by biochar in the top 20 cm of soil lysimeters. Corncob biochar application caused a significant increase (P 0.05) in surface accumulations of total Ni2+, Cd2+, and Pb2+ at all application rates indicating high biochar adsorptive capacity of heavy metals. Results indicated that microbial populations of total counts of bacteria and fungi were gradually and significantly increased over soil incubation time although irrigation with contaminated drainage water in sandy soil amended with corncob biochar compared to control. Also, fungi to bacteria ratios in the sandy soil under investigation were significantly responses and positively related to biochar increasing rates and incubation time. In the sandy soil under examination, soil resistance index (SRI) values reflecting improvements in microbial biomass population of total counts of fungi and bacteria were increased positively throughout the incubation time compared to control and increased significantly as the application rate of corncob biochar increased.