الفهرس 
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Abstract
The aim of this study was to develop best management strategies that espouse maximum agronomic benefits and minimum environmental impacts when applying water hyacinth biochar to sandy soils under arid conditions. The procedures of this research therefore were to conduct two trials in increasing complexity. In each trial, one or more of biochar impacts and beneficial influences were examined moving from maize crop trial under controlled conditions to a more controlled laboratory incubation trial. Maize crop trial was conducted under controlled greenhouse conditions to evaluate water hyacinth biochar suitability at different application rates and methods for amending pristine sandy soil in terms of both improvements in maize nutritional status and yield and changes in soil physical and physicochemical properties. Whereas, incubation trial was conducted to assess effects of water hyacinth biochar addition on some sandy soil biochemical and biological properties and potential carbon sequestration at different application rates and methods.
This research showed that with proper management of water hyacinth biochar, staple crops can be grown on these soils and a high level of productivity can be maintained in short term as following:
1. The applications of water hyacinth biochar to sandy soil necessitate making a one heavy application.
2. Water hyacinth biochar application in combination with artificial fertilizers at no higher than the agronomic rate is required to meet crop nutrients requirements and for preventing agroecosystem contamination.
3. Under arid conditions, the application of water hyacinth biochar that can add excessive amounts of salt or increase soil pH is not recommended. Addition of such biochar to sandy soils under arid conditions can result in unacceptably high soil EC levels and consequently problems with plant growth and microbial activity. The recommended water hyacinth biochar must have pH from 6 to 7 and EC less than 3 dS m-1.
4. Effective utilization of large amount of nutrients present in the large-scale biochar application requires a system such as drip irrigation that decreases the volume of water delivered to the root zone, thereby minimizing leaching losses.
5. Incorporation of water hyacinth biochar into sandy soil has established sufficient plant growth, improved soil physical, chemical and biological properties, compared to broadcasting biochar at the highest application rate of 3%.
6. The rapid incorporation of water hyacinth biochar into sandy soil is recommended to obtain the optimum overall agronomic benefits in combination with the minimum environmental impacts by water hyacinth biochar addition on long term-basis.
7. The incorporation of water hyacinth biochar and the adoption of no-tillage methods can add substantial amounts of organic carbon to these sandy soils.
In general, application of water hyacinth biochar at 3% to sandy soil as incorporation had obvious effects on soil physical, chemical and biological properties; and improved maize growth. Thus, this study confirmed that transforming the abundant water hyacinth biomass in the Nile River into biochar and then adding this biochar to the vast areas of sandy soil existing in Egypt so far can convert these aquatic weeds into a valuable organic matter resource for improving sandy soil physical, chemical and biological properties. An increase in research effort is needed to address these benefits under field arid conditions. However, major considerations in recycling of water hyacinth biochar on sandy soils are the increase in soluble salts. In conclusion, incorporation use of water hyacinth biochar as a soil conditioner and/or fertilizer to these sandy soils that are marginally suited for crop production offers a low-cost alternative for chemical fertilizers and water hyacinth disposal options.