الفهرس 
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Abstract
Urban farming might aid in addressing a city’s social, economic, and environmental problems. Plants may improve the climate of the planet by reducing heat during the summer and holding onto water during heavy rains. Recently, as a result of the intense urban sprawl, notably in Egypt, and encroachment on agricultural lands, it was very important to pay attention to semi-urban agricultural areas. Cities create a lot of organic waste, such as leftovers from recently harvested plants. Compost and biochar made from organic waste can be utilized in urban gardening. Soil organic matter and its biodegradation are very important to agroecosystem productivity; plant wastes afford the main source of this organic matter. Therefore, the most crucial process in soils is the decomposition of organic matter.
The most important carbonaceous component produced by higher plants is cellulose, which is also probably the most prevalent organic substance in nature. Since, plants in most cases contain up to 60% cellulose, cellulose decomposition is a key driver of soil microorganisms, and it is dynamic to the energy flow through soils and to the cycling of C, N, P, and S.
Simply put, cellulose decomposition is a somewhat sophisticated depolymerization process (involving a few saprophytes) followed by hydrolysis to the simple sugar glucose, which is quickly utilized as an energy source by most of heterotrophic soil microbes. By recycling cellulose, the most prevalent carbohydrate made by plants, cellulolytic microbes contribute significantly to the biosphere. The active soil biota has a significant impact on how quickly organic matter decomposes and turns into humus. When a breakdown of soil organic matter is a naturally occurring biological process, soil microbial biomass is essential; hence, any decline in microbial variety or abundance may negatively affect the availability of nutrients in soils and absorption for plant growth.
Fertility and soil health are correlated with farm profitability. Numerous techniques, including the use of cover crops, no-till farming, and the application of manure, have been shown to improve soil fertility and health. However, biochar, a newly developed soil supplement, has the potential to enhance the fertility and health of the soil. Due to its many intriguing properties, including its high carbon content, high pH, high stability, high porosity, and high surface area, biochar is employed as an amendment in agricultural soils. Consequently, throughout the past several years, a number of research studies have been conducted to evaluate the global impact of biochar on various agricultural soils.
Agricultural uses of biochar have been sharply increasing and have received much attention in recent years. Biochar has been considered a potential approach for sustainable agricultural systems and improving the long-term sustainable use of soils for the growth of plants and soil microorganisms. However, biochar technologies are still quite new, and the worldwide factors affecting the long-term fate of biochar in the environment are still poorly understood. Little research has been done to evaluate the potential of biochar amendment in cellulose decomposition. The effects of biochar on cellulose-decomposing soil microbes have gotten significantly less research despite the apparent advantages of biochar for a range of soil chemical parameters. Additionally, the research is lacking on details regarding how biochar affects cellulose decomposition and enzyme activity related to this process.
Therefore, the following were the primary objectives of the current investigation:
• Improve our understanding of biochar’s effect on the cellulose decomposition process.
• Analyze the impact of different biochar application rates on cellulose-decomposing microorganisms and cellulose decomposition rates in two different soils collected from peri-urban agricultural regions near El-Minia city.
• Study the effects of different biochar application rates on plant growth, nodulation and selected enzyme activities related to the carbon cycle.
The obtained results could be summarized as follows:
1. Effects of biochar amendment at different rates on cellulose decomposition.
1.1. Effect on cellulose decomposing microorganisms:
a. There is a significant increase in total counts of cellulose decomposing bacteria, fungi and actinomycetes in both clay and sandy soils with using biochar at different rates comparing to control.
b. Among the treatments investigated, using biochar at the rate of 30 t ha-1 (B3) was the most effective soil amendment followed by biochar at the rate of 20 t ha-1 (B2). At 60 days of incubation, the counts of cellulose decomposing microorganisms reached a high level in both clay and sandy soil then decreased after 90 days of incubation regardless of biochar addition.
c. In general, the counts of cellulose decomposing microorganisms in soil amended with biochar may vary depending on soil type, biochar rates, and agricultural practices.
d. Using biochar as a soil amendment would enhance the soil health and increase the cellulose decomposer counts.
1.2. Fungal/bacterial cellulose decomposers ratio (Fcd/Bcd):
a. The Fcd/Bcd ratio significantly increased when using biochar at the rates of 10 t/ha and 20 t/ha (B1, B2) followed by biochar at the rates of 40 t/ha (B4) after 30 days of incubation time and decreased significantly after 60 days of incubation.
b. For this experiment conditions, the response of cellulose decomposers ratio (Fcd/Bcd) was positively correlated with biochar rates and incubation time with clay soil.
c. The sandy soil cellulose decomposers ratio (Fcd/Bcd) was increased significantly when using high rates of biochar along with the incubation time.
d. The effects of biochar on fungi are more variable and influenced by factors such as biochar properties, biochar rates, soil type and, microbial community composition.
1.3. Microbial-Biomass resistance index (MB-RS)
a. Throughout the trial, the Microbial-Biomass resistance index (MB-RS) values for selected cellulolytic microorganisms were positive. However, they varied according to the rates of biochar used, the length of the trial, and the soil texture.
b. In current study, increasing biochar rates produced a significant decrease in microbial-biomass resistance index. lower MB-RS values were noticed in sandy soil than in clay soil revealing that sandy soil was less resistant to biochar application rates.
c. The MB-RS values in both sandy and clay soil were decreased when biochar applied at 20 t h-1 soil or more during 90 days of incubation.
2. Effect of biochar at different rates on cellulose decomposition rates
a. In general, applying biochar at various application rates accelerated the rate of cellulose decomposition and had a considerable favorable impact on soil microbial activity.
b. Compared to sandy soil, the examined clay soil showed a much faster rate of filter paper decomposition.
c. Over a period of 21 days of incubation, significant variations in cellulose decomposition rates were found in clay soil as compared to sandy soil at 10, 20, 30, and 40 t ha-1 for biochar treatments. This indicated that these soils responded positively to the addition of more biochar.
d. In comparison to the control, filter papers and soils supplemented with biochar showed significant differences in the rates at which cellulose decomposed.
e. In comparison to the biochar-enriched filter paper that was buried beneath soils, losses in biochar-enriched soil samples at all levels were noticeably slower.
f. In comparison to the lower applications of 10 and 20 t ha-1 of biochar, the higher application rates of biochar applied separately at 30 and 40 t ha-1 considerably boosted the breakdown rate of cellulose in both clay and sandy soils.
3. Effect of biochar on plant growth and nodulation
a. There is a significant increase in fresh and dry weight in clay soil compared to sandy when using biochar rate of 30 t ha-1 (B3) followed by biochar rate of 40 t ha-1 (B4).
b. In comparison to sandy soil, clay soil has a greater number of nodules. In both clay and sandy soil, adding biochar as a soil amendment clearly and favorably increased the number of nodules.
c. Biochar increased the correlation between the number of nodules and the fresh and dry weight.
4. Effect of biochar on cellulase and β-glucosidase activities of soils
a. In comparison to the unamended soils examined, all biochar-amended soils generally exhibited significantly greater enzyme activity rates.
b. B4 was the most successful biochar level evaluated for activating cellulase and β-glucosidase activities, followed by B3.
c. With activation percentages of 23.4 and 26.74% in the clay soil, B1 was the least effective in promoting cellulase and β-glucosidase activity. Sandy soil had activation percentages of 24.2 and 34%, respectively.
d. Cellulase and β-glucosidase activation percentages for clay and sandy soil exceeded 60% when employing the maximum rate of biochar (B4).
e. When biochar was used as a soil amendment, the activation rate of soil β-glucosidase was significantly higher than that of cellulase.