Sewage sludge (SS), cement kiln dust (CKD), and plant residues (PR) were composted at different ratios under different conditions. Increasing CKD application decreased organic carbon content and C/N ratio of the final compost. NPK contents differed only slightly between the different compost types. CKD application only slightly affected total Cd, Cu, Zn and Ni concentrations in the final compost. Concentrations were lower than maximum permissible concentration for agricultural use.
The changing of soil biological characteristics due to the addition of raw and composted sewage sludge (at 0, 1.5 and 3.0%) were evaluated during a 165-day incubation experiment. Generally, increasing the addition rate of sewage sludge and its compost up to 3%, total organic C content (TOC), cumulative organic C decomposition (COCD), biomass C and basal respiration in soil were significantly increased. The increase in biomass C and basal respiration were significantly higher in sewage sludge-treated soil as compared with compost-treated soil. By extending the incubation period, TOC content biomass C and basal respiration were significantly decreased and COCD was significantly increasedThe differences in biomass C/TOC ratio at the beginning and end of the incubation experiment were significantly higher in waste-amended soil as compared with the untreated soil. Such differences were much higher when the soil treated with sewage sludge as compared to the soil treated with compost.At the beginning of the experiment, all values of metabolic quotient (qCO2) in the waste-amended soil were significantly higher as compared with the untreated one. Sewage sludge-amended soil had usually greater qCO2 values compared with compost-treated soil at the used two application rates.High positive correlations were observed between biomass C, basal respiration and the biomass C/TOC ratio. Any of these may be used as a bio-indicator of a soil biological activity after amendment by organic materials.
A field experiment was carried out during 2000/2001-growth season at the Experimental Farm of the Faculty of Agriculture, Suez Canal University. The aim of the present work is to evaluate two strawberry (Fragaria x aananssa) cultivars (Camarosa and Chandler) yields response and compositions to varying rates (0, 40 and 60 m 3 ha -1 ) of different composted sewage sludge, plant residues and cement kiln dust (5:5:0, 5:5:0.4, 5:5:0.8 and 5:5:1.6 v/v).Fresh and dry weights, NPK contents and uptakes of shoot and fruit of strawberry were significantly increased as result of applying different compost mixtures to the soil as compared with untreated soil. Also, Fe, Mn, Zn, Cu and Ni contents of shoot and fruit of strawberry were significantly increased (but they were still in safe concentrations, often do not build-up to phytotoxic levels) as result of applying different compost mixtures to the soil as compared with untreated soil. All measured parameters were also increased with increasing compost application rates. There are different responses for the two strawberry cultivars in yield, metal contents and uptakes as result of applying of different compost mixtures and rates. Generally, although fresh weights of shoot, fruit, and total yield and dry weights of shoot and total yield of Chandler cultivar were more significantly higher in the compost untreated soil, they more responded to the application of the compost to the soil in Camarosa cultivar.
Ten-week composting experiment was conducted at Faculty of Agriculture Farm, Suez Canal University, Ismailia Governorate, during Summer 1999. Sewage sludge has been stabilized by composting in mixtures with the following plant residues at rates 10 and 20 : 1 w/w; 1) wood carpentry refuse, 2) peanut shells 3) rice straw, 4) wheat straw, 5) corn straw, 6) sugar cane refuse, 7) grass clippings, 8) peanut shoots, 9) chickpea residues and 10) lupine residues. The objective of the experiment is to produce a compost environmentally safe material that is free from pathogens, and can be used beneficially on agricultural newly reclaimed soil as a organic fertilizer by composting of sewage sludge with plant wastes.The data indicated that, organic C content of sludge-plant residue treatments was gradually significant decreased with the time till the end of the experiment (10 th week). Increasing the rate of sewage sludge application resulted in a marked decrease in total N content of the mixture. It can be arrange the different plant residues according to low C/N ratio as well `as high organic C decomposition rate in the following order: chickpea residues peanut shoots wheat straw lupine residues corn straw grass clippings sugar can refuse wood carpentry refuse peanut shells rice straw at 10:1 sewage sludge : plant waste. While, wood carpentry refuse corn straw = grass clippings peanut shoots chickpea residues = sugar can refuse wheat straw lupine residues rice straw peanut shells at 20:1 sewage sludge : plant waste.Salinity levels of the different treatments of the final compost product were still low and practice for agricultural use, K content not significantly increased, N content decreased and P content significantly increased by increasing the rate of sewage sludge upto 20:1 plant residues. Total Cd, Pb, Cu, Zn and Ni concentrations in the final compost are very lower than maximum permissible concentrations for agricultural use.Raw sewage sludge has pathogenic bacteria and parasites in the range of the infective dose to human. However, composting conditions of sewage sludge-plant residues were greatly effective in reduction of total bacteria and coliforms, pathogenic bacteria i.e. Salmonella sp., Shigella sp. and Vibrio sp and pathogenic parasites i.e. Ascaris lumbericoides, Trichuris trichiura, Entrobius vermiculus and Hyenolepis spp.
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