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Abstract The effect of farmyard manure, town refuse compost and sewage sludge on the chemical and biological properties of alluvial and calcareous soils was investigated. A weight of 60 g of each manure was added to 3 kg of each soil in 4 replicates pot experiment. Soil samples were taken at 0, 1, 2, 4, 6, 8, 10 and 12 weeks intervals for microbial and chemical analyses. Microbiological determinations comprised the counts of total microbial flora, actinomycetes, fungi, aerobic nitrogen fixers, CI. Easteuria~, nitrifiers and aerobic cellulose decomposers. Soil samples were analysed for total organic carbon content, total nitrogen, C/N ratio, total available nitrogen, water soluble phosphorus, available P and soil pH. The obtained results were as follows: 1. The sOils under experimentation were clay and clay loam textured for the alluvial and calcareous sails, respectively. 2. The application of organic manures slightly increased the total microbial counts. Tbe sewage sludge was the most effective in this respect in both alluvial and calcareous soils. Similar results were noticed also in the case of actinomycetes count.3. The numbers of the fungal colonies appearing on the count plates showed lower densities in the treated samples than the control of alluvial soil and the lowest numbers were observed in the sewage sludge treatment. This was attributed to the competition between the bacterial and fungal population. However the counts of fungi in calcareous soil treated with organic manures were remarkably higher than those in the control treatment. 4. The growth of aerobic nitrogen fixers represented by azotobacter was enhanced by the application of organic manures in both soils. 5. The used organic manures enhanced the growth of Cl. pasteurianum when they were applied to the alluvial soil~ while in the calcareous soil the counts were almost similar to those of the control. 6. The addition of different organic manures enhanced the nitrification process as indicated by the increase of the nitrifying organisms. Also~ the counts of aerobic cellulose decomposers were enhanced by the application of organic manures. 7. The application of different organic manures clearly increased the organic matter content of the two. soils in the order: Sewage sludge ) Town refuse compost ”/ Fa rmya rd manu re • 8. The total ni~rogen content of the two tested soils was increased as a result of the addition of organic manures and also during the course of experiment. 9. The C/N ratio of the soil treated with sewage sludge showed the lowest value followed by farmyard manure then town refuse compost which showed also lower value than control. 10. The application of sewage sludge to the alluvial soil was more effective than either farmyard manure or town refuse compost in regard to their enhancing effect on nitrogen availability. The results of available nitrogen in the calcareous soil showed decreasing amounts, sewage sludge showing the sharpest decrease in this concern. 11. The level of soluble P fraction in both allUVial and calcareous soils was not significantly affected by organic manu ring. At certa in inte rvals ~ 0 rganic manu ring reduced the soluble fraction of soil P as compared with the control treatment. Such trend can be attributed to a decrease in P potential because of P adsorption on effective organic compounds. 12. The application of different organic manures increased P availability in both alluvial and calcareous soils~ especially in the first intervals. Sewage sludge was more effective in this respect then both _anures on- b~th types of .soils.13. The application of sewage sludge to the alluvial soil lowered its pH than did farmyard manure or town refuse compost, while manuring the calcareous soil exerted, in general, slightly higher figures of pH values as compared with the control treatment through most of the sod L samples removed. |