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Abstract main objective of this investigation is to study the effect of some organic fertilizers, i.e. composts, fannyard and .biog as manures on nutrients availability in sandy and clay soils and hence their uptake by corn plants. TwO pot experiments were carried out under green house conditions. The first experiment (incubation) was performed to investigate the chemical availability of N,P and K in the tested soils as affected by the manuring treatments. The tested manures were applied at the rate of 2% (WIW) to both tested soils and incubated for 8 weeks. The soil analyses were run at 0,4,6 and 8 weeks incubation periods. The second experiment (cultivation) was conducted to study the combined effect of different manures and NFK fertilizers applied at the recommended doses on the availability and uptake of N,P, and K by com plants. The obtained results reveal the following: 5.1. Incubation experiment: 1) Manures application increased significantly and consistendy allover the tested periods, both available soil Nand P in the order : biog as M. > compoIT> comp- 1> FYM· On contrarY soil available K the inducing trend decreased in the order: comp- IT> eomp. I> FYM > biogas M., with significant differences betWeen any treatment and each other one. 78 [§ummarY] 2) The application of organic manures increased the soil organic matter content allover the tested incubation periods, while compost I followed by compost II were favourite for the sandy soil, compost II followed by biogas M. were more effective in the clay soil. 5.2. Cultivation experiment: 1) The addition of different fertilizer sources significantly increased the dry matter yield of com plants in both tested soils, particularly the biogas manure which exceeded mostly the other organic sources and even the mineral source in many cases. 2) The different fertilizer sources increased significantly the N uptake by com plants (shoots, roots and whole plants) in both tested soils. The biogas manure followed by the mineral fertilizers source were the most effective treatments with respect to the increase in N uptake by com plants after different growth periods (4, 6 and 8 weeks) in both sandy and clay soils. 3) The application of different fertilizer sources increased significantly the P uptake of com plants in both tested soils. Results may suggest in general, that biogas M. followed by compost II were more effective manures in increasing P uptake by com plants than the other sources, in the sandy soil. Biogas manure and compost I exceeded the other sources in the clay soil, while the mineral fertilizers source was the most inferior source. 4) The different fertilizer sources increased significantly the total K uptake by corn plants in the sandy and clay soils, where compost I exceeded compost n under the sandy soil conditions, whereas compost II followed by biogas M. were the most effective under the clay soil conditions. The mineral fertilizers source was the least efficient in the sandy and clay soils. S) The biogas manure followed by compost n were favourite for increasing the availableN in the sandy soil, whereas, FYM and the mineral fertilizers source gave the least effect. As for the clay soil, while the mineral fertilizers source followed by the biogas M. were the most effective on the level of soil available N, compost I was the least effective under com growth conditions. 6) The tested fertilizer sources increased significantly soil available P allover the growth periods, the sandy soils, recorded higher efficiency than the clay one allover the growth periods. 7) The different fertilizer sources increased the soil available K in the sandy and clay soils under com growth conditions. Compost II followed by compost I were the most effective, while mineral fertilizers source and/or biogas M. were the least effective for increasing available K in sandy and clay soils. 8) The application of the different organic manures increased the soil organic matter content under com growth conditions, the most effective sources in both soils were compost 1 followed by compost II. |