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Abstract This work was carried out to’investigate the use of some synthetic materials (polyvinyl alcohol ”PVAn, Polyvinyl acetate ”PVAc” and Bitumen) as well as natural materials (Shale, Farmyard manure ”FYM” and Gypsum) as soil conditioners on three soils. The soils were (a) a sandy soil from EI-Salheya, (b) a sandy clay loam calcareous soil from El-Nobareya, and (c) a sandy clay loam saline-sodic soil from Abeece. Two greenhouse experiments were carried out on the first two soils using barley as an indicator plant, and a laboratory experiment was carried out on the third soil. Treatments involved application of conditioners in different manners: (a) each applied singly, (b) each applied in combination with FYM (in the case of the first two soils), and (c) each applied in combination with gypsum (in the case of the third soil). Shale was used only with the first soil, and gypsum was used only with the third one. applications of conditioners were Three rates of used. They were as follows: PVA (or PVAc): 0.67%, 1.00\ and 1.33%; Bitumen: 1.00\, 1.50% and 2.00%: FYM : 1.33\, 2.00% and 2.67% and shale 4.67%, 7.00% and 9.33%. Results with the first two soils indicated that all conditioners showed improvement in soil properties, as they decreased bulk density and increased soil aggregation. aggregation index ”AI”. mean weight diameter ”MWD”. Wind erosion index ”WEI”, pore size distribution~ soi 1 water retention and avail abl e moi sture particularly with increasing their rates of application. As an example of effect on the sandy soil, during its 45 days following experiments, the treated conditioned soil showed 48%, 46%, 37%, 36% and 30% total aggregates in the cases of Bitumen. PVAc, shale, PVA and FYM, respectively (average of three rates), while untreated soil had total aggregates of 14%. Total porosity values for the same soil during the same period were 38%, 47%, 46%, 45%. 44% and 42% for control, Bitumen, PVAc, FYM, PVA and shale treatments, respectively. Bulk densities of the treatments were 1.62, 1 •32, 1. 42, 1. 46, 1. 47 and 1. 51 for the con tr 0 l, Bitumen, PVAc, PVA, FYM and shale, respectively. In the sandy soil, treatments receiving both FYM and shale led to a slight increase in electric conductivity ”EC” of the soil extract~ apparently due to the improved conditions for plant growth which led to more water being used during the season, as well as salt contents of the materials. Also, the cation exchange capacity increased from 1.54 meq/l00 g for the control to 1.69, 1.64 and 1.63 for PVA, PVAc, and Bitumen, respectively as compared with 5.41 and 4.27 for shale and FYM, which could be due to the colloidal nature of the last two materials. The other heavier soil showed similar results. This soil being rather saline (EC = 6.16 mmhos/cm/2SoC), all treatments and the control showed at the end of the experiment~values of EC smaller than the initial EC, due to leaching. Compared with the control, FYM in particular showed higher EC values which may have been due to its relativelY high content of salts. Time duration led to a decrease in the improvements on physical and chemical properties already occurred following application, particularly with FYM, apparently due to the decay of the conditioning materials. Treatments receiving shale showed the least change with time reflecting its stability. Application of conditioners caused a delay and a decrease in seed germination possibly due to impervious layers formed around seeds, but eventually plant growth as well as its uptake of N, P and K were increased. Treatments receiving soil conditioners in combination with FYM also showed patterns of response similar to those where conditioners were applied singly; however the magnitude of the response was greater. Time duration, also led to a decrease in the improvements and the extent was greater in this respect than when conditioners were applied singly. Results of the laboratory experiment (the third soil) showed improvement of soil physical properties by application of soil conditioners. Salinity and exchangeab1e sodium percentage ”ESP” were decreased by application of conditioners. EC waS originally 7.88 mmhos/ cm/250C, it decreased to reach a value of nearly one sixth that of the original. ESP was 19.20\ originally; it decreased to as low as 4.30% by treatments giving an indication of a decrease in EC of all treatments during the course of experiment. conditioners applied in combination with gypsum were more effective in improving soil physical and chemical properties than when applied singly. |