الفهرس 
Introduction and Literature reviewOnly 14 pages are availabe for public view
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Abstract
The aim of this work is to prepare a hydrogel from polyacrylamide (PAAm) and rice straw (RS) to absorb and retain the irrigated water in the desert lands, conservation of the environment and to optimize the use of natural resources by recycling rice straw using either ionizing radiation or thermal treatment.
The first method: Study the exposure of PAAm and the composite of PAAm/ RS to the ionizing radiation (gamma irradiation) to prepare PAAm/ RS hydrogel, which has a high capacity to absorb water so that it can be used to increase the retention of sandy soil for water and cultivation of large areas with a small amount of water.
The second method: Study the heating of PAAm and the PAAm/ RS composite and its effect on the ability of water absorption.
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In this regard, the optimal conditions for the preparation of such water gels and the factors affecting water absorption and retention were studied, such as the effect of radiation dose, polymer polymerization ratio, optimal rice straw ratios and its fiber lengths, and the effect of pH, temperature and salts.
The results obtained in the work can be summarized as follows:
First: Preparation of highly absorbent hydrogel by radiation and factors affecting the ability to absorb and retain water:
1. The exposure of PAAm to different irradiation doses (10,20,30, 40 and 50) kGy was studied and the high water absorbance was at irradiation dose of 30 kGy
2. The hydrogels prepared by irradiated polyacrylamide were also prepared, as well as mixed with rice straw to form hydrogel with high ability to absorb and retain water. It has been found that hydrogel (PAAm solution / 50 phr RS) has the highest absorption capacity for water.
3. Types of agricultural waste as rice straw, wheat straw and bagasse were studied. The results showed
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that the rice straw composite was more absorbent than the others.
4. The effect of rice straw fiber length (1 - 5 mm) was also studied. Water absorbance was reduced with increasing RS fiber length and the highest water absorbance was at RS fiber length of 1 mm.
5. The PAAm/ RS composite were studied at different rates and under the influence of radiation dose, where the gel content was obtained by irradiated hydrogel (PAAm solution / 50 phr RS) at 30 kGy (IPRC) was 98.5%.
Second: Preparation of highly absorbent hydrogel by thermal treatment and factors affecting the ability to absorb and retain water:
1. Thermal treatment was used as another method to increase the crosslinking content of the hydrogel and to obtain a lower density hydrogel (0.4 g/ cm3) by heating the PAAm/ RS where the results showed that the best temperature for PAAm/ RS was at 120°C (HPRC).
2. The HPRC was measured at different rates under heat effect where the gel content was obtained of HPRC was 82%.
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3. from water absorbance and gel content, it’s proved that ionizing radiation is better than heating.
Third: Practical use of hydrogels prepared in the field of agriculture:
1. The water absorbance of IPRC in fresh water was greater than in different salts solution. As well as a gradually decreasing in water absorption was noticed with increasing concentration of these solutions.
2. The swelling degree of the IPRC was determined in the saline solutions for different valence cations with the same concentration, where IPRC absorbance was found to be higher in the case of monovalent salts (Na1+), followed by the salts of the divalent cation (Ca2+) and the tri-valence cation salt (Fe3+). While the water absorbance of IPRC was reduced by increasing the size of the cations with the same equivalence: Li+ > K+ > Na+ in the case of mono-valence cation salt and Ca2+> Mg2+ case of divalent cations of salt.
3. Water retention of IPRC was studied under the influence of different temperatures. The lowest water retention was obtained by increasing the average
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temperature of the environment surrounding the hydrogel.
4. The effect of pH on the water absorbance of IPRC was also studied where the highest absorption value was obtained in pH = 6 in the neutral medium, while in the alkaline medium and acidic medium was the lowest.
5. The degree of retention of sandy soil with IPRC showed that the retention of water in sand soil was increased by increasing the amount of hydrogel added to the soil.
6. The absorption of urea (as fertilizer) was studied. It was found that high retention capacity and retention of high concentration of urea were obtained (20 g / L).
7. The function of soil membrane for retention of water was studied, where the addition of PVA/ Borax membrane system on the surface of sandy soil gave an ideal performance of swelling process and water retention of almost the irrigated water.
8. The concentration of PVA was studied, where it was found that the membrane must be containing 3% of PVA as a solid content to allow water permeability
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and to also prevent the accumulation of water for irrigation and root rot.
Fourth: IPRC were used in sandy soils to increase water retention and their effect on the growth of bean plant. The results showed the following:
1. Effect of different types of IPRC, IPRC with membrane, as well as the effect of different concentrations of IPRC on germination ratio, average plant length, average leaf width, Bean yield, dry weight and plant arrival time to wilt after stopping plant irrigation were studied.
2. The results showed that the percentage of bean germination was increased with different hydrogel compared to the untreated soils where germination rates were faster if hydrogel was used only or with hydrogel membrane.