الفهرس 
Introduction
Soil amendmentsOnly 14 pages are availabe for public view
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Abstract
The present study aimed to investigate the beneficial effect of soil amendments (sand, gypsum and farmyard manure) on soil physical, chemical properties of heavy textured soil, and also evaluation their effect on plant growth and chemical composition of the two crops (cowpea and potato). Two field experiments were conducted during the two successive seasons of 2000 and 2001 in a clayey soil having more than 60% in Gamallia district, Dakahlia Governorate. Each of soil amendments used was added individually and in combination with other at two rates, (sand was added at 10 and 20 t/fed), (gypsum was added at 2.5 and 5 t/fed) and (FYM was added at 10 and 20 t/fed). A randomized complete block design (R.C.B) was used with 10 treatments (control, sand 10 t/fed, sand 20 t/fed, gypsum 2.5 t/fed, gypsum 5 t/fed, FYM 10 t/fed, FYM 20 t/fed, sand 10 t/fed + FYM 10 t/fed, sand 10 t/fed + gypsum 2.5 t/fed and FYM 10 t/fed + gypsum 2.5 t/fed). The soil amendments were ploughed before cultivating each crop. All agricultural practices were done as followed by farmers in this region. The obtained results could be summarized as follows: 1 Effect of soil amendments used on soil physical properties: ??Hygroscopic water percentage was reduced by adding soil amendments sand, but gypsum and FYM increased it with highly increase. The highest increase in hygroscopic water percentage was obtained with using FYM at 20 t/fed. ??The result showed that there was a highly increase in saturation percentage with the addition of all soil amendments. The highest increase was occurred with FYM at 20 t/fed under cowpea and potato crops. ??The effect of soil amendments on the hydraulic conductivity showed that the addition of each treatment increased soil hydraulic conductivity. The highest increase in H.C. under cowpea crop was recorded with sand added at 20 t/fed, but the highest increase in H.C. under potato crop was achieved with FYM mixed with gypsum. ??Soil amendments used affected soil penetration rate in all studied treatments. The best rate was found with gypsum added at 2.5 t/fed under cowpea and potato crops. ??All of sand, gypsum and FYM decreased bulk density in all treatments, but real density was increased in all treatments. ??Porosity was increased by adding all soil amendments used. 2 Effect of soil amendments used on soil chemical properties: ??The addition of soil amendments under cowpea and potato crops decreased soil pH. The highest decrease in pH value was occurred with gypsum addition at 2.5 t/fed, and FYM at 20 t/fed. ??The application of sand decreased EC (dS/m) at the two rates of 10 and 20 t/fed, while FYM application increased E.C at its tow rates used. In contrast gypsum reduced Ec at its two rates used. Sand mixed with FYM increase EC, but sand mixed with gypsum reduced it, while FYM mixed with gypsum increased EC. The increase in EC with FYM may be attributed to the presence of salts in the organic manure, and to the dissolving of the different soil soluble salts in soil solution, due to acidic effect of humic substances. ??The sand application decrease OM% and OC%, while gypsum and FYM increased it. Sand mixed with gypsum decreased OM% and OC%. The highest increase in OM% was obtained with FYM at 20 t/fed under cowpea crop, but under potato crop it was happened by using sand+gypsum. ??Sand addition at two rates of 10 and 20 t/fed increased bicarbonate, and FYM also increased it, but gypsum decreased bicarbonate anion. Sand mixed with FYM increased it, while sand mixed with gypsum decreased it. Using FYM + gypsum increased it under cowpea and potato crops. ??All soil amendments (sand, FYM, and gypsum) reduced soluble chloride in all treatments. The highest decrease was occurred with gypsum at 5 t/fed under cowpea crop, but highest decreased was found with adding gypsum at 2.5 t/fed, under potato crop. ??Soluble sulphate was affected by different addition of soil amendments. Soil amendments increased soluble sulphate in all treatments. The highest increase was achieved with gypsum at 5 and 2.5 t/fed under cowpea and potato crops. ??Added sand at 10 and 20 t/fed. increased soluble sodium. On the other hand, gypsum and FYM reduce soluble sodium. Sand + FYM reduced Na. Sand + gypsum reduced soluble Na, but FYM mixed with gypsum increased soluble Na cation under cowpea crop. This effect was obvious under potato crop in all treatments which reduced soluble Na. ??FYM has a good effect on soluble potassium under cowpea and potato crops. FYM at the two rates increased soluble K. Also, their mixing with sand or with gypsum increased soluble K. But the addition of sand and/or gypsum reduced soluble K under cowpea crop because of the contrast effect between Ca++ and K+. But under potato crop adding sand at 10 and 20 t/fed increased soluble K because of its need to high potassium fertilization. ??Soluble calcium and magnesium were increased with addition of all soil amendments in different application rates and the combinations between them. ??All soil amendments decreased sodium adsorption ratio in all treatments under cowpea and potato crops. ??Gypsum requirement (GR) was decreased by adding soil amendments (sand, gypsum, and FYM) in all treatments. 3 Effect of soil amendments used on cowpea crop: ??The addition of soil amendments increased seed yield, and buds yield. The highest increase in both was found with FYM (10 t/fed) mixed with gypsum (2.5 t/fed). 4 Effect of soil amendments used on potato crop: ??Tuber number/plant, leaves number/plant were increased with adding sand, FYM, and gypsum. ??Total tuber yield also increased with adding soil amendments. The highest increase was recorded with gypsum at 5 t/fed. ??Soil amendments have highly significant effect in chemical composition of the two crops (cowpea and potato). N, P, and K contents and their uptakes were also highly significant increased. ??Finally, it could be recommended to use soil amendments especially FYM at 20 t/fed, gypsum at 5 t/fed and FYM (10 t/fed.) mixed with gypsum at 2.5 t/fed for improving the properties of the high clayey soil and also for increasing its productivity with high quality.