الفهرس 
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Abstract
Field experiments were conducted at the Farm of Soil and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Inshas, Egypt. Situated at 30o 24` N latitude, 31o 35` E longitude, while the altitude is 20m above sea level, to study the effect of fresh and irrigation water salinity on actual evapotranspiration (ETa), crop coefficient (Kc), water stress coefficient (Ks), yield, water use efficiency of both groundnut and wheat plants cultivated in sandy soil under trickle irrigation system. Complete randomized block design (CRBD) was used with four replicates and five different irrigation water treatments; Fresh water as a control FW (0.50 dS m-1) and other four saline water treatments containing; S1 (2.4 dS m-1), S2 (2.7 dS m-1), S3 (3.3 dS m-1), and S4 (4.4 dS m-1) for groundnut crop while they were S1 (4.9 dS m-1), S2 (6.3 dS m-1), S3 (8.7 dS m-1), and S4 (13.0 dS m-1) for wheat crop. Penman-Monteith equation was used to calculate reference evapotranspiration (ETo) based on the agro-metrological data collected for the studied area using CROPWAT v.7.0 program. Soil moisture content was monitored after and before the next irrigation using neutron moisture meter. The obtained results could be summarized as follows: br 1 - Emission uniformity (EU): br The emission uniformity (EU) of the trickle irrigation system under studied area was (96.13 %), it is classified as Excellent. br 2 - Reference evapotranspiration (ETo): br a - Groundnut experiment: br The total value of reference evapotranspiration (ETo) during the growth season was 871.6 mm. The value of reference evapotranspiration (ETo) through the growth season indicate they were high at the beginning of season and decreased till harvesting. br b - Wheat experiment: br The total value of reference evapotranspiration (ETo) during the growth season was 504.4 mm. The value of reference evapotranspiration (ETo) through the growth season indicate they were high at the beginning of season and increased till harvesting. This is may be due to the changes in the climatologically norms and cultivated season in this area. br 3- Actual evapotranspiration (ETa): br a - Groundnut experiment: br Values of actual evapotranspiration (ETa) reveal that the total amount of water consumed by plants during the plant growth season under the effect of the increased irrigation water salinity follows the order: FW (629.8 mm) -gt; S1 (608.9 mm) -gt; S2 (598.9 mm) -gt; S3 (596.8 mm) -gt; S4 (545.1 mm). br b - Wheat experiment: br Values of actual evapotranspiration (ETa) reveal that the total amount of water consumed by plants during the plant growth season under the effect of the increased irrigation water salinity follows the order: FW (439.4 mm) -gt; S1 (408.8 mm) -gt; S2 (408.7 mm) -gt; S3 (384.4 mm) -gt; S4 (382.3 mm). The ETa may deviate -#102;-#114;-#111;-#109; ETc due to non-optimal conditions such as soil salinity. This may reduce the actual evapotranspiration (ETa) rate below crop evapotranspiration (ETc). br 4 - Crop coefficient (Kc): br The calculated crop coefficient (Kc) values during the crop development and late-season stages of both groundnut and wheat crops are similar to those suggested by FAO-33. But, the initial and mid-season stages were less than that suggested by FAO-33. br 5 - Water stress coefficient (Ks): br The effects of water stress coefficient (Ks) on crop evapotranspiration (ETc) are described by reducing the value of the crop coefficient (Kc), by multiplying the Kc by Ks. br a - Groundnut experiment: br The average values of water stress coefficient (Ks) follow this order: br FW (1.00) › S1 (0.91) › S2 (0.86) › S3 (0.77) › S4 (0.71) br b - Wheat experiment: br The average values of water stress coefficient (Ks) follow this order: br FW (1.00) = S1 (1.00) › S2 (0.99) › S3 (0.97) › S4 (0.93). br 6- Crop evapotranspiration (ETc): br a - Groundnut experiment: br Under standard conditions the total value of crop evapotranspiration (ETc) was (677.3 mm). For non-optimal conditions the total values of ETc adj were; S1 (598.9 mm) -gt; S2 (565.6 mm) -gt; S3 (515.2 mm) -gt; S4 (472.7 mm). br b - Wheat experiment: br Under standard conditions the total value of crop evapotranspiration (ETc) was (452.6 mm). For non-optimal conditions the total values of ETc adj were; S1 (423.0 mm) -gt; S2 (418.6 mm) -gt; S3 (389.9 mm) -gt; S4 (378.1 mm). br 7 - Vegetative growth and yield br a - Groundnut experiment: br The total (shelled nuts) yield following these order: FW (3893 kg ha-1) -gt; S1 (2193 kg ha-1) -gt; S2 (1627 kg ha-1) -gt; S3 (1541 kg ha-1) -gt; S4 (1185 kg ha-1). Very high significant differences were obtained between FW yield and other salinity treatments; also, between S1 and S4 treatments, S1, S2 and S3 treatments gave the same yield approximately; -#119;-#104;-#101;-#114;-#101; there is no significant difference between them. As well as, there are no significant differences between S2, S3 and S4 treatments, br b - Wheat experiment: br The obtained yield follows the descending -#111;-#114;-#100;-#101;-#114; of: FW (6053kg ha-1) -gt; S1 (4989 kg ha-1) -gt; S2 (4906 kg ha-1) -gt; S3 (4631 kg ha-1) -gt; S4 (2909 kg ha-1). Significant differences were obtained between FW yield and other salinity treatments. On the other hand, S1, S2 and S3 treatments gave the same yield approximately; -#119;-#104;-#101;-#114;-#101; no significant differences between them, whenever there is significant different between all treatments and S4, also, there is significant differences between S1 and S4 treatments. br 8 - Water use efficiency (WUE) and irrigation water use efficiency (IWUE): br a - Groundnut experiment: br Increasing salinity level of irrigation water progressively decreased WUE and IWUE. The values of WUE and IWUE were 0.62, 0.36, 0.27, 0.26, and 0.22 kg m-3 and 0.56, 0.31, 0.23, 0.22 and 0.17 kg m-3 for FW, S1, S2, S3 and S4, respectively. br B - Wheat experiment: br The values of WUE and IWUE were 1.38, 1.23, 1.20, 1.20, and 0.76 kg m-3 and 1.10, 0.91, 0.89, 0.84 and 0.53 kg m-3 for FW, S1, S2, S3 and S4, respectively. br 9 - Changes in soil chemical properties by the end of cultivation: br The values of electrical conductivity (Ece) tended to increase with the progress in growth stages of groundnut and wheat plants. The maximum values of Ece in the root zoon of groundnut plant was obtained at the mid-season stage, whereas in the case of wheat at was obtained at the late stage of growth. Na+ concentration in the saturation soil past extract (collected in the active root zoon -#102;-#114;-#111;-#109; 0-30 cm approximately) was higher than the other cations. It was 10.2, 10.2, 12.1 and 12.4 times, that of the FW, in the case of groundnut, whereas it was 6.8, 9.7, 16.1 and 16.7 times that of the FW in the case of wheat plant, for S1, S2, S3 and S4, respectively. However, data reveal that the increase in Cl- concentration due to irrigation with S1, S2, S3 and S4 by 12.5, 13.3, 16.6 and 16.4 times, and 7.0, 10.5, 20.1, 18.0 times for groundnut and wheat crops, respectively, higher than those irrigated with FW. Cations concentrations in groundnut and wheat experiment soil have the following order: Na+ -gt; Mg++ -gt; Ca++ -gt; K+, but for the anions concentrations of groundnut experiment soil were: Cl- -gt; HCO3- -gt; SO4--, and Cl- -gt; SO4-- -gt; HCO3- for wheat crop. br According to the obtained results the following recommendations are recommended: br • Water stress coefficient (Ks) could be used under nonstandard conditions (low-quality irrigation water) to optimize irrigation water requirements under these circumstances. br • Available crop data reported in FAO texts could be used only as a guide because it does not reflect the real conditions of most farming areas in the world. br • Under high saline water -gt; 2.7 Ds m-1 groundnut just grows for oil production or as green manure in newly reclaimed lands. br • It possible to cultivate wheat crop in sandy soil irrigated with saline water -lt; 8.7 Ds m-1, -#119;-#104;-#101;-#114;-#101; the reduction of yield was less than 25 % which is acceptable in Egypt. br • It could be emphasis that the importance of adding excess water as a leaching requirement before the next cultivation in the soils which previously irrigated using saline water to keep it is -#102;-#114;-#111;-#109; deterioration. br • The use of neutron scattering method led to save time and effort especially when using to estimate soil moisture content and the actual evapotranspiration.