الفهرس 
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Abstract
A field experiment was carried out on a sandy soil at the experimental farm of Soil and Water Research Department, Nuclear Research Center in 2014- 2015located at Inshas, Sharkia Governorate, Atomic Energy Authority, Egypt. The latitude and longitude of the experiment site is 30o 17` 7`` N, 31o 23` 47`` E, respectively, and the altitude is 27 m above the sea level to study the effect of water stress on wheat crop variety Misr2 (Triticum astivum L.) using neutron scattering technique under trickle irrigation system with emission uniformity (92.02%) with study some properties of sandy soil, wheat production, actual evapotranspiration (ETa), crop coefficient (Kc), water stress coefficient (Ks),water use efficiency, irrigation water use efficiency and water productivity.
Complete randomized block design (CRBD) was used with four replicates and four different irrigation water treatments; 100, 80, 60 and 40% of crop evapotranspiration (ETc) for T1, T2, T3 and T4, respectively, that calculated from Weather station data. Each treatment was irrigated twice a week based on the daily crop evapotranspiration (ETc) that calculated from reference evapotranspiration (ETo) using Penman-Monteith equation depending on the climatic parameters during the growing season .
The Neutron scattering technique used to detect the soil moisture contents during the growing season after and before the next irrigation using neutron moisture meter that at depths 30, 50, 70 and 90 cm .
The aim of this study was:
Estimating actual and crop evapotranspiration (ETa & ETc) for wheat crop by climatic method (Penman Monteith) under trickle irrigation system using neutron scattering method.
Optimizing the irrigation water requirement via determine adjustable crop evapotranspiration (ETc adj), water stress coefficient (Ks) and modified crop coefficient (Kc) under water stress conditions.
The data released from the recent study could be summarized as following:-
The amount of reference evapotranspiration during the growing season of (2014-2015) was 66.54, 180.87, 201.91 and 177.46 mm/stage for initial, development, mid-season and late stage, respectively and the annual reference evapotranspiration was 626.78 mm. The values of (ETo) through growth season indicate that it is lowest with the beginning of season and increased till harvesting time. This is may be due to evapotranspiration rates vary between plant species and vary for different times of the year and different stages of plant growth.
The recommended values of Kc (FAO, No.56) for Kc ini, Kc dev, Kc mid and Kcend were 0.35, 0.75, 1.13 and 0.70, respectively but the calculated values was lower in the late season stage (0.57) at range of (18.6 %), but it was higher in the mid-season stage (1.20) at range (5.8 %). Meanwhile, at the development stage, the average Kc value was closed to the average Kc value suggested by FAO, No. 56.
The total amount of crop evapotranspiration (ETc) during the growing season of (2014-2015) was 23.29, 139.01, 244.51 and 102.43 mm/stage for initial, development, mid-season and late stage, respectively and the annual crop evapotranspiration was 509.24 mm/season.
The values of Ks close to 1.0 in T1 treatment however had a little effect on soil water stress on it, where in the other treatment the values of Ks were 0.97, 0.95 and 0.90 in initial stage, 0.90, 0.85 and 0.76 in development stage, 0.81, 0.74 and 0.58, in mid-season and for late stage were 0.89, 0.84 and 0.72, for T2, T3 and T4 treatments, respectively.
The total amount of the actual evapotranspiration (ETa) of plants irrigated as 100% of crop evapotranspiration T1 was higher (441.90 mm/season) compared with that of 80, 60 and 40% of crop evapotranspiration (ETc) for T2, T3 and T4, respectively, where it was 353.60, 262.20 and 179.10 (mm/season), receptively.
The total amount of the adjustable crop evapotranspiration (ETc adj) of plants irrigated as 100% of crop evapotranspiration T1 was higher (444.54 mm/season) compared with that of 80, 60 and 40% of crop evapotranspiration (ETc) for T2, T3 and T4, respectively, where it was 424.65, 392.20 and 320.19 (mm/season), receptively.
The total yield varied between 4.48 to 3.13 ton ha-1. Higher grain yield was weighted in control treatment (T1), while lower grain yield per plant was attained in T4 treatments. T1 and T2 treatments gave the same yield approximately; where there is no significant difference between them, so we recommend to use the treatment T2 in the new recent soil. In term of percentage, more decrease was recorded in T4 treatment by 30%, while less decrease by 5% in T2 treatment but in T3 treatment, the decrease percentage reached 18% when compared with the control.
WUE ranged from 0.88 to 1.54 kg m-3 under the irrigated treatments. There was increase in the WUE with increasing water stress of the used irrigation water from T1 up to T3 but the highest increase appeared with treatment T4. The obtained WUE followed the order of: T4 > T3 > T2 > T1.
The values of IWUE and WP were 0.64, 0.76, 0.87 and 1.12 kg m-3 and 1.02, 1.21, 1.39 and 1.75 for T1, T2, T3 and T4 treatments respectively.
Plant height of wheat was measured in cm and the highest value of plant height was obtained in control treatment (T1), while lower grain yield per plant was attained in T4 treatment.
Emission uniformity of the trickle irrigation system under study was (92.02%), it classified as ”excellent”
Neutron scattering technique helps more to study the water movements in the soil profile.