Available online xxxKeywords: Evapotranspiration Growing degree days Spring wheat WUE HUE Neutron probe a b s t r a c t Estimation of actual evapotranspiration (ET a ) is an important part of agricultural water management in local and regional water balance studies. At the field scale, ET a is important in irrigation planning and scheduling and is an integral part of field management decision support tools. The conventional approach of estimating actual evapotranspiration is difficult and needs more calculations and extensive data on soil-plant-atmosphere. A field experiment was conducted to simplify the measurement and calculation of actual evapotranspiration by using thermal units (heat units) for spring wheat crop under trickle irrigation system in sandy soil. Two irrigation methods were applied; the first one (A) using the crop evapotranspiration (ET c ) that depends on whether parameters, and the second (B) is the depletion from field capacity which dependent on soil parameters. Three varieties of wheat namely Sids12, Misr2 and Gemmeza10 were cultivated on sand soil and treatments arranged in complete randomized block design with three replicates. Application of treatment (B) resulted in highly significant increase in yield production of Gemmeza10 and Misr2 as compared to treatment (A). Grain yield of different wheat varieties grown under treatment (B) could be ranked in the following descending order: Misr2 > Gemmeza10 > Sids12. While under treatment (A) it could be arranged in the following descending order: Misr2 > Sids12 > Gemmeza10. On the other hand, the overall means indicated non-significant difference between all wheat verities. The highest values of water and irrigation use efficiency as well as heat use efficiency were obtained with treatment (B). The equation used in the present study is available to estimate ET a under arid climate with drip irrigation system. journal h omepage: http :/ / www .e lsev ie r. co m/ lo cate/ j rras 1

This work aims to study soil moisture behavior in sandy soil under drip irrigation system in order to control the management in sandy soil using neutron scattering technique. Studying soil moisture distribution through the soil profile is important to management the irrigation water, to achieve the maximum benefit from irrigation water. To achieve this aim, an experiment was carried out at the farm of Soil and Water Department, Nuclear Research Center, Atomic Energy Authority, Inshas (latitude longitude 30˚ N longitude 31˚ E), during onion growing season (2008/2009). Drip irrigation system was used for applying irrigation water. The uniformity of emitters' water application was checked to judge the system. Data showed that it's possible to use the combination work between neutron scattering technique and soil moisture retention models to study the direction of soil water movement within sandy soil profile. As well as predicting some soil plant concepts (i.e., active rooting depth and depth of collective active roots for water absorption); these concepts used to determine evapotranspiration, drainage rate and active rooting zone. Detecting total hydraulic potential within the wet area around the dripper along dripper lines and between lateral lines helps to study the behavior of soil moisture values within soil profile. The obtained data show also that the actual evapotranspiration of onion plant differs from site to site in wet area according to soil moisture availability. Surfer computer program also shows soil profile can be classified into different areas after and before irrigation within the wet area around drippers.