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Öğe Evapotranspiration of orange trees in greenhouse lysimeters(Springer, 2003) Yang, SL; Aydin, M; Yano, T; Li, XEight-year-old Murcott orange trees (Citrus sinensis (L.) Murcott) grown in greenhouse lysimeters filled with sandy soil were used to investigate seasonal variations in daily and hourly evapotranspiration. The study was conducted in Japan during the summer of 2000 and the winter of 2001. Weighing lysimeters of 1.5 in diameter and 1.6 in depth (three replications) planted with a tree were irrigated when average soil moisture in 0-120 cm of soil depth was depleted to below 70% of the field capacity (FC). Evapotranspiration (ET) showed significant seasonal variations. Average ET rate exceeded 4.4 mm/day in the summer period, and dropped to 0.6 mm/day in the winter months. The average seasonal crop coefficient (KC) was 0.91 and 0.75 during the summer and winter periods, respectively. Hourly variations in ET exhibited a time difference with season. The time of maximum ET was 0900 hours for winter and 1200 hours for summer; Moreover, some evaporative losses of soil water occurred even during the night in both summer and winter seasons. Soil evaporation (E) was 33% of ET during the winter period; while E was only 11% of ET during summer. Maximum water uptake by the trees was found at a depth of 30-60 cm, and soil water depletion was observed in the 0-120 cm depth of the profile during the summer period. However, during the winter season, water depletion occurred only from 0-30 cm depth of the soil profile.Öğe Short term effects of saline irrigation on evapotranspiration from lysimeter-grown citrus trees(Elsevier, 2002) Yang, SL; Yano, T; Aydin, M; Kitamura, Y; Takeuchi, SEight-year-old Murcott orange trees grown in greenhouse lysimeters filled with sandy soil were subjected to irrigation with saline water to investigate the influence of salinity on daily evapotranspiration (ET). The study was conducted in Japan from 1 August to 15 September 2000. The study duration was divided into three periods of about 2 weeks each. In period I, all lysimeters. planted with a tree were irrigated with 60 mm of non-saline water at the water content of 70% of field capacity (FC). Salinity treatments for period II started on 14 August. The treatments during period II were as follows: Lysimeter 1 (L1) had 32 nun non-saline water with an electrical conductivity (EC1) of 1.0 dS/m applied. At the same time Lysimeter 2 (L2) had 32 mm of saline water with an EC1 of 8.6 dS/m applied when the water content decreased to 70% of FC. Lysimeter 3 (L3) had 16 mm saline water (EC1 = 8.6 dS/m) applied at 85% of FC. The irrigation amounts during period II were equal to those corresponding to 1.2 times of water required to reach FC. Treatments in period III were the same as in period I. Daily ET was similar for all weighing lysimeters during period 1, The average relative ET for L2 and L3 with respect to L1 (L2/L1 and L3/L1) were similar during this period, with a mean value of 0.99. During period II. ET from L1 was consistently higher than that from L2 and L3. In addition, L3 with a higher irrigation frequency because of irrigation at higher soil water content resulted in higher ET than L2. The average relative ET of period II was 0.71 and 0. 88 for both L2 and L3, During the last half of period III, reductions occurred in the ET differences between the saline treatments (L2 and U) and non-saline control (L1). Evaporation rates from soil did not exceed 0.7 mm per day. Transpiration rates from L1. L2 and L3 during period II varied between 6.3 and 3,1 mm per day. 4.5 and 2.2 mm per day, and 5.8 and 3.0 mm per day, respectively. The results reflected a tangible difference of water extraction by roots from individual soil layers. Maximum water uptake by these trees was observed at layer of 30-60 cm. Nevertheless. no clear differences in water extraction pattern between trees were observed. Approximately, 95% of drainage occurred during the first 2 days following irrigation. The electrical conductivity of soil water (ECs) and the electrical conductivity of drainage water (ECD) for the saline water treatments (L2 and L3). compared to the control (L1) were significantly different during period II. ECs values were 2-5 times higher in saline treatments compared to the control treatment. After irrigating trees with saline water. ECs increased from 5 to 14 and 16 dS/m in L2 and L3, respectively. Similarly, in both saline treatments. ECD values were greatly increased after irrigation. During period III, ECD values increased from 5 to 8 dS/m in L2, and from 3 to 11 dS/m in L3. By contrast. ECs declined from 14 to 5 dS/m in L2. and from 16 to 3 dS/m in L3 over the same period. (C) 2002 Elsevier Science B.V All. rights reserved.Öğe Test of a simple model for estimating evaporation from bare soils in different environments(Elsevier Science Bv, 2005) Aydin, M; Yang, SL; Kurt, N; Yano, TA simplified model originally proposed by Aydin [Aydin, M., 1998a. A new model for predicting evaporation from bare field soil. In: Proceedings of the International Symposium and second Chinese National Conference on Rainwater Utilization, Xuzhou-Jiangsu, China, pp. 283-287] for estimating actual evaporation from bare soils was tested under different environmental conditions. Field experiments were carried out on clay soils in a semi-arid region of Turkey. A sandy soil column-experiment in a drying chamber and a study with the same sand media in a greenhouse were conducted at Arid Land Research Center, Tottori University, Japan, in order to test the performance of the model. The model is based on the relations among potential and actual soil evaporation and soil-water potential at the top surface layer of the soil, with some simplifying assumptions. Input parameters of the model are simple and relatively obtainable viz. climatic parameters for the calculations of potential soil evaporation and matric potential measured near the soil surface. Despite some differences between calculated and measured soil evaporation, the agreement was reasonable at all sites. This agreement seems to support the model assumptions, and the model is potentially valuable, but the objective measurement of soil-water potential near the surface of the profile is difficult, especially for a drier upper layer. (C) 2004 Elsevier B.V. All rights reserved.
