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- Bali, Khaled M., et al.
(författare)
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Nutrient and salinity management for spinach production under sprinkler irrigation in the low desert region of California
- 2021
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Ingår i: Irrigation Science. - : Springer Science and Business Media LLC. - 0342-7188 .- 1432-1319. ; 39:6, s. 735-749
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of irrigation, as well as optimization of nutrients, affect spinach yield in all growth stages. In this study, the sensitivity of spinach (early and mature yields) to shallow saline groundwater and the effect of fertigation treatments on mature yield were experimentally investigated. The sprinkler irrigation experiments were conducted on 0.47 ha of silty clay soil at the University of California Desert Research and Extension Center (DREC) in Imperial Valley, California. Twelve beds in the experimental field were chosen randomly to investigate the effect of three fertigation treatments on spinach yield. Three rates of urea ammonium nitrate (UAN-32) fertilizer; T1: 200 kg ha−1 (150%), T2: 133.3 kg ha−1 (100%), and T3: 66.7 kg ha−1 (50%) in four replicates were applied. Soil samples to depths of up to 120 cm were collected at baby leaves and mature harvesting dates (17th October and 19th November 2019, respectively) for salinity measurements. Additionally, soil matric potential through the 120 cm soil depth was measured and groundwater levels in five observation wells were recorded during the growing season. Results showed that average soil salinity at baby leaves harvesting stage through the top 60 cm active root zone depth ranged from 0.61 to 1.48 dS m−1, which is lower than the spinach salinity threshold limit (2 dS m−1), while the average groundwater depth was 1.90 m with salinity ranging from 6.35 to 10.60 dS m−1. Correlation analysis showed that the baby spinach leaves yield was weakly correlated (r = 0.40) to the average soil salinity in the top 60 cm soil depth. Although groundwater and top 60 cm soil salinity showed an increase at the mature yield harvesting stage, the mature yield was weakly correlated to soil salinity (p = 0.116). As the UAN-32 rate increased, the mature spinach yield increased. The mature spinach yields were 17.31, 14.00, and 12.54 ton ha−1 for T1, T2, and T3 fertigation treatments, respectively. However, only a 10% reduction in yield occurred in T3 treatment corresponding to a 50% reduction in UAN-32 rate by 66.7 kg ha−1. Based on the results of this study, shallow saline groundwater has little impact on spinach yield. In addition, the 50% increase in UAN-32 rate had a significant impact on mature spinach yield. The 150% UAN-32 rate resulted in an increase in spinach yield and could be used in arid and semiarid regions with similar conditions to the Imperial Valley but additional measures to minimize the leaching of nitrate from the root zone and to reduce the load of nitrogen in drainage water are needed to minimize the potential negative impact of over-fertigation on the environment.
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- Dile, Yihun Taddele, et al.
(författare)
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Hydrological Response to Climate Change for Gilgel Abay River, in the Lake Tana Basin - Upper Blue Nile Basin of Ethiopia
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:10
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is likely to have severe effects on water availability in Ethiopia. The aim of the present study was to assess the impact of climate change on the Gilgel Abay River, Upper Blue Nile Basin. The Statistical Downscaling Tool (SDSM) was used to downscale the HadCM3 (Hadley centre Climate Model 3) Global Circulation Model (GCM) scenario data into finer scale resolution. The Soil and Water Assessment Tool (SWAT) was set up, calibrated, and validated. SDSM downscaled climate outputs were used as an input to the SWAT model. The climate projection analysis was done by dividing the period 2010-2100 into three time windows with each 30 years of data. The period 1990-2001 was taken as the baseline period against which comparison was made. Results showed that annual mean precipitation may decrease in the first 30-year period but increase in the following two 30-year periods. The decrease in mean monthly precipitation may be as much as about -30% during 2010-2040 but the increase may be more than +30% in 2070-2100. The impact of climate change may cause a decrease in mean monthly flow volume between -40% to -50% during 2010-2040 but may increase by more than the double during 2070-2100. Climate change appears to have negligible effect on low flow conditions of the river. Seasonal mean flow volume, however, may increase by more than the double and +30% to +40% for the Belg (small rainy season) and Kiremit (main rainy season) periods, respectively. Overall, it appears that climate change will result in an annual increase in flow volume for the Gilgel Abay River. The increase in flow is likely to have considerable importance for local small scale irrigation activities. Moreover, it will help harnessing a significant amount of water for ongoing dam projects in the Gilgel Abay River Basin.
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