Deficit Irrigation Using Saline Water of Fruit Trees under Water Scarcity Conditions of Southern Tunisia

Both water scarcity and salinity are major obstacles for crop production in arid parts of Tunisia and require adoption of strategies aimed at improving water-use efficiency. Field experiments on deficit irrigation (DI) of table olive, orange trees, and grapevines with saline water (2 dS m  1) were conducted in the arid region of M denine, Tunisia. Three irrigation treatments were compared with the farmer’s method (FM) over two years (2013–2014): deficit irrigation (DI75) and (DI50), which received 75% and 50% less water than full irrigation (FI), respectively, and full compensation of the crop evapotranspiration (FI). Measurements included seasonal changes in soil water content, soil salinity, yield, fruit quality, and economic return. Results showed that in-season water limitations, roughly between 700–250 mm, caused significant reductions in yield and fruit weight, but improved the total soluble solids of fruits. Under FI, DI75, DI50, and FM, average yields were 26.6, 20.1, 14.7, and 21.2 t ha  1 for orange, 4.5, 4.0, 3.1, and 3.5 t ha  1 for table olive, and 3.8, 3.4, 3.1, and 3.5 t ha  1 for grapevine, respectively. Soil salinity build up increased linearly with decreasing irrigation water. Irrigation water productivity (IWP), although lowest for FM, was relatively high (3.30–4.30 kg m  3 for orange, 0.65–1.20 kg m  3 for table olive, and 0.74–1.30 kg m  3 for grapevine). Economic evaluation showed that the FI strategy generated the greatest net income (1800–6630 USD ha  1), followed by DI75 (1350–3940 USD ha  1), FM (844–4340 USD ha  1), and DI50 (600–2400 USD ha  1). The results show an important potential for reasonably sustaining farmer’s income under increased water scarcity

Saline water use for vegetable crops production in smallholders farms

Field studies on saline water use (6 dS/m) for carrot, lettuce and pepper production in smallholder's farms were conducted in the arid region of Medenine-Tunisia. The irrigation regimes were full (FI) and deficit (DI-80, DI-60, FI-DI60) irrigated with levels of 100, 80 and 60% of ETc when 40% of total available water in the root zone in the FI treatment was depleted, and farmer method (Farmers). Results show that the greatest values of soil salinity were observed under farmer and DI-60 treatments. Relatively low ECe values were also recorded under FI-DI60 and DI-80 treatments. The highest mean yields of carrot (26.8-28.7-29.5 t/ha), lettuce (42.6-45.8 t/ha) and pepper (22.3-24.4 t/ha) were recorded for the FI treatment who is not significantly different with the FI-DI60 and DI-80 treatments. Compared with FI100, significant reductions in carrot, lettuce and pepper yields were observed under the DI60 and farmers treatments resulting from a reduction in yield components. The farmer’s method increased soil salinity and resulted in an increase of water use of 43-57% for carrot, 26-29% for lettuce and 11.5-16% for pepper. Water productivity (WP) values reflected the differences in yields and varied between 3.4 (Farmers) and 9.7 kg/m3 (DI-80) for carrot, 7.5 and 19.1 kg/m3 for lettuce and 2.4 and 5.5 kg/m3 for pepper across different years and treatments. The soil water balance-based irrigation method (FI) generated the greatest net income compared to the Farmers treatment in carrot, lettuce and pepper productions under arid environment and the lowest soil salinization. FI scheduling technique is suggested for optimizing saline water use for vegetable crops. Under water scarcity, the adoption of the FI-DI60 and DI-80 strategies results in 4.5 to 20% water savings as compared to FI with small impact on salinity in the root zone and yield and net income reductions

Здійснення адміністративно-територіальних реформ у місцях компактного проживання німців Криму в 20-30-х роках ХХ ст.

Статтю присвячено вивченню національної політики більшовиків у Криму на прикладі німців. Розкрито історію формування національних районів і селищних рад. Окремо розглянуто проведення більшовиками кадрової політики, динаміку розширення мережі національних сільських рад, проблеми переведення діловодства на німецьку мову. Показано, як сприймали німці національну політику радянської влади.Статья посвящена изучению национальной политики большевиков в Крыму на примере немцев. Раскрыта история формирования национальных районов и сельских советов. Отдельно рассмотрено проведение большевиками кадровой политики, динамику расширения сети национальных сельских советов, проблемы перевода делопроизводства на немецкий язык. Показано, как воспринимали немцы национальную политику советской власти.The article is devoted to the study of the national policy of the Bolsheviks in the Crimea on the example of the Germans. Reveals the history of the formation of national and rural councils. Separately, the Bolsheviks considered the holding of personnel policy, the dynamics of the expanding network of national rural councils, the problems associated with the transfer of proceedings in the German language. We show how Germans perceive the national policy of Soviet power

Impacts of irrigation regimes with saline water on carrot productivity and soil salinity

A three-year study was conducted to evaluate the effects of different irrigation regimes with saline water on soil salinity, yield and water productivity of carrot as a fall-winter crop under actual commercial-farming conditions in the arid region of Tunisia. Carrot was grown on a sandy soil and surface-irrigated with a water having an ECi of 3.6 dS/m. For the three years, a complete randomized block design with four replicates was used to evaluate five irrigation regimes. Four irrigation methods were based on the use of soil water balance (SWB) to estimate irrigation amounts and timing while the fifth consisted of using traditional farmers practices. SWB methods consisted in replacement of cumulated ETc when readily available water is depleted with levels of 100% (FI-100), 80% (DI-80) and 60% (DI-60). FI-100 was considered as full irrigation while DI-80 and DI-60 were considered as deficit irrigation regimes. Regulated deficit irrigation regime where 40% reduction is applied only during ripening stage (FI-DI60) was also used. Farmer method (Farmer) consisted in giving fixed amounts of water (25 mm) every 7 days from planting till harvest. Results on carrot production and soil salinization are globally consistent between the three-year experiments and shows significant difference between irrigation regimes. Higher soil salinity in the root zone is observed at harvest under DI-60 (3.1, 3.4, 3.9 dS/m, respectively, for the three years) and farmer irrigation (3.3, 3.6, 3.9 dS/m) treatments compared to FI-100 treatment (2.3, 2.6 and 3.1 dS/m). Relatively low ECe values were also observed under FI-DI60 and DI-80 treatments with respectively (2.7, 3, 3.5 dS/m) and (2.5, 2.9, 3.3 dS/m). ECe values under the different irrigation treatments were generally lower than or equal to the EC of irrigation water used. Rainfall received during fall and/or winter periods (57, 26 and 29 mm, respectively, during the three years) contributed probably to leaching soluble salts from the root zone. Highest carrot yields for the three years were obtained with SWB scheduling technique FI-100, (29.5, 28.7 and 26.8 t/ha) although we didn’t find significant differences with the regulated deficit irrigation regime (FI-DI60). Compared to FI-100, significant reductions in carrot yields were observed under DI-80 and DI-60 deficit irrigation treatments resulting from a reduction in roots number/m2 and average root weight. The farmer’s method not only caused significant reductions in yield but also resulted in using 43–57% more water and increased soil salinity. For all irrigation treatments, carrot yields were higher in the first year compared to the two following years. Water productivity (WP) values reflected this difference and varied between 3.2 and 9.7 kg/m3. The lowest WP values were observed for the farmer’s method, while the highest values were obtained under DI-60 deficit irrigation treatment. The scheduling technique using SWB with variable doses is more efficient than the traditional technique used by farmers in carrot production. The FI-100 irrigation scheduling seems to optimize the use of saline water in carrot production and to control soil salinity. Under situations of water shortage, adopting deficit irrigation strategies (FI-DI60 and DI-80) could be an alternative for irrigation scheduling of carrot crop under the conditions of Mediterranean arid in southern Tunisia

Effects of surface and subsurface drip irrigation regimes with saline water on yield and water use efficiency of potato in arid conditions of Tunisia

Field experiments were conducted on a sandy soil during spring of 2009 and autumn of 2010 in southern Tunisia for evaluating the effects of two drip irrigation methods and three irrigation regimes on soil moisture and salinity, yield and water use efficiency of potato (Solanum tuberosum L.). The surface drip (SDI) and subsurface drip (SSDI) irrigation methods were used. Irrigation regimes consisted in replacement of cumulated ETc when readily available water is depleted with levels of 100% (FI100), 60% (DI60) and 30% (DI30). FI100 was considered as full irrigation while DI60 and DI30 were considered as deficit irrigation regimes. Well water with an ECi of 7.0 dS/m was used for irrigation. Findings are globally consistent between the two experiments. Results show that soil moisture content and salinity were significantly affected by irrigation treatments and methods. Higher soil moisture content and lower soil salinity were maintained with SSDI than SDI for all irrigation treatments. For both irrigation methods, higher salinity and lower moisture content in the root zone are observed under DI60 and DI30 treatments compared to FI100. Potato yields were highest over two cropping periods for the SSDI method although no significant differences were observed with the SDI. Irrigation regimes resulted in significant difference in both irrigation methods on yield and its components. Yields were highest under FI100. Compared to FI100, considerable reductions in potato yields were observed under DI60 and DI30 deficit treatments resulting from a reduction in tubers number/m² and average tuber weight and size. Water use efficiency (WUE) was found to vary significantly among irrigation methods and treatments and varied between 5.9 and 20.5 kg/m3. WUE of SSDI method had generally higher values than SDI. The lowest WUE values were observed for the FI100 treatment, while the highest values were obtained under DI30 treatment for both methods. SSDI method provides significant advantage on yield and WUE and reduces the soil salinity compared to the SDI in potato production under experimental conditions. The SSDI and FI100 irrigation techniques seem to optimize the use of saline water in potato production and to control soil salinity. Under situations of water shortage, adopting deficit irrigation treatment (DI60) could be an alternative for irrigation scheduling of spring and autumn potato under the arid conditions of southern Tunisia

Soil salinity under deficit drip irrigation of potato and millet in in an arid environment

The influence of deficit irrigation (DI) with saline water on soil salinity in a drip-irrigated potato and millet fields was investigated. We had compared proportional soil salinity developed under Full and DI under drip irrigation. For both experiments, the treatments were (1) Full, control treatment where rooting zone soil water content was increased to field capacity at each irrigation; (2) DI80; (3) DI60 and DI40; 20, 40 and 60% deficit irrigation compared to Full treatment were applied, respectively. Soil salinity was assessed using the isosalinity maps constructed with grid soil sampling of plant root zone at harvest. Results show that high spatial variability was observed in salinity along soil profiles when applying saline water with drip irrigation for potato. For the DI40 and DI60 treatments, high soil salinity was recorded in the upper soil layer close to the emitter. Increase of soil salinity within soil depths of 30 cm or below was also observed under DI60 and DI40 treatments. The lowest increase was noted under the full treatment. Surface soil salinity was somewhat higher under DI60 and DI40 compared with that of full and DI80 irrigation treatments. The distribution of salts around the dripper changes during the crop season according to applied irrigation treatments, with overall higher concentrations between the drippers and towards the margin of wetted band. Iso-salinity maps at harvest of potato showed that the surface layer of 30 cm depth had the lowest salinity which gradually increased at deeper zones irrespective of the treatment. Salt accumulation essentially occurred at wetting front between the drippers and the plant row. Although salt accumulation was relatively highest along the row under DI treatments, the area of accumulation was relatively shifted toward the center between the rows and the drip line. The results also show the importance of the potato cropping season to benefit from the leaching of soluble salts with the received rainfall. For millet experiments, salinity was lowest under emitters and highest midway to the margin of wetted bands and higher soil salinity was maintained in the root zone with deficit irrigation treatments than full irrigation. Millet and potato yields were highest under Full treatment. Yields decreased almost linearly when applied water was reduced. However, reduction in quality was significantly important for DI60 and DI40. The analysis outcome of the crops sensitivity to salt indicated respectively for autumn, winter and spring potato and millet crops that thresholds are close to the value calculated from published salt tolerance data (1.9, 1.55, 1.85 vs. 1.7 dS/m for potato and 3.46 vs. 3.65 dS/m for millet) but the slopes are considerably steeper (34, 54, 47 vs. 12%; 17 vs. 6.7%), apparently because of the combined effect of salinity and water stresses. The results provide information’s to farmers for formulating improved planning regarding irrigation management practices. The results support the practicality of using the full irrigation (100% of ETc) methodology to optimize irrigation with saline water for potato and millet production and to control soil salinity. Under situations of water shortage, the deficit irrigation strategy (DI80 and DI60) is recommended as a tool to schedule irrigation of potato and millet crops in arid regions of Tunisia

Impact of land use on soil water content in a hilly rainfed agrosystem : a case study in the Cap Bon peninsula in Tunisia

Understanding the temporal and spatial variability of soil moisture is fundamental for improving the management of water and soil resources on rainfed agrosystems. The present study focused on the soil moisture (SM) patterns observed in a hilly rainfed agrosystem. We analyzed five datasets from measurement at 15 sites during various crop growth cycles under the common cereals/legumes/pasture cropping systems within the Kamech catchment in Tunisia. Results indicated a strong seasonality in the precipitation and evapotranspiration dynamics that strongly influences soil moisture patterns, with a strong reduction in the water availability during summer (average SM = 0.20 m3/m3) as compared to winter (average SM = 0.40 m3/m3). The data of two consecutive years showed that the spatial variability, expressed through the coefficient of variation of soil moisture, was at its highest point during spring. The averaged soil moisture of the two years yielded a reasonable significant linear relation (R2=0.67**), indicating temporal stability of the spatial pattern. Actual evapotranspiration was found to be the predominant factor influencing the dynamics of soil moisture

Measuring crop evapotranspiration over hilly areas

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