scenarios with plastic and irrigation in alternate furrows showed a reduction in transpiration and yield, more water loss due to deep drainage, and less water lost due to evaporation. However, similar crop yields were obtained for this alternate furrow strategy as for the control furrow surface treatments. When only half the water was used for irrigation in this scenario, the reduction in yield was less than 20 % compared to the control treatments, producing higher water-use efficiency.
Soil salinity increases when growers are forced to use higher salinity irrigation waters due to water shortages. It is necessary to estimate the impact of irrigation water on soil properties and conditions for crop growth to manage the effects of salinity on perennial crops. Therefore, in this study, we monitored root zone salinity in five almond and pistachio orchards in eastern and western San Joaquin Valley (SJV), California (CA). Volumetric soil water contents and bulk electrical conductivities were measured at four root-zone depths. Evapotranspiration was measured by eddy covariance along with three other types of data. The first is seasonal precipitation and irrigation patterns, including the temporal distribution of rains, irrigation events, and irrigation water salinity. The second is soil chemistry, including the initial sodium adsorption ratio (SAR) and soil solute electrical conductivity (ECe). The third type is the physical properties, including soil type, hydraulic conductivity, and bulk density. As expected, we found low salinity at the eastern sites and higher salinity at the western sites. The western sites have finer textured soils and lower quality irrigation water; measured actual ET was about 90% of modeled crop ET. Across the three western sites, the annual average apparent leaching fraction ranged from 11 to 28%. At the eastern sites, measured ET almost exactly matched modeled crop ET each year. Apparent leaching fractions in the eastern sites were approximately 20%.
California is increasingly experiencing drought conditions that restrict irrigation deliveries to perennial nut crops such as almonds and pistachios. During drought, poorer quality groundwater is often used to maintain these crops, but this use often results in secondary salinization that requires skilled management. Process-based models can help improve management guidelines under these challenging circumstances. The main objective of this work was to assess seasonal soil salinity and root water uptake as a function of irrigation water salinity and annual rain amounts. The manuscript presents a comparison of three-year experimental and numerically simulated root zone salinities in and below the root zone of almond and pistachio drip-irrigated orchards at multiple locations in the San Joaquin Valley (SJV), California, with different meteorological characteristics. The HYDRUS-1D numerical model was calibrated and validated using field measurements of soil water contents and soil solute bulk electrical conductivities at four root zone depths and measured soil hydraulic conductivities. The remaining soil hydraulic parameters were estimated inversely. Observations and simulations showed that the effects of rain on root zone salinity were higher in fields with initially low salinities than in fields with high salinities. The maximum reduction in simulated root water uptake (7%) occurred in response to initially high soil salinity conditions and saline irrigation water. The minimum reduction in simulated water uptake (2.5%) occurred in response to initially low soil salinity conditions and a wet rain year. Simulated water uptake reductions and leaching fractions varied at early and late times of the growing season, depending on irrigation water salinity. Root water uptake reduction was highly correlated with the cumulative effects of using saline waters in prior years, more than salt leaching during a particular season, even when rain was sufficient to leach salts during a wet year.
Recently maintenance operation is considered one of the main axes of engineering management of pressurized irrigation systems. There for the aim of this research work was to select the most suitable maintenance programs to improve drip irrigation systems laterals performance, and decrease the damages caused by emitter clogging as a result of bad maintenance applications. The physical maintenance programs included lateral end flushing with two different operation times"5, 10 minutes at the end of each irrigation", at four interval times "weekly, Biweekly , monthly, and at the end of each season". The flushing 5minutes was applied once continuous, and the other intermitted. The systems performance was evaluated through three parameters: discharge, clogging, and pressure through seven evaluation criteria mentioned in the research. The results showed that biweekly flushing for 5 min. continuously (MS 1 P 1 2) proved to be the best flushing with fresh water program which decreases clogged emitters 44.21 % to be closer to the standard (control) with 4.85 %. Also partially clogged emitters decreased by 46.7 %, Emission uniformity(EU%) increased 19.4 %, and distribution uniformity(DU%) 13.9 % more than the control treatment. (MS 1 P 1 2) was followed by the weekly flushing for 10 min. continuously. (MS 3 P 1 1) as it raised (DU%) with 12.3 % and gave the highest value of pressure uniformity (UP%) that reaches 93.14%.
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