Groundwater uptake and sustainability of farm plantations on saline sites in Punjab province, Pakistan
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Keywords:
Eucalyptus camaldulensis
Soil salinity control
Saline water
Soil salinity control
Water use
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Saline water
Soil salinity control
Dryland salinity
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Water table management in irrigated areas may increase shallow groundwater use by crops. But the high salt content of groundwater results in faster buildup of salinity in crop root zone,which in turn affects leaching schedule of the irrigation districts. Based on general salt and water balance in crop fields in irrigated areas, a simplified model was proposed in this paper to calculate leaching cycle for crops that use shallow groundwater at different water table depth, considering the salt accumulation process in root zone of crops. Subsequently,leaching cycles were calculated for two study sites with soil salinity measurements. For the case study in a semi-arid irrigation area,under the current irrigation scheduling and the average rainfall condition,the calculated leaching cycle for cotton fields is 100 days for water table depth at 1 m and 140 days for water table depth at 1.5 m with the groundwater salinity maintained at 4.43 g/L;when the water table depth is greater than 2 m,the calculated leaching cycle is longer than the growing period. In another case study in an arid irrigation area with saline groundwater buried at 1.5 m deep,the calculated leaching cycle for plastic mulched and drip irrigated cotton is 78 days,applying slightly saline irrigation water with salinity of 2.81 g/L. These results indicate that managing water table depth under controlled drainage practice may increase crop use of shallow groundwater that contains dissolved salts, the rate of salinity buildup, however, is relatively slow, leaving a time window for making proper leaching schedule. The results from this study provide theoretical reference for salinity management in irrigated agricultural regions that adopt controlled drainage technique.
Soil salinity control
Saline water
DNS root zone
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Saline water
Water potential
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Abstract Understanding the long‐term soil water and salt balances in coastal salt‐affected farming areas is important for developing appropriate management practices, controlling salinization and maximizing crop production. An integrated spatial agro‐hydro‐salinity model (SahysMod) was employed to analyse water and salt balances of rainfed salt‐affected farmland. The model was calibrated using the observed soil and groundwater data, and the potential influence of various field management practices on rootzone salinity and groundwater properties was simulated using the calibrated model. Results revealed that rootzone soil salinity (EC e ) generally decreased at an annual average rate of 2.2 dS m −1 under existing conditions, and the decreasing rate of rootzone salinity ranged from 1.9 to 2.7 dS m −1 yr −1 under the other scenarios. Practices including subsurface drainage systems and plastic film mulching were suggested for managing soil salinity and stabilizing the groundwater table. Irrigation with brackish water in the dry season was not recommended since it increased soil and groundwater salinity in comparison with existing conditions. It was concluded that subsurface drainage was the most high‐efficient approach for salt leaching, whereas plastic film mulching was more economic and effective to control soil and groundwater salinization when considering the additional cost and environmental effects. Copyright © 2017 John Wiley & Sons, Ltd.
Soil salinity control
Dryland salinity
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Soil salinity control
Well drainage
Drainage system (geomorphology)
Table (database)
Watertable control
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Root zone salinity is one of the major factors adversely affecting crop production. A saline shallow water table can contribute significantly to salinity increases in the root zone. A soil salinity model (LEACHC) was used to simulate the effects of various management alternatives and initial conditions on root zone salinity, given a consistently high water table. The impact of water table salinity levels, irrigation management strategies, soil types, and crop types on the accumulation of salts in the root zone and on crop yields was evaluated. There were clear differences in soil salinity accumulations depending upon the depth and salinity of the water table. In general, increasing water table depth reduced average soil profile salinity, as did having lower salinity in the water table. Among the four irrigation strategies that were compared, the 14-day irrigation interval with replenishment of 75% of evapotranspiration (ET) resulted in the lowest soil salinity. With a 4-day interval and 50% ET replenishment, a wheat yield reduction of nearly 40% was predicted after three years of salt accumulation. Soil type and crop type had minimal or no impact on soil salinity accumulation. Under all conditions, soil water average electrical conductivity increased during the 3-year simulation period. This trend continued when the simulation period was extended to 6 years. Under the conditions shown to develop the highest average soil salinity (high water table, low irrigation), an annual presowing irrigation of 125 mm caused a nearly 50% reduction in soil salinity at the end of the 6-year simulation period, as compared with the soil salinity given no presowing irrigation.
Soil salinity control
DNS root zone
Dryland salinity
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