Recent prolonged droughts in California have emphasized the urgent need to implement more efficie... more Recent prolonged droughts in California have emphasized the urgent need to implement more efficient water management practices for high value tree crops. Accurate estimation of evapotranspiration (ET), a main component of consumptive water use, is critical for improving management of micro-irrigated pistachio orchards grown in the San Joaquin Valley of California. We estimated ET of three mature commercial pistachio orchards on non-saline and increasingly saline soils in 2015 and 2016, using the Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) method and Landsat 8 satellite observations. Based on a comparison with field observations at 8 sites, we modified the parameterizations of the momentum roughness length and net radiation for pistachio tree crops and reduced the uncertainty of daily ET estimates. When compared with field data, the recalibrated METRIC ET estimates had an R 2 of 0.59, a mean absolute error of 1.1 mm/day, and a RMSE of 1.4 mm/day during Landsat overpass dates (n = 72). The METRIC ET map captured the temporal dynamics and spatial heterogeneity both within and among the orchards. The mean annual crop season estimated ET (mid-March to mid-October in 2016) with remote sensing decreased by 32% from 1064 ± 99 mm in the non-salt affected control orchard to 725 ± 82 mm in the orchard with the highest level of soil-water salinity. The ET reduction was consistent with canopy volume differences among the study orchards, as shown by summer Normalized Difference Vegetation Index (NDVI) from Landsat observations, e.g., 0.72 ± 0.06 in the control vs. 0.52 ± 0.06 in the most saline orchard. The available energy was controlled mostly by canopy features and explained 64% of daily ET variation among all Landsat pixels and satellite overpass days. The normalized differenced water index (NDWI) could be considered as an important parameter to capture the partitioning of available energy for ET (R 2 = 0.38), suggesting that the lower soil osmotic potential in saline orchards further reduced crop ET. California's Central Valley, an area of about 155,000 km 2 , is among one of the world's most productive agricultural regions. A total of 101,327 bearing hectares (1180 km 2 ) of pistachios generated an overall production of 448,000 metric tons and a $1.5 billion in revenue in 2016 (California Department of Food and Agriculture (CDFA), 2016). Approximately 95% of the US commercial pistachios are produced in the San Joaquin Valley. In the last decades, pistachio acreage expanded largely to areas with saline soils previously used for cotton . Soil salinity is a known constraint on agricultural production in the Central Valley, particularly in the western San Joaquin Valley, where soils are naturally high in salts due to the marine origin of their Coastal Range alluvium parent material . Although the need of subsurface drainage was long understood for these agricultural production areas, it failed to materialize due to lack of collective actions
nonirrigated ice plants were close to ambient air temperature. Hence, the leaf temperature method... more nonirrigated ice plants were close to ambient air temperature. Hence, the leaf temperature method of measuring stress would not be useful in most areas of California where wind velocities are frequently greater than 5 mph unless the relationship between wind velocity and leaf temperature were known with some precision. Xylosma foliage, further above the ground, with thinner leaves that dissipate heat by conduction and convection more rapidly than those of ice plant, were only 10°F warmer than the surrounding air when air movement was less than 5 mph.
A model has been developed to determine how the electrical conductivity of a given irrigation wat... more A model has been developed to determine how the electrical conductivity of a given irrigation water supply affects crop production while taking annual rainfall into account. The model builds upon the principles and assumptions described by Ayers and Westcot (1985) and relates the electrical conductivity of the irrigation water (ECw) to the seasonal average rootzone salinity, expressed as the electrical conductivity of the saturated paste (ECe). The model considers the timing and quantity of applied irrigation water, the quantity and distribution of rainfall, and realistic assumptions related to soil water principles based on soil type. The program can be used to either quantify the extent by which an irrigation water supply with a given EC would decrease the yield potential for a given crop under sitespecific conditions or to determine the maximum EC of an irrigation water supply, that if used as the sole source of irrigation water over the long term, is fully protective of crop pro...
Three devices that physically treat irrigation water were tested in the laboratory and the field.... more Three devices that physically treat irrigation water were tested in the laboratory and the field. Results of these experiments indicate these water conditioners were ineffective in increasing the infiltration rate of water into the soil or in preventing calcium carbonate precipitates from clogging drip emitters under the conditions in which they were tested.
Irrigation management can have a profound influence on olive oil production. We initiated a 2-yea... more Irrigation management can have a profound influence on olive oil production. We initiated a 2-year study in the spring of 2002 to identify the optimal level of applied water on a super high tree-density (spacing 1.5 m  3.9 m) olive (Olea europaea L.'Arbequina I-18') orchard. Irrigation water was applied by drip irrigation to produce different
L. Ferguson*, B. Sanden*, S. Grattan**, H.C. Reyes***, C. Wilson**** and E. Cross**** *Department... more L. Ferguson*, B. Sanden*, S. Grattan**, H.C. Reyes***, C. Wilson**** and E. Cross**** *Department of Pomology, UCD @ Kearney Agricultural Center, 9240 S Riverbend Avenue, Parlier, CA 93648, USA **Department of Land, Air and Water Resources, UCD @ Kearney Agricultural Center, 9240 S Riverbend Avenue, Parlier, CA 93648, USA ***Department of Pomology, UCD @ Kearney Agricultural Center, 9240 S Riverbend Avenue, Parlier, CA 93648, USA ****United States Department of Agriculture (USDA-ARS), Soil Salinity Laboratory, 450 Big Springs Road Riverside, Riverside, CA 92507-4617, USA
Pistachio acreage is rapidly expanding in California thanks to its economic profitability and cap... more Pistachio acreage is rapidly expanding in California thanks to its economic profitability and capacity to grow and produce in salt-affected soils. Our team at University of California is updating information on actual water use (ET) of mature pistachio orchards grown on saline soils under micro-irrigation methods. Actual Evapotranspiration (ETa) and Crop Coefficients (Ka) were determined for the 2015 and 2016 crop seasons on four pistachio orchards grown in the San Joaquin Valley (SJV) on grounds with increasing levels of soil-water salinity, using the residual of energy balance method with a combination of eddy covariance and surface renewal equipment. Tree canopy cover, light interception, and plant water status across the orchards were also measured and evaluated. Our preliminary results show that salinity strongly affects the tree water use, resulting in 10-30% less ET for medium to high salt-affected soils. Salinity also showed a strong effect on tree water status and light int...
This article presents findings from a field research study conducted in the San Joaquin Valley of... more This article presents findings from a field research study conducted in the San Joaquin Valley of California in 2016–2018 to appraise the effects of soil salinity and sodicity on evapotranspiration and energy balance components of micro-irrigated pistachio orchards. Actual evapotranspiration (ETa) and tree physiologic parameters were measured during consecutive growing seasons in mature orchards grown on non-saline and saline/sodic soils. Salinity and sodicity decreased pistachio water use by about 30%, with ETa reductions varying along the growing season. Accurate information on the dynamics of ETa and energy balance components along the growing season can improve water management for nut orchards exposed to long-term saline-sodic conditions. Results show that the main driver of ETa was the net radiation (Rn), which supplied most of the energy to vaporize water, irrespective of the growth period and level of salinity/sodicity. Field observations revealed that Rn was lower for salt-affected trees due to smaller canopies, which intercepted less light than non-saline trees. Secondarily, the exchange of sensible heat (H) between the ambient air and tree canopies was affected by the interaction between salinity–sodicity and seasonality. Early in the season, salinity and sodicity affected ETa mainly through the reduced canopy growth, which decreased the available energy (Rn–G) for ETa and reduced the water uptake as a result of the lower soil water potential. Late in the season, an increase in H and a decrease in the contribution of the aerodynamic component (β coefficient) to the latent heat flux (LE) occurred, which determined a further reduction of ETa due to a physiological response. The decrease in the β coefficient during the late season was associated with a direct impact of ion accumulation on leaf functionality. Collecting data on the contribution of the aerodynamic component to LE offers a low-cost method to detect and quantify physiological stress, while providing useful information for managing irrigation in salt-affected orchards. The results presented in this article provide insights to improve irrigation management of salt-affected pistachio through integration of weather measurements, energy balance components, and plant-based parameters.
S oil salinity is an important stress affecting irrigated crops in many areas of California. This... more S oil salinity is an important stress affecting irrigated crops in many areas of California. This stress is often exacerbated during drought years. Over time, salts can accumulate in the soils as crops extract water, leaving the salts behind in the root zone. Without sufficient leaching, accumulated salts will eventually reach a level that will damage crops. Even if irrigation water is low in salinity, salts will eventually build up in the soil to damaging levels without sufficient leaching from rainfall or excess irrigation water. Under drought conditions, high-quality surface water supplies may not be available in sufficient quantities to meet crop needs and may be supplemented or completely replaced with poorer-quality ground or surface water. Ironically, irrigation water higher in salinity will require more water in order to maintain the same level of soil salinity; that is, poorer-quality water requires more leaching. But regardless of the quality of the water applied, deficit irrigation combined with poor quality water will exaggerate the salinity problem. All soils and irrigation water contains dissolved salts, but these salts vary in both concentration and composition. The major dissolved salts are the cations sodium (Na +), calcium (Ca 2+), and magnesium (Mg 2+), and the anions chloride (Cl-), sulfate (SO4 2-), and bicarbonate (HCO3-). Typically, groundwater has naturally higher concentrations of these constituents, and some soils have higher salinity than others. These dissolved salts can be growth-limiting when concentrations in the root zone exceed critical levels, as described below. Salinity is best characterized by the electrical conductivity (EC) of the irrigation water (ECw) or the EC of the saturated soil paste (ECe); the higher the dissolved salt concentration, the higher the EC. The units of EC are expressed in dS/m or mmho/cm where 1 dS/m = 1 mmho/cm. For EC values less than 5 dS/m, 1 dS/m = 640 mg/L total dissolved solids (TDS) and 1 dS/m = about 800 mg/L for EC values above 8 dS/m.
Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing... more Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.
The scarcity of high quality irrigation water is a global issue facing rice growers, forcing many... more The scarcity of high quality irrigation water is a global issue facing rice growers, forcing many to adopt water management systems that may result in increased salinity and yield reductions. While salt concentrations in field water have been shown to vary depending on water management, the distribution and build-up patterns of dissolved salts are unclear. This study was conducted to elucidate the within field spatial and temporal salinity dynamics in water-seeded rice cropping systems, and to assess current salinity thresholds for rice yield reduction. In this two-year study, water and soil salinity concentrations of eleven field sites were monitored weekly, with three sampling points being established in the top, middle and bottom basins of each field. There was a consistent spatio-temporal water salinity pattern among all fields: the maximum water salinity within a field occurred during week 2 to week 7 after planting, and was greatest farther from the irrigation inlet and where soil salinity was high. A model developed to predict water salinity within a field indicates that, averaged over an entire growing season, the position within a field contributed to 82% of the variation explained by the model, while preseason soil salinity contributed to 18%. Importantly, field water salinity was determined to be the most sensitive salinity metric for rice yield, as preseason soil salinity was a poor predictor of yield loss. The threshold field water salinity concentration was estimated at 0.88 dS m −1 , lower than the previous report of 1.9 dS m −1. These results illustrate the ability to predict water salinity in a rice field with few parameters, while highlighting the importance of field water salinity as the main salinity metric for rice cropping systems.
In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on ... more In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information developed nearly two decades ago from experiments conducted in non-saline orchards sprinkler-irrigated with good quality water. No information is currently available that quantify the effect of salinity or combined salinity and sodicity on water use of micro-irrigated pistachio orchards, even though such information would help growers schedule irrigations and control soil salinity through leaching. To fill this gap, a field research study was conducted in 2016 and 2017 to measure the actual evapotranspiration (ETa) from commercial pistachio orchards grown on non-saline and saline-sodic soils in the southern portion of the San Joaquin Valley of California. The study aimed at investigating the functional relations between soil salinity/sodicity and t...
Reuse of saline drainage water for crop irrigation has been proposed as one strategy to reduce th... more Reuse of saline drainage water for crop irrigation has been proposed as one strategy to reduce the drainage volume requiring disposal in California. A 6 y study to assess the feasibility of cyclic saline drainage reuse in a processing tomato/ cotton /cotton rotation was conducted. Treatments were: 1. fresh water applied throughout, 2. saline water applied after 1st flower to tomatoes, 3. saline water applied to tomato and the next cotton crop. Saline water generally improved tomato fruit quality, but did not reduce yields during the first 4 years. In year 6, yields were reduced 17% (n.s.) and 30% (p<0.05) in treatments 2 and 3 respectively, relative to the control. Monitoring of the root zone showed that boron has accumulated over time in saline treatments and may be limiting crop production more than soil salinity. Selenium was readily leached by periodic fresh water use and did not accumulate to levels of concern in tomato tissues. Other work has shown that salinity can enhance...
Performance ofKerman'pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica De... more Performance ofKerman'pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica Desf., P. integerrima Stewart andUCB-1', a P. atlantica× P. integerrima hybrid) was evaluated with 2-year-old trees grown in sand-tank lysimeters under combined SO 4 2-...
Irrigation water quality can have a profound impact on crop production. All irrigation water cont... more Irrigation water quality can have a profound impact on crop production. All irrigation water contains dissolved mineral salts, but the concentration and composition of the dissolved salts vary depending on the source of the irrigation water. For example, snow melt or water supplies from the Sierra Nevada contain very small amounts of salt whereas groundwater or wastewater typically has higher salt levels. Too much salt can reduce or even prohibit crop production while too little salt can reduce water infiltration, which indirectly affects the crop. An understanding of the quality of water used for irrigation and its potential negative impacts on crop growth is essential to avoid problems and to optimize production. For more information on any of the issues found in this publication, please contact your local University of California Cooperative Extension office.
Salinity of the irrigation water and soil solution is expressed by electrical conductivity (EC), ... more Salinity of the irrigation water and soil solution is expressed by electrical conductivity (EC), and the internationally accepted reporting unit for EC is deciSiemens per meter (dS/m). (This unit is equal to millimhos per centimeter [mmhos/ cm], which equal 1,000 micromhos per centimeter [µmhos/cm]). Because dissolved salts form ions in solution, the solution
Recent prolonged droughts in California have emphasized the urgent need to implement more efficie... more Recent prolonged droughts in California have emphasized the urgent need to implement more efficient water management practices for high value tree crops. Accurate estimation of evapotranspiration (ET), a main component of consumptive water use, is critical for improving management of micro-irrigated pistachio orchards grown in the San Joaquin Valley of California. We estimated ET of three mature commercial pistachio orchards on non-saline and increasingly saline soils in 2015 and 2016, using the Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) method and Landsat 8 satellite observations. Based on a comparison with field observations at 8 sites, we modified the parameterizations of the momentum roughness length and net radiation for pistachio tree crops and reduced the uncertainty of daily ET estimates. When compared with field data, the recalibrated METRIC ET estimates had an R 2 of 0.59, a mean absolute error of 1.1 mm/day, and a RMSE of 1.4 mm/day during Landsat overpass dates (n = 72). The METRIC ET map captured the temporal dynamics and spatial heterogeneity both within and among the orchards. The mean annual crop season estimated ET (mid-March to mid-October in 2016) with remote sensing decreased by 32% from 1064 ± 99 mm in the non-salt affected control orchard to 725 ± 82 mm in the orchard with the highest level of soil-water salinity. The ET reduction was consistent with canopy volume differences among the study orchards, as shown by summer Normalized Difference Vegetation Index (NDVI) from Landsat observations, e.g., 0.72 ± 0.06 in the control vs. 0.52 ± 0.06 in the most saline orchard. The available energy was controlled mostly by canopy features and explained 64% of daily ET variation among all Landsat pixels and satellite overpass days. The normalized differenced water index (NDWI) could be considered as an important parameter to capture the partitioning of available energy for ET (R 2 = 0.38), suggesting that the lower soil osmotic potential in saline orchards further reduced crop ET. California's Central Valley, an area of about 155,000 km 2 , is among one of the world's most productive agricultural regions. A total of 101,327 bearing hectares (1180 km 2 ) of pistachios generated an overall production of 448,000 metric tons and a $1.5 billion in revenue in 2016 (California Department of Food and Agriculture (CDFA), 2016). Approximately 95% of the US commercial pistachios are produced in the San Joaquin Valley. In the last decades, pistachio acreage expanded largely to areas with saline soils previously used for cotton . Soil salinity is a known constraint on agricultural production in the Central Valley, particularly in the western San Joaquin Valley, where soils are naturally high in salts due to the marine origin of their Coastal Range alluvium parent material . Although the need of subsurface drainage was long understood for these agricultural production areas, it failed to materialize due to lack of collective actions
nonirrigated ice plants were close to ambient air temperature. Hence, the leaf temperature method... more nonirrigated ice plants were close to ambient air temperature. Hence, the leaf temperature method of measuring stress would not be useful in most areas of California where wind velocities are frequently greater than 5 mph unless the relationship between wind velocity and leaf temperature were known with some precision. Xylosma foliage, further above the ground, with thinner leaves that dissipate heat by conduction and convection more rapidly than those of ice plant, were only 10°F warmer than the surrounding air when air movement was less than 5 mph.
A model has been developed to determine how the electrical conductivity of a given irrigation wat... more A model has been developed to determine how the electrical conductivity of a given irrigation water supply affects crop production while taking annual rainfall into account. The model builds upon the principles and assumptions described by Ayers and Westcot (1985) and relates the electrical conductivity of the irrigation water (ECw) to the seasonal average rootzone salinity, expressed as the electrical conductivity of the saturated paste (ECe). The model considers the timing and quantity of applied irrigation water, the quantity and distribution of rainfall, and realistic assumptions related to soil water principles based on soil type. The program can be used to either quantify the extent by which an irrigation water supply with a given EC would decrease the yield potential for a given crop under sitespecific conditions or to determine the maximum EC of an irrigation water supply, that if used as the sole source of irrigation water over the long term, is fully protective of crop pro...
Three devices that physically treat irrigation water were tested in the laboratory and the field.... more Three devices that physically treat irrigation water were tested in the laboratory and the field. Results of these experiments indicate these water conditioners were ineffective in increasing the infiltration rate of water into the soil or in preventing calcium carbonate precipitates from clogging drip emitters under the conditions in which they were tested.
Irrigation management can have a profound influence on olive oil production. We initiated a 2-yea... more Irrigation management can have a profound influence on olive oil production. We initiated a 2-year study in the spring of 2002 to identify the optimal level of applied water on a super high tree-density (spacing 1.5 m  3.9 m) olive (Olea europaea L.'Arbequina I-18') orchard. Irrigation water was applied by drip irrigation to produce different
L. Ferguson*, B. Sanden*, S. Grattan**, H.C. Reyes***, C. Wilson**** and E. Cross**** *Department... more L. Ferguson*, B. Sanden*, S. Grattan**, H.C. Reyes***, C. Wilson**** and E. Cross**** *Department of Pomology, UCD @ Kearney Agricultural Center, 9240 S Riverbend Avenue, Parlier, CA 93648, USA **Department of Land, Air and Water Resources, UCD @ Kearney Agricultural Center, 9240 S Riverbend Avenue, Parlier, CA 93648, USA ***Department of Pomology, UCD @ Kearney Agricultural Center, 9240 S Riverbend Avenue, Parlier, CA 93648, USA ****United States Department of Agriculture (USDA-ARS), Soil Salinity Laboratory, 450 Big Springs Road Riverside, Riverside, CA 92507-4617, USA
Pistachio acreage is rapidly expanding in California thanks to its economic profitability and cap... more Pistachio acreage is rapidly expanding in California thanks to its economic profitability and capacity to grow and produce in salt-affected soils. Our team at University of California is updating information on actual water use (ET) of mature pistachio orchards grown on saline soils under micro-irrigation methods. Actual Evapotranspiration (ETa) and Crop Coefficients (Ka) were determined for the 2015 and 2016 crop seasons on four pistachio orchards grown in the San Joaquin Valley (SJV) on grounds with increasing levels of soil-water salinity, using the residual of energy balance method with a combination of eddy covariance and surface renewal equipment. Tree canopy cover, light interception, and plant water status across the orchards were also measured and evaluated. Our preliminary results show that salinity strongly affects the tree water use, resulting in 10-30% less ET for medium to high salt-affected soils. Salinity also showed a strong effect on tree water status and light int...
This article presents findings from a field research study conducted in the San Joaquin Valley of... more This article presents findings from a field research study conducted in the San Joaquin Valley of California in 2016–2018 to appraise the effects of soil salinity and sodicity on evapotranspiration and energy balance components of micro-irrigated pistachio orchards. Actual evapotranspiration (ETa) and tree physiologic parameters were measured during consecutive growing seasons in mature orchards grown on non-saline and saline/sodic soils. Salinity and sodicity decreased pistachio water use by about 30%, with ETa reductions varying along the growing season. Accurate information on the dynamics of ETa and energy balance components along the growing season can improve water management for nut orchards exposed to long-term saline-sodic conditions. Results show that the main driver of ETa was the net radiation (Rn), which supplied most of the energy to vaporize water, irrespective of the growth period and level of salinity/sodicity. Field observations revealed that Rn was lower for salt-affected trees due to smaller canopies, which intercepted less light than non-saline trees. Secondarily, the exchange of sensible heat (H) between the ambient air and tree canopies was affected by the interaction between salinity–sodicity and seasonality. Early in the season, salinity and sodicity affected ETa mainly through the reduced canopy growth, which decreased the available energy (Rn–G) for ETa and reduced the water uptake as a result of the lower soil water potential. Late in the season, an increase in H and a decrease in the contribution of the aerodynamic component (β coefficient) to the latent heat flux (LE) occurred, which determined a further reduction of ETa due to a physiological response. The decrease in the β coefficient during the late season was associated with a direct impact of ion accumulation on leaf functionality. Collecting data on the contribution of the aerodynamic component to LE offers a low-cost method to detect and quantify physiological stress, while providing useful information for managing irrigation in salt-affected orchards. The results presented in this article provide insights to improve irrigation management of salt-affected pistachio through integration of weather measurements, energy balance components, and plant-based parameters.
S oil salinity is an important stress affecting irrigated crops in many areas of California. This... more S oil salinity is an important stress affecting irrigated crops in many areas of California. This stress is often exacerbated during drought years. Over time, salts can accumulate in the soils as crops extract water, leaving the salts behind in the root zone. Without sufficient leaching, accumulated salts will eventually reach a level that will damage crops. Even if irrigation water is low in salinity, salts will eventually build up in the soil to damaging levels without sufficient leaching from rainfall or excess irrigation water. Under drought conditions, high-quality surface water supplies may not be available in sufficient quantities to meet crop needs and may be supplemented or completely replaced with poorer-quality ground or surface water. Ironically, irrigation water higher in salinity will require more water in order to maintain the same level of soil salinity; that is, poorer-quality water requires more leaching. But regardless of the quality of the water applied, deficit irrigation combined with poor quality water will exaggerate the salinity problem. All soils and irrigation water contains dissolved salts, but these salts vary in both concentration and composition. The major dissolved salts are the cations sodium (Na +), calcium (Ca 2+), and magnesium (Mg 2+), and the anions chloride (Cl-), sulfate (SO4 2-), and bicarbonate (HCO3-). Typically, groundwater has naturally higher concentrations of these constituents, and some soils have higher salinity than others. These dissolved salts can be growth-limiting when concentrations in the root zone exceed critical levels, as described below. Salinity is best characterized by the electrical conductivity (EC) of the irrigation water (ECw) or the EC of the saturated soil paste (ECe); the higher the dissolved salt concentration, the higher the EC. The units of EC are expressed in dS/m or mmho/cm where 1 dS/m = 1 mmho/cm. For EC values less than 5 dS/m, 1 dS/m = 640 mg/L total dissolved solids (TDS) and 1 dS/m = about 800 mg/L for EC values above 8 dS/m.
Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing... more Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.
The scarcity of high quality irrigation water is a global issue facing rice growers, forcing many... more The scarcity of high quality irrigation water is a global issue facing rice growers, forcing many to adopt water management systems that may result in increased salinity and yield reductions. While salt concentrations in field water have been shown to vary depending on water management, the distribution and build-up patterns of dissolved salts are unclear. This study was conducted to elucidate the within field spatial and temporal salinity dynamics in water-seeded rice cropping systems, and to assess current salinity thresholds for rice yield reduction. In this two-year study, water and soil salinity concentrations of eleven field sites were monitored weekly, with three sampling points being established in the top, middle and bottom basins of each field. There was a consistent spatio-temporal water salinity pattern among all fields: the maximum water salinity within a field occurred during week 2 to week 7 after planting, and was greatest farther from the irrigation inlet and where soil salinity was high. A model developed to predict water salinity within a field indicates that, averaged over an entire growing season, the position within a field contributed to 82% of the variation explained by the model, while preseason soil salinity contributed to 18%. Importantly, field water salinity was determined to be the most sensitive salinity metric for rice yield, as preseason soil salinity was a poor predictor of yield loss. The threshold field water salinity concentration was estimated at 0.88 dS m −1 , lower than the previous report of 1.9 dS m −1. These results illustrate the ability to predict water salinity in a rice field with few parameters, while highlighting the importance of field water salinity as the main salinity metric for rice cropping systems.
In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on ... more In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information developed nearly two decades ago from experiments conducted in non-saline orchards sprinkler-irrigated with good quality water. No information is currently available that quantify the effect of salinity or combined salinity and sodicity on water use of micro-irrigated pistachio orchards, even though such information would help growers schedule irrigations and control soil salinity through leaching. To fill this gap, a field research study was conducted in 2016 and 2017 to measure the actual evapotranspiration (ETa) from commercial pistachio orchards grown on non-saline and saline-sodic soils in the southern portion of the San Joaquin Valley of California. The study aimed at investigating the functional relations between soil salinity/sodicity and t...
Reuse of saline drainage water for crop irrigation has been proposed as one strategy to reduce th... more Reuse of saline drainage water for crop irrigation has been proposed as one strategy to reduce the drainage volume requiring disposal in California. A 6 y study to assess the feasibility of cyclic saline drainage reuse in a processing tomato/ cotton /cotton rotation was conducted. Treatments were: 1. fresh water applied throughout, 2. saline water applied after 1st flower to tomatoes, 3. saline water applied to tomato and the next cotton crop. Saline water generally improved tomato fruit quality, but did not reduce yields during the first 4 years. In year 6, yields were reduced 17% (n.s.) and 30% (p<0.05) in treatments 2 and 3 respectively, relative to the control. Monitoring of the root zone showed that boron has accumulated over time in saline treatments and may be limiting crop production more than soil salinity. Selenium was readily leached by periodic fresh water use and did not accumulate to levels of concern in tomato tissues. Other work has shown that salinity can enhance...
Performance ofKerman'pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica De... more Performance ofKerman'pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica Desf., P. integerrima Stewart andUCB-1', a P. atlantica× P. integerrima hybrid) was evaluated with 2-year-old trees grown in sand-tank lysimeters under combined SO 4 2-...
Irrigation water quality can have a profound impact on crop production. All irrigation water cont... more Irrigation water quality can have a profound impact on crop production. All irrigation water contains dissolved mineral salts, but the concentration and composition of the dissolved salts vary depending on the source of the irrigation water. For example, snow melt or water supplies from the Sierra Nevada contain very small amounts of salt whereas groundwater or wastewater typically has higher salt levels. Too much salt can reduce or even prohibit crop production while too little salt can reduce water infiltration, which indirectly affects the crop. An understanding of the quality of water used for irrigation and its potential negative impacts on crop growth is essential to avoid problems and to optimize production. For more information on any of the issues found in this publication, please contact your local University of California Cooperative Extension office.
Salinity of the irrigation water and soil solution is expressed by electrical conductivity (EC), ... more Salinity of the irrigation water and soil solution is expressed by electrical conductivity (EC), and the internationally accepted reporting unit for EC is deciSiemens per meter (dS/m). (This unit is equal to millimhos per centimeter [mmhos/ cm], which equal 1,000 micromhos per centimeter [µmhos/cm]). Because dissolved salts form ions in solution, the solution
Uploads
Papers by Steve Grattan