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California Agriculture, Vol. 68, No.3

Water efficiency: Recycled water, irrigation technology
Cover:  As California enters the third year of an historic drought, with reservoirs at all-time lows and thousands of acres lying fallow, scientists and policymakers are looking for ways to increase water conservation and efficiency across the state. New UC research demonstrates the possibilities and challenges of irrigating crops with recycled wastewater (pages 59, 68, 75) and employing technology to reduce water use in surface-irrigated fields (page 82). Shown is Trinitas Cellars, which has irrigated its 12-acre vineyard in Napa County with recycled water for over seven years. The color purple on the irrigation tubing is used universally to signify recycled or reclaimed water. Photo by Will Suckow
July-September 2014
Volume 68, Number 3

Peer-reviewed research and review articles

Clarification and Correction
by Editors
Full text HTML  | PDF  
Recycled water causes no salinity or toxicity issues in Napa vineyards
by Edward Weber, Stephen R. Grattan, Blaine R. Hanson, Gaetano A. Vivaldi, Roland D. Meyer, Terry L. Prichard, Larry J. Schwankl
| Full text HTML  | PDF  
Treated wastewater proves suitable for irrigation in the Carneros and MST regions, although its nitrogen content may concern some growers.
In response to Napa Sanitation District's interest in expanding its delivery of recycled water to vineyards for irrigation, we conducted a feasibility study to assess the suitability of the water for this use. We adopted two approaches: comparing the water quality characteristics of the recycled water with those of other local sources of irrigation water, and evaluating soil samples from a vineyard that was irrigated for 8 years with the recycled water. Results indicate that the quality of the recycled water is suitable for irrigation, and also that long-term accumulation of salts and toxic ions have not occurred in the vineyards studied and are unlikely to occur. Nutrients in the recycled water may be beneficial to vineyards, though the levels of nitrogen may need to be reduced by planting cover crops in some vineyards.
Chloride levels increase after 13 years of recycled water use in the Salinas Valley
by Belinda E. Platts, Mark E. Grismer
| Full text HTML  | PDF  
At half the test sites receiving recycled water since 1998, chloride levels exceeded the thresholds for chloride-sensitive crops such as strawberries.
The use of recycled water for agriculture is a long-term water strategy in California. A study in the 1980s in Monterey County showed recycled water increased soil salinity but not to a level unacceptable for agriculture. Most growers in the northern Salinas Valley have been using it since 1998, and yet providers of the water and many growers are concerned that the sustained use of recycled water might cause deterioration of the soil. An ongoing study, initiated in 2000, compares the changes in soil salinity between a field receiving only well water and eight fields that receive recycled water. In 13 years of data, the average soil salinity parameters at each site were highly correlated with the average water quality values of the recycled water. Soil salinity did increase, though not deleteriously. Of most concern was the accumulation of chloride at four of the sites, to levels above the critical threshold values for chloride-sensitive crops.
Rainfall leaching is critical for long-term use of recycled water in the Salinas Valley
by Belinda E. Platts, Mark E. Grismer
| Full text HTML  | PDF  
Leaching with recycled water correlated with increasing soil salinity in this study, whereas rainfall leaching decreased soil salinity.
In 1998, Monterey County Water Recycling Projects began delivering water to 12,000 acres in the northern Salinas Valley. Two years later, an ongoing study began assessing the effects of the recycled water on soil salinity. Eight sites are receiving recycled water and a control site is receiving only well water. In data collected from 2000 to 2012, soil salinity of the 36-inch-deep profile was on average approximately double that of the applied water, suggesting significant leaching from applied water (irrigation) or rainfall. In this study, we investigated some of the soil water hydrology factors possibly controlling the soil salinity results. Using soil water balance modeling, we found that rainfall had more effect on soil salinity than did leaching from irrigation. Increasing applied water usually only correlated significantly with soil salinity parameters in the shallow soil profile (1 to 12 inches depth) and at 24 to 36 inches at sites receiving fairly undiluted recycled water. Winter rains, though, had a critical effect. Increasing rainfall depths were significantly correlated with decreasing soil salinity of the shallow soil at all test sites, though this effect also diminished with increased soil depth. When applied water had high salinity levels, winter rainfall in this area was inadequate to prevent soil salinity from increasing.
Water advance model and sensor system can reduce tail runoff in irrigated alfalfa fields
by Brad J. Arnold, Shrinivasa K. Upadhyaya, Jedediah Roach, Parasappa S. Kanannavar, Daniel H. Putnam
| Full text HTML  | PDF  
A water inflow cutoff model and wireless sensors used in surface-irrigated alfalfa fields to reduce tail runoff save time, labor and water.
Surface irrigation, such as flood or furrow, is the predominant form of irrigation in California for agronomic crops. Compared to other irrigation methods, however, it is inefficient in terms of water use; large quantities of water, instead of being used for crop production, are lost to excess deep percolation and tail runoff. In surface-irrigated fields, irrigators commonly cut off the inflow of water when the water advance reaches a familiar or convenient location downfield, but this experience-based strategy has not been very successful in reducing the tail runoff water. Our study compared conventional cutoff practices to a retroactively applied model-based cutoff method in four commercially producing alfalfa fields in Northern California, and evaluated the model using a simple sensor system for practical application in typical alfalfa fields. These field tests illustrated that the model can be used to reduce tail runoff in typical surface-irrigated fields, and using it with a wireless sensor system saves time and labor as well as water.
Predicting invasive plants in California
by Elizabeth D. Brusati, Douglas W. Johnson, Joseph M. DiTomaso
| Full text HTML  | PDF  
Ornamental plants at high risk for future invasion include 60 species that naturalized after 1940, and 94 species that have not yet naturalized.
Preventing plant invasions or eradicating incipient populations is much less costly than confronting large well-established populations of invasive plants. We developed a preliminary determination of plants that pose the greatest risk of becoming invasive in California, primarily through the horticultural industry. We identified 774 species that are invasive elsewhere in Mediterranean climates but not yet invasive in California. From this list, we determined which species are sold through the horticulture industry, whether they are sold in California and whether they have been reported as naturalized in California. We narrowed the list to 186 species with the greatest potential for introduction and/or invasiveness to California through the horticultural trade. This study provides a basis for determining species to evaluate further through a more detailed risk assessment that may subsequently prevent importation via the horticultural pathway. Our results can also help land managers know which species to watch for in wildlands.

Editorial, News, Letters and Science Briefs

NEWS
New license plate supports youth agricultural programs
by Robin Meadows
Full text HTML  | PDF  
EDITORIAL
UC ANR applies innovative research and programs to state's water scarcity
by Doug Parker
Full text HTML  | PDF  
OUTLOOK
Out of sight but not out of mind: California refocuses on groundwater
by Thomas Harter, Helen E. Dahlke
Full text HTML  | PDF  
RESEARCH NEWS
UC Cooperative Extension helps Californians use water wisely
by Robin Meadows
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Irrigation of deciduous orchards and vineyards influenced by plant-soil-water relationships in individual situations
by W. J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Can irrigation with municipal wastewater conserve energy?
by W. J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Improved leaching practices save water, reduce drainage problems
by W. J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Placement of tensiometers as guides to irrigation practices
by W.J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Eucalyptus fuel dynamics, and fire hazard in the Oakland hills
by W. J. Coats
Full text HTML  | PDF  
100 WAYS COOPERATION EXTENSION CHANGED CALIFORNIA
The Rise of the Kiwifruit
by Marissa Palin Stein
Full text HTML  | PDF  

General Information

About California Agriculture
by Editor
Full text HTML  | PDF  
Webmaster Email: wsuckow@ucanr.edu

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California Agriculture, Vol. 68, No.3

Water efficiency: Recycled water, irrigation technology
Cover:  As California enters the third year of an historic drought, with reservoirs at all-time lows and thousands of acres lying fallow, scientists and policymakers are looking for ways to increase water conservation and efficiency across the state. New UC research demonstrates the possibilities and challenges of irrigating crops with recycled wastewater (pages 59, 68, 75) and employing technology to reduce water use in surface-irrigated fields (page 82). Shown is Trinitas Cellars, which has irrigated its 12-acre vineyard in Napa County with recycled water for over seven years. The color purple on the irrigation tubing is used universally to signify recycled or reclaimed water. Photo by Will Suckow
July-September 2014
Volume 68, Number 3

Peer-reviewed research and review articles

Clarification and Correction
by Editors
Full text HTML  | PDF  
Recycled water causes no salinity or toxicity issues in Napa vineyards
by Edward Weber, Stephen R. Grattan, Blaine R. Hanson, Gaetano A. Vivaldi, Roland D. Meyer, Terry L. Prichard, Larry J. Schwankl
| Full text HTML  | PDF  
Treated wastewater proves suitable for irrigation in the Carneros and MST regions, although its nitrogen content may concern some growers.
In response to Napa Sanitation District's interest in expanding its delivery of recycled water to vineyards for irrigation, we conducted a feasibility study to assess the suitability of the water for this use. We adopted two approaches: comparing the water quality characteristics of the recycled water with those of other local sources of irrigation water, and evaluating soil samples from a vineyard that was irrigated for 8 years with the recycled water. Results indicate that the quality of the recycled water is suitable for irrigation, and also that long-term accumulation of salts and toxic ions have not occurred in the vineyards studied and are unlikely to occur. Nutrients in the recycled water may be beneficial to vineyards, though the levels of nitrogen may need to be reduced by planting cover crops in some vineyards.
Chloride levels increase after 13 years of recycled water use in the Salinas Valley
by Belinda E. Platts, Mark E. Grismer
| Full text HTML  | PDF  
At half the test sites receiving recycled water since 1998, chloride levels exceeded the thresholds for chloride-sensitive crops such as strawberries.
The use of recycled water for agriculture is a long-term water strategy in California. A study in the 1980s in Monterey County showed recycled water increased soil salinity but not to a level unacceptable for agriculture. Most growers in the northern Salinas Valley have been using it since 1998, and yet providers of the water and many growers are concerned that the sustained use of recycled water might cause deterioration of the soil. An ongoing study, initiated in 2000, compares the changes in soil salinity between a field receiving only well water and eight fields that receive recycled water. In 13 years of data, the average soil salinity parameters at each site were highly correlated with the average water quality values of the recycled water. Soil salinity did increase, though not deleteriously. Of most concern was the accumulation of chloride at four of the sites, to levels above the critical threshold values for chloride-sensitive crops.
Rainfall leaching is critical for long-term use of recycled water in the Salinas Valley
by Belinda E. Platts, Mark E. Grismer
| Full text HTML  | PDF  
Leaching with recycled water correlated with increasing soil salinity in this study, whereas rainfall leaching decreased soil salinity.
In 1998, Monterey County Water Recycling Projects began delivering water to 12,000 acres in the northern Salinas Valley. Two years later, an ongoing study began assessing the effects of the recycled water on soil salinity. Eight sites are receiving recycled water and a control site is receiving only well water. In data collected from 2000 to 2012, soil salinity of the 36-inch-deep profile was on average approximately double that of the applied water, suggesting significant leaching from applied water (irrigation) or rainfall. In this study, we investigated some of the soil water hydrology factors possibly controlling the soil salinity results. Using soil water balance modeling, we found that rainfall had more effect on soil salinity than did leaching from irrigation. Increasing applied water usually only correlated significantly with soil salinity parameters in the shallow soil profile (1 to 12 inches depth) and at 24 to 36 inches at sites receiving fairly undiluted recycled water. Winter rains, though, had a critical effect. Increasing rainfall depths were significantly correlated with decreasing soil salinity of the shallow soil at all test sites, though this effect also diminished with increased soil depth. When applied water had high salinity levels, winter rainfall in this area was inadequate to prevent soil salinity from increasing.
Water advance model and sensor system can reduce tail runoff in irrigated alfalfa fields
by Brad J. Arnold, Shrinivasa K. Upadhyaya, Jedediah Roach, Parasappa S. Kanannavar, Daniel H. Putnam
| Full text HTML  | PDF  
A water inflow cutoff model and wireless sensors used in surface-irrigated alfalfa fields to reduce tail runoff save time, labor and water.
Surface irrigation, such as flood or furrow, is the predominant form of irrigation in California for agronomic crops. Compared to other irrigation methods, however, it is inefficient in terms of water use; large quantities of water, instead of being used for crop production, are lost to excess deep percolation and tail runoff. In surface-irrigated fields, irrigators commonly cut off the inflow of water when the water advance reaches a familiar or convenient location downfield, but this experience-based strategy has not been very successful in reducing the tail runoff water. Our study compared conventional cutoff practices to a retroactively applied model-based cutoff method in four commercially producing alfalfa fields in Northern California, and evaluated the model using a simple sensor system for practical application in typical alfalfa fields. These field tests illustrated that the model can be used to reduce tail runoff in typical surface-irrigated fields, and using it with a wireless sensor system saves time and labor as well as water.
Predicting invasive plants in California
by Elizabeth D. Brusati, Douglas W. Johnson, Joseph M. DiTomaso
| Full text HTML  | PDF  
Ornamental plants at high risk for future invasion include 60 species that naturalized after 1940, and 94 species that have not yet naturalized.
Preventing plant invasions or eradicating incipient populations is much less costly than confronting large well-established populations of invasive plants. We developed a preliminary determination of plants that pose the greatest risk of becoming invasive in California, primarily through the horticultural industry. We identified 774 species that are invasive elsewhere in Mediterranean climates but not yet invasive in California. From this list, we determined which species are sold through the horticulture industry, whether they are sold in California and whether they have been reported as naturalized in California. We narrowed the list to 186 species with the greatest potential for introduction and/or invasiveness to California through the horticultural trade. This study provides a basis for determining species to evaluate further through a more detailed risk assessment that may subsequently prevent importation via the horticultural pathway. Our results can also help land managers know which species to watch for in wildlands.

Editorial, News, Letters and Science Briefs

NEWS
New license plate supports youth agricultural programs
by Robin Meadows
Full text HTML  | PDF  
EDITORIAL
UC ANR applies innovative research and programs to state's water scarcity
by Doug Parker
Full text HTML  | PDF  
OUTLOOK
Out of sight but not out of mind: California refocuses on groundwater
by Thomas Harter, Helen E. Dahlke
Full text HTML  | PDF  
RESEARCH NEWS
UC Cooperative Extension helps Californians use water wisely
by Robin Meadows
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Irrigation of deciduous orchards and vineyards influenced by plant-soil-water relationships in individual situations
by W. J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Can irrigation with municipal wastewater conserve energy?
by W. J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Improved leaching practices save water, reduce drainage problems
by W. J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Placement of tensiometers as guides to irrigation practices
by W.J. Coats
Full text HTML  | PDF  
UC COOPERATIVE EXTENSION HISTORY
UC COOPERATIVE EXTENSION CENTENNIAL: Eucalyptus fuel dynamics, and fire hazard in the Oakland hills
by W. J. Coats
Full text HTML  | PDF  
100 WAYS COOPERATION EXTENSION CHANGED CALIFORNIA
The Rise of the Kiwifruit
by Marissa Palin Stein
Full text HTML  | PDF  

General Information

About California Agriculture
by Editor
Full text HTML  | PDF  

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