Photo: Irrigation, Southwest Montana. © 2020 Delena Norris-Tull
Improving water use practices
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western,
September 2020.
In her book Braiding Sweetgrass, Dr. Robin Wall Kimmerer, a plant ecologist and a tribal member of the Citizen Potawatomi Nation, provides a glimpse of indigenous ways of knowing about nature.
“Traditional Onondaga understand a world in which all beings were given a gift, a gift that simultaneously engenders a responsibility to the world. Water's gift is its role as life sustainer, and its duties are manifold: making plants grow, creating homes for fish and mayflies, and, for me today, offering a cool drink” ((Kimmerer, 2013, p. 310).
“The Haudenosuanee were given the Thanksgiving Address to remind themselves to greet and thank all the members of the natural world whenever they gathered. To the waters they say: ‘We give thanks to all the Waters of the world. We are grateful that the waters are still here and doing their duty of sustaining life on Mother Earth. Water is life, quenching our thirst and providing us with strength, making the plants grow and sustaining us all. Let us gather our minds together and with one mind, we send greetings and thanks to the Waters’” (Kimmerer, 2013, p. 311).
“These words reflect the sacred purpose of the people. For just as water was given certain responsibilities for sustaining the world, so were the people. Chief among their duties was to give thanks for the gifts of the earth and to care for them” (Kimmerer, 2013, p. 311).
Rice growing example
Rice provides a food staple for over three billion people (Bouman, 2018). With an annual yield of over 700 million tons, rice is “the biggest user of ‘developed’ fresh water worldwide.” Wild rice originated in wetlands. Thus, unlike other grains, domesticated rice can grow in flooded fields. Most rice is grown in flooded fields from planting till harvest. The main purpose of flooding rice fields is to suppress the growth of weeds.
Flooding uses large amounts of water. But Dr. Bas Bouman, senior scientist in water management with the International Rice Research Institute, points out that 50% of the water used to flood rice fields is not “lost.” It percolates through the soil and re-enters either ground or surface water systems. Rice loses about the same amount of water to evapotranspiration as does wheat.
Dr. Bouman recommends a variety of techniques to both reduce the amount of water used in growing rice, and to increase the amount of water recovered for re-use.
Comparison of irrigation systems
Sutton, et al., 2006, reported that “the adoption of conservation tillage as a sustainable production practice has been limited in California in part because of the need for tillage to maintain furrows for irrigation and to control weeds.” They report that furrow irrigation is the most common type of irrigation used in California row crops. But it uses more water, and has a higher water runoff, than does subsurface drip irrigation. “Soil beds in furrow-irrigated systems are maintained by frequent tillage, which leads to high levels of dust production.”
In a two-year comparison of irrigation practices in tomato fields in Davis, California, Sutton, et al., 2006, compared tomato crop yield and effectiveness in weed control, in fields treated with: subsurface drip irrigation (with conservation tillage or standard tillage) versus furrow irrigation (with conservation tillage or standard tillage). They also compared subplots with and without herbicides (rimsulfuron and glyphosate). The conservation tillage plots received no tillage. Because there were no significant weeds in the subsurface drip irrigation plots after the first year, they decided not to till the drip irrigation plots that they had intended to treat with standard tillage the second year.
Glyphosate was applied after the winter fallow to reduce winter weeds. 11 weed species were found in the plots. They analyzed data from three weed species. Results differed somewhat between noxious weed species. “Neither tillage nor herbicides had a significant effect on common lambsquarters density. This species was absent in the subsurface drip plots in 2003 and present in only one [drip irrigation] plot in 2004… [In both years] pigweed density was greater in furrow than in subsurface drip-irrigated plots… [In the furrow-irrigated plots, standard] tillage or herbicide treatments each reduced pigweed density by over 45% in 2004. The standard tillage treatment was effective at controlling pigweed plants on the sides of the bed and furrow, but did not control weeds in the tomato plant line. The herbicide treatment controlled most emerged pigweed, but because furrow irrigation was used in this trial, rimsulfuron was not ideally incorporated and residual control was poor.” Black nightshade: “The subsurface drip-irrigated plots had less nightshade than the furrow-irrigated plots; but within furrow irrigation, the standard tillage, herbicide treated plots had less nightshade than the standard tillage, no herbicide plots, or conservation tillage plots…. Herbicide treatment did not improve nightshade control in the furrow-irrigated conservation tillage plots… [In furrow irrigated plots,] standard tillage effectively eliminated all the nightshade with the exception of the those weeds growing directly in the plant line, and the herbicide treatment slightly reduced that number. [In year two,] nightshade density was higher in furrow-irrigated than in subsurface drip-irrigated plots….
[Overall results:] "Weed biomass, similar to density, was highest in the furrow irrigation treatments, with most weed biomass in the furrow….In standard tillage plots, weed biomass in the furrows was less than the weed biomass in the furrows of conservation tillage plots. Tillage eliminated weeds in the furrow area, but in conservation tillage plots where no mechanical tillage was used, weeds continued to germinate and grow with each irrigation….Total marketable fruit yields were highest in the furrow-irrigated, standard tillage plots with herbicide in 2003… In 2004, subsurface drip-plots had about 10% higher fruit and marketable yields than furrow-irrigated plots… Herbicide treatment also improved total fruit by 13% and marketable yield by 16% in 2005.” Sutton, et al., 2006, concluded that “subsurface drip irrigation could substantially reduce weed density and growth in limited-rainfall environments.” Subsurface drip irrigation can also facilitate the use of conservation tillage with less use of herbicides.
The irrigation water wars in the West
The Eastern States do not typically have the drought challenges found in Western States. It was not until I moved from Florida to Texas as a child, that I began to understand the challenges of regular droughts, and the legal battles over water rights that have been waged in Western States for decades.
I have now lived in Montana since 2004. The first few years I lived in Southwestern Montana the drought was so severe that I thought the hillsides were permanently brown. The first year that we finally had a decent amount of spring rainfall, I was astounded to see the hillsides turning green. A few months later, I was equally astounded to drive by farm fields soaked in summer rains, while the fields were being simultaneously irrigated. This seemed like a waste of water beyond my comprehension. I soon leaned that Montana ranchers and farmers have designated water allotments. If the landowners do not use their allotted amount of irrigation water, their allotment will be reduced in subsequent years. The high likelihood that next year there will be a drought makes it essential that farmers keep their allotments the same from year to year.
Magleby, et al., 1995, reported on the impact of water on the loss of soils in the USA. “Agricultural soil erosion is increasingly regarded as important to water quality and is the largest source of nonpoint pollutants in the Nation's waterways…. The movement of water over the soil surface causes about three-fifths of the estimated erosion on U.S. land.” Their report includes a discussion of the effectiveness of various Federal and State programs, in regards to water conservation.
Fortunately, Western States have largely adopted effective water conservation systems. Hellerstein, et al., 2019, report that, “Between 1984 and 2013, acreage in water-efficient sprinkler and drip/trickle systems rose from 37 to 76 percent of irrigated area in the Western United States.”
It would behoove the US Congress to tackle water rights issues, with the aim of resolving the Western water wars. It would be wonderful if Western States could jointly adopt water management systems that preserve our water and the livelihoods of Western farmers and ranchers. But this level of cooperation seems impossible in the current political climate.
Return to:
Agricultural Best Practices
Links to more Innovative Solutions:
Improving water use practices
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western,
September 2020.
In her book Braiding Sweetgrass, Dr. Robin Wall Kimmerer, a plant ecologist and a tribal member of the Citizen Potawatomi Nation, provides a glimpse of indigenous ways of knowing about nature.
“Traditional Onondaga understand a world in which all beings were given a gift, a gift that simultaneously engenders a responsibility to the world. Water's gift is its role as life sustainer, and its duties are manifold: making plants grow, creating homes for fish and mayflies, and, for me today, offering a cool drink” ((Kimmerer, 2013, p. 310).
“The Haudenosuanee were given the Thanksgiving Address to remind themselves to greet and thank all the members of the natural world whenever they gathered. To the waters they say: ‘We give thanks to all the Waters of the world. We are grateful that the waters are still here and doing their duty of sustaining life on Mother Earth. Water is life, quenching our thirst and providing us with strength, making the plants grow and sustaining us all. Let us gather our minds together and with one mind, we send greetings and thanks to the Waters’” (Kimmerer, 2013, p. 311).
“These words reflect the sacred purpose of the people. For just as water was given certain responsibilities for sustaining the world, so were the people. Chief among their duties was to give thanks for the gifts of the earth and to care for them” (Kimmerer, 2013, p. 311).
Rice growing example
Rice provides a food staple for over three billion people (Bouman, 2018). With an annual yield of over 700 million tons, rice is “the biggest user of ‘developed’ fresh water worldwide.” Wild rice originated in wetlands. Thus, unlike other grains, domesticated rice can grow in flooded fields. Most rice is grown in flooded fields from planting till harvest. The main purpose of flooding rice fields is to suppress the growth of weeds.
Flooding uses large amounts of water. But Dr. Bas Bouman, senior scientist in water management with the International Rice Research Institute, points out that 50% of the water used to flood rice fields is not “lost.” It percolates through the soil and re-enters either ground or surface water systems. Rice loses about the same amount of water to evapotranspiration as does wheat.
Dr. Bouman recommends a variety of techniques to both reduce the amount of water used in growing rice, and to increase the amount of water recovered for re-use.
- Use a system of alternate wetting and drying, which allows fields to dry out for a few days at a time.
- Grow aerobic rice: with this practice, the field is wetted rather than flooded, similar to the way maize and wheat are typically irrigated.
- Improve water re-capture systems, to enable the re-use of water within the same fields. Water can be re-captured using pumps, or small dams, or reservoirs.
Comparison of irrigation systems
Sutton, et al., 2006, reported that “the adoption of conservation tillage as a sustainable production practice has been limited in California in part because of the need for tillage to maintain furrows for irrigation and to control weeds.” They report that furrow irrigation is the most common type of irrigation used in California row crops. But it uses more water, and has a higher water runoff, than does subsurface drip irrigation. “Soil beds in furrow-irrigated systems are maintained by frequent tillage, which leads to high levels of dust production.”
In a two-year comparison of irrigation practices in tomato fields in Davis, California, Sutton, et al., 2006, compared tomato crop yield and effectiveness in weed control, in fields treated with: subsurface drip irrigation (with conservation tillage or standard tillage) versus furrow irrigation (with conservation tillage or standard tillage). They also compared subplots with and without herbicides (rimsulfuron and glyphosate). The conservation tillage plots received no tillage. Because there were no significant weeds in the subsurface drip irrigation plots after the first year, they decided not to till the drip irrigation plots that they had intended to treat with standard tillage the second year.
Glyphosate was applied after the winter fallow to reduce winter weeds. 11 weed species were found in the plots. They analyzed data from three weed species. Results differed somewhat between noxious weed species. “Neither tillage nor herbicides had a significant effect on common lambsquarters density. This species was absent in the subsurface drip plots in 2003 and present in only one [drip irrigation] plot in 2004… [In both years] pigweed density was greater in furrow than in subsurface drip-irrigated plots… [In the furrow-irrigated plots, standard] tillage or herbicide treatments each reduced pigweed density by over 45% in 2004. The standard tillage treatment was effective at controlling pigweed plants on the sides of the bed and furrow, but did not control weeds in the tomato plant line. The herbicide treatment controlled most emerged pigweed, but because furrow irrigation was used in this trial, rimsulfuron was not ideally incorporated and residual control was poor.” Black nightshade: “The subsurface drip-irrigated plots had less nightshade than the furrow-irrigated plots; but within furrow irrigation, the standard tillage, herbicide treated plots had less nightshade than the standard tillage, no herbicide plots, or conservation tillage plots…. Herbicide treatment did not improve nightshade control in the furrow-irrigated conservation tillage plots… [In furrow irrigated plots,] standard tillage effectively eliminated all the nightshade with the exception of the those weeds growing directly in the plant line, and the herbicide treatment slightly reduced that number. [In year two,] nightshade density was higher in furrow-irrigated than in subsurface drip-irrigated plots….
[Overall results:] "Weed biomass, similar to density, was highest in the furrow irrigation treatments, with most weed biomass in the furrow….In standard tillage plots, weed biomass in the furrows was less than the weed biomass in the furrows of conservation tillage plots. Tillage eliminated weeds in the furrow area, but in conservation tillage plots where no mechanical tillage was used, weeds continued to germinate and grow with each irrigation….Total marketable fruit yields were highest in the furrow-irrigated, standard tillage plots with herbicide in 2003… In 2004, subsurface drip-plots had about 10% higher fruit and marketable yields than furrow-irrigated plots… Herbicide treatment also improved total fruit by 13% and marketable yield by 16% in 2005.” Sutton, et al., 2006, concluded that “subsurface drip irrigation could substantially reduce weed density and growth in limited-rainfall environments.” Subsurface drip irrigation can also facilitate the use of conservation tillage with less use of herbicides.
The irrigation water wars in the West
The Eastern States do not typically have the drought challenges found in Western States. It was not until I moved from Florida to Texas as a child, that I began to understand the challenges of regular droughts, and the legal battles over water rights that have been waged in Western States for decades.
I have now lived in Montana since 2004. The first few years I lived in Southwestern Montana the drought was so severe that I thought the hillsides were permanently brown. The first year that we finally had a decent amount of spring rainfall, I was astounded to see the hillsides turning green. A few months later, I was equally astounded to drive by farm fields soaked in summer rains, while the fields were being simultaneously irrigated. This seemed like a waste of water beyond my comprehension. I soon leaned that Montana ranchers and farmers have designated water allotments. If the landowners do not use their allotted amount of irrigation water, their allotment will be reduced in subsequent years. The high likelihood that next year there will be a drought makes it essential that farmers keep their allotments the same from year to year.
Magleby, et al., 1995, reported on the impact of water on the loss of soils in the USA. “Agricultural soil erosion is increasingly regarded as important to water quality and is the largest source of nonpoint pollutants in the Nation's waterways…. The movement of water over the soil surface causes about three-fifths of the estimated erosion on U.S. land.” Their report includes a discussion of the effectiveness of various Federal and State programs, in regards to water conservation.
Fortunately, Western States have largely adopted effective water conservation systems. Hellerstein, et al., 2019, report that, “Between 1984 and 2013, acreage in water-efficient sprinkler and drip/trickle systems rose from 37 to 76 percent of irrigated area in the Western United States.”
It would behoove the US Congress to tackle water rights issues, with the aim of resolving the Western water wars. It would be wonderful if Western States could jointly adopt water management systems that preserve our water and the livelihoods of Western farmers and ranchers. But this level of cooperation seems impossible in the current political climate.
Return to:
Agricultural Best Practices
Links to more Innovative Solutions: