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Alfalfa water stewardship suggested

Alfalfa uses more water than any other crop in California, almost 20 percent annually of the state's agricultural water use.

That is not necessarily news because alfalfa has been a target of people who want to take agriculture's water and claim the forage crop's water use is excessive. This despite the fact that the crop represents $700 million to $1 billion in revenue to the state's economy and is the key crop for sustaining the state's $4.5 billion dairy industry.

While the supply picture has not improved any, moving to the forefront of water issues in the state is water quality. There, alfalfa is not a bad actor since it is a relatively low-intensity pesticide user and growers are quickly switching from products implicated in water quality contamination.

Agriculture's (more specifically) the alfalfa industry's response to these issues will be one of the most important determinants of farm viability in the future in California, says Dan Putnam, University of California forage specialist.

Putnam told producers and others at the 33rd annual California Alfalfa Symposium in Monterey that alfalfa needs an environmental stewardship program to address water quality issues.

While alfalfa is a relatively low intensity pesticide use crop, there are several used on alfalfa that have been implicated in surface and groundwater contamination.

Organophosphates have been the most often implicated, but their use is declining. In fact, Putnam reported overall insecticide use in alfalfa was reduced by 12 percent from 2001 to 2002, despite a 15 percent increase in acreage.

Less insecticide

Putnam said of the major insecticides, use of chlorpyrifos, methomyl and endosulfan decreased dramatically.

Pyrethroids have been used as replacements for chlorpyrifos while the decrease in methomyl is likely attributed to the rapid acceptance of Steward (indoxacarb) for late season armyworm control. Steward became the 10th most popular active ingredient in a single year, going from no use in 2001 to more than 7,000 pounds in 2002. It was the seventh most popular alfalfa insecticide in terms of treated acres.

While alfalfa uses only about a third of the pesticides used on cotton, “this does not mean alfalfa is a non-player in terms of pesticide use.

Herbicide use for winter weed control is another area of environmental concern, said Putnam.

Several years ago, herbicides used in the upper San Joaquin Valley were found in a few wells. UC research found that there was no significant movement of two implicated compounds in the soil, but that the compounds were collecting in ditches and collecting ponds at the end of fields.

While tailwater ponds are useful in re-using irrigation water, Putnam said the groundwater contamination issue behooves grower to make sure the design of these systems precludes groundwater contamination. This could mean more efficient water use and lining of these ponds.


Putnam and the UC alfalfa working group suggest offer these suggestions for mitigating possible water pollution:

  • Growers switch pesticides in sensitive soils where off-site water movement is likely.

  • Line catch basins and tailwater ditches where there is a likelihood of pesticides seeping into the groundwater.

  • Improving spray technology to avoid offsite oversprays and possibly change pesticide labels to reduce usage where there is likelihood for higher runoff.

  • Use polymers to aggregate soil to possibly prevent pesticide movement on soil particles.

  • Use activated charcoal, peat or other filtering agents where water leaves a ranch.

  • Create buffer zones between alfalfa and waterways.

  • Use filter strips of legumes and grasses to mitigate offsite pesticide movement.

  • Use berseem clover, oats, ryegrass or red clover overseeded into older alfalfa stands to negate the insecticide getting into the soil of thin stands.

  • Restrict pesticide use in thin or newly cut alfalfa stands. Open canopies may lead to offsite movement of pesticides.

  • More vigorous implementation of integrated pest management techniques.

  • Improve irrigation management to prevent irrigation runoff.

“Irrigation management is so central to the offsite movement of soluble components in irrigation water, that it is difficult to overemphasize this as a central theme for prevention of offsite movement of pesticides,” said Putnam.

Putnam said an alfalfa stewardship program developing and promoting practices to reduce known sources of pollution from alfalfa would not only minimize the problem, but could help growers avoid more onerous regulations.

e-mail: [email protected]

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