IRRIGATION specialist Baryohay Davidoff stands over a row of tangled tomato plants with a pleased look. ``This farmer has done well,'' he says, pointing out white water pipelines running through the field. The pipes irrigate crops more efficiently and, most important, they help maintain water quality.
Water quality is becoming a key agricultural issue in the United States. Study after study is showing how widespread the problem is. Here in California and in a few other states, politicians, environmental experts, and farmers are beginning to act.
``There's just a lot more attention being focused on water quality,'' says Dennis Keeney, director of the Leopold Center for Sustainable Agriculture at Iowa State University.
This attention to water quality has broad implications. Some environmental scientists predict that farmers in the next decade will be forced to try new, less damaging production methods that would have been considered outlandish just a few years ago.
``It's coming down the road, and growers will have to recognize this,'' says Ken Tanji, coordinator of agricultural water quality projects for the University of California. ``Farmers will have to change their ways in terms of producing crops.''
Although most of the concern in the US is focused on groundwater - water that lies below the surface - farmers here on the western side of the San Joaquin River Valley face a special problem: selenium leached into the water by irrigation.
Selenium is a naturally occurring element in the soils here. It is thought to be necessary to the diet at very low levels (50 millionths to 200 millionths of a gram per day for adults), but it's toxic at higher concentrations. In 1983, high selenium levels were linked to the death and deformation of waterfowl at California's Kesterson Reservoir. The reservoir was fed by agricultural drainage waters, but the inflow was stopped in 1986 because of the selenium.
The selenium problem has complicated farmers' long battle against the buildup of salts in their soil. Irrigation water naturally carries salt with it. Traditionally, farmers here used extra irrigation water beyond plant needs to wash the salt down - below the root zone of their crops. But with the closing of Kesterson, they have no outlet to drain the excess water that is building up in the soil. Scientists and farmers are scrambling for solutions.
Mr. Davidoff's nine demonstration projects for the state Department of Water Resources are part of the intensive effort, which includes university researchers, private consultants, and the farmers themselves.
``There is a lot of room for improvement of existing irrigation systems. Farmers here will be more and more involved in water management and in applying the water according to the needs of the plant,'' Davidoff says.
In several of the projects, Davidoff is trying to show how various technologies - such as shorter irrigation furrows, underground drip irrigation, a low-energy, precision water applicator, and water-table controls - can reduce the amount of salty drainage water. Another project reuses the drainage by diverting it into a plot of water-absorbing eucalyptus trees, then sending it to a field of an even more salt-tolerant groundcover crop.
In theory, the less water farmers have to drain, the cheaper it is to treat it or dispose of it. One disposal method, soon to be tested, involves injecting the water into a well deeper than the groundwater layer. Another plan envisions building a natural-gas plant and using its excess heat to evaporate the drainage water.
``I think it has become clear to most people that there is no single solution,'' says Stephen Hall, executive director of an association of 13 California districts on the western side of the valley. ``Like most complicated resource problems, we will manage the problem'' rather than eliminate it.
One of the most promising developments is the farmers' involvement.
``We have seen a tremendous amount of interest in ways to improve irrigation,'' says Don Upton, a spokesman for the Westlands Water District, which has some of the worst selenium problems in the region. Farmers have put up hundreds of thousands of dollars and donated land for demonstration projects. Under a cost-sharing arrangement, they are using private consultants to improve their irrigation practices.
The local interest is understandable, since by some estimates, the area has only about seven to 10 years before significant amounts of farmland become so salt-laden that they become unfarmable. But farmers' concerns about water quality reach beyond the San Joaquin and California. Even environmental groups concede that many farmers are looking for solutions.
``It's varied,'' says Jennifer Curtis of the Natural Resource Defense Council of the response from the agricultural community. But ``I think it's going to hit home.''
Certainly, the potential contamination is widespread. Cautioning that not all the data had been scientifically verified yet, the Environmental Protection Agency last December reported that 46 agriculture-related chemicals, typically from pesticides and fertilizer, were found in the groundwater of 26 states. According to US Department of Agriculture estimates, nearly half of all the nation's counties may have polluted groundwater, most of them in rural areas. The contamination may pose a threat to at least a share of the 50 million Americans who get their drinking water from wells.
Congress and several governors are looking into the problem. Last week, Minnesota's Gov. Rudy Perpich signed a $17 million groundwater protection bill.
But the approach most widely applauded by environmental scientists and activists is Iowa's 1987 groundwater protection measure. Instead of using California's regulatory approach, Iowa's measure emphasizes education, research, and demonstration of alternative methods of farming, usually called sustainable agriculture. Typically, these methods mean reduced reliance on chemical pesticides and fertilizers and increased reliance on environmentally sensitive practices, such as crop rotations.
``Farmers at this point - at least in Minnesota and the neighboring states in the upper Midwest - are ready to do something different,'' says Jim Anderson, director of the University of Minnesota's agricultural water quality center. Two things may discourage an immediate move, he cautions. Farmers, mindful of the recent farm crisis, will be less willing to experiment with new practices. Also, certain institutional arrangements, such as farm programs, encourage repeated production of a crop and discourage innovation.
But he and other scientists see an emerging, environmental ethic taking shape on the American farm.
``I think we are looking at the turn of the century'' before the change takes hold, says Mr. Keeney of Iowa's Leopold center. But ``the train at least is fired up and it's starting to leave the station.''