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MADRAS, Ore. - After five years of trials using drip irrigation to grow carrot seed crops, Oregon State University Agricultural Experiment Station researchers are calling the method a success in the central Oregon.

Drip irrigation is a relatively new method to the region. Using the method, carrot seed crop yields and quality were high and disease incidence was low, when compared with carrot seed crops irrigated by traditional overhead sprinkler systems, explained Marvin Butler, crop scientist and superintendent of OSU's Central Oregon Agricultural Research Center in Madras.

With drip irrigation growers can use only half as much water as traditional sprinkler irrigation on carrot seed. In addition, carrots can be planted in areas where sprinkler irrigation cannot be used - in steeper country, for example.

"What's not to like about drip irrigation?" Butler said. "We've had higher seed yields using half as much water. With increased yields, water savings and higher quality seed, the drip tape pays for itself."

To prevent diseases spreading from one generation of vegetables to the next, the seed for vegetable crops is often grown far from where the vegetable crops are grown. For instance, most fresh market carrots are grown in California.

However, the warm days and cool nights on central Oregon's high lava plateaus produce high quality seed, according to OSU researchers and seed companies. The region's relative isolation makes for less disease and its relative dryness makes for high seed set.

Each August, the OSU researchers and local growers plant carrot seed near the surface of the soil. The following spring, they installed drip tape a few inches to the side and buried below the growing carrots, drip side down.

This drip "tape" is manufactured as long rolls of flattened plastic tube with microscopic holes at eight- to 10-inch intervals down long rows in the cooperating growers' fields. When the tape is filled with water, a cone of wet soil extends out down into the soil to the planted carrot seed, explained Butler.

In OSU's trials, yields of carrot seed were 20 percent higher in drip-irrigated fields than in sprinkled fields. Germination rates were 3 percent higher in the seed crop produced with drip methods. And it looks like there is the potential to reduce a disease that knocks out fresh market carrot crops called carrot bacterial blight, or Xanthomonas.

"Until we get more typical dry springs that tend to suppress Xanthomonas, we can't say for sure," said Butler.

Learning how to grow seed crops with drip irrigation has been a fulfilling partnership for OSU researchers at the Central Oregon Agricultural Research Center, local growers and the vegetable seed industry.

"None of us could have done this alone," said Butler. "We learned together to produce this crop a new way together for the huge fresh market vegetable industry.

OSU researchers, along with the growers and seed companies are all hoping that drip irrigation will work as well on other seed crops grown in the region, including parsley, radish, Chinese cabbage, coriander, kale and arugula seed, all traditionally grown using overhead sprinkling or furrow irrigation.

Local growers are increasingly interested in trying the new irrigation technique. In 2002, four farmers volunteered some land for the experiment on four fields, 22 acres total. By this summer, 15 growers will be growing carrot seed for the experiment in 25 fields that cover 700 acres.

The only major stumbling block with drip irrigation in central Oregon has been with rodents chewing through the tape, the researchers say. Last year's mild winter led to booming populations of voles and mice, and about half the growers last season experienced rodents chewing on their drip tapes.

The OSU researchers are planning research this coming season to evaluate several strategies for rodent control. However, the boom in rodent numbers will probably crash at some point, as predators like hawks and coyotes will probably soon have them in control.

"Nature is full of boom and bust cycles," said Butler.