Industrial agriculture companies producing seeds in Hawaii mainly for corn research and reproduction had a second consecutive season of steady operations after three years of declines, according to a preliminary government estimate.

The U.S. Department of Agriculture issued its estimate Thursday in a report that pegs the statewide production value of seeds at $145.3 million in the 2016-17 season, which wraps up this month. That is up less than 1 percent from $144.5 million in the prior season.

The industry’s relative flatness this season comes as one of Hawaii’s dominant seed producers, Swiss-based Syngenta, works to complete a sale of its local operations to Wisconsin-based Hartung Brothers Inc.

Since 2006, seeds have been regarded as the biggest crop in the state by production value as compared with traditional food crops, whose values are measured by crop sale value, which typically is more than the cost of production.

Hawaii’s seed crop industry value is calculated by the cost of production because the companies that grow seeds here don’t sell them. Instead, they try to produce plants with desired traits — using genetic modification and traditional breeding techniques — and the seeds of such plants are sent to the mainland for mass reproduction and sale to farmers.

The peak value for seeds statewide was $241.6 million in the 2011-12 season, which was followed by three annual declines driven by a maturing industry and corn price declines.

“Falling global demand for these and other global commodities as inputs — from bio-fuels in energy production to uses as oils, sugars, and other carbohydrates in food consumption — all reduced corn grain prices and farmers’ demand for corn seed as a use of it,” the industry’s trade group, the Hawaii Crop Improvement Association, said in a September report. “As a result, Hawaii’s corn seed industry has shrunk.”

Hawaii’s seed industry is made up of five companies: BASF, Dow AgroSciences, Monsanto, Pioneer Hi-Bred International and Syngenta. Together they operated 11 farms on Oahu, Maui, Molokai and Kauai covering 4,010 acres under cultivation in the most recent season.

In the prior season there were 10 farms covering 3,980 acres, the USDA report said.

Corn represented 97 percent of the seed in both recent seasons. Other seed crops grown in Hawaii have included soybeans, wheat, sunflowers, rice, rapeseed and sorghum.

Shipments of seeds out of Hawaii ticked up 6 percent to 6.1 million pounds in the latest season from 5.7 million pounds in the prior season. The record was 12 million pounds in the 2009-10 season.

The USDA estimate, which is based on surveys of seed producers with assistance from the state Department of Agriculture, is subject to possible revision. In August the USDA initially pegged Hawaii’s seed crop value for the 2015-16 season at $151 million; it later revised that down to $144.5 million.

Seed producers have had a presence in Hawaii since the 1960s, favoring the climate in part because corn can be planted and raised to maturity three or four times in a year compared with only once on the mainland.

Many local agriculture leaders view the seed business as a good force that has kept workers employed and farmland productive in the wake of sugar cane’s disappearance, though environmentalists and natural-food proponents detest the industry because much of the work involves genetic engineering. Such concerns have led to litigation as well as state and county initiatives to restrict or ban work with genetically modified organisms.