Hawaii’s seed crop industry continued expanding last season as companies spent more money on operations, though the pace of growth slowed and shipments of seeds declined, according to a government report.

A preliminary estimate by the Hawaii office of the National Agricultural Statistics Service last month pegged the value of local seed crops at $247 million in the 2010-11 season, up 5 percent over a revised value of $236 million for the prior season.

The modest growth reflected maturing of an industry that grew at rates between 23 percent and 37 percent in each of the previous six years.

Fred Perlak, president of the Hawaii Crop Improvement Association, noted that last season’s growth occurred despite a tough economy and still makes seeds the biggest agricultural commodity in the state.

“The contributions of Hawaii’s seed crop industry are significant,” he said. “The seed industry continues to be a stable source for tax revenues, employee salaries, jobs and community support.”

Seeds — primarily seed corn — have been Hawaii’s largest crop by value since overtaking pineapple in 2006, though other crops are bigger in terms of contribution to the local food supply.

Seed production primarily involves studying plant genes and properties, breeding plants with desired genes both traditionally and using biotechnology, testing the resulting plants and growing large quantities of favorable plants to produce parent seed that is sent to the mainland for mass reproduction and sale to farmers.

Because the seeds produced aren’t sold, the Agricultural Statistics Service, a unit of the U.S. Department of Agriculture, calculates industry value based on operating expenses excluding land purchases.

Seed production actually decreased last season. The report said shipments of seed declined 19 percent to 9.8 million pounds from a record 12 million pounds a year earlier.

Perlak said some companies could have been devoting more work to research instead of production last season, though wetter weather last season probably decreased seed yields.

“There’s going to be variations year to year based on the yield in the field,” said Perlak, who is vice president of research and business operations for Monsanto in Hawaii.

According to the report, land devoted to seed crops totaled 7,100 acres last season, up 9 percent from 6,500 acres in the prior season.

The number of farms decreased to 10 from 11 last season as Monsanto closed a small operation on Kauai.

Five seed companies — BASF, Dow AgroSciences, Monsanto, Pioneer Hi-Bred International and Syngenta — have seed farm operations in the state.

The companies were attracted to Hawaii because corn can be planted and raised to maturity three or four times in one year compared with only once on the mainland, thereby allowing faster advancement of research.

Seed crops can be grown all year in Hawaii, though the main season is from November to June.

Among types of seeds grown, corn is the main crop in Hawaii, accounting for $236 million of the industry value last season. Seeds from other plants such as soybean, wheat, sunflower, rice, rapeseed and sorghum are also produced and represented about $11 million of industry value last season.