CALDWELL, Idaho — Dustin Batt, a straw hat shielding him from the sun on a blistering summer day, walks through chest-high acres of corn. He carries an electronic tablet where he writes down bits of information about each plant — height, hardiness, length of ears.

He's looking for corn that will be bred and rebred. The plants will create seed for corn that will show up at your grocery store or in a can of sweet corn you buy for dinner.

In a year, Batt will pass by a million corn plants and save only about 500 of them.

"They are the best of the best," he said.

Batt, 34, is a corn breeder for Crookham Co., a 101-year-old agriculture business in Caldwell that processes millions of pounds of seed — corn, popcorn and onion — each year for growers around the world.

It has plenty of company locally. About 40 seed companies — including big corporations such as Harris Moran, Monsanto and Syngenta and small businesses like Crookham — are taking advantage of spectacular growing conditions in the Treasure Valley.

It is unclear how many people they employ. But Crookham and Nunhems, a part of Germany-based Bayer Crop Science, each might employ more than 200 people during peak periods when seeds are processed.

Much of the Treasure Valley seed business operates on a similar model. Companies create hybrids, generate parent seed and then contract with independent growers to plant those seeds to generate more seeds.

The growers raise and harvest the crops and bring their seeds back to companies such as Crookham, where they are screened, packaged and sold to growers who will turn them into crops for eating.

Companies say there is a worldwide demand for more and better seed.

Nunhems, whose U.S. headquarters is seven miles north of Parma, underwent a 50 percent, $30 million expansion in seed processing capacity in 2010 in Parma to help it meet a projected 75 percent increase in demand for seeds between 2010 and 2020.

"We were at the gills," said Shane Roe, Nunhems facility and maintenance manager.

This fall, Nunhems plans another expansion to triple the size of its 7,500-square-foot quality-assurance area to meet demands for more testing as quantities of seeds shipped continue to rise, Roe said.

Nunhems' Parma plant processes onion and carrot seed, from seed grown by farmers in Idaho and Oregon. It also processes watermelon, tomatoes, cabbage, broccoli and other seeds from plants harvested elsewhere in the country. Nearly two-thirds of the processed crops at Parma come from Idaho and Eastern Oregon. Nearly a quarter come from California.

Demand for seed is growing inside and outside the United States as demand for food rises, said Stacy Woodruff, Nunhems' global head of processing.

Canyon County's location is part of the reason for growth in the seed industry in Idaho. Its arid climate and cold winters — good for killing bugs — make the region ideal for growing many types of seed. "There are not many places around the globe that are as conducive for seeds," Woodruff said.

In nearby Parma, Jon Watson, whose family has been growing crops in the region for a century, operates on two sides of the seed business.

He's a large onion grower and regularly spends $400 to $500 an acre for seed for his 450 acres of onions, part of his 2,000 acres between Parma and Middleton.

He plants Nunhems seeds that are designed to endure long daylight hours during growing periods and to produce onions that store well in sheds after the summer harvest and before they are shipped the next fall, winter and spring. They also produce the double-fisted-size onions that show up in restaurants, like those in Outback Steakhouse's deep-fried onion blossoms.

But Watson's J.C. Watson Co. also grows seeds for such crops as beans, alfalfa and sweet corn. Seed crops take about 25 percent of his acreage. They keep parcels of land in production and generating income while the fields are in rotation for his onions and other crops. The seed crops bring in better prices than crops raised for people to eat.

Growing is as much art as science. With some crops, Watson must be careful of irrigation. "Too much (there is) scalding," he said. Too little and the plant dries up.

For seed companies, the business requires constant research, looking for ways to bring together the best traits of various plants and come up with better seeds.