The Robinson family of Kauai has stepped up to preserve about 21,000 acres of agricultural land it owns before the county selects prime private farmland for protection, but state agencies have raised concerns about a portion of the family’s plan.

Robinson Family Partners, one of Kauai’s biggest landowners, with historical connections to sugar cane farming and cattle ranching, has filed a petition with the state Land Use Commission to restrict what amounts to about 75 percent of the agricultural land it owns mainly between Waimea and Hanapepe in southwestern Kauai for farm use in perpetuity.

The petition is the ninth filed by large private Hawaii landowners under laws the Legislature created in 2005 and 2008 to preserve “important agricultural land,” or IAL.

Under the IAL laws, landowners can receive tax credits and other benefits for voluntarily locking up productive ag land for ag use. Another benefit for landowners is to pre-empt counties from involuntarily restricting private ag land for ag use if the private landowners voluntarily protect at least 50 percent of their ag land.

The Robinson family is going considerably above the 50 percent threshold. But the state Department of Agriculture and state Office of Planning raised concerns about whether some land was deserving of protection. Most of the land selected for preservation is of poor quality and used for cattle grazing.

The partnership led by Bruce Robinson said in its petition that a related company, Gay &Robinson Inc., intends to expand its Makaweli Meat Co. ranching operation, which occupies 25,000 acres, including 18,700 acres in the petition area, and represents an important local food source branded as Makaweli Beef.

“Makaweli Beef shall be a very important component of the island’s future food sustainability plans,” the petition said.

The ranch contains 3,500 to 4,000 head of cattle, about half of which are on the petition site at any one time because the cattle also graze on adjacent land not selected for preservation.

Under the Robinson expansion plan, land with irrigated pastures would expand to 1,400 acres from 400 acres over five years, which along with upgrades to nonirrigated pastures would allow for the addition of 1,500 cattle. The herd now represents about 9 percent of Kauai beef production, which would increase to 12 percent with the addition, the petition said.

Scott Enright, director of the Department of Agriculture, said the agency supports most of the request but has “strong reservations” about 3,260 acres of upper-elevation land that includes steep slopes, rocky outcroppings and no plans to improve pastures.

“The petition does not provide convincing evidence of agricultural use within the area,” Enright said in a comment letter.

In response, the Robinson partnership said the upper-elevation ranchland does not support as many cattle but is still “integral” to the business.

Leo Asuncion, director of the Office of Planning, recommended the entire petition area be approved, though he said his agency has concerns with much of the land being designated as IAL.

“Large areas of this parcel are considered less productive agricultural lands due to steep land slopes over 20 percent consisting of ravines and gulches and overall poor soil qualities,” he said.

Asuncion also noted that the county general plan designates much of the upper pasture area as “open” use, not agriculture use; maps that the county developed for making involuntary IAL designations give most of the Robinson petition area low scores, indicating that it meets relatively few criteria for protection.

Still, Asuncion didn’t object to the petition being granted in its entirety. He said his agency appreciates the Robinson family’s commitment to long-term production of grass-fed beef.

“The ranch will continue to contribute to and be a productive and vital component of the island’s agricultural industry,” he said in a comment letter.

Michael Dahilig, director of the county Planning Department, raised no concerns in a letter of support.

Generally, the better-quality Robinson ag lands lie more makai of the ranch area. This high-quality area includes 2,188 acres that are part of the petition for protection and are leased to DuPont Pioneer and a subsidiary of Dow Chemical for seed production.

Another 6,300 acres that run all the way to the ocean also are used for pasture or leased to the seed producers but is excluded from protection. Some of this property borders land zoned for urban use, including the planned Kapalawai Resort in Pakala, which involves the Robinson family.

Curtis Tabata, an attorney representing the Robinson family, said there are no plans to pursue a different use of the most makai ag lands, which if done would require zoning changes. Yet the family had to consider possible other uses far into the future.

“IAL is intended to be forever,” he said. “Even though they don’t have any plans now, you’re forced to look generations into the future.”

One benefit under the IAL law that the Robinson partnership has waived allows a private landowner to urbanize ag land equivalent to 15 percent of the area preserved. The eight previous IAL petitions approved for major landowners including Kamehameha Schools, Alexander &Baldwin, Parker Ranch, Castle &Cooke and Grove Farm Co. also included this waiver.

Other benefits that can be claimed include loan guarantees and placement of employee housing on farmland.

A public hearing on the Robinson petition is scheduled by the Land Use Commission for 1 p.m. Wednesday in the State Building at 3060 Eiwa St. in Lihue.

If approved, the petition will help support continued ranching by the Robinson family, which has gone on for more than 150 years.

The Robinson family acquired its Makaweli lands in 1865 when the family matriarch, Elizabeth McHutcheson Sinclair, bought about 21,000 acres from Victoria Kamamalu, sister of King Kamehameha V, a year after she bought the neighboring island of Niihau. As more Kauai land acquisitions were made, Sinclair partnered with her daughter and grandson, Francis Gay and Aubrey Robinson, to raise cattle and farm sugar cane.

Gay &Robinson shut its sugar plantation in 2009. Ranching, however, continued, and the company spent over $1 million in 2013 to build a new slaughterhouse and processing plant, the petition said.