On the Side: There's a secret to the sweetness of Joe Jacobs' berries, and fewer and fewer growers share it.

MILMAY, N.J. - At Bertuzzi's Farm here, a regular stop on the way to the Shore, Joe Jacobs attributes the particularly juicy sweetness of his strawberries to what at first seems a rather unlikely secret - his salt-hay mulch.

He isn't the only local grower using the fine, wiry stuff, harvested since colonial times in the Down Jersey salt marshes along Delaware Bay.

But he is one of a shrinking band of Mohicans as far larger growers stripe their fields in the plastic sheeting that gives them impressive yields and typically a somewhat longer season.

The trade-off, though, says Jacobs, is that the berry varieties that he favors for heft and juice and abiding fruitiness don't always yield well under plastic and are harder to come by as, locally, the far-more-prolific Chandlers dominate the field.

On a sunny day last week, wearing his trademark scuffed knee pads, Jacobs knelt in the sandy loam of his 35-acre spread, riffling the matted salt hay, explaining his technique.

He has been farming for 39 years, with his wife, Carolyn (a Bertuzzi), and son, Joe Jr., growing tender broccoli rabe from seed threshed by hand and saved year to year, and onions, Sunbeam tomatoes and blackberries, crops that bracket the brief (about 10 more days) strawberry season.

This season he's picking Dar Select, dark and lush; Cabot, a gentler, sweet berry; Jewel; and Clancy. (The berries are heavy with juice. We weighed a heaping quart carton at the farm stand; it was close to two pounds, a good half-pound more than many West Coast quart containers.)

Not one of the berries goes off to the wholesale market. They're all sold at the farm stand here, the lion's share to customers heading to the beach on Route 557.

All are handpicked, not by migrant labor but mostly by Jacobs on his bad knees and his wife (who favors the bend-and-pick method) - roughly 3,500 quarts a season.

The berry plants are planted in so-called matted rows in June. Then in December, Jacobs uses a hay blower to cover the fields in the fine salt hay he picks up from one of the last of the Down Jersey harvesters near Port Norris.

Partly, the salt hay acts like any mulch - protecting against weather, preserving moisture. But it has other properties that, say, common straw does not: It doesn't rot and break down, nor does it have weed seeds that counter its weed-suppression function.

But importantly in this shifting, sandy soil, Jacobs says, the hay stays put, making picking easier and keeping the sand off the fruit.

Does it enhance the flavor itself? "[It] seems to bring [it] out," says Jacobs. "But then it could be my imagination."

Salt hay does have another growing utility in South Jersey, though one not necessarily beneficial to the health and well-being of agriculture.

At the construction sites that gnaw at the edges of farm country, salt hay is still a favored insulation to protect untold tons of fresh, wet concrete from freezing over.