The soil worked by most farmers in Butler County isn’t made of the best ingredients for agriculture, but it can be productive with the right management.

Most soil in the county is made of sandstone and shale and needs good management to be productive, but soil in the northwest corner of the county is made of glacial material, which is more fertile but requires drainage.

“The majority was formed from sandstone and shale, which is naturally lower in fertility than soil in Center and Lancaster counties that was formed from limestone,” said Alex Dado, a soil scientist with the Natural Resource Conservation Service, a division of the U.S. Department of Agriculture, in Butler.

“Our sandstone and shale soil is inherently lower in productivity, but they can still be excellent ag(ricultural) soils if they are managed properly.”

Proper management involves adding planting cover crops when fields aren’t in use. The roots of cover crops add organic material to soil and help control erosion between plantings of cash crops, Dado said. Cover crops are plowed into the soil before cash crops are planted.

Contour strip cropping — which involves planting strips of cash crops between strips of hay or wheat to prevent erosion on slopes — no-till farming and minimizing surface disturbance also help organic material to build up and prevent erosion, he said.

Steep slopes and wet land are better for grazing pastures than crops because they are harder to work with farm machinery.

Dado said soil in Butler is similar to soil throughout southwestern Pennsylvania where those management practices are commonly used.

In the county’s northwest reaches, like Worth, Slippery Rock and Mercer townships, the soil is made from glacial deposits from the last ice age.

Soil there is a little flatter and a little more fertile than it is in the rest of the county because there is some limestone in the glacial deposits, but the dirt sits on top of a thick layer of dense hardpan that lets little water permeate.

“You have more wet soil in that part of the county. It has hardpan that doesn’t let water flow through. A little water gets through, but most either builds up or flows laterally,” Dado said.

Hardpan is a dense layer of material left behind when the glaciers retreated. It lies about two feet below the surface and can be “one to five or more feet thick,” he said.

Glaciers also rounded off hilltops leaving flatter ground when they retreated, he said.

Tile drainage, which uses a series of underground pipes laid in a pattern to drain water from soil, is a common practice on farms in those areas.

“Once it’s drained, the soil is productive. It’s a little flatter and has less slopes. It’s slightly higher in natural fertility because there is some limestone in the glacial material,” Dado said.

The soil in the county is slightly more fertile than the rest of southwestern Pennsylvania, but soil in the region is very similar, he said.

Soil in Jefferson and Cambria counties is less fertile because it contains a lot of rocks, he said.

The USDA has soil surveys for every county in the state. The surveys used to be published in books and Butler County’s most recent book came out in 1989.

However modern technology now allows the NRCS to add updates every year based on completed research, Dado said.

The latest USDA survey classifies less than 20 percent — 16.3 percent, to be exact — of the agricultural land in the county as prime, said Justin Brackenrich, a field and forage crop educator for the Penn State Extension office in Butler.

He said planting row crops on slopes without planting cover crops in the offseason leads to erosion, nutrient loss and soil degradation.