Lester Loam

The Lester loam is Minnesota's official state soil. It sits on the gently rolling ground moraines of south-central Minnesota — the same landscape of corn fields, grain elevators, and small towns that defines the agricultural heart of the state.

Lester is a well-drained loamy soil with a deep dark surface and a clay-enriched subsoil. Below both of those layers lies calcareous glacial till — limestone-rich material deposited by glaciers pushing in from the northwest. The lime in that till is part of why Lester soil is so productive: it buffers the soil chemistry and releases nutrients slowly to crop roots.

The Lester series was first described and mapped in 1939 in McLeod County, near the town of Lester Prairie in south-central Minnesota. The series was named after that town.

In 1985, the Minnesota Association of Professional Soil Scientists (MAPSS) formed a committee to select a state soil. Two years later, in 1987, the members voted to designate Lester as their unofficial choice. The criteria: the soil had to be based in Minnesota, cover a large area, be economically important, and look good in a profile photograph. Lester qualified on all four counts.

It took another 25 years for the Legislature to act. The bill was authored by Senator Gen Olson and Representative Mark Murdock. Governor Mark Dayton signed it into law on April 28, 2012, making the Lester loam Minnesota's official state soil.

Lester loam has five main layers. The most striking feature is the dark surface — called the Mollic epipedon — which runs seven inches deep and looks nearly black compared to the lighter soil below. That dark color comes from centuries of organic matter building up under prairie grasses and hardwood forest.

Below the dark surface is the argillic horizon: a clay-enriched zone where clay minerals were carried down by water and deposited. The clay makes this layer denser, stickier, and better at holding nutrients. Below that is the calcareous parent till — yellowish-brown glacial material full of calcium carbonate from ground-up limestone.

Lester loam covers over 600,000 acres across 17 counties in south-central Minnesota. It sits on the gently rolling ground moraines deposited by the Des Moines Lobe of the Laurentide Ice Sheet, which pushed into Minnesota from the northwest during the last ice age.

The soil is concentrated in the zone where the tallgrass prairie once met the Big Woods — the dense hardwood forest that once covered the region before European settlement. That transition zone, sometimes called the forest-prairie border, produced some of the most fertile soils in the state.

Lester loam also extends into north-central Iowa, where the same glacial landscape continues south across the state line. In Minnesota, it is found primarily in the arc of counties running from Kandiyohi and Meeker south through McLeod and Sibley to Blue Earth and Brown.

Lester loam is prime corn and soybean country. The deep dark surface holds organic matter and nutrients. The clay-enriched subsoil retains water during dry spells. The calcareous till underneath keeps the pH balanced. The result is one of the most consistently productive farm soils in Minnesota.

Before European settlers broke the sod and cleared the Big Woods in the 1850s through 1890s, Lester loam supported a mix of tallgrass prairie and hardwood forest. Prairie species included big bluestem, indiangrass, and switchgrass. The Big Woods brought sugar maple, basswood, northern red oak, and American elm — some of the most productive hardwood forest in the Midwest.

Today nearly all Lester loam is in row crop production. Corn and soybeans rotate across most of it each year. Some is used for pasture and hay. The soil requires little amendment to be highly productive — the calcareous parent material keeps lime applications minimal and the argillic horizon holds fertilizer well.