Moderately Weathered, Fertile Soils (Mollisol)

Typical Characteristics:

Formation: Mollisols form by the accumulation of calcium-rich organic matter. In the Midwestern United States, these soils formed in the dense root system of prairie grasses.
Physical Traits: The surface horizon of Mollisols is deep and rich in calcium, magnesium, and organic matter. The soil is often dark in color and has a soft texture. The CEC of these soils is more than 50% saturated with calcium, magnesium, nitrate, and magnesium. These soils can contain swelling clays that have poor drainage.
Productivity: Mollisols are naturally highly productive soils.

There are many soil series that fall into the order of Mollisols on Maui. The Paia Series is one series that has agricultural importance.

Location: The Paia eries is located in the isthmus of Maui, among which the majority of the island’s Mollisols moderately-weathered, fertile soils are located. The Paia Series comprises of 5,600 acres in the uplands, with elevations ranging between sea level and 1,000 ft.
Texture: Silty clay
Rainfall and Temperature: The average annual rainfall is between 25 and 40 inches, and the average annual temperature is approximately 73 degrees F.
Slope: Gentle to moderate
Parent Material: The Paia Series formed from weathered basic igneous rock, and some volcanic ash.
Depth: Surface layer is very deep and extends 19 inches. Subsoil is 41 inches in depth.
Physical Traits: The soil is well-drained with slow to medium runoff and moderate permeability.
Color of Surface Horizon: Dark reddish brown
Fertility: The Paia Series is naturally high in plant nutrients, such as calcium.
Acidity: mildly alkaline
Natural Vegetation<: ilima, kiawe, lantana, among others.
Agricultural Use: Irrigated sugarcane.

The Paia Series is exemplified by an alkaline pH and relatively high levels of calcium.

Paia Series
Photo by Tai McClellan