Volcanic ash soils (Andisol)

Typical Characteristics:

• Parent Material: Volcanic soils, also known as Andisols, are formed from volcanic ash and cinder deposits. While most of the world’s volcanic soils are not highly weathered, there are notable exceptions on Maui.

• Mineralogy: Volcanic soils largely consist of non-crystalline (amorphous) minerals, such as allophone and imogolite.
• These minerals form strong bonds with organic matter. As a result, organic matter generally accumulates in the surface horizon.
• In addition to organic matter, volcanic soils may also contain high amounts of volcanic glass material with the possibility of amorphous iron and aluminum minerals.

• Physical Traits: Andisols are usually light and fluffy and are easily tilled. Like a sponge, these soils also hold a lot of water.

• Fertility: When not highly weathered, volcanic soils are typically very fertile soils. However, volcanic soils form strong complexes with phosphorus. When poorly managed, phosphorus can be limiting. Additionally, the amorphous minerals that dominate volcanic soil can generate an anion exchange capacity (AEC) when under acidic conditions and depleted in organic matter. Fertility problems may be corrected with additions of organic matter, lime and/or fertilizer amendments.

Volcanic soils of Maui:

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GLASSY, DRY VOLCANIC ASH SOIL (VITRITORRAND)

• Alae Series
• Oanapuka Series

HOT, DRY VOLCANIC ASH SOIL (HAPLOTORRAND)

• Makena series

MOIST/DRY VOLCANIC ASH SOIL (HAPLUSTAND)

• Io Series
• Kaipoipoi Series
• Kula Series
• Laumaia Series
• Oli Series
• Olinda Series
• Pane Series
• Puu Pa Series
• Ulupalakua Series

VOLCANIC ASH SOIL WITH VERY HIGH WATER RETENTION (HYDRUDAND)

• Hana Series
• Kailua Series
• Honomanu Series

Unique Characteristics of Volcanic Ash Soils of Maui County:

Although there are several different types of volcanic soils on Maui, we will discuss two soils that are agriculturally significant.

• Moderately weathered volcanic ash soil
• Highly weathered volcanic ash soil.

enlarge the map Moderately weathered volcanic soil