Soil and Permafrost Ooooh! Exciting 

Soil Soil is from parent rock It takes 200 years to form a layer of soil...1cm thick! Soil forms distinct layers over time. Layers can be distinguished by color, texture and composition The layers are called HORIZONS

O horizon – Organic Matter Topmost layer High % of dead organic matter. Ie: leaves, stems, fruits, seeds, pine needles Formed from decomposition of organic matter. (humus)

A horizon - Topsoil Seeds germinate and plant roots grow in this dark- colored layer. It is made up of humus (decomposed organic matter) mixed with mineral particles. Mixture of soil from below and the humus above.

B horizon - Subsoil Trees with deep roots draw nutrients from this layer It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips through the soil. Leached from layers above Clay and many minerals Iron Aluminum Calcium

C horizon – Fragmented Parent Rock Can be saturated in groundwater Formed through the disintegration of the underlying parent rock. It consists of slightly broken-up bedrock.

R Horizon – Unaltered Parent Rock Plant roots do not penetrate into this layer. Starting point for soil formation

Soil Conditions Three conditions must be met for soil to be suitable for plant life to form: Water soluble nutrients Adequate moisture Appropriate soil pH Soil to acidic or alkaline jeopardizes the transfer of mineral nutrients

Permafrost Ground whose temperature has been 0o or lower for at least two years.

Permafrost The upper layer thaws in the summer and some growing occurs, this layer is the active layer Permafrost makes construction difficult and agriculture nearly impossible Inuit people build their homes on piles that pass through the active layer and sit directly on the permafrost

Texture and pH

Soil Texture Soil texture is the single most important physical property of the soil. Knowing the soil texture alone will provide information about: 1) water flow potential, 2) water holding capacity, 3) fertility potential, 4) suitability for many urban uses like bearing capacity

To determine texture The Percent of sand, silt, clay in a soil sample Critical for understanding soil behavior and management Soil texture is not subject to change in the field but can be changed in potting mixes.

Buffering Capacity pH is measured on a scale of 0 (very acidic)-14(very alkaline) Soil should ideally be between 6-7 to allow for maximum nutrient absorption Soil has the ability to resist pH changes, when acidic or alkaline compounds are added this is it`s BUFFERING CAPACITY