What is Soil? Unit: Soil Science, Lesson 1

Soil O An unconsolidated collection of natural components that make up earth’s surface; provides nourishment and support to growing plants; a mixture of minerals, organic matter, water and air

Soil’s Key Functions O Nourishes and supports the plants O we eat O we depend on for oxygen O animals eat which we in turn use for food and clothing O we use for decorative purposes (flowers, landscaping, lawns, etc.) O Determines where and how we can construct homes and all other buildings O Filters and protects the groundwater we use for consumption, bathing, irrigating, etc. O Filters the moving water found on earth’s surface (creeks, streams) O Provides a habitat for organisms that break down other dead organisms

Nebraska’s State Soil O Holdrege O Nearly 2 million acres of Holdrege soil in Nebraska; especially in the south-central area of the state O Level or gently sloping O Well-drained O Silty texture O Mostly used for crops pasture or rangeland O Much of the land is irrigated

Soil Components SolidsLiquidsGasesSoil

Solid Phase of Soil O Mineral Soils O Less than 20% organic matter (OM) O Organic Soils O More than 20% OM O OM comes from dead plant and animals O Solid components separated by small pore spaces O Provides physical support and nutrients

Liquid Phase of Soil O Water found in the soil pores O May fill or partially fill pore space O Absorbed by and stored in soil O Eventually returns to the atmosphere through evaporation or through use by plants O Forms solutions with soil salts to provide plant nutrients O Provides water and dissolved nutrients to plants

Gaseous Phase of Soil O Fills pore space not occupied by aqueous solutions O N and O 2 concentrations compare to the atmosphere O CO 2 is found in concentrations of nearly 10 times what exists in our atmosphere O Provides oxygen for plants

The Soil Profile O Reno County, Kansas MLRA 79 Photo by Jim Fortner, USDA-NRCS

The Soil Profile O Horizon O: organic material O Horizon A: top soil; contains newly decayed OM; dark in color; contains roots O Horizon E: very light in color because of leaching O Horizon B: sub soil, materials leached from A and E accumulate here, high clay content O Horizon C: large rocks partially broken down O Horizon R: bed rock that evolves into the parent material that will become soil over time