1. Soils
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2. What determines the type of soil?
Parent Material – the type of rocks naturally found in an area
Climate
Topography – geographical features of the area
Organisms
Time

3. Soil formation Rock is broken down over time by weathering
Organisms live and die, adding nutrients and eventually organic matter
Rate: 1cm can take years
Over time, distinct layers called horizons form
A renewable resource, but a slow one

5. Soil profile Made up of soil horizons
Different textures and compositions
Can be observed by digging a soil pit
Mature soils have 3 or more horizons

6. O-Horizon

7. A-Horizon A

8. E horizon

9. B-Horizon Yellow alum oxides Red = iron oxides
White = calcium carbonate

10. C-Horizon

11. Soil Profiles by Biome

12. Soil Matrix

13. What is in soil?
Organic
Inorganic
Pores

14. Soil Texture Particle Type
Determined by the % of each type of particle

15. Soil Texture Importance

16. Porosity and Permeability

17. Soil pH
pH correction

18. Acidic soils Acidic soils Soil in California tends to be basic
Hinder nutrient availability
Increase availability of toxic heavy metals
Major problem for urban gardens in the northeast US
Increase pesticide runoff
Decrease bacteria populations less nitrogen fixation
Soil in California tends to be basic
Soil in the northeastern US is more acidic

19. Weathering
Chemical
Rock decomposes into sediment via chemical reactions. Usually a reaction of rock material with carbon dioxide, oxygen and water
Example: Limestone Caves carved by acidic groundwater percolation
Physical
Large masses of rock are broken into smaller pieces through physical processes
Example: Frost wedging
Biological
Decomposition of rock material via biological activity.
Example: Roots breaking through bedrock, Lichens producing acids that chemically weather the rock.

20. Soil Issues Erosion Happening continuously (flowing water)
Rates can be increased by human action
Ex: changes in plant species, unnatural fires, over use of agricultural lands climate change
Compaction
Decreases pore space and causes water to run off landscape instead of being absorbed.
Salinization
Occurs with irrigation
Irrigation water=ground water=has elevated levels of salts
Over accumulation of salts in soils.

21. Soil Profiles from Time Magazine

22. A toxic white crust runs through irrigated fields in Grand Valley, Colorado: Moisture evaporating from the soil has drawn underground salt to the surface. To keep the salt from damaging the roots of their crops, farmers must add even more water.

23. Thick, six-foot-long roots of sunflowers, side-by-side with the roots of assorted prairie grasses, delve deep into a plot of earth near Salina, Kansas. This soil has never been broken by a plow. These perennials have root systems that expand and strengthen year after year—unlike annual crops that demand much of the soil but provide little in return. Such growth not only helps prevent erosion but also serves as a water-storage system that enables the plants to survive during droughts.

24. Virgin Prairie—Kansas, United States.
Rancher Jim Duggan holds a stalk of big bluestem, one of the native grasses growing on 40 acres of his farmland that have never been plowed. "This land is the best there is," he says. "It's class-one river-bottom soil." Compared with tilled fields, the parcel has deeper, richer topsoil and soaks up more rain.

25. Reclaimed Fields—Keita District, Niger.
Mariama Abdoulaye feeds her family with millet she grows on once barren land. After severe droughts in the 1970s and ’80s, the UN Food and Agricultural Organization enlisted Abdoulaye and 10,000 other women to plant millions of trees. Tree roots block wind-driven erosion and help rain penetrate the earth.

26. Rice Terrace—Yunnan Province, China.
Perched on an earthen retaining wall, Zhu Minying holds cords used to bundle harvested rice. Soil here reflects human activities that began with reshaping hillsides into grand staircases of grain. Rice stubble left to decay in the field, manure, and fish raised in the paddy water, all add nutrients to Zhu's soil.

27. Dry Land—Khanasser Valley, Syria.
Farmers like Ismail Hassoun Hariri struggle to grow even hardy barley in this parched land. Soil and rock eroded from surrounding hills lie thick in the valley, but annual rainfall averages only nine inches. In some very dry years the barley crop fails to mature and can only be used to feed sheep and goats.

28. After losing a foot of soil from parts of their Iowa corn farm, the Reed family changed the way they prepare fields for planting, to limit erosion. Cletus Reed, 80, hopes his grandson, Sam, will work these acres someday. "The land takes care of us as we care for it," he says.

29. Tiny earthworks stipple bare slopes in China's Zizhou County, each intended to cradle a single sapling. Government mandated reforestation programs are intended to halt erosion, but many earlier efforts here in the Loess Plateau failed when newly planted trees died.

30. Organically farmed soils (at left) have a more cohesive structure, which results in less silty runoff than found with conventionally farmed soils (at right). These samples come from the Farming Systems Trial at the Rodale Institute near Kutztown, Pennsylvania. For 28 years, a plot of land there has been managed organically: Researchers rotate crops regularly, grow cover crops in winter, and apply no chemical fertilizers or pesticides. Laboratory analysis shows that organically managed soils produce lots of glomalin, a gluey protein that helps earth hold its ground.