ecosystem
YANGYANG
SoilsandAgriculture.pptxSoils and Agriculture
ECS 111
7 February 2018
What sets up agricultural capacity ?
Birth of Agriculture
The Harvest
Agriculture began in fits and starts over the last 8-12 thousand years.
- Ahu Hureyra (rye cultivation)
- Çatalhöyük (early full agriculture)
Taking of fish and animals as prey has a longer history.
- Hunting the wild
- Domestication
10,000 BP Jordon NYT Oct 2016
Role of temperature
Water supplies
Soil histories
Technology
Competing species
Birth of Agriculture
Spread of Rice after 10,000 BP
New Revolutions:
To what degree have the soils cultures inherit set their resource bases?
Soils and water go hand in hand; 1) soils are created through erosion of bed rock; 2) Water is needed for production of organic matter.
How do soils change with the advent of agriculture?
Much of the decline in death rates is tied to better health and sanitation.
What is the correlated role of nutrition?
The large growth in populations implicit in both of these sets of curves has been maintained by a revolution in farming – The Green Revolution
To what extent is the scatter in this plot tied to the wealth of the land and agricultural bounty?
What issues define this scene?
Nat. Geo. 2004
Missing cultures
Pre-Columbian cultures in the Amazon
National Geographic September 2008
Changes in monsoons and N. Hemisphere Temperature
Medieval Warm Period
Little Ice Age
Locusts and Agriculture Loss
What about North America?
The Dust Bowl
Decadal Climate Variations
1930’s
Climates from model simulations
Arthur Rothstein (1936)
Cimarron Co. Oklahoma
LIFE Feb. 26, 1940
Atmospheric General Circulation Models (AGCMs)
Computer models describing the equations of motion for the Earth’s atmosphere.
NASA Seasonal-to-Interannual Prediction Project (NSIPPP) – Climate of the 20th Century
3 X 3.75 degree (latitude/ longitude) grid
Ensemble runs with proscribed SST
Based on Dorothea Lange’s photography of a migrant mother in Nipomo, California 1936
The Great Dust Bowl:
(1929-1939)
https://www.ncdc.noaa.gov/
Miami Herald
May 17, 2007
Causes of Soil Degradation
Soil and Agriculture on the Rocks:
ECS 111
February 4, 2015
Dr. Olson
A Global View of Soil Degradation
Who competes for soil?
Soil supports a regular flora (plants) that in turn have a endemic (native) fauna.
Agriculture fundamentally disturbs this system: Mono-culture
This and climate variables set up conditions for invasive species.
A Global View of Soil Degradation
Soil and other issues:
Global Trend: Where Did All the Farms Go?
Poor farming practices = loss of soils and farmland
Erosion
Salinization
Development in United States = loss of 1.4 million acres of farmland per year
Global Trend: Where Did All the Farms Go?
Poor farming practices = loss of soils and farmland
Erosion
Salinization
Development in United States = loss of 1.4 million acres of farmland per year
To what extent can farmland recover?
Global Trend: Where Did All the Farms Go?
Poor farming practices = loss of soils and farmland
Erosion
Salinization
Development in United States = loss of 1.4 million acres of farmland per year
How easy is it to recover farmland from development?
Why a Study of Soil Is Important
90% of the world’s food comes from land-based agriculture.
Maintenance of soil is the cornerstone of sustainable civilizations.
Simply stated, it is the “foundation” of terrestrial life.
What is Soil?
Medium for plant growth.
Regulator of water supplies.
Recycler of raw materials.
Habitat for organisms.
Engineering medium.
Topsoil Formation
Soil Profile
Soil Profile
Any or all of these can be missing in a particular soil horizon.
Example from a simpler soil profile from Robinson (1982)
Example from a simpler soil profile from Robinson (1982)
How do ecologists or geologist sample soils?
Example from a simpler soil profile from Robinson (1982)
How do ecologists or geologist sample soils?
They dig a trench!
Soil Texture
Soil texture refers to the percentage of each type of particle found in the soil.
Loam soil is approximately 40% sand, 40% silt, and 20% clay.
Each of these has a particular character: sand is hard grained; silt is fine, and clays consist of sheets of material.
Soil Texture
Sand
Silt
Clay
Large
Small
Smaller
Soil Texture
Soil Texture and Properties (see Table 8-2)
| Texture | Water Infiltration | Water-holding Capacity | Nutrient-holding Capacity | Aeration |
| Sand | Good | Poor | Poor | Good |
| Silt | Medium | Medium | Medium | Medium |
| Clay | Poor | Good | Good | Poor |
| Loam | Medium | Medium | Medium | Medium |
Soil Classes
Mollisols: fertile soils with deep A horizon; best agriculture soils Ex. Illinois, Pampas, Steppes of Ukraine.
Oxisols: iron and aluminum oxides in B horizon; little O horizon; poor agriculture soils Ex. Amazon
Alfisols: Moderately weathered forest soils. Canadian forests, Siberia
Aridisols: Drylands and deserts. American West
Classifying Everything
Robinson 1982. Basic Physical Geology lists 10 soil types.
Keeps geologists busy.
Engineers like to classify them by their physical properties.
Soils by climate characteristics and their distribution across the US.
From Brady and Weil (1999)
Soil Chemistry: Strongly influenced by Temperature and Water content
Soil cross sections.
Brady and Weil (1999)
Plant–Soil–Water Relationships
Water Transport by Transpiration
Productive Soil
Good supply of nutrients and nutrient-holding capacity (NO₃ , PO₄, SO₄, …)
Infiltration, good water-holding capacity, resists evaporative water loss
Porous structure for aeration (O₂ respiration)
Near-neutral pH (Both Acidic and Alkaline Conditions are bad)
Low salt content (Some NCl but just a little)
The Soil Community
Humus
Partly decomposed organic matter
High capacity for holding water and nutrients
Typically found in O horizon
Formation of Humus
Humus and Development of Soil Structure
The Importance of Humus to Topsoil
Soil Degradation
Erosion
Drylands and desertification
Irrigation and salinization
The Results of Removal of Topsoil: Sand and Gravel
Erosion: Wind or Water
Splash erosion: impact of falling raindrops breaks up the clumpy structure of topsoil
Sheet erosion: running water carries off the fine particles on the soil surface
Gully erosion: water volume and velocity carries away large quantities of soil, causing gullies (see Fig. 8-14)
Desertification
Formation and expansion of degraded areas of soil and vegetation cover in arid, semiarid, and seasonally dry areas, caused by climatic variations and human activities.
Dryland Areas
Cover one-third of Earth’s land area
Defined by precipitation, not temperature
United Nations Convention to Combat Desertification (UNCCD)
Fund projects to reverse land degradation
In 2003, $500 million available in grants to fund projects
Dry lands and Desertification: Formation of Desert Pavement
A Global View of Soil Degradation
Irrigation
Flood irrigation (see Fig. 8-21)
Center-pivot irrigation (see Fig. 7-16)
Can extract as much as 10,000 gallons/minute
Irrigated lands
67 million acres or one-fifth of all cultivated cropland in the United States
667 million acres worldwide, a 35% increase over the past 30 years
165 year experiment in the American West past the 100 meridian
Salinization
A process of distilling out dissolved salts in irrigated water and leaving it on the land
A form of desertification, since land is rendered useless
Worldwide an estimated 3.7 million acres of agricultural land is lost annually to salinization and waterlogging
Salinization: What It Looks Like
Conserving the Soil
Cover the soil
Minimal or zero tillage
Mulch for nutrients
Maximize biomass production
Maximize biodiversity
Contour Farming and Shelterbelts
